Definition

Cardiac tamponade is a syndrome caused by the impairment of diastolic filling of the heart because of continuous increases in intrapericardial pressure. Slow accumulation of fluid in the pericardial space can cause minute increases in intrapericardial pressure. This occurs as a result of the pericardium’s ability to stretch to accommodate this increase in volume. If the pericardial fluid accumulates rapidly, the presence of a few hundred milliliters may cause a significant increase in intrapericardial pressure that may result in cardiovascular collapse, and this process is known as cardiac compressive shock. Cardiac tamponade is the cause of cardiac compressive shock that can result in inadequate peripheral perfusion, acidosis, and death.

Classification of the causes of cardiac tamponade includes: (1) trauma, including sharp or blunt trauma to the chest and dissecting aortic aneurysms; (2) causes associated with cardiac surgery; (3) malignancy within the mediastinum; and (4) expansion of pericardial effusions after any form of pericarditis.

Pathophysiology

Normal intrapericardial pressure is subatmospheric. Accumulation of pericardial fluid leads to an increase in intrapericardial pressure. As a result, diastolic expansion of the ventricles decreases. As in constrictive pericarditis, poor ventricular filling leads to peripheral congestion and a decrease in SV and CO. The decrease in SV stimulates compensatory mechanisms for maintaining CO (tachycardia, vasoconstriction, and an increase in venous pressure). If these mechanisms fail, cardiac collapse can occur. The LV pressure volume loop associated with cardiac tamponade represents decreased LV volume and decreased SV caused by compression.