# Case report of an ST-elevation Myocardial Infarction-like presentation of an immune checkpoint (PD-1/PD-L1) inhibitor-associated myocarditis

## TL;DR

A 72-year-old cancer patient developed severe heart inflammation after immune therapy, which initially looked like a heart attack but was later diagnosed as a rare side effect.

## Contribution

This case report highlights a rare and fatal presentation of ICI-associated myocarditis mimicking STEMI.

## Key findings

- The patient's symptoms and ECG mimicked ST-elevation myocardial infarction but were due to immune checkpoint inhibitor-induced myocarditis.
- Endomyocardial biopsy confirmed the diagnosis of acute ICI-associated myocarditis.
- The patient's condition deteriorated despite treatment, leading to a fatal outcome.

## Abstract

ICI-associated myocarditis is a rare but severe and potentially life-threatening complication that typically manifests shortly after treatment initiation. It may present in many different ways, ranging from fulminant to non-fulminant, even including clinical and electrocardiographic findings mimicking ST-elevation Myocardial Infarction (STEMI).

A 72-year-old woman with a history of non-small cell lung carcinoma presented at the emergency department with symptoms of general asthenia and chest pain, following recent ICI-therapy initiation. Electrocardiogram showed ST elevation in the lateral leads and led to prompt admission for urgent invasive coronary angiography, which ruled out significant coronary artery disease. Urgent cardiac magnetic resonance had to be aborted due to claustrophobia. Endomyocardial biopsy—performed the day after urgent hospital admission and before starting high-dose corticosteroids—confirmed acute ICI-associated myocarditis. On the sixth day of hospitalization, the patient developed transient complete heart block and non-sustained ventricular tachycardia, necessitating temporary transjugular pacemaker insertion. Cellcept (mycophenolate mofetil) was associated due to rising troponin levels. Following a three-week hospital stay, the patient was discharged with a regimen of gradually tapering steroids and continued Cellcept therapy. Two months post-discharge, the patient was readmitted due to severe pneumonia, ultimately resulting in the patient’s demise.

We present the case of a fulminant ICI-associated myocarditis. The case illustrates the diagnostic workup and treatment strategies of an (in the end) fatal adverse event from the use of immune checkpoint inhibitors.