Cardiac tamponade is a life-threatening emergency in which fluid accumulates within the pericardial sac (the membrane surrounding the heart) under sufficient pressure to compress the heart chambers and prevent them from filling normally. The pericardium is a relatively inelastic sac; once it contains enough fluid, even small additional volumes cause a steep rise in intrapericardial pressure, compressing the thin-walled atria and right ventricle and severely reducing cardiac output.
Fluid can accumulate from several causes including trauma, cancer (malignant pericardial effusion), pericarditis, aortic dissection extending into the pericardium, and complications of cardiac procedures such as central line insertion or pacemaker implantation. Haemopericardium (blood in the pericardial sac) after trauma or aortic dissection can develop with dangerous rapidity.
Cardiac tamponade produces the classic Beck’s triad: hypotension (low blood pressure), muffled heart sounds, and distended neck veins. It also causes pulsus paradoxus (an abnormally large fall in blood pressure during inspiration). The diagnosis is confirmed by echocardiography, which shows fluid around the heart and collapse of the right atrium or right ventricle. Untreated, cardiac tamponade can rapidly progress to cardiac arrest.
Treatment is pericardiocentesis: drainage of the pericardial fluid using a needle inserted into the pericardial space under ultrasound guidance, which can be life-saving within minutes. In traumatic tamponade or where blood clot is present, surgical drainage (pericardial window) may be required. After the initial emergency, the underlying cause must be treated to prevent recurrence.
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