Abstract
A thirty-five-year-old woman without organic heart disease who has exercise-induced ventricular arrhythmias suppressed by propranolol and diltiazem is reported. Treadmill exercise provoked reproducibly nonsustained ventricular tachycardia (NSVT) and salvos of ventricular premature contraction (VPC). QRS morphology of these ventricular arrhythmias showed left bundle branch block pattern and right axis deviation. Oral propranolol (20 mg) and diltiazem (90 mg) prevented exercise provocation of NSVT and VPC. However, oral mexiletine (200 mg) and procainamide (500 mg) could not prevent exercise provocation of these ventricular arrhythmias. No ventricular arrhythmias could be induced by any form of ventricular extrastimulations. Right ventricular pacing at a rate of 210 beats/minute provoked NSVT of which the QRS morphology was similar to that of exercise-induced NSVT. Triggered activity may be a possible electrophysiologic mechanism for exercise-induced ventricular arrhythmias in this patient, although other mechanisms such as reentry and enhanced automaticity could not be completely excluded.
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