Comparison of T-wave alternans and QT interval dispersion to predict ventricular tachyarrhythmia in patients with dilated cardiomyopathy and without antiarrhythmic drugs - A prospective study

Microvolt T-wave alternans (TWA) and QT interval dispersion (QTD), which re flect temporal and spatial repolarization abnormalities, respectively, have been proposed as useful indices to identify patients at risk for ventricul ar tachyarrhythmias (VTs). The purpose of this study was to clarify which r epolarization abnormality marker is more useful in predicting arrhythmic ev ents in patients with dilated cardiomyopathy (DCM). Forty-two consecutive nonischemic DCM patients underwent the assessment of TWA and QTD. Patients undergoing antiarrhythmic pharmacotherapy, except bet a -blockers and those with irregular basic rhythms, were excluded from entr y. Eight patients were also excluded because of indeterminate test results. Therefore, 34 DCM patients were prospectively assessed. The end point of t he study was the documentation of VT defined as greater than or equal to 5 consecutive ectopic beats during the follow-up period. TWA and QTD ( greater than or equal to 65 msec) were positive in 24 (80%) a nd 11 (37%) of 30 patients with available follow-up data, respectively. The re was no relationship between TWA and QTD. During a follow-up of 13 +/- 11 months, VTs occurred in 13 patients (43%). In Cox regression analysis, TWA was a significant risk stratifier (P=0.02), whereas QTD was not. The sensi tivity, specificity, and positive and negative predictive values of TWA in predicting VTs were 100%, 35%, 54%, and 100%, respectively. TWA could be a useful noninvasive index to identify patients at risk for VT s in the setting of DCM. This study may suggest that temporal repolarizatio n abnormality is associated more with arrhythmogenesis than with spatial re polarization abnormality in DCM patients.