Alternans Before Cardioverter Defibrillator - ABCD
The goal of the trial was to evaluate microvolt T-wave alternans (MTWA) directed therapy compared with electrophysiological study (EPS) directed therapy in predicting ventricular tachyarrhythmic events among patients with ischemic cardiomyopathy.
MTWA, a noninvasive test used to direct therapy, would be noninferior to EPS, an invasive test used to direct therapy.
Patients Screened: 629
Patients Enrolled: 566
NYHA Class: class I (30%), class II (51%), class III (19%)
Mean Follow Up: Median follow-up, 1.9 years
Mean Patient Age: 65 years
Mean Ejection Fraction: 28%
- Coronary artery disease with LVEF ≤40%
- Nonsustained ventricular tachycardia
- Prior cardiac arrest or sustained ventricular arrhythmia
- Use of antiarrhythmic drugs
- NYHA class IV heart failure
- Unstable coronary syndrome
- Unexplained syncope
- Myocardial infarction within 28 days
- History of coronary artery bypass grafting or percutaneous coronary intervention
- Permanent atrial fibrillation
- Either the first appropriate ICD discharge or the occurrence of sudden cardiac death at 1 year
All patients underwent MTWA and EPS evaluation within 28 days of each other. Among patients who were EPS or MTWA positive, an implantable cardioverter defibrillator (ICD) was required. Among patients who were EPS and MTWA negative, an ICD was encouraged but not mandated. Those with indeterminate MTWA but positive EPS were considered positive.
At baseline, the use of angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker was 89%, beta-blocker was 86%, statin was 81%, diuretic was 61%, digoxin was 34%, and calcium channel blocker was 10%.
Mean left ventricular ejection fraction (LVEF) at baseline was 28%. The majority of patients had New York Heart Association (NYHA) heart failure class II (51%) or class I (30%), with the remaining 19% in class III. EPS was positive in 40% of patients and negative in 60%; MTWA was positive in 46%, negative in 29%, and indeterminate in 25%.
Positive predictive values of the test were similar in the two groups (11% for EPS and 10% for MTWA, p = NS), as were negative predictive values (95% and 95%, respectively, p = NS). The rate of arrhythmic events was 7.5% during the first year and 14% through 2 years. The highest event rate was among patients who were MTWA and EPS positive (12.6%) and the lowest was among those who were MTWA and EPS negative (2.3%), with intermediate rates among those MTWA negative but EPS positive (7.8%) and those MTWA positive but EPS negative (5.9%). In an analysis of event timing, EPS was predictive from 9 months onward but not earlier, whereas MTWA was predictive early, but only through 12 months.
Among patients with ischemic cardiomyopathy without a history of ventricular arrhythmias, use of MTWA evaluation was similarly predictive of ventricular tachyarrhythmic events as EPS.
ICDs have been shown to be effective for reducing sudden cardiac death among patients with prior myocardial infarction and impaired left ventricular (LV) function in the MADIT-II trial. However, identifying candidates for whom ICD therapy is most effective has been difficult. A large percentage of patients implanted with an ICD never have an arrhythmic event. Given the high cost of these devices at approximately $235,000 per year of life saved in the recent MADIT-II economic analysis, tools to better risk stratify which patients should and should not get an ICD implanted are needed.
The present study demonstrated that noninvasive MTWA testing was as effective as EPS for identifying those most likely to have an arrhythmic event. Additionally, the two studies provided additional prognostic information together, with those patients positive with both tests at highest risk of an event and those negative with both tests at lowest risk.
Costantini O, Hohnloser SH, Kirk MM, et al., on behalf of the ABCD Trial Investigators. The ABCD (Alternans Before Cardioverter Defibrillator) Trial: Strategies Using T-Wave Alternans to Improve Efficiency of Sudden Cardiac Death Prevention. J Am Coll Cardiol 2009;53:471-82.
Presented by Dr. Ottorino Costantini at the American Heart Association Annual Scientific Sessions, Chicago, IL, November 2006.
Keywords: Coronary Artery Disease, Myocardial Infarction, Tachycardia, Ventricular, Cardiomyopathies, Heart Conduction System, Heart Failure, Stroke Volume, Glucans, Death, Sudden, Cardiac, Defibrillators, Implantable
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