Brief communication

Idiopathic recurrent sustained ventricular tachycardia responsive to verapamil: An ECG-electrophysiologic entity

Intravenous amiodarone, infused on-site by ambulance personnel, slowed the ventricular rate to 144 beats/min and the patient was transferred to our hospital. On arrival, we suspected a verapamil-sensitive fascicular ventricular tachycardia (VT)2,3 and administered 5 mg of intravenous verapamil. This led to immediate tachycardia termination.

It is generally considered a benign arrhythmia even when ventricular rates faster than 200 beats/min are recorded. Idiopathic left ventricular (right bundle branch block pattern with mostly left-axis but rarely right-axis morphology) verapamil-responsive VT14–16 is the second most common form of monomorphic idiopathic VT7 and is rarely exercise induced.17,18 Here too, the prognosis is good except for rare cases of tachycardia-induced cardiomyopathy.7

Right axis deviation is seen in 5%–10%.69 This tachycardia is thought to be due to a reentry circuit in the vicinity of the left posterior fascicle and has commonly been referred to as fascicular VT. 68,70,71 It had been thought that the circuit includes antegrade conduction down the left fascicle and then moves upward along an adjacent branch of conductive tissue.72 This tachycardia is characteristically sensitive to verapamil and occasionally may respond to adenosine, but not to Valsalva maneuvers.73

Class IV drugs have minimal effects on re-entrant ventricular arrhythmias [62] but are effective for ventricular arrhythmias based on triggered activity. Thus, class IV drugs are useful for Belhassen VT (left septal or verapamil-sensitive VT) [63], for right ventricular outflow tract VT [64], for catecholaminergic polymorphic VT [65], and for some VTs related to acute myocardial ischemia, particularly those associated with coronary artery spasm [66]. A meta-analysis of RCTs of class IV drugs included 26 trials of 21,644 patients who had prior MI and reported that class IV drugs had no effect on all-cause mortality (OR, 1.03; 95% CI, 0.94–1.13) [7].