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BackgroundChronic thromboembolic pulmonary hypertension (CTEPH) is generally recognized to be caused by persistent organized thrombi that occlude the pulmonary arteries. The aim of this study was to investigate the characteristics of small vessel remodeling and its impact on the hemodynamics in CTEPH patients.Methods and ResultsHemodynamic data were obtained from right heart catheterization in 17 CTEPH patients before pulmonary endarterectomy (PEA). Lung tissue specimens were obtained at the time of PEA. Pathological observations and evaluation of quantitative changes in pulmonary muscular arteries and veins were performed using light microscopy on 423 slides in 17 patients. The relationship between the results and the hemodynamics of CTEPH was investigated. Pulmonary arteriopathy and venopathy were recognized in most cases, although no plexiform lesions and no capillary-hemangiomatosis-like lesions were detected in any of the specimens. The severity of pulmonary arteriopathy was correlated with pulmonary vascular resistance (PVR) in the postoperative and follow-up periods. The PVR and mean pulmonary arterial pressure were significantly higher in the high-obstruction group than in the low-obstruction group. The findings in pulmonary venopathy were similar to the findings seen in pulmonary veno-occlusive disease in some cases, although severe venopathy was only observed in a portion of the pulmonary veins. There was a significant correlation between the extent of pulmonary arteriopathy and venopathy, although an effect of pulmonary venopathy to hemodynamics, including pulmonary arterial wedged pressure (PAWP), could not be identified.ConclusionThe vascular remodeling of the pulmonary muscular arteries was closely associated with the hemodynamics of CTEPH. Severe pulmonary arteriopathy might be related to residual pulmonary hypertension after PEA. Those altered pulmonary arteries might be a new target for the persistent PH after the operation.

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Survival in CTEPH in the recent era has significantly improved, especially in non-PEA patients. BPA and selective pulmonary vasodilators could improve survival in the non-PEA group. In the present study, no difference in survival was found between PEA and non-PEA.

Abstract. In general, intravascular thrombus formation in the pulmonary arteries is considered to be the most common cause of chronic thromboembolic pulmonary hypertension (CTEPH). The current mainstay of therapy for patients with CTEPH is pulmonary endarterectomy (PEA). Recently, the existence of myofibroblast-like cells in endarterectomized tissues has been demonstrated. At the 2nd passage of these myofibroblast-like cells, a pleomorphic cell type was isolated. Pulmonary intimal sarcoma is a very uncommon neoplastic tumor thought to originate from subendothelial-mesenchymal cells of the pulmonary vascular wall. Because these pleomorphic cells were isolated from the pulmonary vascular beds, it is believed that the analysis of these cells may contribute to the understanding of pulmonary intimal sarcoma. We isolated cells from the endarterectomized tissue from patients with CTEPH and identified one type as sarcoma-like cells (SCLs). The SCLs were characterized as hyperproliferative, anchorage-independent, invasive and serum-independent. Moreover, C.B-17/lcr-scid/ scidJcl mice injected subcutaneously with SCLs developed solid, undifferentiated tumors at the site of injection, and those injected intravenously with SCLs via the tail vein developed tumors which grew along the intimal surface of the pulmonary vessels, thus, demonstrating the high tumorigenic potential of these cells. The behavior of SCLs indicated that these cells may have a vascular cell-like potential which can affiliate them with the intimal surface of the pulmonary artery, and which may be shared with pulmonary intimal sarcoma. A further investigation of this mouse model with SCLs may elucidate the mechanism(s) underlying the development of pulmonary intimal sarcoma.

Background and objective: Chronic thromboembolic pulmonary hypertension (CTEPH) is a progressive disease in some patients, despite improved treatments. Microvasculopathy has been implicated in the poor outcomes of patients with CTEPH. A reduction in the diffusing capacity for carbon monoxide (DL CO ) was previously suggested to indicate microvasculopathy in CTEPH patients; therefore, we assessed DL CO /alveolar ventilation (DL CO /V A ) as a prognostic and pathophysiological marker in CTEPH. Methods: We performed a retrospective cohort study of 214 CTEPH patients consecutively diagnosed between 1986 and 2011. After exclusion of 24 patients because of missing DL CO data or severe obstructive impairment, the mortality rates of medically treated patients classified with normal or decreased DL CO values were compared, and prognostic factors were determined. The relationship between long-term surgical outcomes and DL CO /V A was also investigated. Results: Ninety-one inoperable patients were treated medically, two of whom underwent balloon pulmonary angioplasty. Ninety-nine underwent pulmonary endarterectomy. The 5-year survival rate of medically treated patients was significantly lower in patients with decreased DL CO /V A than in those with normal values (61.4% vs 90.4%, P = 0.017). Decreased preoperative DL CO /V A was associated with a smaller percent decrease in post-operative pulmonary vascular resistance, but not with the extent of proximal thrombi; these results may support our hypothesis that DL CO reflects microvascular involvement. Conclusion: Decreased DL CO /V A was associated with poor outcomes of medically treated CTEPH patients; and may be useful for identifying high-risk patients,