Aggravation of arrhythmia induced with antiarrhythmic drugs during electrophysiologic testing.

There is evidence that antiarrhythmic drugs can worsen ventricular arrhythmias in patients. In a previous study ventricular arrhythmias worsened 11% when noninvasive monitoring and exercise tests were performed to evaluate drug effect. How frequently this complication occurs when patients undergo electrophysiologic studies is not known. Electrophysiologic (EP) tests were carried out in 63 patients who had a history of malignant, sustained ventricular tachyarrhythmias. Monitoring and exercise tests showed low-frequency or nonreproducible ventricular arrhythmia. Criteria for definite drug-induced aggravation of arrhythmia included conversion of nonsustained ventricular tachycardia to a sustained ventricular arrhythmia and provocation of the end point with one extrastimulus when three were required during control. Aggravation was deemed possible when, as compared to a control group, the end point resulted with the use of one less extrastimulus and sustained tachycardia with a more rapid rate was provoked. A total of 216 single drug studies were performed (3.4/patient). In general, definite or possible aggravation occurred in 35 tests (16%). In 28 cases (12.9%) aggravation was categorized as definite, while in 7 cases (3.2%) the induced arrhythmia was deemed as possibly related to the use of the antiarrhythmic drugs. Drug tests with multiple agents caused aggravation of arrhythmia in 19 patients (30%). Therefore, exacerbation of arrhythmia by antiarrhythmic drugs also occurs during electrophysiologic study. The incidence approximates that reported when monitoring and exercise tests are used for evaluating drug efficacy.