Pulmonary arterial hypertension (PAH) is a complex, multidisciplinary disorder resulting from restricted flow through the pulmonary arterial circulation; this results in increased pulmonary vascular resistance and, ultimately, right heart failure. PAH has been thought of as a rare disease, but recent evidence suggests that the incidence may be higher than what has been previously reported.
The American College of Cardiology Foundation (ACCF) and the American Heart Association (AHA) issued their first expert consensus document on PAH. Published in both the April 28, 2009 issues of Circulation and the Journal of the American College of Cardiology, the guideline is intended to inform practitioners about the evolving areas of clinical practice and/or technologies widely available. The document also includes a table on prognostic factors for PAH in addition to diagnostic and treatment algorithms.
The Details of PAH
The prognosis of PAH is poor, with about a 15% mortality rate within 1 year on modern therapy. The ACCF/AHA guideline outlines predictors of a poor prognosis, including advanced functional class, poor exercise capacity, high right atrial pressure, significant right ventricular (RV) dysfunction, RV failure, low cardiac index, elevated brain natriuretic peptide, and the scleroderma spectrum of diseases. Idiopathic PAH (IPAH) appears to be the most common type of PAH; it’s more common in younger women who tend to present with nonspecific symptoms (eg, shortness of breath or fatigue). Familial PAH is often the result of a mutation in the BMPR2 gene, which is found in up to 25% of patients with IPAH. PAH is also associated with:
- Congenital heart disease.
- Connective tissue diseases.
- Drugs and toxins.
- Portal hypertension.
Patients with a family history of PAH, scleroderma spectrum of diseases, or portal hypertension who are undergoing evaluation for liver transplantation should undergo periodic screening. An echocardiogram is the most appropriate study to obtain in patients suspected of having PAH.
Diagnosis & Treatment
According to the consensus, the diagnosis of PAH requires confirmation with a complete right heart catheterization. The hemodynamic definition of PAH is a mean pulmonary artery pressure greater than 25 mm Hg; a pulmonary capillary wedge pressure, left atrial pressure, or left ventricular end-diastolic pressure of 15 mm Hg or lower; and a pulmonary vascular resistance greater than 3 Wood units.
Sodium restricted diet, graded aerobic exercise, appropriate vaccinations, and avoidance of pregnancy are considered the general treatment approaches for PAH. Patients suffering with IPAH should undergo warfarin anticoagulation treatment. Continuous IV epoprostenol is the preferred treatment option for critically ill patients with IPAH. Endothelin receptor antagonists and phosphodiesterase inhibitors have also been shown to improve exercise capacity in PAH. Recently, two phosphodiesterase inhibitors (sildenafil and tadalafil)—which were originally approved by the FDA for erectile dysfunction—have been approved for PAH to relax blood vessels in the lungs.
Careful monitoring is critical, and the ACCF/AHA document is the first to provide physicians with guidance on how often patients need to be seen. Even though many therapies are available for PAH, mortality rates are high, and patients should be followed closely.