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CTEPH: treatment


The first and only treatment approved for CTEPH


This review provides a brief overview of CTEPH, discusses the mechanism of action of riociguat and the key clinical trial evidence supporting its use in this condition


Lisa M Mielniczuk MD MSc FRCPC Associate Professor of Medicine, University of Ottawa, Canada


Riociguat is a member of a new class of therapeutic agents called soluble guanylate cyclase (sGC) stimulators and is an effective therapy in the management of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH).1–3


CTEPH


CTEPH is a serious disease characterised by obstruction of the pulmonary vasculature from unresolved thrombi. It is a rare/orphan disease with an epidemiology comparable to PAH. CTEPH results in progressive PH and, in many, right ventricular failure.2


CTEPH


is defined as a raised mean pulmonary artery pressure (≥ 25mmHg at rest) caused by persistent obstruction of pulmonary arteries after pulmonary embolism that has not resolved despite adequate anticoagulation for at least three months.4


It is estimated that the 42


prevalence of CTEPH after acute pulmonary embolism is 0.1–4% after two years. There are known risk factors predisposing to CTEPH development, in terms of both severity of PE as well as patient risk factors. The former includes patients with recurrent venous thromboembolism, large perfusion defects and those with echocardiographic signs of PH at the time of initial presentation. Patient-related risks include those with myeloproliferative disorders, inflammatory bowel disease and the presence of permanent central


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“There are no other PAH-specific therapies currently approved for the use in patients with persistent PH following endarterectomy or inoperable CTEPH”


venous lines, pacemakers or ventriculoatrial shunts.5–7 of these clinical disorders is


Central to all


inflammation and/or infection – both of which likely predispose to the non- dissolution of thromboembolic material.4


Initial trigger for development The initial trigger for CTEPH development is the occlusion of


pulmonary arteries by thromoboembolic material. However, the non-dissolution of this thrombotic material results in the formation of organised scar tissue, or fibrous clots, and intraluminal webs and bands that can partially or completely obstruct pulmonary arteries. The resultant pulmonary blood flow is redirected to non-occluded blood vessels, which become exposed to high intravascular pressures and sheer stress, resulting in endothelial dysfunction, and vascular remodelling of precapillary arteries. These changes resemble findings demonstrated in PAH.8 In the absence of treatment, the survival for patients with CTEPH is poor, with a median survival of less than two years in patients with a mean pulmonary artery pressure >30mmHg at diagnosis.9 Traditionally, the management of these patients included life-long


anticoagulation and, in selected cases, insertion of inferior vena cava filters.4 However, pulmonary endarterectomy is the only potentially curative strategy and the standard of care for eligible patients. Unfortunately, a significant proportion of patients with CTEPH are not eligible for pulmonary endarterectomy because of either technical reasons or comorbidities. In addition, recurrent PH following endarterectomy surgery is not uncommon, and contributes significantly to long-term morbidity and mortality in these patients. In the large European/ Canadian Registry, it was observed that 17% of patients had persistent PH (pulmonary artery pressure >25mmHg following surgery) and at least 31% of patients referred to participating centres were considered inoperable, due either to inaccessibility with vascular


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