ST-T Alternans in Acute Myocardial Infarction as a Risk Predictor for Fatal Ventricular Arrhythmia—Reply

Abstract

COMMENT & RESPONSEIn Reply We express our gratitude to Zhao and Wang for their interest in our recent case report 1 in which we detailed polymorphic ventricular tachycardia (PMVT) triggered by premature beats from Purkinje fibers. This occurred within the context of giant R-wave syndrome stemming from coronary artery disease (CAD). We wholeheartedly concur with the statement that ST-T−wave alternans (STTA), serving as an indicator of focal abnormalities in myocardial electrical repolarization, are associated with ventricular arrhythmias in CAD. 2 Previous research 3 has identified an association of STTA with ischemic heart disease, long QT-interval syndrome, paroxysmal tachycardia, bradycardia, Wolff-Parkinson-White syndrome, drug overdose, hypothermia, and electrolyte disturbances. In the context of ischemic heart disease, STTA appeared notably specific for Prinzmetal angina. Nevertheless, the definition of ST-T alternans remained challenging, especially in the absence of standard 12-lead electrocardiogram evidence. 4 In our case report, 1 we aimed to emphasize the significance of considering CAD as a potential cause of syncope in susceptible patients, even in the absence of chest pain or acute coronary syndrome. Several parameters have been associated with ventricular arrhythmias in ischemic heart disease, such as the duration of episodes, extent of ST-segment elevation, presence of giant R-wave syndrome, STTA, and a greater than 25% increase of the R wave. 5 However, in this case, 1 the patient exhibited giant R-wave syndrome, premature beats from Purkinje fibers, and subsequent PMVT. Notably, the absence of reported chest pain led us to define the condition as CAD rather than specifically diagnosing Prinzmetal angina. Moreover, the electrocardiographic strip was obtained from a 12-lead Holter monitor that showed turbulence of the baseline rather than from a standard 12-lead electrocardiogram. Although we attribute the PMVT primarily to the giant R-wave syndrome and premature beats from Purkinje fibers, we acknowledge that STTA is also a possible factor. We appreciate the valuable insights offered by Zhao and Wang into the mechanism of PMVT in patients with CAD.