CLINICAL STUDIES
Final results of the STent versus directional coronary Atherectomy Randomized Trial (START)
Etsuo Tsuchikane, MDa,
Satoru Sumitsuji, MDa,
Nobuhisa Awata, MDa,
Toshinori Nakamura, MDa,
Tomoko Kobayashi, MDa,
Masahiro Izumi, MDa,
Satoru Otsuji, MDa,
Hitone Tateyama, MDa,
Makoto Sakurai, MDa and
Tohru Kobayashi, MDa
a Department of Cardiology, Osaka Medical Center, Osaka, Japan. There was no financial support for the study
Manuscript received January 5, 1999;
revised manuscript received May 4, 1999,
accepted June 21, 1999.
Reprint requests and correspondence: Dr. Etsuo Tsuchikane, Department of Cardiology, Osaka Medical Center for Cancer and Cardiovascular Diseases, 1-3-3, Nakamichi, Higashinari, Osaka 537-8511, Japan
oscmed1{at}skyblue.ocn.ne.jp
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Abstract
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OBJECTIVES
This study was designed to compare primary stenting with optimal directional coronary atherectomy (DCA).
BACKGROUND
No previous prospective randomized trial comparing stenting and DCA has been performed.
METHODS
One hundred and twenty-two lesions suitable for both Palmaz-Schatz stenting and DCA were randomly assigned to stent (62 lesions) or DCA (60 lesions) arm. Single or multiple stents were implanted with high-pressure dilation in the stent arm. Aggressive debulking using intravascular ultrasound (IVUS) was performed in the DCA arm. Serial quantitative angiography and IVUS were performed preprocedure, postprocedure and at six months. The primary end point was restenosis, defined as  50% diameter stenosis at six months. Clinical event rates at one year were also assessed.
RESULTS
Baseline characteristics were similar. Procedural success was achieved in all lesions. Although the postprocedural lumen diameter was similar (2.79 vs. 2.90 mm, stent vs. DCA), the follow-up lumen diameter was significantly smaller (1.89 vs. 2.18 mm; p = 0.023) in the stent arm. The IVUS revealed that intimal proliferation was significantly larger in the stent arm than in the DCA arm (3.1 vs. 1.1 mm2; p < 0.0001), which accounted for the significantly smaller follow-up lumen area of the stent arm (5.3 vs. 7.0 mm2; p = 0.030). Restenosis was significantly lower (32.8% vs. 15.8%; p = 0.032), and target vessel failure at one year tended to be lower in the DCA arm (33.9% vs. 18.3%; p = 0.056).
CONCLUSIONS
These results suggest that aggressive DCA may provide superior angiographic and clinical outcomes to primary stenting.
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Abbreviations and Acronyms
| | CSA | = cross-sectional area | | CK | = creatine kinase | | DCA | = directional coronary atherectomy | | DS | = percent diameter stenosis | | IVUS | = intravascular ultrasound | | LAD | = left anterior descending artery | | MLD | = minimal lumen diameter | | NHLBI | = National Heart, Lung, Blood Institute | | PA | = plaque plus media cross-sectional area | | QCA | = quantitative coronary angiography | | TIMI | = thrombolysis in myocardial infarction | | TLR | = target lesion revascularization | | TVR | = target vessel revascularization |
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Recently, the use of stents for percutaneous transluminal coronary angioplasty has been expanded. In selected patients, primary implantation of intracoronary stents improves the early and long-term clinical outcomes of angioplasty (1,2). However, extension of stent indications to complex lesions or small vessels produces less favorable
results (3). Directional coronary atherectomy (DCA) was developed to excise obstructive coronary atheroma. Although two early randomized trials failed to show a significant benefit of DCA over conventional balloon angioplasty (4,5), recent clinical trials have shown that "optimal" DCA, in particular when using intravascular ultrasound (IVUS), can be performed safely with favorable long-term outcomes (6–8). A previous retrospective study comparing stent implantation with DCA found that stenting provided more favorable long-term results (9). However, there has been no prospective randomized trial comparing stent implantation and "optimal" DCA. The objective of the present randomized study was to compare angiographic and clinical outcomes between primary stenting and optimal atherectomy by "aggressive" DCA using IVUS, and to evaluate the difference of chronic vessel response as assessed by serial IVUS study.
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Methods
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Study design.
The STent versus directional coronary Atherectomy Randomized Trial (START) was a randomized clinical trial comparing primary stenting with "aggressive" DCA technique. Suitable lesions for both stenting and DCA were selected by angiography, by the IVUS image, and by the clinical condition. Exclusion criteria included the lesion located in the vessel being smaller than 2.8 mm as assessed by on-line quantitative coronary angiography (QCA); the lesion having the arc of superficial calcium greater than 180 degrees as assessed by IVUS; a restenotic lesion after stenting or DCA; a nonprotected left main trunk lesion; an aorto-ostial lesion; a bypass graft lesion or a thrombotic lesion; and the presence of acute myocardial infarction within the previous one month, stroke within the previous three months or peripheral vascular disease that precluded use of a 10F arterial sheath.
Eligible patients were invited to participate in this trial, and informed consent was obtained under a protocol approved by our institutional review board. After online QCA and preprocedural IVUS, patients were randomly assigned either to the stent arm or the DCA arm groups. The primary end point of this study was a six-month angiographic restenosis rate (defined as percent diameter stenosis [DS] 50%).
Procedure and medication.
In the stent arm group, single or multiple Palmaz-Schatz stents were implanted to fully cover the lesion according to standard protocols (10,11). No other type of stent was used. All stents were implanted with high-pressure adjunct balloon angioplasty to achieve targeted stent expansion, namely a minimal lumen cross-sectional area (CSA) 7.5 mm2 as assessed by IVUS.
In the DCA arm group, aggressive debulking was performed using a 7F or 7F graft Simpson Atherocath according to IVUS guidance. Balloon pressures were increased progressively from 10 psi to a maximum 40 psi. Repeated debulking of the plaque using IVUS was performed according to residual percent plaque plus media cross-sectional area (PA). The aim of residual percent PA was less than 50%. Low-pressure adjunct dilation was performed using a conventional balloon (balloon:artery ratio of 1 to 1.2) when necessary, such as in the presence of intimal flap, or oozing of the contrast.
Administration of ticlopidine combined with aspirin was commenced after stenting. Administration of aspirin was continued during the follow-up period in the DCA arm. Glycoprotein IIb/IIIa antagonist, anticoagulant or antiproliferative medications (12,13) were not used in either groups.
QCA and IVUS.
All pre- and postprocedures, and follow-up angiography and IVUS imaging, were conducted immediately after administration of 200 µg of intracoronary nitroglycerin. Angiography was performed so that each lesion was viewed from at least two angles. Off-line QCA was conducted utilizing the view revealing the highest degree of stenosis. Calculations were made using the Cardiovascular Measurement System (CMS-MEDIS, Medical Imaging Systems) by an isolated operator who was blinded to the patient’s group assignment. The lesion length, reference diameter, minimal lumen diameter (MLD) and DS were calculated. Acute gain was defined as the difference between pre- and postprocedural MLD, and late loss was defined as the difference between postprocedural and follow-up MLD. The loss index was calculated as late loss divided by acute gain.
The IVUS studies were performed using a CVIS Insight ultrasonographer incorporating a single-element, 30-MHz beveled transducer within a 3.2F short monorail imaging catheter. Imaging was performed beginning at a point distal to the lesion and ending at the aortic ostium using the motorized pull-back system at 0.5 cm/s. The measurement was obtained at the same point as the smallest lumen of the preprocedure. Care was taken to assess the vessel at the same point during all subsequent imaging by accurately measuring distances from side branches used as landmarks. Calculations were made by an experienced operator who was blinded to the patient’s group assignment. Total vessel CSA and lumen CSA were calculated, and the difference between these two values was defined as PA. The plaque plus media cross-sectional area was then divided by vessel CSA to obtain percent PA. In the stent arm group, stent CSA was calculated after stenting. In some of the stented lesions, vessel CSA could not be calculated owing to the artifact of stent struts. In-stent PA was defined as the difference between stent CSA and lumen CSA. The increase in PA during the follow-up period of the stent arm group was defined as neointima CSA in stent CSA (i.e., the difference between follow-up in-stent PA and after in-stent PA).
Patient follow-up.
In-hospital assessment was performed for all clinical outcomes including hemorrhagic and vascular complications, and routine ascertainment of creatine kinase (CK) and creatine kinase, MB fraction, before treatment, and 4 to 6 h and 24 h postprocedure. After patient discharge, clinical follow-up examinations were conducted on an outpatient basis at least once a month. A clinical follow-up examination was performed at three and six months and at one year to assess the occurrence of an adverse cardiac event (death, myocardial infarction or any repeat revascularization procedure).
Angiographic and IVUS follow-up examinations were performed routinely at three and six months. If target lesion revascularization (TLR) was performed at three months owing to restenosis, preprocedural angiography and IVUS images at three months were used for follow-up QCA and IVUS analysis of the patient. Revascularization of another distal lesion located in the same target vessel at the three-month follow-up examination was defined as target vessel revascularization (TVR), and the patient was excluded from angiographic and IVUS analyses even if the target site showed no evidence of angiographic restenosis until the six-month follow-up examination.
End points.
The prespecified primary angiographic end point was the six-month angiographic restenosis rate, defined as 50% DS. Other angiographic assessments included initial procedural success (defined as <50% residual diameter stenosis in the absence of severe dissections or flow limitation), and MLD and DS at baseline, after the procedure, and at follow-up.
Clinical end points included short-term procedural safety, clinical restenosis surrogates and clinical status at one year. All deaths were considered cardiac-related unless clearly attributable to a noncardiac cause. Documentation of new pathologic Q waves in two or more contiguous leads in an electrocardiogram associated with any elevation of CK-MB was required for a diagnosis of Q-wave myocardial infarction. Non-Q-wave myocardial infarction was defined as the elevation of CK more than twice the upper limit associated with any elevation of CK-MB without the appearance of Q waves.
The need for coronary-aorto bypass surgery or use of a nonrandomized bailout device (stenting in the DCA arm) was judged as emergent if it was performed for overt or threatened abrupt closure. Abrupt closure was defined as reduced coronary flow (Thrombolysis in Myocardial Infarction [TIMI] trial grade 0 or 1) due to mechanical complications that led to emergent coronary-aorto bypass surgery or use of a bailout device or resulted in death, Q-wave myocardial infarction or non-Q-wave myocardial infarction. Threatened abrupt closure was diagnosed by the presence of an National Heart, Lung and Blood Institute (NHLBI) grade B dissection and 50% diameter stenosis, or a dissection of an NHLBI grade C or worse.
Statistical analysis.
We expected that the angiographic restenosis rate would be 30% in the stent arm and 15% in the DCA arm groups. To achieve statistical significance, 60 patients needed to be randomized to each group; hence, the planned sample size was 120 patients. All analyses used intent-to-treat samples. Continuous variables were expressed as the mean ± standard deviation. Variable categories were expressed as frequencies. The Student t test or nonparametric analysis by the Mann-Whitney U test was used for numerical comparisons between groups. The chi-square test or the Fisher exact test was used for comparison of variable categories expressed as frequencies. Linear regression analysis was performed to examine the correlation between paired continuous variables. Survival estimates were computed by use of Kaplan-Meier methods and compared using the log-rank test. Statview version 4.11 was used for data analysis. Statistical significance was established at the p < 0.05 level.
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Results
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Patient characteristics.
Recruitment lasted from October 1995 through March 1997. A total of 909 patients were screened, resulting in the enrollment of 126 patients. Four patients were deregistered owing to documentation of superficial calcified plaque >180 degrees as assessed by preprocedural IVUS (n = 3) or the vessel being smaller than 2.8 mm as measured by online QCA (n = 1). Therefore, 122 patients were randomized after preprocedural assessment, with 62 patients assigned to the stent arm and 60 patients assigned to the DCA arm.
Baseline patient demographic and clinical data are shown in Table 1. No significant differences between the two groups with regard to patient characteristics were observed. The baseline lesion characteristics of the two groups are shown in Tables 2 and 3. No significant difference in angiographic lesion characteristics, morphology and preprocedural QCA data were observed between the two groups. The lesion length of enrolled lesions was longer than that of other previously designed trials (1,2,9).
Procedure performance.
In the stent arm group, multiple stents were implanted in 11 lesions (18%) and the mean number of implanted stents was 1.2 ± 0.4. Adjunct dilation using a balloon:artery ratio of 1.10 ± 0.11 was performed with pressure of 15 ± 3 atm. In 27% of procedures, a 4-mm and larger-sized balloon was used.
The DCA was performed using a 7F catheter in 65% of procedures and 7F graft cutter in the remaining 35% of procedures. The number cut was 22 ± 11, and the maximum balloon pressure during cutting was 34 ± 12 psi. Adjunct dilation was performed in 14 lesions (23%) with a balloon:artery ratio of 1.05 ± 0.15.
The DCA arm group required a longer fluoroscopy time (20.9 ± 13.6 vs. 29.9 ± 14.8 min; p = 0.012) and a greater amount of contrast medium (285 ± 95 vs. 402 ± 132 ml; p = 0.0001) than the stent arm group.
Acute results.
Initial procedural success was obtained in all patients of both arm groups without the use of an unplanned device. No patient of either arm group had any major complications (death, Q-wave myocardial infarction, emergent coronary-aorto bypass surgery) from the procedure throughout the hospital stay. Oozing of the contrast due to debulking was observed in two patients in the DCA arm group, and this was treated solely by adjunct dilation. Hemorrhagic vascular complications without the need of surgical repair were observed in one patient of the stent arm group. Non-Q-wave myocardial infarction occurred in two patients (3.3%) of the DCA arm group and in one (1.6%) of the stent arm group. No subacute thrombosis was observed in the stent arm group.
The QCA analysis showed a similar postprocedural MLD (2.79 ± 0.39 vs. 2.90 ± 0.38 mm, stent vs. DCA) and a similar postprocedural DS (14.8 ± 10.0% vs. 12.9 ± 8.1%) between the two groups (Table 3). Baseline and acute results of the IVUS measurement are shown in Table 4. The immediate lumen CSA was also similar between the two groups (8.1 ± 2.2 vs. 8.5 ± 1.8 mm2). Postprocedural percent PA was obtained in all lesions in the DCA arm group; however, in only 34 lesions of the stent arm group was this obtained because vessel CSA could not be measured in the remaining 28 lesions owing to the artifact of stent struts.
Postprocedural percent PA was significantly higher for the stent arm group than for the DCA arm group (58.6 ± 5.9% vs. 52.4 ± 8.2%; p = 0.0001). The IVUS images, which adequately represented vessel and lumen CSA at the procedure (baseline, postprocedure), were available in 34 lesions of the stent arm group and in 57 lesions of the DCA arm. The mechanisms of lumen enlargement of both devices are illustrated in Fig. 1. Acute luminal gain (6.7 ± 2.3 vs. 6.6 ± 2.1 mm2) was identical in both arm groups. However, the plaque reduction ratio, which accounted for luminal gain (calculated as the decrease in PA divided by luminal gain), was significantly smaller for the stent arm than for the DCA arm group (46.7% vs. 71.6%; p = 0.0014).
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Figure 1 Difference in mechanism of lumen enlargement by stenting (n = 34) and DCA (n = 57). Both strategies provided an identical acute luminal gain by plaque reduction and vessel expansion. However, the plaque reduction ratio, which accounted for luminal gain, was significantly smaller in the stent arm (46.7% vs. 71.6%; p = 0.0014). Striped bars = plaque reduction; gray bars = vessel expansion.
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Angiographic follow-up.
Three-month follow-up angiography could not be performed in two patients: one patient of the DCA arm group who had no recurrent angina or exhibition of a ST depression under stress electrocardiography rejected undergoing follow-up angiography; and one patient of the stent arm group, who was implanted with a single Palmaz-Schatz stent in the mid-left anterior descending artery (LAD), died suddenly just before the follow-up angiography. Therefore, three-month follow-up angiography was performed in a total of 120 patients (61 in the stent arm group and 59 in the DCA arm group). The QCA analysis showed a significantly smaller MLD (1.95 ± 0.65 vs. 2.33 ± 0.63 mm; p = 0.001) and a significantly higher DS (38.0 ± 17.7% vs. 27.9 ± 16.0%; p = 0.001) in the stent arm group. Binary angiographic restenosis rate (23.0% vs. 8.5%; p = 0.030) was also significantly higher in the stent arm group.
After three-month follow-up angiography, two patients in the DCA arm group who escaped target-site restenosis underwent TVR for another distal lesion located in the same target vessel. One patient who had DCA for a proximal LAD lesion and Wiktor stent implantation for a distal LAD lesion underwent TVR due to in-stent restenosis. Another patient who had DCA for an ostial LAD lesion and conventional balloon angioplasty for a lesion in the mid-LAD died due to restenosis in the mid-LAD. Therefore, six-month follow-up angiography was performed in 61 eligible patients in the stent arm group and 57 eligible patients in the DCA arm group 232 ± 84 days after the procedure. The final angiographic follow-up rate was 96.7% (118/122).
Analysis of lumen dynamics until the six-month follow-up angiography is shown in Table 5, and the results of follow-up MLD and DS are shown in Figure 2. The minimal lumen diameter was significantly smaller (1.89 ± 0.73 vs. 2.18 ± 0.62 mm; p = 0.023) and DS significantly higher (40.1 ± 19.2% vs. 32.1 ± 16.9%; p = 0.018) in the stent arm group. Late loss (0.91 ± 0.71 vs. 0.71 ± 0.52 mm; p = 0.075) and loss index (0.52 ± 0.43 vs. 0.40 ± 0.33 mm; p = 0.070) were larger, but not significantly, in the stent arm group. Angiographic restenosis, the primary end point, was significantly lower in the DCA arm group (32.8% vs. 15.8%; p = 0.032).
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Figure 2 Cumulative distribution of minimal lumen diameter (MLD) (A) and diameter stenosis (B) at preprocedure (Pre), immediately after the procedure (Post) and at the six-month angiographic follow-up (F/U). Post-MLD and postdiameter stenosis were almost identical in both groups. However, the DCA arm showed larger MLD and lower diameter stenosis at F/U, with significantly lower (15.8% vs. 32.8%; p = 0.032) binary angiographic restenosis (defined as F/U diameter stenosis 50%).
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Follow-up lesion length of restenotic lesions was longer (14.4 ± 6.2 mm vs. 10.1 ± 4.4 mm; p = 0.078) in the stent arm group. Diffuse restenosis, defined as  15 mm length, was observed in 36.8% (7/19) of the stent arm group and 11.1% (1/9) of the DCA arm group.
Serial IVUS assessment.
Adequate serial IVUS study (baseline, postprocedural and six-month follow-up) was obtained in a total of 112 lesions; 56 lesions in each arm group. The IVUS follow-up rate was 91.8% (112/122). The decrease in lumen CSA from the procedure to the follow-up was significantly larger (2.8 ± 2.1 vs. 1.5 ± 3.0 mm2; p = 0.0041) in the stent arm group. Thus, follow-up lumen CSA was significantly smaller (5.3 ± 2.8 vs. 7.0 ± 3.2 mm2; p = 0.030) in the stent arm group. The mechanism of the reduction in lumen CSA is illustrated in Figure 3. In the stent arm group, the stent CSA did not change until almost follow-up. In the DCA arm group, the change in vessel CSA was correlated with the change in lumen CSA, as shown in Figure 4 (r = 0.695, p < 0.0001). However, it was bidirectional, and the decrease in vessel CSA was only 0.4 ± 2.8 mm2 on the average, as shown in Figure 3. In contrast, the increase in PA was significantly larger (3.1 ± 2.0 vs. 1.1 ± 2.6 mm2; p < 0.0001) in the stent arm group, which mainly accounted for the difference in lumen CSA reduction between the two devices.
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Figure 3 Mechanism of late lumen loss after stenting (n = 56) and DCA (n = 56) assessed by serial IVUS examination. Changes in stent CSA (+0.3 mm2) after stenting and vessel CSA (–0.4 mm2) after DCA were not remarkable. However, the increase in PA was significantly larger (3.1 vs. 1.1 mm2; p < 0.0001) in the stent arm than in the DCA arm, which accounted for the significantly larger reduction in lumen CSA (2.8 vs. 1.5 mm2; p = 0.004).
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Figure 4 Change in lumen CSA (from postprocedure to follow-up) correlated with the change in vessel CSA in the DCA arm group (r = 0.695, p < 0.0001). However, the change in vessel CSA was bi-directional.
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Clinical follow-up.
By the first year there had been one death in the stent arm group (sudden death 90 days after procedure) resulting in a mortality rate of 1.6%. There were no deaths in the DCA arm group. The Q-wave myocardial infarction was not observed in either group. Target lesion revascularization by one year was required in 18 patients (29.0%) of the stent arm and in 9 patients (15.0%) of the DCA arm group; the incidence tended to be slightly lower in the DCA arm group (p = 0.062). Coronary-aorto bypass surgery TVR was performed in two patients in the stent arm group (3.2%): in one patient owing to refractory instent restenosis and in one patient because of progression of a left main trunk lesion. The incidence of TVR was lower in the DCA arm group (32.3% vs. 18.3%; p = 0.086), although not significantly. Target vessel failure, defined as either death or TVR, also tended to be lower in the DCA arm group (33.9% vs. 18.3%; p = 0.056) (Table 6). In the DCA arm group, the number of percutaneous interventions for TLR was once for eight patients and twice for another patient. However, in the stent arm, TLR was required more than twice in three patients owing to refractory in-stent restenosis (three times for two patients and four times for one patient).
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Discussion
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Palmaz-Schatz stents are shown to reduce restenosis rates compared with balloon angioplasty in simple lesions (1,2). However, when stent indications are expanded to complex or small vessels, the efficacy in long-term results is attenuated (3), because the treatment of in-stent restenosis (in particular diffuse in-stent restenosis) remains unsatisfactory (14,15). Directional coronary atherectomy was developed as a way to excise coronary atheroma, providing an alternative to balloon angioplasty. The first two randomized trials comparing DCA with balloon angioplasty, in which tissue resection by DCA was limited, failed to show significant improvement in early or late clinical and angiographic outcomes with DCA (4,5). However, recent multicenter studies have revealed that the "optimal" DCA technique aimed at larger early lumen diameters could produce better clinical and angiographic outcomes (6–8).
Our single-center experience showed that DCA procedure was associated with favorable long-term angiographic results, especially after the introduction of IVUS, and that the most suitable lesion characteristic for DCA was a relatively large vessel (16). Therefore, we hypothesized that in lesions for which both DCA and stenting can be applied, optimal atherectomy by "aggressive" DCA using IVUS would translate into a better long-term angiographic result than that seen in primary stenting. This study was conducted to compare the angiographic and clinical results between "aggressive" DCA and primary Palmaz-Schatz stent implantation. Results of the study indicate that aggressive DCA may provide superior angiographic and clinical outcomes to primary stenting.
Effect of aggressive DCA on angiographic outcomes.
Intravascular ultrasound examination of the target lesion shows the precise plaque distribution, which enables aggressive tissue resection without increasing procedural complications such as major perforation. In patients assigned to the DCA arm group of the present study, tissue resection was performed, repeatedly if necessary, according to the residual percent PA. Consequently, a lower postprocedural percent PA of 52.4% was obtained compared with 57.9% in a previous optimal DCA study (7). This "aggressive" DCA strategy produced a similar angiographic postprocedural MLD (2.90 mm vs. 2.79 mm) and a similar DS (12.9% vs. 14.8%) compared with primary Palmaz-Schatz stent implantation.
However, follow-up angiography showed a larger MLD (2.18 mm vs. 1.89 mm; p = 0.023) and a lower %DS (32.1% vs. 40.1%; p = 0.018) associated with a lower restenosis rate (15.8% vs. 32.8%; p = 0.032) in the DCA arm group than in the stent arm group. These results indicate that more favorable long-term angiographic results can be obtained by aggressive DCA plaque debulking than by primary stenting. The angiographic restenosis rate (32.8%) and loss index (0.52) in the stent arm were higher than those obtained in previous studies (1,2,9). The immediate stent area (8.1 mm2) assessed by IVUS was almost similar to that described in other IVUS-guided stenting trials (17,18). However, the lesion length of enrolled lesions in the present study was not limited, and thus the lesion length of the stent arm (14.1 mm) was longer than in those previous trials (1,2,9), and multiple stent implantation to fully cover the lesion was required in 18% of cases. These differences in baseline characteristics are believed to attenuate the efficacy of primary stenting.
Mechanism of restenosis assessed by IVUS.
Late lumen loss after stenting is caused by intimal hyperplasia within the stent without geometric remodeling (19). In contrast, in nonstented lesions geometric constrictive remodeling is considered to be the main mechanism of restenosis (20). In a previous study we found that patients with DCA exhibited constrictive remodeling process; however, the predominant mechanism of restenosis was intimal hyperplasia (21). Serial IVUS examinations of the present study also revealed that late lumen loss after aggressive DCA was primarily caused by intimal hyperplasia (1.1 mm2), and constrictive remodeling after aggressive DCA was not significant (0.4 mm2). Lansky et al. (22) reported that late lumen loss after optimal DCA correlated more strongly with constrictive remodeling than with intimal hyperplasia. The present study also showed a significant correlation between late lumen loss and geometric remodeling in the DCA group. However, the geometric remodeling was bi-directional. This difference is thought to be due to the lower postprocedural percent PA of 52.4% observed in the present study. We consider that aggressive DCA tends to result in compensatory remodeling. Deep cutting beyond media by aggressive DCA may be one reason for this positive remodeling (23).
Furthermore, aggressive DCA strategy was associated with significantly less intimal hyperplasia (1.1 vs. 3.1 mm2; p < 0.0001) than was primary stenting, and consequently with significantly less late lumen loss (1.5 vs. 2.8 mm2; p = 0.0041). The difference in intimal hyperplasia between the two devices is thought to result partially from the difference in mechanisms of lumen enlargement. Plaque reduction mainly accounted for the luminal gain after DCA (72%), whereas approximately 50% of the gain by stenting was due to an increase in vessel area. These results suggest that vessel expansion by stenting may accelerate smooth muscle cell proliferation induced by expanding or lacerating the media or the adventitia (24).
Clinical benefit of aggressive DCA.
Although not statistically different, the TLR and TVR rates at one year were higher in the stent arm group (29.0% vs. 15.0%; p = 0.062 in TLR, 32.3% vs. 18.3%; p = 0.086 in TVR) than in the DCA arm group. Target vessel failure also tended to be higher in the stent arm (33.9% vs. 18.3%; p = 0.056). These clinical results were consistent with the angiographic follow-up results. Furthermore, it should be noted that stenting always carries the risk of refractory in-stent restenosis, which requires frequent TLR or other revascularization strategies such as coronary-aorto bypass surgery. In the present study, repeated TLR or coronary-aorto bypass surgery was required in four patients (6.5%) of the stent arm group due to refractory in-stent restenosis. In contrast, patients who demonstrated clinical restenosis in the DCA arm group needed percutaneous TLR only once, or at the most twice. Because a consensus concerning the treatment of refractory in-stent restenosis has not been established, we believe aggressive atherectomy to be more effective in long-term clinical outcomes than primary stenting.
Study limitations.
Although this was a prospective randomized study, only 122 patients and only a single center were involved. In contrast to stenting, DCA is a demanding technique. Aggressive DCA can never be performed without IVUS; it requires repeated IVUS examination during the procedure, and it carries the risk of perforations. Furthermore, DCA involves specific procedural techniques, such as the precise evaluation of plaque distribution by IVUS, and the appropriate control of atherocatheters. Consequently, this strategy needs longer procedural and fluoroscopic times as well as in-depth training of operators. Only Palmaz-Schatz stents were used with high-pressure postdilation technique in the present study. Other longer types of stents are now available; these reduce the need for multiple stent placement. High-pressure postdilations are used less frequently than before. Therefore, these differences may conceivably alter the incidence of restenosis observed after stenting.
Conclusions.
This study suggests that "aggressive" DCA strategy may provide superior angiographic and clinical outcomes compared with primary stent implantation. Thus, from the viewpoint of long-term outcome, we believe aggressive DCA should be used as an alternative to primary stenting if DCA can be applied.
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