February 7, 2011 by dailybolusoflr
Slow accumulation of pericardial fluid allows for stretch of the pericardium. When pericardial compliance can no longer increase, tamponade physiology begins as cardiac output drops and circulation is only be maintained by increased HR, contractility and peripheral vasoconstriction. A more rapid accumulation of pericardial fluid leads to a higher risk of developing pericardial tamponade due to the lack of compensatory stretch of the pericardium. The most common etiologies of pericardial tamponade mirror the common etiologies of pericardial effusion: pericarditis, malignancy and iatrogenic account for 50% of cases.
Most patients (approx 88% ) with tamponade complain of dyspnea. The most common findings among patients with cardiac tamponade were tachycardia, elevated jugular venous pressure, and pulsus paradoxus.
Hypotension, muffled heart sounds and low voltage on EKG have low sensitivities for predicting tamponade (20-40%)
A pulsus parodoxus greater than 10 mm Hg in patients WITH a pericardial effusion increases the likelihood of tamponade.
When the pre-test probability is high, certain ultrasound findings make the diagnosis of tamponade:
Right atrial systolic collapse
Right ventricular diastolic collapse
Exaggeration of respirophasic changes in flow velocities across the tricuspic and mitral valves
Linda Regan, MD FACEP
Program Director, Emergency Medicine Residency
Johns Hopkins Medical Institutions