Thromboendarterectomy for Chronic Thromboembolic Pulmonary Hypertension: Insights from histopathological findings of surgical specimens

The pathophysiology of chronic thromboembolic pulmonary hypertension is uncertain. Although thromboendarterectomy has become a common treatment modality, few reports have examined characteristics of surgical thromboendarterectomy specimens with respect to pre-endarterectomy pulmonary artery pressures. We hypothesized that comprehensive clinicopathologic review of specimens at our chronic thromboembolic pulmonary hypertension surgical referral center may provide pathophysiologic insight into this disorder. We reviewed clinical and histopathologic features of patients who underwent pulmonary thromboendarterectomy for chronic thromboembolic pulmonary hypertension at the Massachusetts General Hospital from 2010-2013. A panel of histochemical and immunohistochemical stains was applied. We examined the thromboendarterectomy specimens of 22 women and 20 men (mean age 55 years, range 30-78) who had pulmonary arterial pressures determined by right heart catheterization. 19 patients (45%) had a documented history of deep venous thrombosis. Other comorbid conditions included autoimmune diseases and various cardiopulmonary disorders. Histological examination revealed variably organized pulmonary thrombi, neovascularization, intimal hyperplasia with associated elastic reduplication, medial calcification and increased medial smooth muscle. Thromboendarterectomy specimens that included diffusely organized thrombi were larger than those with acute thrombus or focal organization (p=0.016). Atheromatous change was associated with higher pre-operative mean pulmonary arterial pressures (53 vs. 45 mm Hg, p=0.04). These results suggest that vascular remodeling may be a critical hemodynamic factor in chronic thromboembolic pulmonary hypertension. Correspondence to: Alexandra E. Kovach, Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, 11236 Doctors’ Office Tower, Box 3-9065, 2200 Children’s Way, Nashville, TN 37232-9065, Tel: 615-936-2879; Fax: 615-936-7828; E-mail: alexandra.kovach@vanderbilt.edu