You are seeing Mr. Ataley who is a 54-year-old man with dyspnea. After careful physical examination, you suspect cor pulmonale and pulmonary hypertension. Which of the following tests is required to definitively confirm the diagnosis of pulmonary hypertension and rule out left heart disease as causal?
A. B-type natriuretic peptide
B. Electrocardiogram
C. Exercise stress test
D. Right heart catheterization
E. Transthoracic echocardiogram