Relationship between T-wave alternans magnitude and T-wave amplitude before the onset of ventricular tachyarrhythmias during emergent reperfusion in acute coronary syndrome patients

We greatly appreciate Dr Madias’ remarks on our recent study demonstrating the usefulness of continuous T-wave alternans (TWA) monitoring in ultra-short-term prediction of impending life-threatening ventricular tachyarrhythmias (VTA) during emergent reperfusion therapy in acute coronary syndrome (ACS) patients.1 He raised an interesting question, namely, was there a relationship between the increase in TWA and the possible increase in T-wave amplitude prior to the occurrence of VTA?2 This question is based on his theory that TWA magnitude is affected by T-wave amplitude and should therefore be corrected.3 We evaluated the relationship between TWA magnitude and the corresponding T-wave amplitude (absolute value), both of which were reported for each 15 s of data in modified V1 and V5 leads in the three ACS patients with VTA. Data with noise levels >20 μV or obtained during atrial fibrillation, high-grade atrioventricular block, or paced rhythm were excluded from the analysis. Pearson's correlation was applied to the regression analysis. The data were considered statistically significant when the two-tailed P value was <0.05. There was no significant positive correlation between TWA magnitude and the corresponding T-wave amplitude in either modified V1 or V5 leads in the two patients with ventricular fibrillation or in the patient with sustained ventricular tachycardia (VT). There was a weak negative correlation in modified V5 lead in the patient with VT (Figure 1). These results indicate that the upsurge in TWA before the onset of VTA was not merely a consequence of increased T-wave amplitude but provided a measure of the degree of cardiac electrical instability provoked by myocardial ischaemia-reperfusion. Relationship between T-wave alternans magnitude and the corresponding T-wave amplitude in modified V1 and V5 leads in the three patients with ventricular tachyarrhythmias. (A) Patient with non-ST-segment elevation myocardial infarction and sustained ventricular tachycardia. (B) Patient with ST-segment elevation myocardial infarction and ventricular fibrillation. (C) Patient with unstable angina and ventricular fibrillation. There was no significant positive correlation between T-wave alternans magnitude and the corresponding T-wave amplitude. A weak negative correlation was found in modified V5 lead in patient (A). TWA, T-wave alternans; NS, not significant. We agree that TWA monitoring deserves further evaluation as an independent risk predictor of VTA in ACS patients. Conflict of interest: R.L.V. is an inventor of the Modified Moving Average method for T-wave alternans analysis with patent assigned to Beth Israel Deaconess Medical Center and licensed by GE Healthcare Inc. and Medtronic Inc.