The World Pulmonary Hypertension Symposium added segmental pulmonary hypertension (PH) as a new classification in 2013. An article recently published in the Journal of the American Heart Association described the definition and best practices for management.
Segmental PH is defined by the following characteristics:
- at least 1 segment of the pulmonary vasculature is nonhypertensive,
- each hypertensive area may present with different severity, and
- symptoms depend on ventilation-to-perfusion mismatch.
Researchers proposed the following definition: “Segmental pulmonary hypertension encompasses any condition with abnormal underlying cardiac or vascular anatomy, usually including varied sources of pulmonary blood supply, which results in distal pulmonary vascular disease that affects various lung segments to differing degrees.”
Segmental PH can result from many conditions, such as complex pulmonary atresia, hemitruncus arteriosus, absence/atresia of a single pulmonary artery, and an anomalous pulmonary artery from the aorta feeding a single lung segment. Furthermore, management of segmental PH is focused around surgical, interventional, and medication therapies.
The goal of surgical interventions in children is to create an adequate pulmonary artery tree supplied by the right ventricle, whereas full unifocalization in adults is often not feasible. In these cases, palliative shunts or dilatation stenting may be used. Pharmacological treatments have shown some efficacy, such as the endothelin-receptor antagonist bosentan or the phosphodiesterase-type 5 inhibitor sildenafil, but more evidence is needed to conclusively demonstrate safety and efficacy.
Assessment and interpretation of pathophysiology require tertiary expertise in both coronary heart disease and PH. As a result, patients should be cared for in tertiary centers with expertise in both diseases, complex noninvasive and invasive investigations, and multidisciplinary support for imaging, catheter, and cardiac surgical interventions.
The authors wrote, “A broad recommendation on the use of [pulmonary arterial hypertension] therapies cannot be made at present given the lack of evidence, though anecdotal experience suggests these therapies may have a role and may be considered empirically on an individualized basis in patients with confirmed segmental PH.”
They added, “Because of significant heterogeneity, coupled with a small patient population, it is unlikely that adequately powered randomized controlled trials will ever be feasible.”
Dimopoulos K, Diller G, Opotowsky A, et al. Definition and management of segmental pulmonary hypertension [published July 4, 2018]. J Am Heart Assoc. doi:10.1161/JAHA.118.008587