[1] Common causes of cardiac tamponade include cancer, kidney failure, chest trauma, myocardial infarction, and pericarditis.

[1] Diagnosis may be suspected based on low blood pressure, jugular venous distension, or quiet heart sounds (together known as Beck's triad).

[1] Other general signs of shock (such as fast heart rate, shortness of breath and decreasing level of consciousness) may also occur.

This is caused by the equilibration of left ventricular filling and pericardial pressure, leading to “severe deterioration of end-organ perfusion.”[11] Some of the symptoms, as a consequence, include abdominal pain due to liver engorgement.

Cardiac tamponade is caused by a large or uncontrolled pericardial effusion, i.e. the buildup of fluid inside the pericardium.

[12] This commonly occurs as a result of chest trauma (both blunt and penetrating),[13] but can also be caused by myocardial infarction, myocardial rupture, cancer (most often Hodgkin lymphoma), uremia, pericarditis, or cardiac surgery,[12] and rarely occurs during retrograde aortic dissection,[14] or while the person is taking anticoagulant therapy.

[19] The outer layer of the heart is made of fibrous tissue[20] which does not easily stretch, so once excess fluid begins to enter the pericardial space, pressure starts to increase.

Eventually, increasing pressure on the heart forces the septum to bend in towards the left ventricle, leading to a decrease in stroke volume.

[12] This causes the development of obstructive shock, which if left untreated may lead to cardiac arrest (often presenting as pulseless electrical activity).

[21] The three classic signs, known as Beck's triad, are low blood pressure, jugular-venous distension, and muffled heart sounds.

[24] Other signs may include pulsus paradoxus (a drop of at least 10 mmHg in arterial blood pressure with inspiration),[12] and ST segment changes on the electrocardiogram,[24] which may also show low voltage QRS complexes.

[25] In a person with trauma presenting with pulseless electrical activity in the absence of hypovolemia and tension pneumothorax, the most likely diagnosis is cardiac tamponade.

Some teams have performed an emergency thoracotomy to release clotting in the pericardium caused by a penetrating chest injury.

[13] This involves the insertion of a needle through the skin and into the pericardium and aspirating fluid under ultrasound guidance preferably.

If the drainage volume drops off, and the blood pressure goes down, this can suggest a tamponade due to chest tube clogging.

[citation needed] If aggressive treatment is offered immediately and no complications arise (shock, AMI or arrhythmia, heart failure, aneurysm, carditis, embolism, or rupture), or they are dealt with quickly and fully contained, then adequate survival is still a distinct possibility.