Pericardial effusions: perspective of the acute cardiac care physician

Pericardial effusions can result in acute haemodynamic compromise and require rapid intervention. Understanding pericardial restraint is essential to determine the approach to newly identified pericardial effusions in the intensive care unit. As pericardial effusions stretch the pericardium, the pericardial compliance reserve is eventually exhausted, with an exponential rise in compressive pericardial pressure. The severity of pericardial pressure increase depends on both the rapidity and volume of pericardial fluid accumulation. This increase in pericardial pressure is reflected in an increase in measured left- and right-sided 'filling' pressures, but paradoxically left ventricular end-diastolic volume (the true left ventricular preload) is decreased. This uncoupling of filling pressures and preload is the hallmark of pericardial restraint. When this occurs acutely from a pericardial effusion, rapid recognition and pericardiocentesis can be lifesaving. In this review, we will discuss the haemodynamics and pathophysiology of acute pericardial effusions, provide a physiological guide to determine the need for pericardiocentesis in acute care, and discuss important caveats to management.