Pericardial and Pleural Effusions in Congestive Heart Failure—Anatomical, Pathophysiologic, and Clinical Considerations

Transudative pleural and pericardial effusions are not uncommon in patients with congestive heart failure. Pericardial effusion forms only with elevation of the right-sided filling pressure in the heart. In patients with biventricular failure, there is no evidence that elevated left-sided pressure, in the absence of elevated right-sided pressure, can cause a pericardial effusion. Pleural effusion forms with acute elevation of the right-sided or the left-sided filling pressure in the heart. In patients with congestive heart failure, elevated right-sided filling pressures are less common than elevated left-sided filling pressures, thus, explaining a lower prevalence of pericardial than pleural effusions. Pleural effusions in patients with congestive heart failure are typically bilateral. However, a unilateral pleural effusion is more commonly seen on the right side. Although multiple theories attempt to explain the right-sided preponderance of pleural effusion, to date, no mechanism has been universally accepted or experimentally proven.