Session P72.8

The Tp-E/QT Ratio Serves as a Universal Arrhythmogenic Index in Patients with Structurally Normal Hearts

JC Laughlin, TJ Rudo, JT Green, A Jones,
S Musco, PR Kowey, GX Yan*

Main Line Health Heart Center
Wynnewood, PA, USA

The down-slope of the T wave (Tp-e) represents dispersion of ventricular repolarization. We tested the hypotheses that the Tp-e/QT ratio rather than the QTc is directly correlated with arrhythmogenic risk.
The QT and Tp-e intervals were measured and their ratio calculated in 4 groups of patients with structurally normal hearts: healthy individuals (n=30), patients with congenital long QT syndrome (LQTS) (n=11), Brugada syndrome (n=7), and congenital short QT syndrome (n=6).
In healthy individuals (16 males and 14 females, QTc=413 ms), the Tp-e/QT ratio in the precordial leads ranged from 0.13 to 0.25, with a mean value of 0.20. There was no significant difference in the ratio between males and females. The ratio remained constant at heart rates from 50 to 100 bpm and decreased with heart rates above 100 bpm. In patients with LQTS (QTc=535 ms), the Tp-e/QT ratio in the left precordial leads ranged from 0.24 to 0.34 (0.29, p<0.01 compared with normals). Patients with a QTc longer than 530 ms had a greater Tp-e/QT ratio than those with a QTc shorter than 530 ms (0.31, n=4 vs. 0.27, n=7; p<0.05). In the Brugada patients (QTc=425 ms, n=7), the Tp-e/QT ratio in the right precordial leads (V1 to V3) was also increased (0.32, p<0.01 compared with normals). Although the Tp-e interval in patients with congenital short QT syndrome (QTc=328 ms, n=6, previously published cases) was not significantly different from that of normal individuals, the Tp-e/QT ratio was significantly greater (0.38, p<0.01).
The normal Tp-e/QT ratio is 0.20 and remains relatively constant for heart rates between 50 and 100 bpm. The Tp-e/QT ratio is significantly higher in patients at arrhythmogenic risk who have structurally normal hearts, regardless of QT interval. This ratio may serve as a universally applicable arrhythmogenic index. Functional reentry may occur when dispersion of ventricular repolarization is increased relatively more than total repolarization time, i.e. that a mismatch exists.

(Abstract Control Number: 9)