Repolarization alternans was of larger magnitude in patients with inducible VT compared to noninducible patients (TWAR 11.1 vs 4.42 at 600 msec, P=0.035) and was distributed later in repolarization.
Observational (n=40)
Does the temporal distribution and magnitude of repolarization alternans differ between patients with and without inducible ventricular tachycardia?
Repolarization alternans is of larger magnitude and distributed later in repolarization in patients with inducible ventricular tachycardia, suggesting late RPA may be a specific marker for VT vulnerability.
Absolute Event Rate: 11.1% vs 4.42%
p-value: p=0.035
INTRODUCTION: Repolarization alternans (RPA) may reflect repolarization heterogeneities underlying VT, yet its temporal dynamics are poorly understood. We hypothesized that RPA occurring late, rather than early, within repolarization reflects a temporal variation in recovery that may predispose to wavefront fractionation and the initiation of reentrant VT, and that this temporal distribution may vary with heart rate. METHODS AND RESULTS: ECG leads I, aVF, and V1 were recorded in 40 patients during electrophysiologic study. RPA across the JT interval was computed spectrally for 64-beat sequences at paced cycle lengths (CLs) of 600, 500, and 400 msec, and expressed as the T wave alternans ratio (TWAR) on the vector ECG lead. Significant RPA (TWAR > or = 3) was reconstructed into the time domain, and its center of area used to represent its temporal distribution. Twenty-two patients were inducible into VT and 18 were not. RPA was of larger magnitude in inducible than noninducible patients (TWAR = 11.1 vs 4.42, P = 0.035; 38.3 vs 5.74, P = 0.004; and 88.8 vs 4.28, P = 0.001 in each, respectively), and was distributed later (P or = 3 to the distal half of the JT segment produced greater specificity for inducible VT (88.9%, 66.7%, and 69.2% at each CL, respectively) than did RPA of the entire JT segment (77.8%, 53.3%, and 69.2%). CONCLUSION: RPA is more specific for inducible VT when distributed late rather than elsewhere in repolarization, and this temporal distribution is heart rate sensitive. Further study is required to interpret these findings in the context of temporal dispersion of refractoriness.
Narayan et al. (Fri,) conducted a observational in Ventricular Tachycardia (n=40). Repolarization alternans (RPA) analysis vs. Noninducible VT patients was evaluated on T wave alternans ratio (TWAR) magnitude at paced cycle length of 600 msec (p=0.035). Repolarization alternans was of larger magnitude in patients with inducible VT compared to noninducible patients (TWAR 11.1 vs 4.42 at 600 msec, P=0.035) and was distributed later in repolarization.