This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
A 44-year-old woman has been complaining of a 4-year history of increasing dyspnea and fatigue. Physical examination reveals increased JVP and a reduced carotid pulse. Precordial examination reveals a left parasternal lift, loud P2, and right-sided S3 and S4. There are no audible murmurs. CXR reveals clear lung fields and an ECG shows evidence of right ventricular hypertrophy. Pulmonary function tests show a slight restrictive pattern. A diagnosis of primary pulmonary hypertension (PPH) is made. Which of the following is the most likely cause of death in this condition? 
Select and explain. 
A. intractable left ventricular failure, B. intractable respiratory failure, C. massive PE, D. intractable right ventricular failure or sudden death
D: intractable right ventricular failure or sudden death
Answer: D: intractable right ventricular failure or sudden death 
Explanation: Death is usually the result of either intractable right heart failure or sudden death. The natural history of the disease is unclear because the disease is asymptomatic for a long period. Survival from diagnosis is dependent on the functional class of the patient. Functional class IV dyspnea suggests a mean survival of only 6 months. Patients with PPH are also at increased risk of veno-thromboembolic disease and current guidelines recommend chronic anticoagulation with warfarin. Left ventricular failure and myocardial infarction are not usual causes of death in patients with PPH.