Safety of maximal exercise-testing in patients at high risk for ventricular arrhythmia

Abstract

While maximal exercise testing is useful for detection of arrhythmias and assessment of antiarrhythmic drug efficacy, few reports have documented the safety of this procedure in patients with malignant ventricular arrhythmias. We reviewed the complications of symptom-limited exercise in 263 patients with such arrhythmias who underwent a total of 1377 maximal treadmill tests. Seventy-four percent of the population studied had a history of ventricular fibrillation or hemodynamically compromising ventricular tachycardia and the remainder had experienced ventricular tachycardia in the setting of either myocardial infarction or poor left ventricular function. A complication was defined as the recurrence of arrhythmia during exercise testing - ventricular fibrillation, ventricular tachycardia, or bradycardia - that mandated immediate medical treatment (cardioversion, use of intravenous drugs, or closed-chest compression). Complications were noted in 24 patients (9.1%) during 32 tests (2.3%), whereas 239 patients (90.9%) were free of complication during 1345 tests (97.7%). There were no deaths, myocardial infarctions, or lasting morbid events. Clinical descriptors associated with complications included male sex, presece of coronary artery disease, and a history of exertional arrhythmia (p.05). Occurrence of a complication was also unaffected by the use of antiarrhythmic drugs at the time of exercise (chi square = 0.19 p > .05). Complication frequency in our study group was compared with that in a reference population of 3444 cardiac patients without histories of symptomatic arrhythmia who underwent 8221 exercise tests. Of these, four subjects (0.12%) developed ventricular fibrillation (0.05% of tests) without fatality or lasting morbidity. We conclude that (1) maximal exercise testing can be conducted safely in patients with malignant arrhythmias and (2) clinical variables previously considered to confer risk during exercise are not predictive of complications in this patient population. Implications for the management of patients at risk for sudden cardiac death are discussed.