Development and Safety of an Exercise Testing Protocol for Patients with an Implanted Cardioverter Defibrillator for Primary or Secondary Indication

Abstract

Performing exercise tests in patients with an implantable cardioverter defibrillator (ICD) presents specific challenges because of susceptibility to ventricular arrhythmias during maximal levels of exertion. The purpose of this paper is to outline the exercise testing protocol from the Anti-Arrhythmic Effects of Exercise after an ICD trial and to report baseline test results and safety outcomes using the protocol. Maximal cardiopulmonary exercise testing was performed to assess levels of physical fitness as part of a randomized trial of walking exercise in patients with ICDs. Subjects were randomized after baseline testing to aerobic exercise plus usual care or usual care alone. A modified Balke treadmill exercise test was used and specific ICD programming procedures were implemented to avoid unnecessary shocks, which included programming off ventricular tachycardia (VT) therapies during testing. To date, 161 baseline tests have been performed. One ventricular fibrillation (VF) cardiac arrest occurred following completion of an exercise test and three tests were stopped by the investigators due to nonsustained ventricular tachycardia. Eleven subjects were not able to achieve maximum exercise, defined as reaching an anaerobic threshold (AT) at baseline testing. There have been no deaths as a result of exercise testing. Symptom-limited maximal exercise testing can be performed safely and effectively in patients with ICDs for both primary and secondary prevention indications. Specific strategies for ICD programming and preparation for treating ventricular arrhythmias needs to be in place before exercise testing is performed.