Cardiogenic Shock From Chronic Immune Checkpoint Inhibitor Associated Myocarditis Causing Predominant Right Ventricular Failure

I mmune checkpoint inhibitor myocarditis (ICI-M) is an adverse effect of immunotherapy with a 1-year case fatality rate for fulminant cases of approximately 29%. 1 Cardiotoxicity from ICI-M usually presents within 2 months of first infusion, 2 although presentations can be atypical, including late onset several months after immunotherapy initiation 3 and those with predominant right ventricular (RV) involvement.4,5 Fulminant cases are associated with a high mortality rate, requiring heightened vigilance for ICI-M.This case highlights a delayed diagnosis of ICI-M with biventricular failure and predominant RV involvement.A 74-year-old man with metastatic urothelial cancer and paroxysmal atrial fibrillation presented with cardiogenic shock 17 months after pembrolizumab initiation.He had been treated with enfortumab and pembrolizumab, a monoclonal antibody that blocks the programmed death-1 (PD-1) receptor, for metastatic urothelial cancer and completed a total of 16 cycles.His medical history was notable for several hospital admissions after starting pembrolizumab (Figure 1).The patient first presented to an outside hospital 3 months after pembrolizumab initiation following an episode of syncope and was found to have atrial fibrillation with a slow ventricular response of 40 beats/ min, necessitating permanent pacemaker implant.Initial troponin-I level at the time of pacemaker implant was 0.894 ng/mL (normal 1.7 cm) and normal left ventricular (LV) function.Then, 15 months after pembrolizumab initiation, the patient was rehospitalized for a heart failure exacerbation.His hs-TnI was 4,427 ng/L (normal