Endovascular Management of Chronic TEPH: Is Coronary Management Extrapolatable in This Scenario?

Chronic thromboembolic pulmonary hypertension (CTEPH) is a condition that causes significant functional limitation. Its surgical treatment, known as pulmonary endarterectomy (PEA), has improved the survival of these patients; however, a high percentage of them are not candidates for this procedure.

Balloon pulmonary angioplasty (BPA) is a therapeutic option for patients with CTEPH who are not candidates for surgery. Previous studies have compared its hemodynamic benefits, including a significantly greater reduction in pulmonary vascular resistance compared to medical treatment.

Unfortunately, BPA is still a limited alternative: it is performed in selected specialized centers and it has a high incidence of procedural complications. Some series have reported mortality rates of up to 14%. The probable causes for this include perforation of the treated pulmonary vessel, and circumstances related to the progression time of thrombosis (abundant collagen deposition by fibroblasts) and/or the associated vascular physiology (much greater distensibility compared to regular systemic characteristics).

Currently, there are no specific tools or devices designed for this situation, so treatment is conducted using materials designed for coronary procedures. Due to these limitations, S.J. Perkins et al. conducted a study aimed at defining the mechanical properties of chronic endoluminal thrombosis in CTEPH and, as a secondary objective, characterizing the histological characteristics of the thrombus and the vascular wall.

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The study included nine patients who underwent pulmonary endarterectomy (PEA) at University of Michigan over a period of 9 months. Samples of 19 pulmonary artery intima and 7 intraluminal CTEPH lesions were obtained and mechanically and histopathologically assessed.

Subsequently, a 3D ex vivo model was created, and the samples were placed in it to evaluate the force required (with a force transducer) for crossing, comparing the intraluminal samples with those from the pulmonary artery intima.

The force required to perforate the pulmonary artery wall was significantly greater than the force required to cross CTEPH lesions. Among all patients, the peak force required to cross the vessel wall was 1.75 ± 0.10 N (n = 121), while the peak force for the intraluminal lesion was 0.30 ± 0.04 N (n = 56; a 5.83x difference, P <0.001).

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It should be noted that “workhorse” coronary guidewires have a penetration force of around 0.008 N, which, according to the results shown, would be insufficient for effective crossing of chronic lesions found in CTEPH.

Conclusions

CTEPH lesions, mainly due to fibrosis and rigidity, are difficult to control with the materials used, which have been designed for the treatment of coronary disease. This results in high rates of complications and procedural failure. In the ex vivo tests evaluated in this study, force values for adequate crossing were shown to exceed 40 times what is provided by conventional coronary guidewires. Additionally, there is evidence of a safety window in the procedure, as the force required to cause vessel rupture is 6x more than what is needed to penetrate the thrombus, which could help in the creation of specific tools or devices.

Original Title: Safety Window for Effective Lesion Crossing in Patients With Chronic Thromboembolic Pulmonary Hypertension.

Reference: Sidney J. Perkins, Miguel Funes, Daniel Cheah, Christian Argenti, Jorge Vinales, David Gordon, Jonathan W. Haft, David M. Williams, Vallerie V. Mclaughlin, Prachi P. Agarwal, Victor M. Moles, Thomas Cascino, Andrea Obi, Aditya Pandey, Albert Shih, Vikas Aggarwal. Safety Window for Effective Lesion Crossing in Patients With Chronic Thromboembolic Pulmonary Hypertension, Journal of the Society for Cardiovascular Angiography & Interventions, 2024, 102142. https://doi.org/10.1016/j.jscai.2024.102142.