Bart Hooft van Huysduynen

Validation of ECG Indices of Ventricular Repolarization Heterogeneity: A Computer Simulation Study

Introduction: Repolarization heterogeneity (RH) is functionally linked to dispersion in refractoriness and to arrhythmogenicity. In the current study, we validate several proposed electrocardiogram (ECG) indices for RH: T‐wave amplitude, ‐area, ‐complexity, and ‐symmetry ratio, QT dispersion, and the Tapex‐end interval (the latter being an index of transmural dispersion of the repolarization (TDR)).

Hypertensive Stress Increases Dispersion of Repolarization

Several electrocardiographic indices for repolarization heterogeneity have been proposed previously. The behavior of these indices under two different stressors at the same heart rate (i.e., normotensive gravitational stress, and hypertensive isometric stress) was studied. ECG and blood pressure were recorded in 56 healthy men during rest (sitting with horizontal legs), hypertensive stress (performing handgrip), and normotensive stress (sitting with lowered legs). During both stressors, heart rates differed <10% in 41 subjects, who constituted the final study group. Heart rate increased from 63 ± 9 beats/min at rest to 71 ± 11 beats/min during normotensive, and to 71 ± 10 beats/min during hypertensive stress (P < 0.001). Systolic blood pressure was 122 ± 15 mmHg at rest and 121 ± 15 mmHg during normotensive stress, and increased to 151 ± 17 mmHg during hypertensive stress (P < 0.001). The QT interval was larger during hypertensive (405 ± 27) than during normotensive stress (389 ± 26, P < 0.001). QT dispersion did not differ significantly between the two stressors. The mean interval between the apex and the end of the T wave (Tapex‐Tend) of the mid‐precordial leads was larger during hypertensive (121 ± 17 ms) than during normotensive stress (116 ± 15 ms, P < 0.001). The singular value decomposition T wave index was larger during hypertensive (0.144 ± 0.071) than during normotensive stress (0.089 ± 0.053, P < 0.001). Most indices of repolarization heterogeneity were larger during hypertensive stress than during normotensive stress. Hypertensive stressors are associated with arrhythmogeneity in vulnerable hearts. This may in part be explained by the induction of repolarization heterogeneity by hypertensive stress.

Ventricular tachycardia: The challenge of two diagnoses

Article history: Received 19 August 2015 Accepted 21 August 2015 Available online 21 September 2015 tural abnormalities of the heart cardiac magnetic resonance imaging (CMR) was performed showing regional dyssynchronous movement of the right ventricle with a diminished ejection fraction (32%), microaneursyms and fibrofatty replacement of the right and left ventricular posterolateralwall (Movies 1, 2). The patientwas subsequently treated with Metoprolol after which the VT could not be induced by exercise.