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CLINICAL RESEARCH: HEART RHYTHM DISORDER

Predictive Value of Microvolt T-Wave Alternans for Sudden Cardiac Death in Patients With Preserved Cardiac Function After Acute Myocardial Infarction

Results of a Collaborative Cohort Study

Takanori Ikeda, MD, FACC^_*,_*, Hideaki Yoshino, MD^_*, Kaoru Sugi, MD, Kaoru Tanno, MD, Hiroki Shimizu, MD, Jun Watanabe, MD^||, Yuji Kasamaki, MD^¶, Akihiro Yoshida, MD^# and Takao Kato, MD^_**

^_* Second Department of Internal Medicine, Kyorin University, Tokyo, Japan
Division of Cardiology, Toho University, Tokyo, Japan
Third Department of Internal Medicine, Showa University, Tokyo, Japan
First Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan
^|| Division of Cardiology, Tohoku University, Sendai, Japan
^¶ Second Department of Internal Medicine, Nihon University, Tokyo, Japan
^# Division of Cardiology, Kobe University, Kobe, Japan
^_** First Department of Internal Medicine, Nippon Medical School, Tokyo, Japan

Manuscript received April 17, 2006; revised manuscript received May 23, 2006, accepted June 19, 2006.

^_* Reprint requests and correspondence: Dr. Takanori Ikeda, Associate Professor of Medicine, Second Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan. (Email: iket{at}kyorin-u.ac.jp).

OBJECTIVES: We conducted a collaborative cohort study to evaluate the predictive power of microvolt T-wave alternans (TWA) in patients with preserved left ventricular ejection fraction (LVEF) after myocardial infarction (MI).

BACKGROUND: There is little information available about the prognostic value of risk stratification markers in this population. Although these patients have a relatively good prognosis, identifying high-risk patients is important in clinical practice.

METHODS: This study enrolled 1,041 post-MI patients with an LVEF 40% (average 55 ± 10%). Microvolt TWA testing was performed 48 ± 66 days after acute MI, and 10 other risk variables were also evaluated. The end points were prospectively defined as sudden cardiac death or life-threatening arrhythmic events.

RESULTS: During a follow-up of 32 ± 14 months, 38 patients (3.7%) died of nonarrhythmic causes and were not considered for analysis. Of the 1,003 evaluable patients, 18 (1.8%) reached an end point. Microvolt TWA was positive in 169 patients (17%), negative in 747 (74%), and indeterminate in 87 (9%). A positive microvolt TWA test, nonsustained ventricular tachycardia, and ventricular late potentials were predictors of events, and percutaneous coronary intervention decreased the risk rate. On multivariate analysis, a positive microvolt TWA test was the most significant predictor, with a hazard ratio of 19.7 (p < 0.0001). This marker had the highest sensitivity and negative predictive value for events.

CONCLUSIONS: In patients with preserved cardiac function, the incidence of indeterminate results of microvolt TWA is low, and a positive test result is associated with arrhythmic events. Microvolt TWA could be used for risk stratification in this low-risk population.

Abbreviations and Acronyms   CI = confidence interval   ICD = implantable cardioverter-defibrillator   LP = late potentials   LV = left ventricular   LVEF = left ventricular ejection fraction   MADIT = Multicenter Automatic Defibrillator Implantation Trial   MI = myocardial infarction   NSVT = nonsustained ventricular tachycardia   SCD-HeFT = Sudden Cardiac Death in Heart Failure Trial   TWA = T-wave alternans

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