Chronic Thromboembolic Pulmonary Hypertension

To the Editor: Pengo et al. (May 27 issue) 1 report an incidence of chronic thromboembolic pulmonary hypertension (CTPH) of approximately 3 percent (diagnosed in 7 of 223 patients) after a first episode of pulmonary embolism. We believe that the angiographic criteria used by the authors to diagnose CTPH may underestimate the real incidence of CTPH after pulmonary embolism. Because Pengo et al. focus on large-vessel CTPH, they could have missed cases of CTPH that were caused by small-vessel chronic thromboembolism. At our institution, 15 percent of cases of CTPH are secondary to small-vessel chronic thromboembolism. The diagnosis of CTPH may . . .