Pericarditis complicating acute myocardial infarction: Incidence of complications and significance of electrocardiogram on admission

The records of 31 patients with pericarditis complicating acute myocardial infarction were reviewed and compared to a control group of 274 patients with infarction but without pericarditis. The cases of pericarditis all occurred within one week of myocardial infarction and were included only if a typical pericardial friction rub was heard by more than one observer. Sex distribution and age were similar in both groups. There was a higher incidence of anterior wall infarction in the group with pericarditis. The incidence of atrial arrhythmias was less than in controls, while the incidence of ventricular arrhythmias, significant congestive heart failure, and death was slightly greater in those with pericarditis. Maximum ST segment elevation on the day of admission in the group with pericarditis was compared with a control group. In those with anterior wall infarction and pericarditis, the average ST segment elevation in the anterior precordium was 5.6 mm. compared to 2.6 mm. in the controls. In those with inferior wall infarction and pericarditis, the average ST segment elevation was 3.6 mm. in Lead III compared to 1.7 mm. in a control group. It is concluded that patients who develop pericarditis within one week of acute myocardial infarction do not have an increased incidence of atrial arrhythmias. The incidence of ventricular arrhythmias, significant congestive heart failure, and death are slightly greater and may be due to more extensive myocardial infarction. The higher initial ST segment elevation in patients with pericarditis may indicate a greater amount of injury or may be a sign of pericardial involvement that is seen before clinical pericarditis is present.