Cardiac tamponade represents a continuum of hemodynamic compromise caused by rising intrapericardial pressure. The pericardium normally contains 15-50 mL of serous fluid. Acute tamponade can occur with as little as 100-200 mL of rapid accumulation, while chronic effusions may reach 1-2 liters before causing tamponade due to gradual pericardial stretch. The pathophysiology involves compression of cardiac chambers, beginning with the right atrium (lowest pressure chamber) during diastole, leading to impaired ventricular filling. This causes interventricular interdependence: as the right ventricle fills during inspiration, the septum shifts leftward, further compromising left ventricular filling and causing pulsus paradoxus. The clinician must rapidly diagnose tamponade using bedside echocardiography, differentiate it from constrictive pericarditis and tension pneumothorax, and initiate definitive management including pericardiocentesis.