Association of Tp-Te/QT Ratio with Ventricular Tachycardia in Patients with Idiopathic Outflow Tract Ventricular Premature Contraction

Author : A. P. Nugraheni , I. A. Arso , E. Maharani
Upload Date : 19-04-2018

Background: Idiopathic outflow tract VPC (ventricular premature contraction) can turn into VT (ventricular tachycardia) through triggered activity mechanism. The presence of M (Masonic midmyocardial Moe) cell creates transmural dispersion of repolarization (TDR) which is susceptible to phase 2 EAD (early afterdepolarization) and could serve as functional substrate for VT. Tp-Te/QT ratio is an arrhythmogenesis index and has been reported to be associated with the incidence of ventricular arrhythmia. This study aims to investigate the association between Tp-Te/QT ratio with VT incidence in idiopathic outflow tract VPC.

Research Methods: Analytical observational research with cross sectional design was done. Ventricular tachycardia episodes were found from retrospective electrocardiogram (ECG), TMT (treadmill test), Holter monitor and electrophysiology study data in Sardjito Hospital patients with idiopathic outflow tract VPC during September to October 2017. Tp-Te/QT was defined as the time from the peak of T wave to the intersection between the tangent and isoeectric line, divided with QT interval. Tp-Te/QT ratio measurement was performed in lead V4, V5 and V6 by single observer. Tp-Te/QT ratio was categorized into increased (>0.25) and normal (<0.25). Chi Square and logistic regression test were performed.

Results: Out of 46 patients, there were 28 patients who had VT. Increased Tp-Te/QT ratio of lead V4 were found in 11 patients, V5 and V6 were 13 patients each. The prevalence ratio (PR) of Tp-Te/QT ratio to VT incidence in lead V4 was 2.059 (95% CI: 1.464-2.895; p=0.007), while in lead V5 and V6 were 2.200 (95% CI: 1.514-3.197; p=0.002). Tp-Te/QT ratio in lead V4, V5 and V6 were not significantly different and equally strong in distinguishing VT events (p<0.001; 95% CI). Adjustment of confounding factor hypertension with multivariate test gave insignificant results (PR: 1.290; 95% CI: 0.444-3.747).

Conclusions: Increased Tp-Te/QT ratio in idiopathic outflow tract VPC patients was associated with higher prevalence ratio for VT, although this was affected by hypertension.

KEYWORDS : idiopathic outflow tract VPC, VT, transmural dispersion of repolarization, Tp-Te/QT ratio.

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