Chapter 30: Pulmonary Hypertension

Introduction

Pulmonary hypertension (PH) describes the finding of a mean pulmonary artery pressure (mPAP) ≥ 25 mm Hg and may occur in many settings. In most cases, PH results from a left heart disease (LHD) that increases pulmonary artery pressure (PAP) by transmission of elevated left heart filling pressures or from lung disease causing hypoxia-mediated pulmonary vasoconstriction. The term pulmonary arterial hypertension (PAH) describes a specific group of diseases characterized hemodynamically by an mPAP ≥ 25 mm Hg and normal left heart filling pressures (pulmonary artery wedge pressure [PAWP] ≤ 15 mm Hg) resulting from vasoconstriction and arteriopathy of the precapillary pulmonary arterioles. PAH may be idiopathic or associated with one or more underlying diseases such as connective tissue disease, human immunodeficiency virus (HIV) infection, or portal hypertension. In patients clinically suspected of having PH, echocardiography is often the first test performed to estimate PAP and evaluate right ventricular function. Further comprehensive testing is required to make a diagnosis and establish the etiology of PH.

PH commonly occurs in patients with LHD and hypoxia from lung disease. The development of PH in patients with heart or lung disease is an ominous sign and is generally associated with reduced survival. Treatment in such cases is directed at the underlying condition (ie, bronchodilators, supplemental oxygen, valve repair, or heart failure treatment). Use of PAH-specific therapy in this setting is not beneficial and can worsen symptoms and mortality. In patients with PAH, vasoconstriction and pulmonary vascular arteriopathy cause increased pulmonary vascular resistance and increased PAP, ultimately causing right heart failure and death. In this setting, PAH-specific therapy improves symptoms, exercise tolerance, and survival. Selection of PAH therapies is complex, and the prescriber must consider PAH severity, associated diseases, toxicities, and drug interactions and provide close follow-up. Early referral and collaboration with a PH specialty center are recommended for confirmation of diagnosis, initiation of appropriate therapy, and monitoring of response to treatment. Despite significant advances in understanding of the clinical profile, pathobiology, and treatment of PAH, delays in diagnosis remain common and patient outcomes remain poor.

General Considerations

PH is defined as a sustained elevation in the mPAP of ≥ 25 mm Hg at rest. This is in contrast to a normal mPAP of 12–16 mm Hg. In healthy humans, the small arteriovenous pressure gradient generated by blood flow across the pulmonary circulation results from the large total vascular surface area and high pulmonary vascular compliance. The pulmonary vascular resistance ...