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
A 56-year-old man presents with shortness of breath, fatigue, and edema. He has also noticed weight gain, abdominal discomfort, and distension. He has a prior history of lung cancer treated with radiotherapy to the chest. There is no history of liver or cardiac disease in the past. On examination, he has an elevated JVP, prominent y descent of neck veins, and positive Kussmaul sign. The heart sounds are normal. The CXR shows a normal cardiac silhouette and the ECG has low voltages.For the above patient with shortness of breath and peripheral edema, select the most likely diagnosis. 
Select and explain. 
A. cardiac tamponade, B. constrictive pericarditis, C. restrictive cardiomyopathy, D. right ventricle myocardial infarction (RVMI)
B: constrictive pericarditis
Answer: B: constrictive pericarditis 
Explanation: Constrictive pericarditis is characterized by a prominent y descent of the neck veins and low voltage on ECG. The presence of a positive Kussmaul sign helps differentiate the syndrome from cor pulmonale and restrictive cardiomyopathies.