Verapamil for the suppression of idiopathic ventricular tachycardia of left bundle branch block-like morphology

Abstract

This study examines the efficacy of verapamil for the suppression of idiopathic ventricular tachycardia (VT) of left bundle branch block LBBB-like morphology. Forty-two patients (mean age 36.2 ± 12.1 years; 20 men and 22 women) with VT and without any underlying cardiac abnormality on clinical examination and noninvasive investigation were studied. The inducibility of clinical VT was examined by treadmill exercise testing and programmed ventricular stimulation (PVS). In 29 patients VT was inducible by exercise testing, in 24 by PVS, and in 23 there was evidence of VT on Holter monitoring. After baseline testing, patients were treated with verapamil 120 mg thrice daily for at least 5 half-lives for the drug to load before evaluation. With Holter monitoring, 74% of patients with evidence of VT at baseline testing demonstrated a change of status from nonsustained VT to no VT or from sustained VT to nonsustained VT. Four patients had nonsustained VT during verapamil treatment but no VT at baseline. There was a significant reduction in the number of ventricular ectopic beats over 24 hours (baseline: 15541 ± 17599 vs verapamil treatment: 8892 ± 15582, p < 0.01). Exercise-induced VT was suppressed in 56% of patients with VT during baseline testing, but no effect of verapamil on the tachycardia was observed in 26%. The remaining patients demonstrated a partial response to verapamil; the rate of VT was unchanged, although the duration of the runs was reduced. Sustained monomorphic VT was inducible in only 5 patients, of whom 4 were rendered noninducible; 1 patient remained inducible. However, of the 13 patients with nonsustained VT inducible at baseline, 4 became sustained, of which 2 were hemodynamically unstable. There was no obvious difference in the age or sex distribution of the patients, axis of VT, presence of abnormal cardiac histology, or late potentials among patients responding to verapamil during Holter monitoring or exercise testing. VT of an inferior axis was more likely to respond to verapamil, whereas VT of a superior axis did not respond to verapamil during Holter monitoring. We conclude that idiopathic VT of LBBB-like morphology can be suppressed in approximately two thirds of the patients by verapamil. In patients with a partial response, the rate of VT is unaffected. Some patients exhibit exacerbation of the arrhythmia and verapamil should be avoided in these cases.