Beat-to-beat T-wave amplitude variability in the risk stratification of right ventricular outflow tract-premature ventricular complex patients

Premature ventricular complexes (PVCs) originating from the right ventricular outflow tract (RVOT) may occasionally trigger monomorphic ventricular tachycardia (MVT), polymorphic ventricular tachycardia (PVT), or ventricular fibrillation (VF). We examined whether an analysis of the ventricular repolarization instability could differentiate PVT/VF triggered by RVOT-PVCs from benign RVOT-PVCs or MVT. We evaluated the ventricular repolarization instability as assessed by the beat-to-beat T-wave amplitude variability (TAV) using Holter recordings in patients with RVOT-PVCs but with no structural heart disease. We determined the prematurity index, defined as the ratio of the coupling interval of the first ventricular tachycardia (VT) beat or isolated PVC to the preceding R-R interval just before the VT or isolated PVC in the Holter recordings. The study patients were classified into RVOT-PVCs/MVT (n = 33) and PVT/VF (n = 10). The two groups did not differ with respect to the age, sex, and left ventricular ejection fraction. There was no significant difference in the prematurity index between the two groups (RVOT-PVCs/MVT 0.66 +/- 0.16 vs. PVT/VF 0.61 +/- 0.13, P = 0.60). The patients with PVT/VF had a significantly larger maximum TAV than those with RVOT-PVCs/MVT (31 +/- 13 vs. 68 +/- 40 A mu V, P < 0.001). Patients with a higher than median value of the TAV (33 A mu V) were at increased risk of PVT/VF vs. those with a lower than median value, after adjusting for the age and sex [9.25 (95% confidence interval: 1.27-19.2); P = 0.03]. The TAV analysis is a useful measure to identify the subset of usually benign RVOT-PVC/MVT patients prone to PVT/VF.