ACC 2004 ANNUAL SESSION HIGHLIGHTS
Cardiac arrhythmias
Stephen C. Hammill, MD, FACC*,*
* Mayo Clinic, Rochester, Minnesota, USA
* Reprint requests and correspondence: Dr. Stephen C. Hammill, Mayo Clinic, Gonda SLW, Room 33S, Rochester, Minnesota 55905-0001, USA.
hammill.stephen{at}mayo.edu
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Late-breaking trials
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The Sudden Cardiac Death-Heart Failure Trial (SCD-HeFT) presented by Bardy et al. (1) included 2,521 patients enrolled between September 1997 and July 2001 and followed until October 2003. Patients had to be on optimal medical therapy and have New York Heart Association (NYHA) functional class II or III congestive heart failure (CHF) with an ejection fraction (EF) of 
35%. The patients were then randomized to either: 1) conventional therapy for heart failure (HF) plus placebo, 2) conventional therapy for HF plus amiodarone, or 3) conventional therapy for HF plus the implantable cardioverter-defibrillator (ICD). The patients' median age was 60 years, with 23% being female and 23% minorities. The median EF was 25%, with 70% of patients being NYHA functional class II and 30% being class III. Fifty-two percent of patients had ischemic cardiomyopathy, and 48% had non-ischemic cardiomyopathy. Patients received excellent medical therapy, with 85% of them on angiotensin-converting enzyme (ACE) inhibitors and 69% of patients taking beta-blockers. The average follow-up was 2.5 years, with 3-year mortality being 22% in the placebo group, 24% in the amiodarone group, and 17% in the ICD group. Table 1 shows the hazard ratios for each group, with a significant benefit from the ICD versus placebo in all patients and in the separate groups of ischemic and non-ischemic cardiomyopathy.
Amiodarone did no better than placebo. This study is the first to support use of the ICD as primary therapy for the prevention of sudden cardiac death in patients with moderate to severe HF and non-ischemic dilated cardiomyopathy; it also supports the results of the COmparison of Medical therapy, Pacing ANd defibrillatION in chronic heart failure (COMPANION) trial in ischemic and non-ischemic cardiomyopathy and backs the findings of Multicenter Automatic Defibrillator Implantation Trial (MADIT II) in patients with ischemic cardiomyopathy. This study suggests that amiodarone use in patients with well-managed CHF does not decrease mortality.
The Defibrillator IN Acute Myocardial Infarction Trial (DINAMIT) presented by Hohnloser et al. (2) enrolled 674 patients within 4 to 40 days of myocardial infarction (MI) with an EF of 35% and impaired autonomic tone assessed by heart rate variability. Patients were randomized to either ICD (332 patients) or control (342 patients) and followed a mean of 2.5 years. The average EF was 28%, and the ICD was implanted a median of seven days following MI. Sixty-five percent of patients received reperfusion therapy, more than 90% were on ACE inhibitors and beta-blockers, and more than 70% were on lipid-lowering drugs. The hazard ratios of ICD versus control were as follows: all cause mortality 1.08; arrhythmic death 0.42; and non-arrhythmic death 1.75. The ICD significantly reduced the incidence of arrhythmic death but, of interest, was associated with an increased incidence of non-arrhythmic death. These patients had a high percentage use of intra-aortic balloon pump to support circulation early after a major anterior wall MI. This study helps to identify the proper timing for ICD placement after MI.
The Prospective Randomized Study Evaluating Biventricular Pacing After Ablate and Pace Therapy (PAVE) trial presented by Doshi et al. (3) enrolled 165 patients with atrioventricular (AV) nodal ablation for atrial fibrillation. Patients were randomized 2:1 to biventricular (BiV) versus right ventricular pacing. The mean age was 68 years, with 85% of patients having NYHA functional class I to III CHF. The mean EF was 45%. These patients were followed for six months. Biventricular pacing was associated with a statistically significant benefit over right ventricular pacing in 6-min walk (26-m gain), quality of life (on the Short Form-36), and peak oxygen consumption (1 ml/kg/min gain).
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Basic studies in cardiac arrhythmias
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An important study by Hong et al. (4) reported on two families with the short QT syndrome (QT interval 210 to 270 ms) and a strong family history of sudden unexpected death. A missense mutation was identified that resulted in an amino acid change in the pore-forming region of the Kr channel (KCNH2 HERG). This leads to heterogeneous abbreviation of the action potential duration and refractoriness, creating a potential re-entry substrate.
A second basic study of interest was reported by Wolf et al. (5) evaluating myotonic dystrophy in transgenic mice. Myotonic dystrophy is caused by a CTG trinucleotide expansion on chromosome 19. Their study showed that larger CTG expansions were associated with a higher risk of conduction disease.
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Pulmonary vein isolation for treating atrial fibrillation
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The long-term efficacy of pulmonary vein isolation (PVI) in 167 patients with paroxysmal atrial fibrillation (AF) was compared with 20 patients with persistent AF in a study by Oral et al. (6). As a group, 11% of patients required a repeat ablation and 2% had complications but no symptomatic pulmonary vein stenosis. During two years of follow-up, 70% of patients with paroxysmal AF were in sinus rhythm compared with 25% of patients with persistent AF. A second study comparing the outcome of PVI in patients with normal hearts (194 patients) and those with heart disease (183 patients) was reported by Khaykin et al. (7). Heart disease was defined as an EF under 40%, presence of valvular heart disease, or prior coronary artery bypass grafting. Patients were followed for a mean of 16 months, with 3.7% of patients having complications and 25% requiring a second PVI. As a group, 85% of patients were free from AF at last follow-up, showing no significant difference in outcome between patients with normal hearts and those with heart disease. These studies stress the changing approach to treating patients with AF by PVI. It appears that ablating a wider circumference around the pulmonary veins achieves excellent outcome both in patients with otherwise normal hearts and patients with associated heart disease.
Advanced surgical and catheter ablation for cardiac arrhythmias.
A study by Vigilance et al. (8) sought to answer whether or not a linear line between the circumferential ablation around the left pulmonary veins (PVI) and the mitral valve was important in preventing postoperative AF in patients undergoing surgical ablation to treat their AF. They found no difference in the incidence of postoperative AF (67%) or atrial flutter by comparing the 118 patients who had PVI plus a connecting mitral valve lesion to the 69 patients who had only the PVI. An interesting study by Ernst et al. (9) reported on a new magnetic catheter navigation system guided through a joy-stick, which positions the catheter tip. Patients were treated with radiofrequency ablation for re-entry within the AV node, counterclockwise atrial flutter, AV re-entry tachycardia, and atrial tachycardia. The investigators reported a success rate of >95% with no complications and requiring only a mean of 12.3 min of fluoroscopy time. The procedures included a retrograde aortic approach in three patients and a trans-septal approach to the left atrium in another three patients.
A report from Omran et al. (10) of 20 patients treated with a percutaneous left atrial occlusion device to prevent thromboembolism associated with chronic AF showed no cerebral emboli by magnetic resonance imaging scanning and no thrombus on the occlusion device at 12 months of follow-up in the absence of anticoagulation. This important study demonstrates the safety of this new procedure as an alternative approach to preventing thromboembolic events in patients with chronic AF who are not candidates for anticoagulation.
Cardiac resynchronization therapy.
The question of whether or not AV delay optimization benefits patients with cardiac resynchronization therapy (CRT) was reported in a study by Kedia et al. (11). They did AV delay optimization using Doppler echocardiography and Ritter methods within three months of CRT implantation in 116 patients. The final settings were changed in only 22% of patients. This suggests that the initial settings at the time of implantation of the CRT device were adequate in the majority of patients and they did not benefit by routinely scheduled optimization within three months of implantation. Seidle et al. (12) reported on CRT in patients with central sleep apnea and showed that CRT significantly improved sleep-related breathing disorders. A study by Bhargava et al. (13) reported that comparable improvement in EF was observed in patients treated with CRT using either a transvenous coronary sinus lead or an epicardial left ventricular lead. This study indicates that patients who would benefit from CRT and in whom a coronary sinus lead cannot be placed should proceed with BiV pacing using a left ventricular epicardial lead.
In summary, the American College of Cardiology (ACC) Scientific Sessions for 2004 helped to define which patients benefit from an ICD as primary prevention therapy for life-threatening ventricular arrhythmias. The importance of PVI to treat patients with AF was a highlight of the 2004 significant sessions. Application of this technique is being extended to patients with associated heart disease, and the incidence of serious complications is decreasing in the larger, more recent series. Further understanding for CRT was presented during the session.
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References
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- Bardy GH, Lee KL, Mark DB, et al. Sudden Cardiac Death-Heart Failure Trial (SCD-HeFT). Paper presented at: American College of Cardiology Annual Scientific Sessions, New Orleans 2004–Late Breaking Trial; March 7 to 10, 2004; New Orleans, LA.
- Connolly SJ, Hohnloser SH, on behalf of the DINAMIT Steering Committee and Investigators. Randomized Trial of Prophylactic Implantable Defibrillator Therapy Versus Optimal Medical Treatment Early After Myocardial Infarction: the Defibrillator in Acute Myocardial Infarction Trial (DINAMIT). Paper presented at: American College of Cardiology Annual Scientific Sessions, New Orleans 2004–Late Breaking Trial; March 7 to 10, 2004; New Orleans, LA.
- Doshi R, Daoud E, Fellows C, Turk K, Duran A, Hamdan M. The First Prospective, Randomized Study Evaluating BV Pacing After Ablate and Pace Therapy (PAVE). Paper presented at: American College of Cardiology Annual Scientific Sessions, New Orleans 2004–Late Breaking Trial; March 7 to 10, 2004; New Orleans, LA.
- Hong K, Dumaine R, Cordeiro J, et al. Genetic and biophysical basis for sudden death in the short QT syndrome. (abstr)J Am Coll Cardiol. 2004;43(Suppl A):121A
- Wolf CM, Sherwood MC, Branco D, Reddy S, Berul CI. CUG expansions in a myotonic dystrophy mouse model caused cardiac conduction abnormalities and pathologic electrophysiology findings. J Am Coll Cardiol. 2004;43(Suppl A):122A
- Oral H, Chugh A, Hall BW, et al. Pulmonary vein isolation to prevent atrial fibrillation: Long term safety, efficacy, and predictors of outcome. J Am Coll Cardiol. 2004;43(Suppl A):132A
- Khaykin Y, Chen M, Marrouche N, et al. Structural heart disease does not effect outcomes of pulmonary vein isolation for treatment of atrial fibrillation. J Am Coll Cardiol. 2004;43(Suppl A):133A
- Vigilance DW, Kim B, Garrido M, et al. The success of surgical pulmonary vein isolation for atrial fibrillation is not influenced by omission of the mitral annular connecting lesion. J Am Coll Cardiol. 2004;43(Suppl A):148A
- Ernst S, Ouyang F, Linder C, Antz M, Kuck KH. Remote catheter ablation using the new magnetic navigation system Niobe. J Am Coll Cardiol. 2004;43(Suppl A):149A
- Omran H, Schmidt H, Bernhardt P, et al. . The incidence of cerebral embolism after percutaneous occlusion of the left atrial appendage: A serial and prospective study using cerebral magnetic resonance imaging scanning. J Am Coll Cardiol. 2004;43(Suppl A):151A
- Kedia N, Agler D, Popovic ZB, Ching B, Wilkoff B, Grimm RA. Utility of atrioventricular delay optimization in patients undergoing cardiac resynchronization therapy. J Am Coll Cardiol. 2004;43(Suppl A):152A
- Seidl K, Rameken M, Becker T, Vater M, Senges J. Cardiac resynchronization therapy improves sleep related breathing disorders in patients with chronic heart failure. J Am Coll Cardiol. 2004;43(Suppl A):152A
- Bhargava M, Belden W, Burkhardt D, et al. Comparative change in the left ventricular ejection fraction in patients undergoing biventricular defibrillator implantation using transvenous coronary sinus versus epicardial left ventricular leads. J Am Coll Cardiol. 2004;203(Suppl A):127A
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M. A. Hlatky, G. D. Sanders, and D. K. Owens
Evidence-Based Medicine And Policy: The Case Of The Implantable Cardioverter Defibrillator
Health Aff.,
January 1, 2005;
24(1):
42 - 51.
[Abstract]
[Full Text]
[PDF]
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Late-breaking trials
Basic studies in cardiac...