674 the Potential Clinical Impact of Cardiovascular Magnetic Resonance on Eligibility for Implantable Cardioverter Defibrillators

In patients with established left ventricular dysfunction, ejection fraction (EF) is one criterion used to select patients for implantable cardioverter defibrillator (ICD) placement. Guidelines give strict EF thresholds for ICD eligibility, however they generally do not specify the technique by which it should be measured. CMR is now considered the gold standard for EF assessment. We sought to investigate the clinical impact of CMR assessment of ejection fraction on ICD eligibility. Patients being considered for ICD implantation were included if they had undergone CMR within 30 days of echocardiography. Echocardiographic EF was determined by Simpson's biplane method while CMR EF was measured by manual planimetry of contiguous short axis cine images. CMR viability images were also examined for left ventricular thrombus. Readings were performed independently by two expert observers blinded to other results. Fifty-two (52) patients were identified with a mean EF by CMR of 35 +/− 14 % and a median delay between echocardiography and CMR of 3 days (interquartile range 1-9). The limits of agreement comparing CMR and echocardiographic EF were - 16 to +10 percentage points. CMR resulted in 11 of 52 (21%) and 5 of 52 (10%) of patients being reclassified regarding ICD eligibility at the EF thresholds of 35 and 30% respectively. Among patients with an echocardiographic EF of between 25 and 40%, 9 of 22 (41%) were reclassified by CMR at either the 35 or 30% EF threshold. Echocardiography identified only 1 of the 6 patients with left ventricular thrombus seen on CMR. In this study, CMR assessment of EF resulted in 21% of patients being reclassified regarding ICD eligibility and detected unexpected left ventricular thrombus in almost 10% of patients. CMR may provide valuable information and alter management in patients being considered for ICD implantation.