Chronic thromboembolic pulmonary hypertension (CTEPH) is an underdiagnosed, but potentially curable pulmonary vascular disease. The increased pulmonary vascular resistance in CTEPH is caused by unresolved proximal thrombus and secondary microvasculopathy in the pulmonary vasculature, leading to adaptive and maladaptive remodeling of the right ventricle (RV), eventual right heart failure, and death. Knowledge on the RV remodeling process in CTEPH is limited. The progression to RV failure in CTEPH is a markedly slower process. A detailed understanding of the pathophysiology and underlying mechanisms of RV remodeling may facilitate early diagnosis and the development of targeted therapy. While ultrasound, magnetic resonance imaging, right heart catheterization, and serum biomarkers have been used to assess cardiac function, the current treatment strategies reduce the afterload of the right heart, but are less effective in improving the maladaptive remodeling of the right heart. This review systematically summarizes the current knowledge on adaptive and maladaptive remodeling of the right heart in CTEPH from molecular mechanisms to clinical practice.

Background: The cause of atherosclerotic lesions in the pulmonary artery of patients with chronic thromboembolic pulmonary hypertension (CTEPH) remains unclear. We aimed to discuss the clinical characteristics of CTEPH patients with atherosclerotic lesions and further explore the unique metabolic pathway of atherosclerosis in the pulmonary artery. Methods: Following detailed pathological examination of the pulmonary endarterectomy (PEA) specimen, CTEPH patients were divided into two age- and sex-matched groups, those with and without atherosclerotic lesion (n=25 each), and their clinical characteristics were compared. Untargeted metabolomics were used to determine the different metabolites in the proximal lesions of the pulmonary artery. Results: 27.2% (25/92) of all PEA specimens were found with atherosclerotic lesions. Patients with atherosclerotic lesions were more likely to have a history of symptomatic embolism than those without atherosclerotic lesion (88% vs. 56%, P=0.012), including pulmonary embolism and deep venous thrombosis. Patients with atherosclerotic lesions were found to have longer symptom duration (8.0±6.5 vs. 4.7±4.2, P=0.039) and a lower rate of residual pulmonary hypertension after PEA than those without atherosclerotic lesion (40% vs. 56%). However, the existence of atherosclerotic lesion was not associated with pre-operative hemodynamic parameters and cardiac function. Metabolomic profiling revealed that the formation of atherosclerotic lesion in CTEPH is closely related to glycine, serine and threonine metabolic axes involved in cellular aging and energy metabolism. Conclusions: The occurrence of atherosclerotic lesions in the pulmonary artery of CTEPH was associated with symptomatic thromboembolic history and extended symptom duration. The results suggested a new link between atherosclerotic lesions and aberrant amino acid metabolism in the context of CTEPH. Further investigations focused on atherosclerotic lesion and pulmonary vascular remodeling may provide novel insight into the pathophysiology and new therapeutic strategies for CTEPH.