Calcium-Channel Blockers in Primary Pulmonary Hypertension

To the Editor: In the July 9 issue, Rich et al.* present strong evidence that patients with primary pulmonary hypertension whose pulmonary vascular resistance and pulmonary-artery pressure respond to treatment with calcium-channel blockers have markedly improved survival, as compared with both historical controls who were not selected on the basis of their responsiveness to calcium-channel blockers and patients who are not responsive to calcium-channel blockers. Unfortunately, it remains unclear whether this improved survival is a result of pharmacotherapy or whether a responsive pulmonary vasculature is prognostically favorable, independent of therapy. The authors have addressed this concern by demonstrating that survival…