Early Post-MI Pericardial Effusion

Abstract & Commentary

Synopsis: A mild pericardial effusion within 48 hours of a first acute ST segment elevation MI is associated with a higher risk of later moderate/severe effusion due to hemopericardium and two thirds of the later patients will develop free wall rupture or tamponade.

Source: Figueras J, et al. Am Heart J. 2002;144: 251-258.

Left ventricular free wall rupture is an early and usually catastrophic complication of acute myocardial infarction (MI). Figueras and colleagues from Spain explored the hypothesis that pericardial effusion on echocardiography within the first 48 hours would identify those at higher risk of free wall rupture. They studied 1149 patients with and 324 patients without ST elevation and first acute MI. A second echo was done in 300 patients 2-4 days post-MI; 100 with and 200 without an initial mild-pericardial effusion and in patients with moderate-to-severe effusion or hypotension. The first echo showed a mild effusion in 177 (12%) and a moderate-to-severe one in 51 (3%). Moderate effusion was seen almost exclusively in those with ST elevation MI and was more commonly associated with atrial fibrillation, low ejection fraction, electromechanical disassociation, and death. On the routine second echo, those with mild effusion on the first echo were more likely to have moderate/severe effusion than those without effusion on the first echo (15% vs 6%) and those with effusion on the first echo more often developed echo evidence of tamponade (7% vs 1%). Of the total 92 patients with moderate-to-severe effusion on echo 1 or 2, 60 (65%) developed tamponade and 44 died of free wall rupture (82%), cardiogenic shock (14%), or noncardiac causes (49%). Among the 64 patients with moderate/severe effusion who underwent pericardiocentesis, the fluid was sanguinous in 98%. Figueras et al concluded that a mild pericardial effusion within 48 hours of a first acute ST segment elevation MI is associated with a higher risk of later moderate/severe effusion due to hemopericardium and two thirds of the later patients will develop free wall rupture or tamponade.

Comment by Michael H. Crawford, MD

Many centers routinely perform echocardiography within 48 hours of acute MI to evaluate left ventricular function and assess for unsuspected complications. Although small pericardial effusions are occasionally seen on these studies, their significance has not been well understood. In this study half of those with an early small pericardial effusion eventually developed a large one. Also, a larger effusion in ST elevation MI patients was almost always due to hemopericardium, most likely caused by free wall rupture. Finally, half the patients with large effusions on either echo died, usually of free wall rupture.

There are limitations to this study. It is nonrandomized and most of the patients were treated with thrombolytics rather than primary angioplasty. Also, most patients did not have surgery or autopsy, so the true incidence of free wall rupture is difficult to determine. In addition, the incidence of pericardial effusion, especially larger ones, is higher in this series than others. This may be partly due to the routine performance of 1-2 echoes post-MI and the routine use of thrombolytics and heparin.

This study makes a good case for a routine echocardiogram early post-MI. Those with a small effusion should have a repeat study in 2-4 days to exclude growth of the effusion, and careful attention to blood pressure control and avoidance of strenuous exercise seems prudent to prevent rupture. Those with a moderate-to-large effusion should be considered for pericardiocentesis with surgical standby. Whether such an approach would reduce mortality from acute MI will be difficult to prove and those paying hospital costs may protest the increased use of echocardiography.

Dr. Crawford is Professor of Medicine, Mayo Medical School; Consultant in Cardiovascular Diseases, and Director of Research, Mayo Clinic, Scottsdale, AZ.