RISK STRATIFICATION FOR SUDDEN CARDIAC DEATH USING MICROVOLT T-WAVE ALTERNANS IN POSTMYOCARDIAL INFARCTION PATIENTS

Title:

RISK STRATIFICATION FOR SUDDEN CARDIAC DEATH USING MICROVOLT T-WAVE ALTERNANS IN POSTMYOCARDIAL INFARCTION PATIENTS

DOI No:

10.1142/9789812702234_0051

Source:

ADVANCES IN ELECTROCARDIOLOGY 2004 (pp 182-191)

Author(s):

TAKANORI IKEDA
Address for correspondence: Takanori Ikeda, MD, PhD, FACC, Director, Cardiac Electrophysiology Laboratory, Second Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan, Phone: +81-422-47-5511, Fax: +81-422-41-5137.
Second Department of Internal Medicine, Kyorin University School of Medicine, Tokyo, Japan
KAORU SUGI
Division of Cardiology, Toho University Ohashi Hospital, Tokyo, Japan
HIDEAKI YOSHINO
Second Department of Internal Medicine, Kyorin University School of Medicine, Tokyo, Japan

Abstract:

Background: The most frequently encountered structural heart disease that causes sudden cardiac death (SCD) is coronary artery disease. The aim of this study was to assess the predictive value for serious arrhythmic events of 11 prognostic noninvasive markers including microvolt T-wave alternans (TWA) in patients with myocardial infarction MI.

Methods: This prospective study enrolled 372 consecutive MI survivors. Prognostic markers for arrhythmic events involved age, sex, infarction site, coronary intervention, coronary bypass surgery, antiarrhythmic drug treatment, and beta-blocker treatment, a left ventricular ejection fraction (LVEF) <40%, nonsustained ventricular tachycardia (NSVT) on Holter monitoring, ventricular late potentials (LP) by signal-averaged electrocardiography, and microvolt TWA. The study end point was prospectively defined as SCD, ventricular fibrillation, and sustained ventricular tachycardia.

Results: Nine patients died of non-arrhythmic causes such as pump failure or reinfarction were excluded from analysis. Of 363 MI survivors, 33 patients (9%) reached one of the study end points during a mean follow-up period of 30±13 months. Of the 11 risk markers, microvolt TWA, LVEF <40%, NSVT, LP, coronary bypass surgery, and beta-blocker treatment had significant values. In multivariate Cox regression analysis, only microvolt TWA and LVEF <40% were significant predictors for arrhythmic events (relative hazard, 9.8 [P=0.0003] and 7.8 [P=<0.0001], respectively). Sensitivity and negative predictive value for arrhythmic events of microvolt TWA was higher (91% and 99%, respectively), whereas the positive predictive value was lower (23%). When TWA and LVEF <40% were combined, a higher predictive accuracy were obtained (93%).

Conclusions: This prospective study suggests that microvolt TWA is a powerful predictor for arrhythmic events after acute MI. Combined assessment of microvolt TWA and a reduced LVEF could be useful for prophylactic implantation of a defibrillator to prevent SCD.

Risk stratification for sudden cardiac death (SCD) of patients with myocardial infarction (MI) remains a clinical challenge. At present, various noninvasive indices including microvolt T-wave alternans (TWA)¹ have been proposed as risk stratifiers for SCD in post-MI patients (Figure 1). The evidence reviewed indicates that TWA, which increases the heterogeneity of repolarization, is a tool for assessing vulnerability to ventricular fibrillation that would cause SCD,^2-5 and for elucidating fundamental arrhythmogenic mechanisms (Figure 2).⁶ Although prophylactic implantation of a cardioverter defibrillator (ICD) is considered as a recommended therapy to improve survival,^7,8 precise identification of patients at risk for SCD is crucial for the cost-effectiveness.

In this study, we assessed the predictive values for arrhythmic events of 11 noninvasive prognostic valuables including microvolt TWA and common clinical factors during long-term follow-up in patients with acute MI. We also assessed whether TWA can be a useful predictor to select patients who essentially need an ICD.

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