Incidence, Predictive Factors, and Outcomes of Ischemic High-degree Atrioventricular Block in Acute Coronary Syndrome: A Retrospective Observational Study

Abstract

High-degree atrioventricular block (HD-AVB) is an uncommon but potentially life-threatening complication of acute coronary syndrome (ACS). Its occurrence is associated with increased haemodynamic instability and mortality. This study aimed to assess the incidence, clinical characteristics, predictive factors, and in-hospital prognosis of ischemic HD-AVB and to identify patients who may benefit from permanent pacing.  We conducted a retrospective observational study in the Cardiology Department of the Mohammed VI University Hospital in Marrakesh over a 5-year period, from January 2021 to December 2025. All adult patients admitted with confirmed ACS presenting with complete or high-degree AV block were included. Among ACS admissions during the study period, the prevalence of HD-AVB was 4% (70 patients). The mean age was 65 years (range: 40–74), with a predominance of male patients. More than 80% of patients had modifiable cardiovascular risk factors, led by diabetes mellitus (41%).  ST-segment elevation myocardial infarction (STEMI) was the primary clinical presentation, accounting for 85% of cases, whereas non-ST-segment elevation acute coronary syndrome (NSTEMI) was observed in 15% of patients. Among patients with STEMI, inferior wall involvement was markedly predominant (75% of STEMI cases). Complete AV block accounted for 90% of cases. Coronary angiography revealed significant right coronary artery lesions in 38% and three-vessel disease in 38%. Regarding management, 23% of patients recovered sinus rhythm spontaneously, while 46% required a temporary pacing lead and subsequently returned to sinus rhythm following revascularisation. An additional 16% ultimately required permanent DDD pacemaker implantation, while 15% of patients died during hospitalisation. Ischaemic HD-AVB predominantly complicates inferior STEMI and is usually transient. Temporary pacing is often required acutely, while permanent pacemakers remain limited to persistent blocks. Inferior STEMI was characterised by transient nodal ischemia with an 82.0% electrical recovery rate after revascularisation. Conversely, anterior STEMI carried a significantly higher incidence of cardiogenic shock and higher in-hospital mortality.