T wave alternans as a risk predictor in patients with cardiomyopathy and mild-to-moderate heart failure

The analysis of t wave alternans (TWA) was introduced to identify patients with an increased risk of ventricular tachyarrhythmias. The inducibility of ventricular tachyarrhythmias and the spontaneous arrhythmic events are cor related with a positive TWA in patients with a reduced left ventricular eje ction fraction and survived myocardial infarction. In contrast, this study is the first to investigate the correlation of a survived sudden cardiac de ath and TWA in patients without coronary heart disease and only slightly de creased left ventricular function. Sixty patients were included in the stud y. The TWA analysis was performed using the Cambridge Heart system (CH2000) . Patients were sifting on a bicycle ergometer and exercised with a gradual increase of workload to maintain a heart rate of at least 105 beats/min. T he exercise test was stopped after recording 254 consecutive low noise leve l heart beats. The electrocardiographic signals were digitally processed us ing a spectral analysis method. The magnitude of TWA was measured at a freq uency of 0.5 cycles/beat. A TWA was defined as positive if the ratio betwee n TWA and noise level was > 3.0 and the amplitude of the TWA was > 1.8 mu V . Twelve (20%) of the included 60 patients showed a positive TWA. The sensi tivity concerning a previous arrhythmic event amounted to 65%, the specific ity up to 98%, respectively. The alternans ratio was significantly higher i n patients with a previous event (30.3 +/- 53.2 vs 2.4 +/- 5.9, P < 0.001) and cumulative alternans voltage (4.67 +/- 3.55 vs 1.75 +/- 1.88 mu V, P < 0.001). In 19 patients, invasively investigated by an electrophysiological study, a significant correlation between inducibility of tachyarrhythmias a nd a positive TWA result was found (Spearman R = 0.51, P = 0.01). In conclu sion, the TWA analysis seems to identify patients with nonischemic cardiomy opathy who are at an increased risk of ventricular tachyarrhythmias.