Ventricular tachycardia induced by slow ventricular pacing.

Two patients are described, in whom ventricular pacing at physiological rates (72 to 75 beats/min) repeatedly induced ventricular tachycardia (VT). In the first patient, pacing was required because of complete atrioventricular block following an inferior and right ventricular (RV) myocardial infarction. VT developed during RV posterobasal pacing, but not during RV outflow tract pacing at similar rates. The second patient had a postinfarction left ventricular aneurysm and was paced because of amiodarone-induced sinus node dysfunction. VT developed when the rate of ventricular pacing was similar to that of the sinus rate. We conclude that in patients whom VT is induced at physiological rates of pacing, the following factors may be involved in the triggering of VT: the rate of pacing, the site of ventricular stimulation; and the administration of antiarrhythmic drugs. Early recognition of these factors, which may facilitate reentry by aggravating previously existing intraventricular conduction disturbances, is imperative for the effective management of the arrhythmia.