Abstract 12770: Immune Checkpoint Inhibitor Induced Myocarditis: An Interesting Case of Reversible Complete Heart Block

BACKGROUND: Immune checkpoint inhibitors (ICI) have changed the treatment scope for malignancies. The mechanism of ICIs is targeting of immune checkpoints that can suppress a response to a stimulus which can effect any organ. Adverse effects are usually mild but myocarditis, although rare, is becoming more recognized as a life threatening entity. The increase in mortality seen with ICI-induced myocarditis is more frequent with combination therapy. Most cases of ICI-induced myocarditis are limited to direct myocardial injury but there is a lack of evidence regarding conduction disease. CASE DESCRIPTION: We present a 74-year-old man with known metastatic malignancy recently started on ICI with ipilimumab and nivolumab who presented with complaints of abdominal pain, SOB and chest pain. His ED workup was consistent with colitis and acute PE without RV strain. Troponins and BNP were elevated and his ECG showed 3rd degree AV block. A coronary angiogram was negative for obstructive CAD and a temporary trans-venous pacemaker was placed. Cardiac MR showed LGE with active inflammation of the mid-myocardium. The patient had complex presentation as a side effect of ICI leading to myocarditis, 3rd degree AV block, colitis and PE. He was started on high dose methylprednisolone 1gm daily. Within 24 hours there was improvement evidenced by intermittent return of intrinsic conduction. At 48 hours there was marked improvement with restoration of sinus rhythm without evidence of AV block and/or use of the temporary pacemaker. Discussion: Early recognition of disease processes is difficult when there is minimal data to support a cause and effect. Increasing clinical awareness regarding adverse effects of ICI is paramount in decreasing the risk for unnecessary therapies, in our case, placement of a permanent pacemaker. Although there have been case reports of ICI-induced myocarditis, there has not been expert consensus regarding management of conduction pathway abnormalities.