Associations between scar characteristics by cardiac magnetic resonance and changes in left ventricular ejection fraction in primary prevention defibrillator recipients

Background Left ventricular ejection fraction (LVEF) improves over time in 25%–40% of patients with cardiomyopathy with primary prevention implantable cardioverter-defibrillator (ICD). The determinants of LVEF improvement, however, are not well characterized. Objectives We sought to examine the associations of clinical risk factors and cardiac imaging markers with changes in LVEF after ICD implantation. Methods We conducted a retrospective analysis of cardiac magnetic resonance images in 202 patients who underwent primary prevention ICD implantation to quantify the amount of heterogeneous myocardial tissue (gray zone), dense core, and total scar. LVEF was reassessed at least once after ICD implantation. Results Over a mean follow-up of 3 years, LVEF decreased in 43 (21.3%), improved in 88 (43.6%), and was unchanged in 71 (35.1%) of the patients. Baseline LVEF and myocardial scar characteristics were the strongest determinants of LVEF trajectory with high scar burden and increasing lack of myocardial viability associated with a greater decline in LVEF. There was a trend toward an association between both changes in LVEF and scar extent with subsequent appropriate ICD shock. Changes in LVEF were also strongly associated with heart failure hospitalizations. Conclusion Scar burden and characteristics were strong determinants, independent of baseline LVEF and other traditional cardiovascular risk factors, of changes in LVEF. Both worsened LVEF and high scar extent were associated with a trend toward increased risk of appropriate shock. These findings suggest that baseline cardiac magnetic resonance imaging of the myocardial substrate may provide important prognostic information on subsequent left ventricular remodeling and adverse events.