Idiopathic sustained ventricular tachycardia responsive to verapamil: clinical electrocardiographic and electrophysiologic considerations.

Abstract

Fifteen cases of idiopathic VT responsive to verapamil were studied to examine its clinical, electrocardiographic and electrophysiologic features. All patients were male, aged 15-49, average age 28. Initial onset of VT occurred at ages 9-48 (average 21). Time from onset of VT to first admission was 1-20 years (average 8.2 years), and patients had been followed for 17-40 months (average 27 months). 13 cases had palpitations, 5 had faintness, 1 had syncope, but no deaths were reported. ECG's at time of VT exhibited CRBBB + LAD pattern in 12 cases, CRBBB + RAD pattern in 1, and LBBB in 2. VT rate was 130-200 bpm (average 163 bpm), with QRS width of 0.11 - 0.16 sec (average 0.14 sec). ECG's during sinus rhythm revealed no ST/T abnormalities, although in 6 cases they were found post-VT. 5 cases had recognizable H waves during VT, and HV intervals were shorter than that during sinus rhythm. VT could be induced by programmed electrical stimulation in 14 cases. VT or RVR could be induced by atrial pacing in 6 of 14, single RV extra-stimuli in 12 of 14, paired pulses in 5 of 12, RV overdrive pacing in 7 of 14, and burst pacing in 6 of 14 cases. VT could be terminated by RV burst pacing in 14 of the 15 cases, while single RV stimuli were effective in 5 out of 12 cases. Among the 12 cases in which VT could be induced by single RV extra-stimuli, the relationship between changes in premature interval for the induction of VT and the echo interval of VT (extrastimulus to first VT complex) was examined. 8 showed an inverse relationship, 3 showed a concordant relationship and 1 case could not be assessed. An inverse relationship was found between changes in paced cycle length and echo interval for the 2 cases in which VT could be induced by rapid pacing. Verapamil terminated sustained VT in 12 out of 13 cases, and in another case had a pronounced decelerating effect. Prior to termination, VT rate was drastically reduced (from 163 +/- 29 bpm to 128 +/- 29 bpm). Verapamil was able to prevent the induction of VT in 6 out of 14 cases, while in 6 cases the VT zone was expanded and in 2 cases the VT zone was narrowed.(ABSTRACT TRUNCATED AT 400 WORDS)