REPETITIVE NONSUSTAINED MONOMORPHIC VENTRICULAR-TACHYCARDIA ABORTED BY METHOXAMINE AND SLEEP HEART-RATE DEPENDENT VENTRICULAR-TACHYCARDIA

Methoxamine, an alpha adrenoreceptor agonist, and sleep abolished repetitive nonsustained monomorphic ventricular tachycardia in a 41-year-old man without detectable underlying heart disease. Detailed pacing studies revealed that the occurrence of ventricular tachycardia was totally dependent on the basic heart rate. Sleep and the alpha adrenoreceptor agonist abolished the ventricular tachycardia by slowing the basic heart rate. Verapmil, propranolol, and disopyramide were able to decrease the upper limit of the tachycardia-initiating heart rate, but none of them were able to increase the lower limit (75/min). Failure to increase the lower limit of the tachycardia-initiating heart rate was a major reason why these conventional antiarrhythmic drugs were unable to suppress his daytime episodes of repetitive ventricular tachycardia.