YEAR IN CARDIOLOGY SERIES
The Year in Interventional Cardiology
Simon R. Dixon, MBChB, FRACP, FACC*,1,*,
Cindy L. Grines, MD, FACC*,2 and
William W. O’Neill, MD, FACC ,3
* William Beaumont Hospital, Royal Oak, Michigan
University of Miami, Miami, FLorida.
Manuscript received January 22, 2007;
revised manuscript received March 22, 2007,
accepted April 4, 2007.
* Reprint requests and correspondence: Dr. Simon R. Dixon, Division of Cardiology, William Beaumont Hospital, 3601 West 13 Mile Road, Royal Oak, Michigan 48073. (Email: sdixon{at}beaumont.edu).
We are honored to review the major original research in the field of interventional cardiology published in the year 2006. Given space constraints, we have attempted to summarize key articles that we believe have relevance to the busy clinician. In addition, we have included late-breaking trials presented at the American College of Cardiology (ACC), Transcatheter Cardiovascular Therapeutics, and American Heart Association (AHA) conferences. Finally, in collaboration with the Steering Committee for the ACC Innovations in Intervention (I2) Summit, we also present the top 10 articles in the field for 2006.
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ACC/AHA/Society for Cardiovascular Angiography and Interventions Percutaneous Coronary Intervention (PCI) Guidelines
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An update of the 2002 PCI guidelines was published in 2006 (1). These practice guidelines have evolved from a review of best practice to a quasi-legal document with increasing influence with hospital credentialing committees, payors, Centers for Medicare and Medicaid Services, U.S. Food and Drug Administration (FDA), and the tort bar. Even state regulatory authorities are using this document to formulate hospital licensing standards. For this reason, a careful reading of this document is essential for those involved in the practice of interventional cardiology. We will point out particular areas that contain substantive changes from the 2002 report and also areas of great debate.
Certain "hot button" issues need to be highlighted. Operator and institutional volume standards continue to conclude that patients have the best outcomes with high-volume (>75 per year) operators, in high-volume centers (>400 per year) for elective procedures. Similarly for ST-segment elevation myocardial infarction (STEMI), results seem better when performed by operators who do at least 11 STEMI interventions and institutions that perform >36 STEMI procedures per year. Thus a Class III recommendation exists for low-volume operators at low-volume centers. Another contentious recommendation is that elective PCI should not be done without surgical standby. With respect to indications for intervention, an early invasive strategy for high-risk unstable angina/non-STEMI patients is endorsed (Class I, Level of Evidence A). Use of PCI for STEMI is now strongly endorsed (Class I, Level of Evidence A) when it is done for patients <12 h after onset of symptoms by experienced operators working in high-volume centers. In addition, a door-to-balloon time (DBT) of  90 min is endorsed as a goal. The ACC is now using this recommendation as part of a national quality initiative. Percutaneous coronary intervention should not be performed immediately in a nonculprit artery during STEMI intervention (Class III, Level of Evidence C). Ad hoc angioplasty is cautiously endorsed for simple lesions. Importantly, the committee stated that this procedure is not mandatory or standard and that staging interventions was appropriate to risk stratify, optimally prepare, and inform the patient. Staging was especially indicated for patients with poor renal or left ventricular (LV) function and when suitability for coronary artery bypass graft surgery is a consideration.
A portion of the guidelines will need constant updating. For example, drug-eluting stents (DES) will constantly evolve. Pharmacotherapy is likely to evolve ever faster. Recommendations on dosing and duration of clopidogrel are outdated already. Use of bivalirudin could not take the ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) trial into account. For these reasons, a revision is already being planned to update recommendations based on new trial data.
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Acute Myocardial Infarction (AMI)
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Primary PCI versus thrombolysis.
Although several trials have shown a benefit of primary PCI over thrombolysis, some have questioned whether primary PCI would be superior in daily practice, or when compared with pre-hospital thrombolysis. Stenestrand et al. (2) reported a large registry of consecutive STEMI patients representing more than 95% of all patients admitted to Swedish coronary care units between 1999 and 2004, and followed up through December 2005. Reperfusion therapy included primary PCI (n = 7,084), pre-hospital thrombolysis (n = 3,078), and in-hospital thrombolysis (n = 16,043). After adjusting for age and comorbidities, pre-hospital thrombolysis was superior to in-hospital thrombolysis at reducing mortality, particularly in patients who presented within 2 h of symptom onset. However, primary PCI was superior to both in-hospital and pre-hospital thrombolysis at reducing 30-day mortality (hazard ratio [HR] 0.61, 95% confidence interval [CI] 0.53 to 0.71; HR 0.70, 95% CI 0.58 to 0.85, respectively) and 1-year mortality (HR 0.68, 95% CI 0.60 to 0.76; HR 0.81, 95% CI 0.69 to 0.94, respectively) (Fig. 1). The benefits of primary PCI persisted regardless of treatment delay. Moreover, primary PCI was associated with shorter hospital stay and less reinfarction. Therefore, both randomized trials and large registries continue to show the benefit of primary PCI over thrombolysis, and call into question whether primary PCI should be preferred over thrombolysis even when the delay to the catheterization laboratory exceeds 120 min.
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Figure 1 Estimated Cumulative Mortality Curves
Estimated cumulative mortality curves for patients receiving reperfusion treatment within or after 2 h of symptom onset. Mortality curves are calculated using a Cox regression analysis including a propensity score for primary percutaneous coronary intervention (PCI). Reprinted with permission from Stenestrand et al. (2).
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PCI after thrombolysis.
The inherent delay in mobilizing the catheterization laboratory for primary PCI may result in further myocardial necrosis and worse outcomes. The ASSENT-4 PCI trial (Assessment of Safety and Efficacy of a New Treatment Strategy With Percutaneous Coronary Intervention) enrolled 1,667 STEMI patients with anticipated delay to the laboratory of 1 to 3 h and randomized them to primary PCI (n = 838) or tenecteplase-facilitated PCI (n = 829) (3). The trial was stopped short of the anticipated 4,000 patients because of higher in-hospital mortality in the facilitated group (6% vs. 3%, p = 0.0105). The primary end point of death, heart failure, or shock at 90 days also was higher in the facilitated arm (19% vs. 13%, p = 0.0045). Moreover, patients in the facilitated PCI arm had more strokes (1.8% vs. 0%, p < 0.0001), reinfarction (6% vs. 4%, p = 0.027), repeat target vessel revascularizations (TVRs) (7% vs. 3%, p = 0.0041), and bleeding complications. No subgroup seemed to benefit from the facilitated approach, including those with early infarcts (<2 h from symptom onset) or patients experiencing an excessive delay to the catheterization laboratory (>2 h delay from randomization to balloon inflation).
Keeley et al. (4) conducted a meta-analysis of 17 trials that randomized 4,504 patients to facilitated PCI (with thrombolytic agents, glycoprotein [GP] IIb/IIIa agents, or both) versus primary PCI. As expected, the facilitated approach improved initial Thrombolysis In Myocardial Infarction (TIMI) flow grade 3 (37% vs. 15% of patients, p < 0.0001), but post-PCI TIMI flow grade 3 was similar (89% vs. 88% of patients, p = 0.30). Facilitated PCI was associated with high rates of death (5% vs. 3%, p = 0.04), nonfatal reinfarction (3% vs. 2%, p = 0.006), TVR (4% vs. 1%, p = 0.01), hemorrhagic stroke (0.7% vs. 0.1%, p = 0.0014), total stroke (1.1% vs. 0.3%, p = 0.0008), and major bleeding (7% vs. 5%, p = 0.01). The increased rates of adverse events occurred exclusively in thrombolytic-facilitated patients, whereas GPIIb/IIIa-facilitated patients had equivalent outcomes to those with primary PCI. A review article of facilitated PCI also concluded that facilitated PCI does not offer any advantage over primary PCI, and may be harmful (5). The investigators concluded that although some studies comparing facilitated PCI with thrombolytic agents alone have shown benefit, this advantage was likely because of the addition of PCI rather than the combined approach.
Because of conflicting results among randomized trials performing rescue PCI after failed thrombolysis versus conservative care, Patel et al. (6) published a meta-analysis of 5 trials. They reported a 36% reduction in the risk of death (p = 0.048), a 28% reduction in the risk of heart failure (p = 0.06), but a trend for increased risk of thromboembolic stroke (p = 0.07). These data suggest that rescue PCI be confined to patients with large infarcts, at risk of death or heart failure, with careful catheter technique to avoid embolic events.
Collet et al. (7) conducted a meta-analysis of randomized trials comparing different PCI approaches to the management of postlysis patients. Their report confirmed the benefit of rescue PCI for failed thrombolysis and the harm of facilitated PCI. In addition, they found that systematic early PCI after thrombolysis in trials conducted during the "stent era" showed a trend for reduced mortality (3.8% vs. 6.7%, odds ratio [OR] = 0.56, 95% CI 0.29 to 1.05, p = 0.07) and a significant reduction in death or reinfarction (7.5% vs. 13.2%, OR = 0.53, 95% CI 0.33 to 0.83, p = 0.0067). This is in contrast to the "balloon era," in which worse outcomes were observed with PCI.
Delayed PCI for persistent occlusion.
Two publications in 2006 questioned the utility of delayed PCI of a totally occluded vessel after STEMI. The OAT (Occluded Artery Trial) study was stopped before the 3,200-patient sample size was achieved because of recruitment difficulties (8). A total of 2,166 stable patients 3 to 28 days after MI with an occluded infarct artery (TIMI flow grade 0 to 1) were randomized to receive PCI or medical therapy. Patients were excluded if they had post-MI angina or severe ischemia on stress testing. Mean left ventricular ejection fraction (LVEF) was 48%, collaterals were present in 88%, and the median time to randomization was 8 days. The primary end point of death, myocardial infarction (MI), or class IV heart failure occurred in 17.2% of PCI patients versus 15.6% of medical therapy patients (p = 0.20). The rate of nonfatal reinfarction was nonsignificantly increased in the PCI group (6.9% vs. 5%, p = 0.08), some of which (0.6%) was because of periprocedural MI. In subgroup analysis, no group seemed to benefit from PCI (including left anterior descending artery–related infarctions), and young patients (<65 years) had an increase in the primary event rate (17.0% vs. 13.2%, p = 0.05).
The TOSCA-2 (Total Occlusion Study of Canada) trial was a subgroup of 381 patients enrolled in the OAT study, of which 332 patients underwent follow-up catheterization at 1 year (9). Initial PCI was successful in 92%, and at 1 year infarct artery patency was observed in 83% of PCI-treated patients versus 25% of medically treated patients (p < 0.001). Ejection fraction increase was similar in both groups (4.2% vs. 3.5%), and there were slight but not significant differences in LV volume and regional wall motion favoring the PCI group.
Therefore, late restoration of flow did not improve LV function, death, reinfarction, or heart failure. Based on these 2 studies, interventionalists should continue to follow the ACC/AHA guidelines that do not recommend PCI in asymptomatic patients after AMI without ischemia on stress testing.
Improving access to primary PCI.
Given overwhelming evidence from randomized trials regarding the benefits of mechanical reperfusion, there has been tremendous interest in developing strategies to improve the availability of primary PCI. The AHA recently convened the Acute Myocardial Infarction Advisory Working Group to explore specific recommendations and has issued a call to action to improve both the implementation and the timeliness of primary PCI for STEMI patients in the U.S. (10). One of the major obstacles in the U.S. at present is the lack of a coordinated system of STEMI care, such as that used for level I trauma patients (11). With this in mind, a report from the Vienna STEMI Registry is not only timely, but also has important implications for health care delivery (12). After organization of a cooperative network for STEMI care in Vienna, there was a substantial increase in the use of primary PCI, as well as a decrease in the proportion of patients not receiving any reperfusion therapy. Notably, there was a significant decrease in overall in-hospital mortality from 16% to 9.5% during the study period. Establishment of similar coordinated systems of STEMI care in the U.S. will have a number of potential challenges, but clearly needs urgent attention to further improve AMI outcomes.
Time-to-treatment issues.
Decreasing delays from patient arrival to PCI-mediated reperfusion (DBT) has become a component of institutional quality assessment by the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) and Center for Medicare and Medicaid Services (CMS). This quality measure has also been embraced by the ACC in a national DBT campaign. The year 2006 started with a sobering assessment of the national status of this quality measure in the National Registry of Myocardial Infarction (NRMI)-3 and -4 registries (13). As of 2002, the mean DBT was 100 min in the 421 participating U.S. hospitals, and <30% of patients were treated in <90 min. No significant decrease in time delay had occurred from 1999 to 2002, although high-volume centers did see a substantial decline.
There has been some controversy regarding whether DBT independently affects survival or is merely a surrogate for severity of illness or institutional quality. A number of publications shed light on this matter. Brodie et al. (14) assessed the impact of high-risk versus low-risk patients and DBT on long-term survival. They found that DBT strongly affected survival for high-risk patients presenting within 3 h of symptom onset. Similarly, McNamara et al. (15) examined the NRMI-3 and -4 dataset and found a striking relationship between mortality and DBT for high-risk but not for low-risk patients. Pinto et al. (16) further examined the NRMI-3 and -4 dataset and found that institutions with both treatment options lose the advantage of PCI when treatment delays are excessive. Curtis et al. (17) found that significant decreases in time delay occurred when a pre-hospital electrocardiogram was obtained. Although each of these publications discuss confounding issues such as institutional PCI STEMI volume, severity of illness, and interaction with time of presentation, decreasing treatment delay has become a national priority. To this end, Bradley et al. (18) have examined health care organizational components that can decrease treatment delay. Importantly, integrated systems with emergency department physician, ambulance system, and cardiologist coordination, as well as institutional physician champions, can dramatically improve these delays.
Outcomes research.
In 2006, there were several important articles regarding measurement of quality indicators and hospital performance for AMI. The ACC/AHA Task Force on Performance Measures provided a report on the ACC/AHA STEMI/non-STEMI set of performance measures (19). By design, this performance measurement set is similar to the 9 Core Measures for AMI implemented by the JCAHO in 2002, but does have some notable differences. These include: 1) addition of angiotensin receptor blockers to the angiotensin-converting enzyme inhibitor measure; 2) use of median time to fibrinolytic therapy or PCI, instead of mean time; 3) incorporation of a 90-min DBT rather than the previous 120-min standard; and 4) addition of a reperfusion therapy measure.
Bradley et al. (20) provided an interesting report on the correlation between the JCAHO/CMS quality process measures for AMI and hospital outcome, using data from 962 hospitals participating in the NRMI. In this analysis, only 3 of the core measures (timely reperfusion, aspirin at discharge, beta-blocker at discharge) were significantly correlated (p < 0.001) with risk-standardized 30-day mortality rates, and together these measures explained only 6.0% of hospital-level variation in the short-term mortality rates for AMI. These data suggest that additional process measures are needed to explain more of the variation in AMI outcomes and better reflect hospital performance. Presently hospitals should continue to report not only the current core measures but also short-term risk-standardized mortality rates to provide an overall assessment of hospital quality.
Currently many PCI-capable hospitals in the U.S. offer both PCI and fibrinolysis for STEMI patients, however, there has been debate whether this "selective" approach is appropriate in light of contemporary data regarding the benefits of PCI. In 2006, Nallamothu et al. (21) provided a timely and important report on the relationship between hospital specialization for primary PCI and in-hospital mortality. Specialization was defined as the relative proportion of reperfusion-treated patients (PCI or fibrinolysis) who were treated with PCI. Greater specialization with primary PCI was associated with lower in-hospital mortality and shorter DBTs, and of note, this relationship seemed to be independent of PCI volumes. These data suggest that hospitals committed to PCI as the predominant reperfusion strategy achieve the best outcomes, and emphasize the need for hospitals to focus on providing primary PCI alone rather than using a selective approach to reperfusion therapy.
Halkin et al. (22) examined the relationship between peak creatine kinase (CK) level and clinical outcome after primary PCI in the CADILLAC (Controlled Abciximab and Device Investigation to Lower Late Angioplasty Complications) trial. Peak CK was an independent predictor of 1-year mortality and was independent of post-PCI TIMI flow grade. Improvement in LVEF at 7 months was inversely related to the peak CK level.
Adjunctive therapies and devices.
Results of 3 randomized trials of adjunctive thrombectomy showed conflicting results. In the DEAR-MI (Dethrombosis to Enhance Acute Reperfusion in Myocardial Infarction) trial, use of the manual aspiration Pronto extraction catheter (Vascular Solutions, Minneapolis, Minnesota) was associated with a lower incidence of distal embolization or no-reflow, improved myocardial reperfusion, and a lower peak CK level compared with stenting without thrombectomy (23). On the other hand, the AIMI (AngioJet Rheolytic Thrombectomy in Patients Undergoing Primary Angioplasty for Acute Myocardial Infarction) (24) and Kaltoft et al. (25) studies found no benefit from thrombectomy. In the AIMI trial, patients treated with the AngioJet thrombectomy catheter (Possis Medical, Minneapolis, Minnesota) had a larger final infarct size, as well as a higher rate of major adverse cardiac events (MACE) at 30 days (6.7% vs. 1.7%, p = 0.01) (24). Some of the difference in outcome may be explained by the lower than expected event rate in the control arm, and some have questioned the study design because angiographic evidence of thrombus was not required. In the study by Kaltoft et al. (25), there was no significant difference in myocardial salvage (assessed with sestamibi single-photon emission computed tomography imaging) in patients treated with the Boston Scientific Rescue catheter. Overall, these data suggest that there is no role for routine use of thrombectomy during primary PCI.
Results of trials evaluating pharmacologic adjuncts for mechanical reperfusion were also disappointing. In the APEX-MI (Assessment of Pexelizumab in Acute Myocardial Infarction) trial, 5,745 patients undergoing primary PCI were randomized to receive intravenous pexelizumab or placebo. At 30 days, there was no difference in the incidence of 30-day mortality (4.06% for pexelizumab vs. 3.92% for placebo) (26). Hudson et al. (27) investigated whether PG-116800, an oral matrix metalloproteinase inhibitor, would improve LV remodeling after AMI evaluated with serial echocardiography. The agent was well tolerated, however, at 90 days, there was no significant improvement in LV systolic and diastolic volumes, ejection fraction, or sphericity index in patients receiving the matrix metalloproteinase inhibitor. In another study, the amino acid L-arginine failed to improve vascular stiffness measurements or LV function after AMI (28). One study from Japan, however, provided some hope in this field. In 603 subjects, administration of atrial natriuretic peptide was associated with a 14% reduction in infarct size assessed by CK release kinetics (29).
DES.
Results of 2 trials evaluating DES in AMI were published in 2006. In the TYPHOON (Trial to Assess the Use of the Cypher Stent in Acute Myocardial Infarction Treated With Angioplasty) study, 712 patients were randomized to undergo stenting with either a sirolimus-eluting stent (SES) or any uncoated stent (30). The primary end point, target vessel failure at 1 year, was significantly reduced in the SES group (7.3% vs. 14.3%, p = 0.004), driven entirely by a decrease in the rate of TVR (5.6% vs. 13.4%, p < 0.001). In contrast, the PASSION (Paclitaxel Eluting Stent Versus Conventional Stent in ST-Segment Elevation Myocardial Infarction) trial investigators found only a nonsignificant trend in favor of the paclitaxel-eluting stent (PES) in 629 AMI patients (31). At 12 months, the incidence of the composite end point (death, MI, and target lesion revascularization [TLR]) was 8.8% in the PES group and 12.8% in the bare-metal stent (BMS) group (p = 0.12). Of note, there was no significant difference in the incidence of stent thrombosis in either study. Given the relatively small number of patients enrolled in these trials, the discordant results of the studies, and recent concerns about late stent thrombosis, we believe that further data are required to determine whether routine use of DES is safe or beneficial in AMI patients.
Cell-based cardiac repair.
In 2006, there were numerous publications regarding cellular therapy for myocardial regeneration after AMI (Table 1). The REPAIR-AMI (Reinfusion of Enriched Progenitor Cells and Infarct Remodeling in Acute Myocardial Infarction) trial randomized 204 STEMI patients who had undergone successful primary PCI to receive intracoronary infusion of placebo versus bone marrow-derived cells (BMC) 3 to 7 days after PCI (32). The BMC group showed greater improvement in LVEF at 4 months (5.5 ± 7.3% vs. 3.0 ± 6.5%, p = 0.01) and reduction in the combined end point of death, reinfarction, or revascularization at 1 year (4.0% vs. 2.3%, p = 0.01). The ASTAMI (Autologous Stem-Cell Transplantation in Acute Myocardial Infarction) study randomized 100 patients with anterior AMI treated with PCI to intracoronary infusion of BMC at a median of day 6 versus control (no bone marrow aspiration or infusion) (33). The LVEF was assessed at baseline and at 6 months by echocardiography, single-photon emission computed tomography imaging, and magnetic resonance imaging. No difference was observed between the 2 treatment groups. Similarly, Janssens et al. (34) found that intracoronary infusion of BMC (n = 33) versus placebo (n = 34) resulted in a similar LVEF. They did note a suggestion of improved infarct size with BMC infusion, but multiple other end points were negative. Kang et al. (35) compared the effects of intracoronary stem cell infusion versus control in acute and old (>14 days) MI. They reported that stem cell infusion in AMI patients improved LVEF and remodeling compared with controls, but not in older infarctions. The BOOST (Bone Marrow Transfer to Enhance ST-Elevation Infarct Regeneration) trial reported follow-up at 18 months (36). Although bone infusion was associated with higher LVEF at 6 months, there was a catch up in the control group resulting in no significant difference by 18 months.
Because granulocyte colony-stimulating factor (G-CSF) mobilizes stem cells from the bone marrow and increases their numbers in the peripheral blood, many investigators have questioned whether G-CSF–induced circulating stem cells would be sufficient to improve LVEF. Three trials were published in 2006, all of which randomized STEMI patients treated with primary PCI to subcutaneous injections of placebo versus G-CSF 10 µ/kg for 5 days (37–39). Each study failed to show benefit in LV functional recovery.
Therefore, numerous reports are in conflict regarding the efficacy of cellular therapy in AMI. These differences may be because of high baseline ejection fraction, small sample size, timing of cell infusions relative to infarction, or timing of follow-up imaging studies. In addition, some studies used bone marrow aspiration and others collected stem cells from peripheral blood after G-CSF stimulation. Differences in cell counts, cell type, and degree of homing to infarcted myocardium may vary, all of which may play a role in study results.
Cardiogenic shock.
Long-term outcome data for patients enrolled in the randomized SHOCK (Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock) trial were reported in 2006 (40). At a median follow-up of 6 years, there was a substantial improvement in overall survival (32.8% vs. 19.6%) in those patients assigned to early revascularization compared with intensive medical therapy. A similar improvement in late outcome was seen among the 143 hospital survivors (62.4% vs. 44.4%). These data further reinforce the importance of an early revascularization strategy in cardiogenic shock patients.
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Acute Coronary Syndrome (ACS)
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An early invasive strategy has been shown to be superior to conservative care with regard to decreasing recurrent ischemia, readmission, and revascularization. However, MI and death outcomes have conflicted with some studies showing improved and other studies showing worsened outcomes with an invasive strategy. Bavry et al. (41) conducted a meta-analysis of 7 trials enrolling 8,375 patients with ACS randomized to an early invasive strategy versus conservative care. At a mean follow up of 2 years, the early invasive strategy was associated with reduced mortality (4.9% vs. 6.5%, risk ratio [RR] = 0.75, 95% CI 0.63 to 0.90, p = 0.001) and nonfatal MI (7.6% vs. 9.1%, RR = 0.83, 95% CI 0.72 to 0.96, p = 0.012), suggesting long-term clinical benefit.
The FRISC-II (Fragmin and Fast Revascularization During Instability in Coronary Disease) investigators reported 5-year follow-up of 2,457 patients with non-STEMI randomized to invasive versus conservative care (42). The primary end point of death and/or MI was improved in the invasive group (19.9% vs. 24.5%, RR = 0.81, 95% CI 0.69 to 0.95, p = 0.009). Myocardial infarction at 5 years was significantly improved (12.9% vs. 17.7%, RR = 0.73, 95% CI 0.60 to 0.89, p = 0.002), whereas mortality was similar (9.7% vs. 10.1%, RR = 0.95, p = 0.693).
The use of invasive strategies and potent antithrombotic drugs may improve clinical outcome, but also increase the risk of bleeding. In a pooled analysis of 34,146 patients with ACS (43), risk factors for major bleeding included age, diabetes, stroke, low blood pressure, high serum creatinine, and ST changes on the presenting electrocardiogram. Major bleeding was independently associated with increased risk of death at 30 days (HR 5.37, 95% CI 3.97 to 7.26, p < 0.0001) and between 1 and 6 months (HR 1.54, 95% CI 1.01 to 2.37, p = 0.047). The authors concluded that awareness of importance of bleeding should lead to evaluation of strategies to reduce bleeding and improve outcome.
The OASIS-5 (Fifth Organization to Assess Strategies in Acute Ischemic Syndromes) study randomized 20,078 patients with ACS to receive fondaparinux (2.5 mg daily) versus enoxaparin (1 mg/kg twice per day) for a mean of 6 days (44). The primary end point of death, MI, or refractory ischemia at 9 days was similar between the 2 groups (5.8% vs. 5.7%). However, major bleeding at 9 days was significantly lower with fondaparinux (2.2% vs. 4.1%, p < 0.001). In addition, fondaparinux was associated with reduced mortality at 30 and 180 days.
Gibson et al. (45) reported a trial of 857 ACS patients randomized to one of 3 arms (eptifibatide + unfractionated heparin, eptifibatide + enoxaparin, or bivalirudin monotherapy). Angiographic and clinical end points were conflicting with bivalirudin showing improved minor bleeding (0.4% vs. 2.5%, p = 0.027) and transfusion rates (0.4% vs. 4.4%, p < 0.001) as well as improved coronary flow reserve, but worse rates of post-PCI TIMI flow grade 3 (50.9% vs. 57.9%, p = 0.048) and longer duration of post-PCI ischemia on Holter monitor (169 min vs. 36 min, p = 0.013).
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PCI for Chronic Coronary Artery Disease
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Outcomes research.
Although public reporting on quality surrogate measures is now required by the JCAHO and CMS, the impact of collection and improvement of quality indicators on clinical outcomes is unknown. Moscucci et al. (46) provide fascinating and timely data from their report of 5 hospitals in Michigan that embarked on a quality improvement project between 1998 and 2002. The investigators collected data on preprocedure aspirin use, total contrast dose, and postprocedure heparin use. Initially there was wide variation between hospitals (postprocedure heparin use varied from 15% to 74% of cases, GP receptor blockade varied from 14% to 48%, and average total contrast varied from 333 to 247 ml/case). After intervention, all of these parameters improved and institute variations were largely eliminated. Most importantly, MACE decreased from 5.28% to 3.75% (p = 0.0003) and overall mortality tended to be lower (1.74% to 1.27%, p = 0.06).
Other investigators sought to determine predictors of outcomes after PCI. Wu et al. (47) developed a risk model to predict outcomes in the New York State database. Saw et al. (48) showed that the presence of overt peripheral artery disease was associated with a higher 1-year mortality in 9 randomized PCI trials. Whether this is an independent effect or reflects the worse renal function, more frequent presence of diabetes, previous cerebrovascular accident, or previous congestive heart failure is problematic. Suffice it to say that a history of peripheral artery disease must be noted as an adverse prognostic marker for these patients.
Gyenes et al. (49) provided 7-year follow-up for 11,855 PCI patients in the APPROACH (Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease) registry. They examined the impact of insignificant left main coronary artery disease (<50% angiographic stenosis) on survival. The unadjusted survival was slightly lower (86% vs. 88%), but was identical when adjusted for baseline variables.
Left main disease.
There is mounting interest in randomized trials comparing DES versus coronary artery bypass graft in symptomatic patients with unprotected left main coronary artery disease. In 2006, 5 major articles reviewed outcomes for patients treated with DES. The Scripps group provided sobering data on angiographic restenosis in 50 consecutive patients treated with the Cypher SES (50). Angiography performed at 3 and 9 months revealed restenosis in 42% of patients and subsequent TLR in 38% of patients; 94% of this group had distal bifurcation disease, and most restenosis occurred at the ostium of the circumflex artery. In addition, much of the restenosis was silent, suggesting that routine sentinel angiography needs to be performed in these patients.
Four other reports provided matched comparisons for patients treated with coronary artery bypass graft or PCI from 2002 to 2005 (51–54). Overall, these reports suggest no difference in mortality at 1 year. Given the retrospective, nonrandomized nature of these reports, no other definite conclusions can be reached. These studies suggest a state of equipoise exists and recommendations should await data from large prospective randomized trials (FREEDOM [Future Revascularization Evaluation in Patients With Diabetes: Optimal Management of Multivessel Disease], COMBAT [Comparison of Bypass Surgery Versus Angioplasty in Patients With Left Main Coronary Disease], and SYNTAX [SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery]).
Bifurcation disease.
Bifurcation lesions are difficult to treat and are associated with higher angiographic and clinical complication rates, but have been excluded from most randomized trials. Two publications in 2006 addressed this lesion subset. If one chooses to stent both branches, the "crush" technique may be considered for the side branch. An observational report of 231 patients treated with the DES crush technique noted stent thrombosis by 9 months in 4.3% (55). Restenosis of the main branch was 9.1%, and side branch restenosis occurred in 25.3%. Post-stent kissing balloon inflations seemed to reduce side branch restenosis. The Nordic PCI study group (56) randomized 413 patients with a bifurcation lesion to stenting of the main vessel only, versus stenting of both branches. Stenting of both branches resulted in longer procedure and fluoroscopy times, higher contrast volumes, and higher rates of cardiac enzyme elevations. Clinical follow-up showed similar MACE at 6 months, and angiographic follow-up at 8 months showed similar restenosis rates. Therefore, stenting of the parent vessel with rescue PCI of the side branch (if necessary) seemed to be the preferred strategy.
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DES
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Comparisons of SES and PES.
The multicenter REALITY (Prospective Randomized Multi-Center Head-to-Head Comparison of the Sirolimus-Eluting Stent [Cypher] and the Paclitaxel-Eluting Stent [Taxus]) trial randomized 1,386 patients to receive SES or PES (57). The primary end point, in-lesion restenosis at 8 months, occurred in 9.6% of SES-treated and 11.1% of PES-treated patients (p = 0.31). Sirolimus-eluting stents were associated with less late loss (0.09 mm vs. 0.31 mm, p < 0.001) and less restenosis at 8 months (p < 0.001), but similar MACE compared with PES.
Long lesions are associated with poor outcomes after PCI. The LONG-DES II study randomized 500 patients with long ( 25 mm) native coronary lesions to SES versus PES (58). Mean lesion length was 34 ± 12 mm. In-segment restenosis at 6 months was lower in the SES compared with the PES group (3.3% vs. 14.6%, p < 0.001). Target vessel revascularization was lower in SES-treated patients (2.4% vs. 7.2%, p = 0.012) with similar rates of death and MI.
In a multicenter registry conducted in Italy, 1,676 consecutive patients with de novo coronary lesions were treated with DES (SES = 992, PES = 684) (59). An SES was associated with a 55% reduction in TVR, with similar rates of death or MI. Conversely, a large U.S. registry showed similar safety and TVR between SES-treated (n = 3,873) and PES-treated (n = 2,636) patients (60).
Late stent thrombosis.
Reports have suggested that DES may be associated with delayed endothelialization (61,62), localized hypersensitivity reactions (63), late malapposition (64), and late stent thrombosis. Late (1 to 12 months) stent thrombosis was not readily apparent with BMS, yet was reported to occur in 0.19% of patients in a large DES registry (65). In a meta-analysis of 14 trials that randomized 6,675 patients to DES versus BMS (66), there was no difference in early (<30 days) stent thrombosis (0.44% vs. 0.5%, p = 0.74) or late (>30 days) thrombosis (0.5% vs. 0.28%, p = 0.22). However, among the 8 trials that reported >1 year follow-up, "very late" (>1 year) thrombosis was noted in 0.5% of DES patients and in no BMS patient (RR = 5.02, 95% CI 1.29 to 19.52, p = 0.02).
Predictors of late stent thrombosis have included stenting of small vessels, multiple lesions, long stents, overlapping stents, ostial or bifurcation lesions, prior brachytherapy, suboptimal stent result (underexpansion, malapposition, residual dissection), low ejection fraction, advanced age, diabetes, renal failure, ACS, or premature discontinuation of antiplatelet agents (64–68).
Pfisterer et al. (67) studied 746 patients treated with a DES or BMS. All patients received dual antiplatelet therapy for 6 months, after which aspirin alone was continued. At 30 days, rates of death or nonfatal MI were lower in the DES group (2.0% vs. 4.69%, p = 0.05). However, after discontinuation of clopidogrel at 6 months, late stent thrombosis (2.6% vs. 1.3%) and death or nonfatal MI (4.9% vs. 1.3%) occurred more frequently in the DES group.
Similarly, Eisenstein et al. (68) reported an observational study in 4,666 patients with follow-up at 6, 12, and 24 months after stenting. In patients treated with BMS, continued use of clopidogrel did not influence death or MI rates between 6 and 24 months. Conversely, in DES patients, extended use of clopidogrel at 6, 12, and 24 months was associated with reduced death or death/MI rates at all time intervals.
Spertus et al. (69) published an analysis from the PREMIER (Prospective Registry Evaluating Myocardial Infarction: Events and Recovery) registry of 500 patients with AMI treated with DES. The mortality rate over the next 11 months for those who stopped thienopyridine therapy was 7.5%, compared with 0.7% in those who had not stopped therapy (HR 9.0, p < 0.0001). Factors identified with premature discontinuation of thienopyridine therapy included older age, not having completed high school, not being married, not receiving discharge instructions for medication use, not being referred for cardiac rehabilitation, greater likelihood of having pre-existent cardiovascular disease or anemia, and avoiding health care because of cost. The study investigators concluded that "additional patient education about the rationale for and importance of continuing thienopyridine treatment may be needed—particularly for patients with less formal education."
On December 7 to 8, 2006, the FDA convened an Advisory Panel meeting to discuss stent thrombosis and safety of DES (70). They concluded that there seems to be an excess of late stent thrombosis with DES but the magnitude is uncertain; and off-label use of DES (like BMS) is associated with increased risk compared with on-label use. The panel recommended that future DES studies should have longer follow-up, enroll greater numbers of patients, and include stent thrombosis as a study end point. The Advisory Panel concurred with the ACC/AHA guideline recommendation for 12 months of dual antiplatelet therapy after a DES in patients who are not at high risk of bleeding. However, they stated that a large, randomized trial looking specifically at appropriate duration of dual antiplatelet therapy is needed.
DES for BMS restenosis.
Treatment of bare-metal in-stent restenosis (ISR) remains a challenge; however, recent studies suggest that the benefit of DES can be extended to this patient group. In a 2-center registry, Liistro et al. (71) showed the safety and feasibility of SES implantation for ISR. In the randomized RIBS-II (Restenosis Intra-stent: Balloon Angioplasty Versus Sirolimus-Eluting Stenting) trial, 150 patients with bare-metal ISR were randomized to either balloon angioplasty alone or implantation of an SES (72). At 9-month angiographic follow-up there was a significantly lower incidence of recurrent restenosis in the SES group (11% vs. 39%, p < 0.001). The TAXUS-V ISR trial compared the use of intracoronary brachytherapy (beta-radiation) versus implantation of a PES in 396 patients with ISR (vessel diameter 2.5 to 3.75 mm, lesion length 46 mm) (73). Treatment with a PES was associated with a significant reduction in angiographic restenosis (14.5% vs. 31.2%, p < 0.001) and ischemia-driven TVR at 9 months (20% vs. 34%, p = 0.046). Dibra et al. (74) performed a meta-analysis of 4 randomized trials evaluating use of DES for ISR (ISAR-DESIRE [Intracoronary Stenting and Angiographic Results: Drug-Eluting Stents for In-stent Restenosis], RIBS-II, SISR [Sirolimus-Eluting Stent to Treat In-Stent Restenosis], TAXUS-V ISR). There was a marked reduction in angiographic restenosis and TLR with DES compared with conventional therapy (balloon angioplasty or brachytherapy), although no difference in the composite end point of death or MI was observed. In aggregate, these studies suggest that implantation of a DES should be considered the best treatment strategy in patients with bare-metal ISR.
New lesion subsets.
Although DES improve clinical and angiographic outcomes compared with BMS in simple lesions, limited data exist regarding their benefit in complex coronary lesions. The SCANDSTENT (Stenting Coronary Arteries in Nonstress/Benestent Disease) trial was a multicenter study conducted in Denmark and the Netherlands that randomized 322 patients with complex lesions (occluded 36%, bifurcation 34%, ostial 22%) to SES versus BMS (75). The use of SES in complex lesions was associated with reduced restenosis (2.0% vs. 31.9%, p < 0.001), reduced MACE (4.3% vs. 29.3%, p < 0.001), and a trend for less stent thrombosis at 6 months (0.6% vs. 3.1%, p = 0.15). Suttorp et al. (76) randomized 200 patients with total coronary occlusions to SES versus BMS. The SES group had lower rates of ISR (7% vs. 36%, p < 0.001) and lower TVR and MACE. Vermeersch et al. (77) enrolled 75 patients with 96 lesions in diseased saphenous vein grafts and randomized them to SES versus BMS. At 6 months, SES were associated with reduced ISR (11.3% vs. 30.6%, p = 0.02) and reduced TVR (5.3% vs. 27%, p = 0.012) with similar rates of death or MI.
Sometimes overlapping stents are required to completely cover long lesions or seal dissections. An increased risk of MI and restenosis has been reported after paclitaxel stents, but the safety of overlapping SES was unknown. Kereiakes et al. (78) reviewed patients enrolled in 5 clinical trials of SES, and compared 337 patients with SES overlap, 238 patients with BMS overlap, and 1,162 patients with single stents. Regardless of stent type, stent overlap was associated with increased restenosis. However, among overlap-stent treated patients, SES provided marked reduction in restenosis compared with BMS (6.2% vs. 50.6%, p < 0.001) with no increased risk of MI.
Long-term (2 years) follow-up after SES has been reported in a 508-consecutive-patient registry of nonselected patients (79) and in the randomized SIRIUS (Sirolimus-Eluting Stent in de Novo Native Coronary Lesions) trial (80). Both studies show continued reduction in TVR compared with BMS, with no difference in death or MI rates.
New DES.
The ENDEAVOR-II trial randomized 1,197 patients with a single coronary lesion to receive the Endeavor zotarolimus-eluting phosphorylcholine polymer-coated stent versus the same BMS (81). The Endeavor stent was superior at reducing the primary end point of target vessel failure at 9 months (7.9% vs. 15.1%, p = 0.0001) because of reductions in TLR (4.6% vs. 11.8%, p = 0.0001). The rate of stent thrombosis was not significantly different between DES and BMS (0.5% and 1.2%) respectively. Although the Endeavor stent was associated with less restenosis (13.2% vs. 35.0%, p < 0.0001) and late loss (0.61 vs. 1.03 mm, p < 0.001), inhibition of intimal proliferation was less than that observed with the available FDA-approved DES.
These findings were confirmed in the ENDEAVOR-III trial, which randomized 436 patients in a 3:1 fashion to the Endeavor stent versus an SES (82). At 8 months, angiographic follow-up showed higher restenosis (11.7% vs. 4.3%, p = 0.04), greater late loss (0.34 vs. 0.13 mm, p < 0.001), and more TLR (9.8% vs. 3.5%, p = 0.04) with the Endeavor stent compared with SES.
Concern has been expressed regarding whether the stent polymer is responsible for some of the late inflammatory and thrombogenic responses noted with DES. Accordingly, new DES without a polymer or with a biodegradable polymer are being tested. Mehilli et al. (83) randomized 450 patients to receive a polymer-free, rapamycin-coated Yukon DES versus the Taxus polymer-based PES. Although no significant differences were observed between the Yukon DES and PES, the restenosis rates (14.2% vs. 15.5%) and in-stent late loss (0.48 vs. 0.48 mm) were higher than one would expect from other polymer based "limus" stents such as the Cypher SES. Iofina et al. (84) treated 65 consecutive patients with the Taxus polymer-based PES and compared them to 65 consecutive patients treated with a nonpolymer-based PES (V-Flex Plus, Cook Inc., Bloomington, Indiana). At 6-month follow-up, the Taxus polymer-based PES was superior at reducing intimal proliferation as assessed by intravascular ultrasound, late loss assessed by angiography (0.22 mm vs. 0.74 mm, p < 0.001), ISR (5% vs. 20%, p < 0.001), and MACE (9% vs. 23%, p = 0.03). These 2 studies suggest that with the current stent designs, the polymer may be necessary to achieve the best drug elution kinetics to reduce restenosis.
An abciximab-coated stent may be beneficial to reduce stent thrombosis and restenosis (85). Ninety-six Korean patients with AMI were randomized to the abciximab stent versus BMS. Follow-up catheterization at 6 months showed reduced late loss (0.39 vs. 0.88 mm, p = 0.008), and restenosis (13.9% vs. 34.3%, p = 0.045). Clinical events were similar between the 2 groups.
Re-endothelialization promotes healing after arterial injury. Novel stents coated with an integrin-binding cyclic Arg-Gly-Asp peptide (cRGD), which attracts endothelial progenitor cells, were developed (86). Porcine models were used to compare coronary implantation of cRGD stents, polymer-only stents, and BMS. The cRGD stents were associated with recruitment of endothelial progenitor cells and enhanced endothelial coverage at 4 weeks, and reduced neointimal area by 12 weeks, compared with the other 2 stents. Therefore, stents coated with cRGD may prevent stent thrombosis and reduce restenosis in the future.
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Adjunctive Pharmacotherapy
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Clopidogrel.
The appropriate timing and dose of clopidogrel has received enormous attention. A post-hoc analysis of the CREDO (Clopidogrel for Reduction of Events During Observation) study found that in patients treated with a 300-mg loading dose of clopidogrel compared with a placebo loading dose, little clinical benefit occurred unless the loading dose was given >15 h before PCI (87).
To determine the incidence of antiplatelet "resistance," Lev et al. (88) reported on 150 patients who received aspirin for 1 week but not clopidogrel. Platelet aggregation was measured at baseline and repeated 10 to 24 h after 300 mg clopidogrel. Aspirin resistance was noted in 12.7% of patients, and clopidogrel resistance was noted in 24%. Interestingly, 47% of patients who were resistant to aspirin were also clopidogrel resistant. A small (n = 103) dose ranging study found that higher doses of clopidogrel (600 and 900 mg) resulted in a faster onset of action, greater antiplatelet effects, and reduced platelet activation compared with a 300-mg loading dose (89).
A larger study randomized 292 ACS patients to receive 300 mg versus 600 mg clopidogrel at least 12 h before PCI (90). Despite the 12-h pretreatment, the antiplatelet effect (platelet aggregation and expression of P-selection) was significantly greater after 600 mg clopidogrel compared with 300 mg. Moreover, a 600-mg clopidogrel loading dose was associated with reduced cardiac events at 1 month (5% vs. 12% p = 0.02). Hochholzer et al. (91) reported 802 patients undergoing elective stent placement who were pretreated with 600 mg clopidogrel. Platelet aggregation (to 5 µmol/l adenosine diphosphate) was assessed before PCI. Platelet aggregation above the median of 15% was associated with a 6.7-fold (p = 0.003) increase in 30-day MACE.
GP IIb/IIIa receptor inhibitor.
The ISAR (Intracoronary Stenting and Antithrombotic Regimen) study group has been instrumental in showing the lack of benefit of GP IIb/IIIa agents in stable angina patients who were pretreated with 600 mg clopidogrel several hours before PCI. However, platelet activation occurs in unstable angina, thus the clinical response may differ in ACS patients. The ISAR-REACT 2 (Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment 2) trial enrolled 2,022 patients with non-STEMI ACS undergoing PCI (92). All patients received aspirin 500 mg, and clopidogrel 600 mg at least 2 h before PCI, and were randomized to abciximab plus heparin (70 U/kg) versus placebo with high-dose heparin (140 U/kg). The primary end point of death, MI, or urgent TVR was reduced in the abciximab group (8.9% vs. 11.9%, RR = 0.75, 95% CI 0.58 to 0.97, p = 0.03). There were no differences in major or minor bleeding or transfusion requirement. These data support the guideline recommendation to use abciximab during PCI in ACS patients, even if pretreated with clopidogrel.
A small study randomized 93 high-risk ACS patients undergoing PCI to 3 treatment arms: upstream tirofiban, in-laboratory high-dose tirofiban, or in-laboratory abciximab (93). The upstream GP IIb/IIIa arm was associated with better pre-PCI and post-PCI tissue perfusion as well as reduced troponin levels.
Bertrand et al. (94) evaluated the safety of bolus-only abciximab and same-day discharge after uncomplicated transradial coronary stenting versus overnight hospitalization with abciximab bolus and infusion. At 30 days, the incidence of the primary end point (death, MI, urgent revascularization, major bleeding, repeat hospitalization, access site complications, and severe thrombocytopenia) was 20.4% in the same-day group and 18.2% in the overnight group. These data suggest that the same-day discharge strategy is not inferior to the standard overnight stay in moderate-risk to high-risk patients.
Antithrombin therapy.
As technical safety of PCI has improved, periprocedural safety has taken increasingly important attention (95). In particular, bleeding risk and blood transfusion after PCI was the subject of 2 large trials published in 2006. Results of both trials are summarized in Tables 2, 3, and 4. The STEEPLE (Safety and Efficacy of Enoxaparin in Percutaneous Coronary Intervention Patients: An International Randomized Evaluation) trial evaluated the efficacy and safety of enoxaparin at 2 doses (0.5 or 0.75 mg/kg) versus unfractionated heparin in 3,528 patients undergoing elective PCI (96). The 0.5-mg dose of enoxaparin was associated with a significantly lower incidence of major or minor bleeding at 48 h, whereas the 0.75-mg dosage resulted in similar results to those in the unfractionated heparin group. Of note, enrollment in the 0.5-mg group was stopped early by the Data Safety Monitoring Board because of a slight excess of deaths (statistically nonsignificant).
The ACUITY (Acute Catheterization and Urgent Intervention Triage Strategy) trial studied the safety and efficacy of bivalirudin alone or bivalirudin with adjunctive GP IIb/IIIa receptor inhibitor use versus heparin or enoxaparin with adjunctive IIb/IIIa in moderate-risk to high-risk ACS patients (97). At 30 days, outcomes in the GP IIb/IIIa receptor inhibitor groups were similar. In the bivalirudin-alone group, the rate of ischemic events was similar to the other groups; however, there was a significant reduction in bleeding. Among the 7,789 PCI patients, results in each of the 3 treatment arms were congruent with those of the overall ACUITY trial (98).
Prevention of restenosis.
Oral rapamycin has shown promise in observational studies to reduce restenosis after BMS implantation. In the ORAR II (Oral Treatment of Restenosis II) trial, 100 patients were randomized to receive oral rapamycin for 14 days or no therapy after implantation of a BMS (99). Rapamycin was well tolerated. Angiographic follow-up at 9 months showed a significant reduction in the primary end points of in-segment binary restenosis (11.6% vs. 42.8%, p = 0.001) and late loss (0.66 vs. 1.13 mm, p < 0.001).
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Contrast Nephropathy
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Prevention of contrast-induced nephropathy (CIN) remains an important focus of ongoing research efforts. McCullough et al. (100) presented a meta-analysis of 2,727 patients enrolled in 16 studies comparing iodixanol with other low-osmolar contrast media. Overall there was a smaller increase in serum creatinine in patients receiving iodixanol compared with the pooled low-osmolar contrast media group, especially in patients with chronic kidney disease or chronic kidney disease with diabetes. After this meta-analysis was published, results from 3 additional randomized trials became available (Table 5). In the RECOVER (Renal Toxicity Evaluation and Comparison Between Visipaque and Hexabrix in Patients With Renal Insufficiency Undergoing Coronary Angiography) study, 300 patients with a creatinine clearance 60 ml/min were randomized to receive iodixanol (Visipaque) or ioxaglate (Hexabrix) (101). The incidence of CIN was significantly lower with iodixanol compared with ioxaglate (7.9% vs. 17.0%, p = 0.021). In contrast, however, another smaller study (ICON [Ionic Versus Nonionic Contrast to Obviate Worsening Nephropathy After Angioplasty in Chronic Renal Failure Patients]) evaluating the same contrast media found no difference in CIN (102). In the third study (CARE [Cardiac Angiography in Renally Impaired Patients]), iodixanol and iopamidol (Isovue) were compared in 482 patients with a baseline creatinine clearance <60 ml/min (103). Again, there was no difference in the incidence of CIN between the low-osmolar and iso-osmolar agents.
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Structural Heart Disease
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Percutaneous aortic valve replacement.
The year 2006 brought further encouraging reports and longer follow-up reports of this technology. Cribier et al. (104) now report follow-up as long as 26 months for 36 patients treated with the Cribier-Edwards valve that was deployed using an antegrade transmitral approach. Webb et al. (105) have pioneered the use of the Cribier-Edwards valve in a retrograde approach using a flexible, steerable delivery catheter. They report the first 18 patients treated with the device in Vancouver. The valve area increased from 0.6 cm2 to 1.6 cm2. The major drawback of the system is that a 24-F delivery sheath is required and thus vascular access, vascular trauma, and iliac vessel tortuosity limit the eligibility of many elderly patients.
Grube et al. (106) presented the first clinical series of the Core Valve System. This device is inserted retrogradely and is a self-expanding system that is deployed while patients are on partial or complete bypass. In the 25 patients, procedural success occurred in 84% of patients. Mortality occurred in 20% of patients. This outcome is not unexpected given the high-risk nature of the patients and the early learning experience of the center. Future device modifications, including an 18-F delivery system, will make this device implantable by an entirely percutaneous approach.
The Edwards valve also has been tested in a minimally invasive, transapical surgical approach. Lichtenstein et al. (107) reported 7 patients treated in Vancouver with this technique. This approach will be compared with the percutaneous technique in an upcoming FDA-mandated pivotal U.S. trial.
Finally, Zegdi et al. (108) describe a preclinical experience with a repositionable valve. The device is intended for treatment of deteriorating bioprosthetic valves. Given the large number of bioprosthetic valves now implanted, this device holds great future promise.
Percutaneous mitral valve repair.
This field seems to be lagging compared with percutaneous aortic valve therapy. In 2006, the first clinical report of percutaneous mitral annuloplasty appeared. Webb et al. (109) reported on 5 patients who had an attempt at deployment of a coronary sinus cinching device. Successful deployment was achieved in 4 of 5 patients. Unfortunately, device separation at chronic follow-up in 3 patients led to cessation of the study. Rogers et al. (110) reported a different and more radical technique for annuloplasty. Sheep with tachycardia mediated heart failure were treated with an ingenious device that places an anchor in the coronary sinus, and then a cinch is pulled through the left atrium to place tension on the anteroposterior dimension of the mitral annulus. We need to wait human trials, but the 30-day results appear promising.
Atrial septal defect, patent foramen ovale, ventricular septal defect.
Results of the MIST-1 (Migraine Intervention with STARflex Technology) trial, evaluating closure of patent foramen ovale for migraine, were presented at the ACC meeting (111). One hundred forty-seven patients were randomized to closure with the STARflex device (NMT Medical, Boston, Massachusetts) or to a sham procedure. There was no significant difference in the incidence of headache cessation (the primary end point); however, there was a lower incidence of headache frequency in patients undergoing closure. Mullen et al. (112) described use of a novel bioabsorbable device for closure of atrial septal defects and patient foramen ovale. Successful device implantation was achieved in 57 of 58 (98%) patients. At 6 months, 96% of patients had complete closure by echocardiography. In another study, Vida et al. (113) report on the cost effectiveness of percutaneous versus surgical closure of ostium secundum defects in 111 patients in Guatemala. In this population, percutaneous closure was associated with higher costs than surgical closure, largely because of cost of the device itself.
Fu et al. (114) presented results of a phase I safety and feasibility trial of transcatheter closure of perimembranous ventricular septal defects using the Amplatzer Membranous VSD Occluder (AGA Medical Corp., Golden Valley, Minnesota). The median age of patients was 7.7 years (range 1.2 to 54.4 years). The device was implanted successfully in 32 of 35 (91%) patients. Three patients had serious adverse events including complete heart block, perihepatic bleeding, and rupture of tricuspid chordae tendineae. At 1 and 6 months, complete closure was observed in 78% and 96% of patients, respectively.
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Peripheral Vascular Disease
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ACC/AHA guidelines.
In 2006, guidelines for the diagnosis and treatment of peripheral artery disease were published for the first time (115). This consensus document was endorsed by multiple medical, surgical, and radiologic societies and will serve as an important quality assurance, credentialing, and appropriateness standard. The complete document is beyond the scope of this article, so readers are encouraged to examine the document carefully. In addition, White et al. (116) provided a multidisciplinary science advisory statement on indications for renal arteriography at the time of cardiac catheterization. Screening renal arteriography is considered reasonable in patients at increased risk for atherosclerotic renal artery stenosis who are candidates for revascularization as defined in the ACC/AHA peripheral arterial disease management guideline document.
Carotid stenting.
In 2006, 2 randomized trials and 1 large company-sponsored registry provided further insight into this controversial topic. Safian et al. (117) described 419 patients treated in a prospective clinical high-risk registry of carotid artery stenting (CAS) performed with the Protégé self-expanding nitinol stent and the Spider Embolic Protection System (eV3 Inc., Plymouth, Minnesota) distal embolic protection system. Technical success was achieved in 97% of cases. Thirty-day adverse events were death (1.9%), any stroke (3.3%), and MI (1%). This registry supports that CAS is safe when performed by high-volume, experienced interventionalists who use distal protection.
Two randomized trials of CAS versus surgery, however, did not corroborate this finding. In the SPACE (Secondary Prevention With Antioxidants of Cardiovascular Disease in End-Stage Renal Disease) trial, 1,200 patients with symptomatic carotid artery stenosis (transient ischemic attack or stoke within 6 months) were randomized to CAS or surgery (118). The primary end point, death or ipsilateral ischemic stroke at 30 days, occurred in 6.84% of the CAS group and 6.34% of the surgery group (p = 0.09 for noninferiority). Of note, only 27% of patients in the stent group were treated with an embolic protection device. In the second study, patients with symptomatic carotid stenosis (>60% diameter stenosis) were randomized to stenting or endarterectomy (119). The trial was stopped prematurely after enrollment of 527 patients because of a higher incidence of death or stroke in the stent group (9.6% vs. 3.9%).
When reviewed in aggregate, these 3 trials provide important insight. First, carotid stenting with distal protection is a demanding, intricate procedure and results will vary enormously depending on operator skill and experience. Thus the CREATE (Carotid Revascularization with ev3 Arterial Technology Evolution) investigators achieved a stroke rate 66% lower than the EVA-3S (Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis) group. Second, patients with recent symptoms are likely to have higher event rates than those with remote or no neurological symptoms. The optimal timing of CAS after a neurological event needs to be determined, and it is possible that aggressive adjunctive medical therapy (i.e., Coumadin, aspirin, clopidogrel, and statins) may lower procedural risk. Finally, it is likely that a role for both CAS and surgery will persist. Medically high-risk patients are more likely to benefit from the less-invasive CAS procedure. Conversely, anatomical features that make the CAS procedure difficult or lengthy would favor a surgical approach. No doubt 2007 will bring much more fuel to this raging controversy.
Other vascular beds.
Although stenting is beneficial in significant renal artery stenosis, the definition of hemodynamically significant disease has not been well clarified. In 2006, De Bruyne et al. (120) provided a report on hemodynamic assessment of renal artery stenosis using a pressure monitoring guidewire. A ratio of Pd/Pa < 0.90 (Pd = mean pressure distal to the renal artery stenosis, Pa = mean aortic pressure) was associated with significant increase in plasma renal vein renin concentration, and thus was considered as a threshold value for defining significant renal artery stenosis.
Zeller et al. (121) reported results of a registry using the Silverhawk atherectomy device (FoxHollow Technologies, Redwood City, California) for treatment of femoral-popliteal disease. Acute and 1-year outcomes in patients with de novo disease were comparable to historical studies using stenting. Silva et al. (122) published a report on the use of stenting in 59 patients with chronic mesenteric ischemia. Stenting was associated with excellent procedural outcomes and a low complication rate, and symptom relief occurred in 88% of patients.
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Conclusions
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The year 2006 brought forth many dramatic advances in the field of interventional cardiology. The Innovations in Intervention (I2) steering committee has selected the 10 most important published studies of 2006 (Table 6). Although such a list is subjective, we believe that these trials will stand the test of time with respect to their impact on the field. As expected, the top-10 list is dominated by trials of mechanical reperfusion for AMI and new advances with DES platforms. The OAT trial was voted as the most important study of 2006. We believe it is essential for interventionalists and other serious students of the field to examine these studies carefully. The year 2007 is likely to bring further exciting advances in this rapidly evolving field. We look forward to an equally daunting task of collating and summarizing the trials of 2007.
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Footnotes
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1 Dr. Dixon is a consultant for Boston Scientific, ev3, and TherOx. 
2 Dr. Grines is a consultant for Pfizer, Sanofi-Synthelabo, Bristol-Myers Squibb, and the GlaxoSmithKline Global Cardiovascular Board.
3 Dr. O’Neill is a consultant for Guidant, Medtronic, Johnson & Johnson, Cordis, and Boston Scientific. Dr. O’Neill has equity in TherOx, Radiant Medical, and Accumed. William Beaumont Hospital, Division of Cardiology, has received research support from Abbott, Abiomed, AstraZeneca, Aventis, Boston Scientific, Cardiac Assist, Cordis, Esperion, ev3, GlaxoSmithKline, InnerCool, Medtronic, Otsuka, Pfizer, Radiant Medical, and TherOx
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References
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1386 - 1395.
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ACC/AHA/Society for...
Acute Myocardial Infarction...