Acute Decompensation Requiring Cardiopulmonary Resuscitation in a 15-Year-Old With Undiagnosed Lyme Carditis.

We describe the case of a previously healthy teenager who developed third-degree atrioventricular block due to Lyme disease. While Lyme carditis is common in children, severe conduction anomalies remain rare but can be life-threatening. This case highlights the importance of early recognition, prompt testing, and timely intervention to prevent unnecessary procedures, such as permanent pacemaker implantation, and to ensure favorable outcomes. This case also supports Lyme disease testing in pediatric sudden cardiac death in cases with autopsy findings suggestive of myocarditis or pericarditis.