Chapter 30

Pulmonary hypertension

• A loud pulmonic valve closure sound (P2), a right-sided S4, or a right ventricular heave.
• Electrocardiographic evidence of right ventricular hypertrophy.
• Presence of sustained elevation in mean pulmonary artery pressure ≥ 25 mm Hg.

Pulmonary arterial hypertension

• A subset of pulmonary hypertension.
• Elevated mean pulmonary artery pressure ≥ 25 mm Hg.
• Pulmonary arterial wedge pressure ≤ 15 mm Hg.

Pulmonary hypertension (PH) is a description of the finding of a mean pulmonary artery pressure (mPAP) greater than 25 mm Hg and may occur in many settings. PH most commonly results from a variety of cardiac and pulmonary diseases that increase pulmonary artery pressure (PAP) either passively or through vasoconstriction. The term pulmonary arterial hypertension (PAH) describes a specific group of diseases characterized by a mPAP greater than 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 left heart disease and hypoxemic lung disease. The development of PH in patients with heart or lung disease is an ominous sign and is generally associated with decreased survival. Treatment in this case 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 generally not beneficial and may worsen symptoms and mortality. In patients with PAH, increased pulmonary vascular resistance from vasoconstriction and arteriopathy results in increased PAP, leading rapidly to right heart failure and death. In this setting, PAH-specific therapy improves symptoms, exercise tolerance, and survival. Selection of therapies for patients with PAH is complex and requires understanding of any associated diseases, the severity of the patient's symptoms, as well as toxicities and drug interactions of PAH therapy. Early referral to a specialty center for patients with PAH is often crucial for confirmation of diagnosis, early initiation of appropriate therapy, and monitoring of response to treatment. Significant advances have been made over the past decade in improving clinicians' understanding of the clinical profile, pathobiology, and treatment of PAH.

PH is defined as a sustained elevation in the mPAP of 25 mm Hg or greater 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 (PVR) is quantified using Ohm's law [PVR = (mPAP – PAWP)/cardiac output (CO)] and describes the relationship between the pressure gradient and blood flow.

The World Health Organization has proposed a system to categorize PH into five groups on the basis of underlying etiology (Table 30–1). PH can also be categorized on a hemodynamic basis at right heart catheterization (Figure 30–1). PH is characterized based on the mPAP: mild (25–40 mm Hg), moderate ...

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