VALUE OF TESTING FOR MYOCARDIAL ISCHEMIA IN ISCHEMIC CARDIOMYOPATHY PATIENTS WITH RECURRENT VENTRICULAR ARRHYTHMIA IN A POPULATION BASED COHORT

Abstract

New Myocardial ischemia is a common trigger for ventricular fibrillation (VF), however, ventricular tachycardia (VT) usually results from an underlying myocardial scar. Current guidelines recommend ischemia testing to be considered in patients with monomorphic VT (MMVT) and to be strongly considered in patients with polymorphic VT (PMVT) or VF. To assess whether testing for myocardial ischemia in ischemic cardiomyopathy (ICM) patients presenting with appropriate implantable cardioverter defibrillator (ICD) therapy would change clinical management. The patient population was derived from a provincial ICD registry in Nova Scotia. Medical records were examined retrospectively to determine if testing for myocardial ischemia with myocardial perfusion scan or cardiac catheterization was performed. All patients with ischemic cardiomyopathy and appropriate ICD therapy were included. The outcomes were the rate of coronary revascularization and mortality. A total of 288 patients were eligible for inclusion; 118 patients (41%) were tested for myocardial ischemia. Patients tested for myocardial ischemia were younger (63.3 ± 9.5 vs 67.3 ± 9.8, P=0.0007), had less heart failure (59.3% vs 71.2%, P=0.04) and were more likely to have been revascularized in the past (70.3% vs 55.9%, P=0.01). The reason for testing was MMVT/PMVT/VF in 71 patients (49 MMVT, 22 PMVT/VF) while 42 patients were tested for acute coronary syndrome or heart failure; cause of testing was not clear in 5 patients. In the ventricular arrhythmia group; 5 patients had coronary revascularization (2/49 (4.1%) with MMVT, 3/22 (13.6%) with PMVT/VF, p=0.33), compared to 5 patients in the ACS/HF group (p=0.5). After adjusting for age, gender, ejection fraction and NYHA class; there was no significant difference in mortality between patients who were tested for ischemia and those not tested (HR 0.75 (0.47, 1.21); P=0.24). In ICM patients with appropriate ICD therapy for MMVT; testing for myocardial ischemia rarely led to coronary intervention. In patients with PMVT/VF; testing had a higher chance of impact on clinical management. Testing for ischemia was not associated with a mortality difference in our cohort.