A post-operative cardiac surgical patient developed sudden hypotension, raised central venous pressure, pulsus paradoxus at the 4th post operative hour. Which of the following is the most probable diagnosis?

This patient is showing features suggestive of cardiac tamponade, which occurred secondary to bleeding into the pericardial space following cardiac surgery. Cardiac tamponade occurs when fluid accumulate in the pericardial space in a quantity sufficient to cause serious obstruction to the inflow of blood to the ventricles. Etiology: The three most common causes are neoplastic disease, idiopathic pericarditis, and renal failure. It can also result from bleeding into the pericardial space after cardiac operations, trauma, and treatment of patients with acute pericarditis with anticoagulants. Clinical features: The three principal features are hypotension, soft or absent hea sounds, and jugular venous distention with a prominent x descent but an absent y descent(Beck's triad). Pulsus paradoxus is present. X ray chest shows enlarged cardiac silhouette ECG shows reduction in amplitude of the QRS complexes, and electrical alternansof the P, QRS, or T waves. Ref: Harrison's Internal Medicine, 18th Edition, Chapter 239