Immune-Related Myocarditis Presenting as Shortness of Breath and Complete Heart Block in an Urothelial Cancer Patient Receiving Pembrolizumab: A Case Report

Pembrolizumab is an immune-checkpoint inhibitor (ICI) drug approved for the treatment of patients who have locallyadvanced or metastatic urothelial cancer and are not eligible for cisplatin-containing therapy. However, like other antiPD-1s, pembrolizumab can cause immune- related adverse events (irAEs), some of which can be serious enough to warrantemergency care 3-7. Pembrolizumab-related cardiac irAEs, owing to the increased morbidity and mortality associated withthem, can present a special challenge in the emergency department. Most documented cardiac irAEs occurred in patientsreceiving anti-PD-1s in combination with other agents or in patients with pre-existing heart conditions and were easilyresolved with steroid treatment8. Herein, we describe a case with unclear symptom presentation in a patient with no previouscardiac history receiving only 1 dose of pembrolizumab. Knowledge gained from this case and others will help elucidate theearly- and late-onset toxic effects associated with pembrolizumab and inform the development of effective algorithms for theidentification and management of these effects, thereby optimizing the safety of pembrolizumab and other immunotherapyagents in the Emergency Department.