Abstract 15365: Natural History of Immune Checkpoint Inhibitor Associated Myocarditis With Preserved Ejection Fraction

Abstract

Introduction: Immune Checkpoint Inhibitor (ICI)-associated myocarditis can be fatal, and is often characterized by arrhythmogenicity, although > 50% present with preserved ejection fraction (pEF). The natural history of ICI-myocarditis with pEF is unknown. Methods: We utilized a multicenter network of ICI-myocarditis cases spanning 12 countries to identify 83 cases of definite or probable myocarditis presenting with an EF above 50% on initial echocardiography. We further stratified patients based on continued pEF or worsening EF (rEF) during hospitalization. We compared independent variables, vital signs on presentation, and laboratory values between the two groups. Mortality was defined as those who died or were discharged to hospice within 90 days from admission. Fulminant myocarditis was defined as need for circulatory support, atrioventricular block requiring electrical pacing, ventricular tachycardia or fibrillation, or cardiac arrest while in the hospital. Results: Of the 83 patients, 15 developed a rEF; 68 maintained pEF during hospitalization. Although no significant change in heart rate was noted on presentation, systolic blood pressure was lower in the rEF group (111 vs 129, p=0.010). The rEF cohort were more prone to have a peak troponin elevation (432 vs 41, p=0.021), and to develop fulminant myocarditis (73% vs 26%, p=<0.001). Both in-hospital mortality (46% vs 17%, p=0.015) and 90-day all-cause mortality were significantly increased in those who develop a rEF (72% vs 29%, p=0.007). Overall, there was a 36.8% 90-day mortality rate for all those presenting with an initially normal EF. Conclusions: Patients with ICI-myocarditis can still have a fulminant course despite initial echocardiogram revealing EF>50%. In our database, 18% go on to develop new rEF and 73% die in the following 90 days. Decreased BP and troponin on presentation may identify patients at risk of subsequent rEF and fulminant course.