This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
Beck's triad is seen in 
Select and explain. 
A. Constrictive pericarditis, B. Cardiac tamponade, C. Hyperophic obstructive cardiomyopathy, D. Restrictive cardiomyopathy
B: Cardiac tamponade
Answer: B: Cardiac tamponade 
Explanation: Ref Harrison 19 th ed pg 1573 The three principal features of tamponade (Beck's triad) are hypo- tension, soft or absent hea sounds, and jugular venous distention with a prominent x descent but an absent y descent. The limitations of ventricular filling are responsible for a reduction of cardiac output. The quantity of fluid necessary to produce cardiac tamponade may be as small as 200 mL when the fluid develops rapidly to as much as >2000 mL in slowly developing effusions when the pericardium has had the oppounity to stretch and adapt to an increasing volume.