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Chronic thromboembolic pulmonary hypertension is a long-term disease caused by a blockage in the blood vessels that deliver blood from the heart to the lungs. These blockages cause increased resistance to flow in the pulmonary arterial tree which in turn leads to rise in pressure in these arteries. The blockages either result from organised blood clots that usually originate from the deep veins of the lower limbs of the body and lodge in the pulmonary arterial tree after passing through the right side of the heart. The blockages may also result from scar tissue that forms at the site where the clot has damaged the endothelial lining of the pulmonary arteries, causing permanent fibrous obstruction. Most patients have a combination of microvascular and macrovascular obstruction. Some patients may present with normal or near-normal pulmonary pressures at rest despite symptomatic disease. These patients are labelled as having chronic thromboembolic disease.
Diagnosis is based on findings obtained after at least 3 months of effective anticoagulation therapy in order to discriminate this condition from ‘subacute’ pulmonary embolism. Diagnostic findings for CTEPH are: