This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Following acute failure of left ventricle in man, pulmonary edema generally begins to appear when left atrial pressure approaches: March 2011 
Select and explain. 
A. 5 mm Hg, B. 15 mm Hg, C. 25 mm Hg, D. 35 mm Hg
C: 25 mm Hg
Answer: C: 25 mm Hg 
Explanation: Ans. C: 25 mm Hg Acute LVF may be trigerred by a major event such as MI in a previously healthy hea An increase in the left ventricular diastolic pressure causes the pressure in the LA, pulmonary veins and pulmonary capillaries to rise. When the hydrostatic pressure of the pulmonary capillaries exceeds the oncotic pressure of the plasma (about 25-30 mm Hg), fluid moves from the capillaries into the alveoli