Abstract
<title>Abstract</title> <p>Introduction: Out-of-hospital cardiac arrest (OHCA) caused by acute coronary occlusion remains a time-critical emergency. Complete atrioventricular block (CAVB) is an uncommon complication of anterior ST-elevation myocardial infarction (STEMI), but when present it usually reflects extensive septal ischemia involving the His-Purkinje system and is associated with severe hemodynamic instability and poor prognosis. Case presentation: A 78-year-old man suddenly collapsed while walking in the street. Dispatcher-assisted cardiopulmonary resuscitation was initiated by bystanders. On arrival of the physician-staffed advanced life support team, the patient was in asystolic cardiac arrest. Advanced life support was performed, including endotracheal intubation, two 1-mg doses of intravenous adrenaline, and one 200-J biphasic shock for ventricular fibrillation. Return of spontaneous circulation was achieved after 17 minutes of CPR. The post-ROSC electrocardiogram showed extensive anterior STEMI. Approximately 8 minutes after ROSC, the patient rapidly deteriorated because of complete atrioventricular block with atrioventricular dissociation, atrial activity of approximately 85 beats/min, and a ventricular escape rhythm of approximately 18 beats/min. Continuous monitoring with a ZOLL X Series monitor-defibrillator allowed prompt recognition. Immediate transcutaneous pacing restored effective ventricular activation and hemodynamic stability, allowing safe transfer for definitive hospital care. Conclusions This case highlights the importance of continuous electrocardiographic and hemodynamic reassessment after ROSC. In anterior STEMI complicated by unstable complete atrioventricular block, prehospital transcutaneous pacing may provide a life-saving bridge to definitive coronary reperfusion.</p>