Acute atrial infarction: a relatively neglected and under-recognized entity in clinical practice.

Background: Electrocardiograms (ECGs) and angiographic features indicative of acute atrial infarction (AAI) often go unnoticed and are under-recognized in clinical practice.

Methods: In this retrospective observational study, we analyzed the data of 3981 out of 9803 patients (40.61%) who were referred to our hospital for angiography and/or percutaneous coronary intervention due to acute coronary syndrome (ACS). These patients were diagnosed with acute ST segment elevation myocardial infarction (AMI) affecting the inferior, posterior, and/or right ventricular regions.

Results: Of the 3981 patients, 270 (6.78%) had involvement of the main coronary atrial branch meeting the angiographic criteria for AAI. Among the 270 patients identified, the right coronary artery was diagnosed as the infarct-related artery (IRA) in 187 patients (group R), while the left circumflex artery was the IRA in 83 patients (group L). The incidence of PR-segment deviation was similar between the two groups (65.2% in group R vs. 66.3% in group L, p = 0.870), as was occurrence of atrial tachyarrhythmia (67.4% vs. 55.4%, p = 0.059). The prevalence of P wave morphology abnormalities (29.9% vs. 49.4%, p = 0.005) and sinus bradycardia or arrest (25.1% vs. 66.3%, p < 0.001) was significantly lower in Group R than in Group L.

Conclusion: Acute atrial infarction represents a distinct yet frequently overlooked clinical entity. Clinicians should consider the potential for atrial arrhythmias, thromboembolism, hemodynamic instability, and atrial rupture when diagnosing AAI.