Background: New-onset atrial fibrillation (AF) after acute myocardial infarction (AMI) frequently occurs in association with postinfarction complications, particularly with heart failure (HF).
Aims: To evaluate whether postinfarction HF is associated with the subsequent development of AF and whether AF independently predicts poorer prognosis.
Methods and results: We examined 650 patients with AMI and compared patients with AF (n=320) to those without (n=330). AF patients were classified as either early AF (n=208)-patients who developed AF within 24 h of symptom onset or late AF (n=112)-patients who had AF thereafter. We compared outcomes between these groups, adjusting for differences in baseline characteristics and postinfarction HF. Heart failure was the most important predictor of AF. In most patients, AF occurred secondary to HF. AF patients had poorer outcomes, including higher in-hospital and 7-year mortality. After multivariate adjustment, overall, AF was not an independent predictor of in-hospital [odds ratio (OR)=0.70) and 7-year [relative risk (RR)=1.14] mortality, but late AF remained an independent predictor of 7-year (RR=2.48, 95% confidence interval, 1.26-4.87) mortality.
Conclusions: Heart failure mostly preceded the occurrence of new-onset atrial fibrillation after acute myocardial infarction, but only late atrial fibrillation was independently related to long-term mortality.