Safety And Feasibility Of Stress Testing In Patients With Implantable Cardioverter Defibrillators

Abstract

Stress testing is integral to evaluate patients with heart disease. However, few data are available regarding safety of stress testing in patients with implantable cardioverter defibrillators (ICDs). Some exercise laboratories consider maximal exercise stress testing and pharmacologic stress testing with dobutamine contraindications in patients with ICDs and some laboratories inactivate ICDs prior to stress testing. PURPOSE The aim of this retrospective study was to assess the safety and feasibility of exercise and pharmacologic stress testing (PST) in patients with ICDs. METHODS Patients with ICD implantation and subsequent stress testing were included in this analysis. Chart review was performed. Primary end-points were occurrence of malignant ventricular arrhythmias (MVAs), onset of burst pacing or ICD firing, cardiopulmonary resuscitation (CPR) or death during stress testing. Secondary end-points were need for urgent coronary revascularization based on stress testing results and hospital readmissions for MVAs. RESULTS From January 1999 to December 2003, 1734 patients underwent ICD implantation or generator replacement. A total of 84 patients subsequently underwent 107 stress tests at William Beaumont Hospital, Royal Oak. Mean age was 67±12 years and 76% were men. Indications for ICD implantation were dilated cardiomyopathy (51%), sustained ventricular tachycardia (39%), sudden cardiac death (8%) and long QT syndrome (1%). 41% underwent exercise stress testing and 59% underwent PST utilizing dobutamine (21%) or dipyridamole (38%). Left ventricular ejection fraction was 32±20. 71% had fixed defects and 22% had reversible perfusion defects as determined by myocardial perfusion imaging. None of the ICDs were inactivated prior to stress testing. Heart rate at peak stress averaged 92±27 beats per minute. 83% were on beta-receptor antagonists. Although 4% of patients had self-terminating, non-sustained ventricular tachycardia at peak stress, none had sustained ventricular tachycardia precipitating burst pacing, ICD shock, CPR or death. One patient underwent urgent coronary angiography, but was found to have non-critical coronary disease. There were no hospital readmissions for MVAs. CONCLUSIONS These preliminary findings suggest that stress testing can be performed safely in patients with ICDs. MVAs requiring emergent treatment are rare occurrences during stress testing. Knowledge of programmed ventricular tachycardia and ventricular fibrillation zones may help predetermine maximal heart rates on stress testing and preclude routine inactivation of ICDs prior to testing.