Is there a role of MMA T wave alternans test for risk assessment in Brugada syndrome?

Abstract

We read with interest the scientific letter by Drs. Yalin et al. (1) in The Anatolian Journal of Cardiology on the null outcome of their T-wave alternans (TWA) analysis by the Modified Moving Average method in patients with the Brugada syndrome. To date, TWA has been found in only two studies (2, 3) to predict lethal arrhythmias in Brugada syndrome patients, despite the fact that it is a prominent feature in their ambulatory ECG (AECG) recordings (4). Tada and colleagues (2) reported in a case series of 77 Brugada syndrome patients that overt TWA provoked by pilsicainide predicted spontaneous ventricular fibrillation with odds of 22.2 (95% CI: 3.3-149.9, p<0.001) after multivariate analysis. Most recently, Uchimura-Makita and coworkers (3) used MMA-based TWA in a case series of 42 Brugada syndrome patients and reported that the incidence of VF events was significantly higher among those with TWA ≥60μV than in those with lower TWA levels in lead V2 (p=0.0026). Dr. Yalin et al. (1) indicated that TWA testing was performed at the time of diagnosis of Brugada syndrome but did not state whether the patients were undergoing an exercise stress test or were at rest. While no studies have been undertaken to examine the optimum recording conditions for TWA analysis, it is reasonable to expect that TWA testing should be performed in conjunction with a diagnostic stressor such as the sodium channel blocking agents ajmaline, flecainide, procainamide, pilsicainide (2, 5), which unmask the Brugada syndrome (6), or during spontaneous appearance of the diagnostic Brugada ECG during daily activity at more normal heart rates (7), as is captured on AECG recordings. Indeed, the presence of TWA is considered to support the diagnosis of Brugada syndrome in asymptomatic patients with ST-segment elevation in at least one right precordial lead (6). Nighttime may be a particularly suitable period for AECG recording for TWA analysis, as the majority of ventricular fibrillation episodes in Brugada syndrome patients occur during sleep (8). The finding that TWA level is greatly reduced when heart rate is increased to 80-110 beats/min (7), such as is reached during exercise, may be the key to the failure of TWA testing by the spectral method (9, 10). If TWA had been analyzed from AECGs recorded during daily activity or sleep, it is likely that many if not all of the Brugada syndrome patients enrolled in this study may have shown significant levels of TWA. Determining the most appropriate setting for TWA testing in Brugada Syndrome patients will be an important contribution to stratification of their risk for lethal arrhythmias and ICD discharge. We compliment Dr. Yalin and colleagues on the valuable contributions of their study. With best regards,