Cardiac tamponade, also known as pericardial tamponade (), is a compression of the heart due to pericardial effusion (the build-up of pericardial fluid in the sac around the heart). Onset may be rapid or gradual. Symptoms typically include those of obstructive shock including shortness of breath, weakness, lightheadedness, and cough. Other symptoms may relate to the underlying cause.

Common causes of cardiac tamponade include cancer, kidney failure, chest trauma, myocardial infarction, and pericarditis. Other causes include connective tissues diseases, hypothyroidism, aortic rupture, autoimmune disease, and complications of cardiac surgery. In Africa, tuberculosis is a relatively common cause.

Diagnosis may be suspected based on low blood pressure, jugular venous distension, or quiet heart sounds (together known as Beck's triad). A pericardial rub may be present in cases due to inflammation. The diagnosis may be further supported by specific electrocardiogram (ECG) changes, chest X-ray, or an ultrasound of the heart. If fluid increases slowly the pericardial sac can expand to contain more than 2 liters; however, if the increase is rapid, as little as 200 mL can result in tamponade.

Tamponade is a medical emergency. When it results in symptoms, drainage is necessary. This can be done by pericardiocentesis, surgery to create a pericardial window, or a pericardiectomy. Drainage may also be necessary to rule out infection or cancer. Other treatments may include the use of dobutamine or in those with low blood volume, intravenous fluids. Those with few symptoms and no worrisome features can often be closely followed. The frequency of tamponade is unclear. One estimate from the United States places it at 2 per 10,000 per year.