Chapter 27

Pulmonary Hypertension

• A loud pulmonic valve closure (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 at rest or ≥ 30 mm Hg with exercise.

Pulmonary Arterial Hypertension

• A subset of pulmonary hypertension.
• Elevated mean pulmonary artery pressure ≥ 25 mm Hg.
• Pulmonary arterial wedge pressure ≤ 15 mm Hg.
• Elevated pulmonary vascular resistance > 3 Wood units or > 240 dynes × s × cm–5

Pulmonary hypertension (PH) is caused by a wide array of conditions that increase pulmonary arterial (PA) pressure either passively or through vasoconstriction with or without vascular remodeling. The natural history of PH is heavily influenced by its underlying cause. In the United States, PH most commonly results from left-sided heart disease or chronic lung disease. Pulmonary arterial hypertension (PAH) is a less common but serious condition associated with a dismal prognosis. Diagnosis of PAH requires a high index of clinical suspicion. If PAH is considered likely, echocardiography and right-heart catheterization are commonly used diagnostic tests. Selection of therapies for patients with PH is complex but largely predicated on an understanding of the underlying disease and on the severity of the patient’s symptoms. Prompt referral to specialty centers for patients with PAH is often crucial for confirmation of diagnosis, early initiation of appropriate therapy, and monitoring of response to treatment.

Pulmonary hypertension is a pathologic state defined by a sustained elevation in the mean PA pressure of 25 mm Hg or greater at rest. The PA systolic pressure is normally 20–30 mm Hg and the PA diastolic pressure is normally 8–12 mm Hg. Normal mean PA pressure is 12–16 mm Hg. Normal pulmonary arterial wedge pressure (PAWP) is 8–12 mm Hg. The small arteriovenous pressure gradient generated by blood flow across the pulmonary circulation is a byproduct of such variables as total vascular surface area and pulmonary vascular compliance. This pressure gradient, termed the “pulmonary vascular resistance” (PVR), is quantified using Ohm’s law [PVR = (mean PA – PAWP) / cardiac output (CO)]. Pulmonary arterial hypertension is a subset of PH marked by persistent elevation in the mean PA pressure and PVR. Significant advances have been made over the past decade in improving clinicians’ understanding of the clinical profile, pathobiology, and treatment of PAH.

The World Health Organization has proposed a system to categorize PH into five groups on the basis of underlying etiology (Table 27–1). Pulmonary hypertension can also be categorized on a hemodynamic basis at right heart catheterization (Figure 27–1). Pulmonary hypertension is characterized based on the mean PA pressure: mild (25–40 mm Hg), moderate (41–55 mm Hg), or severe (> 55 mm Hg).

Table 27–1. Revised Classification System for Pulmonary Hypertension.

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