Pericardial Effusion

Pathophysiology

Clinical manifestations of pericardial effusion are highly dependent on the rate of accumulation of fluid in the pericardial sac. Rapid accumulation of pericardial fluid may cause elevated intrapericardial pressures with as little as 80 mL of fluid, while slowly progressing effusions can grow to 2 L without symptoms.

Understanding the properties of the pericardium can help to predict changes within the heart under physiologic stress.

By distributing forces across the heart, the pericardium plays a significant role in the physiologic concept of ventricular interdependence, whereby changes in pressure, volume, and function in one ventricle influence the function of the other.

The pericardium plays a pivotal role in cardiac changes during inspiration. Normally, as the right atrium and ventricle fill during inspiration, the pericardium limits the ability of the left-sided chambers to dilate. This contributes to the bowing of the atrial and ventricular septums to the left, which reduces left ventricular (LV) filling volumes and leads to a drop in cardiac output. As intrapericardial pressures rise, as occurs in the development of a pericardial effusion, this effect becomes pronounced, which can lead to a clinically significant fall in stroke volume and eventually progress to the development of pericardial tamponade.

The pericardium plays a beneficial role during hypervolemic states by limiting acute cardiac cavitary dilatation.