Cardiac tamponade occurs when a pericardial effusion exerts a significant amount of pressure externally on the heart, resulting in impaired right ventricular filling eventually causing decreased cardiac output and hypotension.
Physical exam findings include:
- elevated jugular venous pressure;
- pulsus paradoxus (see below);
- pericardial friction rub (from pericarditis, if present);
- distant heart sounds (from heart sound muffling related to the pericardial effusion); and
- Kussmaul’s sign (rarely) – increase in jugular venous pressure during inspiration.
"Pulsus paradoxus," which is present in cardiac tamponade, reflects a decrease in systolic blood pressure with inspiration of more than 12 mmHg. Pulsus paradoxus also occurs in severe asthma or COPD exacerbations.
The above image shows an arterial pressure waveform tracing superimposed with the respiratory cycle, showing a significant decrease in arterial pressure with inspiration and return to normal in expiration. This hemodynamic effect of a large pericardial effusion causing cardiac tamponade is referred to as “pulsus paradoxus.” Review pulsus paradoxus here.
Diagnosis is clinical, based on hypotension with a large pericardial effusion; however, echocardiography can be helpful and can show right ventricular early diastolic collapse. Variation of > 25% during inspiration of the mitral and tricuspid valve inflow velocities on echocardiography indicate tamponade physiology, as well.
Right heart catheterization will show increased right heart pressures and decreased left heart pressures with inspiration. Also, the diastolic pressures are elevated and equal. Normally, the pericardium can expand as the heart fills; however, with cardiac tamponade from a large pericardial effusion or constrictive pericarditis, this is not able to occur. As a person inspires, venous return is increased to the right heart and the interventricular septum bulges to the left, impairing left ventricular filling, reducing left heart cardiac output and thus decreasing systemic pressure (increasing the “pulsus paradoxus”). As a person exhales, right ventricular filling decreases and the left heart fills, causing the interventricular septum to bulge to the right and impair right ventricular filling. The diastolic pressures are elevated and equal since every cardiac chamber pressure influences the other, considering the heart is not able to expand as mentioned above.
Treatment is pericardiocentesis to remove the pericardial fluid and relieve the pressure. This is usually done percutaneously through a subxiphoid approach. A surgical pericardial window can be done to create communication between the pericardial space and the pleural space. This is done when there is concern that the pericardial effusion will recur, as can be seen in a pericardial effusion from a malignancy. Rarely, left ventricular free wall rupture can occur after an MI causing hemorrhage into the pericardium and cardiac tamponade, which requires emergent surgical repair.