Short-coupled PVCs initiating PVT
A. Implant a defibrillator
The ECG in Figure 1B shows normal sinus rhythm with a normal axis, sinus arrhythmia, nonspecific P wave abnormality, and minor nonspecific T wave changes. There are frequent uniform PVCs with a right bundle branch block morphology and a right superior axis. Retrograde P waves following the PVCs are noted. The PVCs are superimposed on the T waves, most notably in lead aVF (the PVCs start after the peak of the T wave), consistent with the R-on-T phenomenon, with a short coupling interval of approximately 330 milliseconds.
PVCs with short coupling intervals have been shown to trigger PVT and ventricular fibrillation in patients with structurally normal hearts, which can lead to syncope and sudden cardiac death. The episodes of PVT shown in Figure 1A are initiated with a PVC that has an identical morphology and coupling interval to the PVC occurring few beats earlier. The QT interval is not prolonged. There is no coved ST-segment elevation in V1 through V2 to suggest Brugada syndrome. No ST-segment elevation precedes runs of PVT, ruling out coronary spasm as the etiology.