Recent atrial fibrillation in acute myocardial infarction: a sign of pericarditis.

The association between recent atrial fibrillation during the course of acute myocardial infarction and pericarditis or pericardial effusion occurring during the hospital phase of myocardial infarction was studied by means of serial echocardiographic examinations in 192 patients presenting with their first myocardial infarction. Clinical pericarditis was found in 8%, echocardiographic effusion in 43%, and atrial fibrillation in 5% of all patients. Atrial fibrillation was present in only 2% of patients without pericardial effusion compared to 15% of patients with more than minimal effusion (p = 0.0094). Thus, pericarditis might play a role in the development of recent atrial fibrillation during the course of myocardial infarction. Recent atrial fibrillation may be a sign of pericardial effusion which may be otherwise silent.