Prognostic of Interatrial Block after an Acute ST-Segment Elevation Myocardial Infarction

BACKGROUND: The influence of interatrial block (IAB) in the prognosis after an acute ST-segment elevation myocardial infarction (STEMI) is unknown. OBJECTIVES: To assess the prognostic impact of IAB after an acute STEMI regarding long-term mortality, development of atrial fibrillation, and stroke. METHODS: Registry of 972 consecutive patients with STEMI and sinus rhythm at discharge, with a long-term follow-up (49.6 ± 24.9 months). P wave duration was analyzed using digital calipers, and patients were divided into three groups: normal P wave duration (<120 ms), partial IAB (pIAB) (P wave ≥120 ms and positive in inferior leads), and advanced IAB (aIAB) (P wave ≥120 ms plus biphasic [positive/negative] morphology in inferior leads). RESULTS: Mean age was 62.6 ± 13.5 years. A total of 708 patients had normal P wave (72.8%), 207 pIAB (21.3%), and 57 aIAB (5.9%). Patients with aIAB were older (mean age 73 years) than the rest (62 years in the other two groups, p < 0.001). They also had a higher rate of hypertension (70 vs. 55% in pIAB and 49% in normal P wave, p = 0.006) and higher all-cause mortality (26.3 vs. 12.6% in pIAB and 10.3% in normal P wave, p = 0.001). However, multivariable analysis did not show an independent association between IAB and prognosis. CONCLUSION: About a quarter of patients discharged in sinus rhythm after an acute STEMI have IAB. Patients with aIAB have a poor prognosis, although this is explained mainly by the association of aIAB with age and other variables.