Key result
Elevated Tp-Te/QT ratio linked to ~120% higher VT prevalence in idiopathic outflow tract VPCs.
Why the study?
Is an increased Tp-Te/QT ratio associated with a higher incidence of ventricular tachycardia in patients with idiopathic outflow tract VPC?
Cross-Sectional (n=46)
Single-blind
No
Is an increased Tp-Te/QT ratio associated with a higher incidence of ventricular tachycardia in patients with idiopathic outflow tract VPC?
Relative Risk: 2.2 (95% CI 1.514–3.197)
p-value: p=0.002
An increased Tp-Te/QT ratio is associated with a higher prevalence of ventricular tachycardia in patients with idiopathic outflow tract VPC, although this association appears to be confounded by hypertension.
May support Tp-Te/QT monitoring in outflow tract arrhythmias; hypothesis-generating for TDR-targeted strategies in larger trials.
BACKGROUND: Idiopathic outflow tract ventricular premature contraction (VPC) can evolve into ventricular tachycardia (VT) via triggered activity mechanism. Transmural dispersion of repolarization (TDR) might play a role in idiopathic outflow tract VT by inducing phase 2 early afterdepolarization (EAD) and serve as the functional substrate for VT. Tp-Te/QT ratio as an arrhythmogenesis index 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. METHODS: Observational research with cross sectional design was conducted. VT episodes were retrospectively tracked from electrocardiogram (ECG), treadmill test (TMT), Holter monitor and electrophysiology study data in Sardjito Hospital of 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 leads 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 was found in 11 patients, the increased ratios in leads V5 and V6 were found in 13 patients. 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 leads V5 and V6 was 2.200 (95% CI: 1.514 - 3.197; P = 0.002). Tp-Te/QT ratios in leads V4, V5 and V6 were not significantly different and equally strong in predicting 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. Leads V4, V5 and V6 were equally strong in predicting VT events.
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Nugraheni et al. (2018) conducted a cross-sectional in Idiopathic outflow tract ventricular premature contraction (n=46). Increased Tp-Te/QT ratio (> 0.25) vs. Normal Tp-Te/QT ratio (< 0.25) was evaluated on Ventricular tachycardia incidence (PR 2.200, 95% CI 1.514 - 3.197, p=0.002). An increased Tp-Te/QT ratio (>0.25) in leads V5 and V6 was associated with a 2.2-fold higher prevalence of ventricular tachycardia in patients with idiopathic outflow tract VPC.
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