# Sudden Cardiac Arrest in a Young Adult: A Diagnostic Challenge

## TL;DR

A young man with no prior symptoms suffered sudden cardiac arrest, and despite extensive testing, the cause remained undetermined.

## Contribution

This case highlights the diagnostic challenges of sudden cardiac arrest in young adults with negative genetic and structural findings.

## Key findings

- The patient had transient ST-segment elevations attributed to post-resuscitation myocardial stunning.
- Genetic testing and imaging failed to identify a clear cause for the sudden cardiac arrest.
- The patient recovered fully and was implanted with a defibrillator for secondary prevention.

## Abstract

Sudden cardiac arrest (SCA) is a leading cause of mortality in young individuals, often linked to structural heart disease or primary electrical disorders. However, in some cases, the etiology remains unidentified despite extensive diagnostic efforts. This case report describes a 23-year-old male with a family history of hypertrophic cardiomyopathy (HCM) who experienced a sudden cardiac arrest without prior symptoms and had negative genetic testing. The patient, previously healthy, suffered a cardiac arrest while traveling to college. Advanced cardiopulmonary resuscitation (CPR) and multiple defibrillator shocks were necessary to achieve return of spontaneous circulation (ROSC). Transthoracic echocardiography performed immediately post-ROSC showed global hypokinesia with reduced ejection fraction (35%). Coronary angiography at 24 hours post-ROSC was normal. Transient ST-segment elevations resolved within hours and were attributed to post-resuscitation myocardial stunning, with no evidence of ischemia or myocarditis on cardiac magnetic resonance imaging (MRI), which revealed mild interventricular septal hypertrophy without left ventricular outflow tract obstruction. Genetic testing, including a targeted cardiomyopathy panel and whole exome sequencing, did not identify any pathogenic variants, including in MYH7 or MYBPC3. The patient was treated with amiodarone and received an implantable cardioverter-defibrillator (ICD) for secondary prevention. He recovered fully, with no neurologic deficits. This case underscores the challenges of diagnosing and managing SCA in young adults, emphasizing the critical role of genetic and structural assessments. Early intervention, multidisciplinary care, and comprehensive follow-up are essential to reduce recurrence and improve patient outcomes.