Abstract 14843: Electrocardiographic Manifestations of Immune Checkpoint Inhibitor Associated Myocarditis

Abstract

Introduction: Immune checkpoint inhibitor (ICI)-myocarditis is a new syndrome with estimated 50% mortality. Similar to acute cellular rejection (ACR), it is pathologically characterized by lymphocytic infiltration. We aimed to characterize the electrocardiograph features of ICI-myocarditis, compare them to ACR, and evaluate their association with adverse outcome. Methods: Presenting ECG of 130 cases of ICI-myocarditis were collected from a multicenter network spanning 12 countries and compared to 50 cases of ACR. ECG were quantified and interpreted by two blinded cardiologists. 53 patients with ICI-myocarditis had baseline ECG available for comparison via paired univariate analysis. Cox models correcting for age and sex determined association with a composite outcome of life-threatening arrhythmia or myocarditis-related death. Results: ICI-myocarditis patients had average age of 68(58-76), were 61.2% male, and 64.8% had prior cardiovascular disease. QRS prolongation (26% vs 13%, p=0.008), conduction disorders (67% vs 44%, p=0.007) such as left bundle branch block (LBBB) (18% vs 4% p=0.008), ST/T wave changes (50% vs 24%, p=0.004), and PVCs (16% vs 6%, p=0.020) were more prevalent on presenting ECG compared to baseline. ICI-myocarditis showed more PVCs (16% vs 2%, p=0.011) and less ST/T wave changes (41% vs 66%, p=0.002) when compared to ACR. On multivariate analysis, the combined outcome of life-threatening arrhythmia or myocarditis-related death was associated with pathological Q waves (HR=3.60 (1.78-7.27) p<0.001), QRS prolongation (HR=3.35 [1.00-11.21] p=0.05), LBBB (HR=2.24 [1.13-4.45] p=0.021), and supraventricular arrhythmia (HR=2.03 [1.05-3.91] p=0.035) on presenting EKG. Conclusions: ICI-myocarditis manifests as new conduction delays, ST/T-wave changes, and PVCs. QRS prolongation, LBBB, pathological Q waves, and supraventricular arrhythmias were associated with subsequent adverse outcomes.