Abstract Title:	Microvolt T-Wave Alternans as a Predictor of Ventricular Tachyarrhythmias: A Prospective Study Using Atrial Pacing
Presentation Start:	Tuesday, Mar 09, 2004, 1:00 PM - 2:00 PM
Topic:	ECG/Ambulatory Monitoring Signal Averaging
Author Block:	Kaoru Tanno, Norikazu Watanabe, Shunsho Ryu, Yoshino Minoura, Mitsuharu Kawamura, Taku Asano, Youichi Kobayashi, Takashi Katagiri, Showa University, Tokyo, Japan
Background Microvolt T-wave alternans (TWA) is reported to be closely associated with sudden cardiac death and ventricular tachycardia (VT).Animal experiments revealed that microvolt TWA is highly dependent on heart rate. The purpose of this study was to determine if patients with TWA at relatively low heart rates have increased vulnerability to ventricular tachyarrhythmias. Methods & Results Subjects were 248 consecutive patients (men/women=158/90; mean age, 59±17 years) who underwent electrophysiologic study from 1997 to 2000. TWA recording was made in sinus rhythm and at atrial pacing rates of 90, 100, 110, and 120 beats per minute (bpm) with the Cambridge Heart CH2000 system. Alternans voltage (Valt) was measured when the alternans ratio was >3 for a period of > 1 minute in VM, X, Y, Z, or two adjacent precordial leads. Study endpoint was the first appearance of VT/ventricular fibrillation (VF) or appropriate ICD therapy with pacing or shocks. During the 37±12-month follow-up period, 22 patients had sustained VT and 5 patients died from sudden cardiac death. In patients with > 1.9 microvolts of Valt at rates of 90, 100, and 110bpm, incidence of VT/VF was 56%, 28%, and 18%, respectively. Valt of > 2.9 microvolts at a rate of 90bpm had a 70% positive predictive value for VT. However, Valt less than 0.9 microvolts at a rate of 120bpm, negative predictive value was 100%. Conclusion: Patients with TWA at relatively low heart rates are susceptible to ventricular tachyarrhythmias.