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  • • Common signs and symptoms: dyspnea on exertion, syncope–near syncope, chest pain.
  • • Accentuated second heart sound, systolic murmur of tricuspid regurgitation.
  • • Evidence of right heart failure: elevated jugular venous pressure, hepatic congestion, ascites, peripheral edema.
  • • Decreased diffusing capacity, hypoxemia.
  • • Cardiomegaly and enlarged central pulmonary arteries on chest radiograph.
  • • Enlarged right-sided cardiac chambers on echocardiography.

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The pulmonary circulation is usually a low-pressure, low-resistance, high-capacitance circuit that can accommodate large increases in blood flow during exercise without significant increases in pressure. Pulmonary arterial hypertension (PAH) is defined as a resting pulmonary artery mean pressure >25 or >30 with exercise. Previously, PAH had been defined as primary pulmonary hypertension (PPH) or secondary pulmonary hypertension (SPH), but the more general classification of PAH has now been adopted. PAH is a diagnosis of exclusion and treatment of PAH targets the underlying cause when present.

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Approximately 300–1000 new cases of idiopathic PAH are diagnosed in the United States each year, although this may be increasing as a result of increased physician awareness. Women in the third and fourth decades of life are affected more frequently than men (1.7:1). Prior to development of effective treatment, median survival was estimated as 2.8 years from the time of diagnosis with a progressive decline in functional status until death.

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PAH can occur in isolation (idiopathic Primary) or can be associated with a number of other diseases including connective tissue diseases (especially scleroderma), advanced parenchymal lung disease with hypoxemia (ie, interstitial pulmonary fibrosis, emphysema), sleep-disordered breathing, congenital heart disease, advanced liver disease (portopulmonary hypertension), human immunodeficiency virus (HIV), and chronic thromboembolic disease. PAH has also been associated with the use of appetite-suppressive agents, amphetamines, and intravenous drugs. These diseases are all associated with increases in precapillary pulmonary arterial pressure. Other very rare lung diseases cause PAH by increasing postcapillary pulmonary venous pressure, including pulmonary venoocclusive disease and pulmonary capillary hemangiomatosis (Table 18–1).

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Table 18–1. Conditions Associated with PAH.
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PAH is a common complication of connective tissue diseases, especially scleroderma and mixed connective tissue disease. PAH can be found in as many as 60% of patients with the CREST variant of limited scleroderma (Calcinosis cutis, Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangectasias). The presence of PAH with ...

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