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Pulmonary hypertension, an abnormal elevation in pulmonary artery pressure, may be the result of left heart failure, pulmonary parenchymal or vascular disease, thromboembolism, or a combination of these factors. Whether the pulmonary hypertension arises from cardiac, pulmonary, or intrinsic vascular disease, it generally is a feature of advanced disease. Because the causes of pulmonary hypertension are so diverse, it is essential that the etiology underlying the pulmonary hypertension be clearly determined before beginning treatment.

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Pathophysiology

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The right ventricle responds to an increase in pulmonary vascular resistance by increasing right ventricular (RV) systolic pressure to preserve cardiac output. In some patients, chronic changes occur in the pulmonary circulation, resulting in progressive remodeling of the vasculature, which can sustain or promote pulmonary hypertension even if the initiating factor is removed.

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The ability of the RV to adapt to increased vascular resistance is influenced by several factors, including age and the rapidity of the development of pulmonary hypertension. For example, a large acute pulmonary thromboembolism can result in RV failure and shock, whereas chronic thromboembolic disease of equal severity may result in only mild exercise intolerance. Coexisting hypoxemia can impair the ability of the ventricle to compensate. Studies support the concept that RV failure occurs in pulmonary hypertension when the RV myocardium becomes ischemic as a result of excessive demands and inadequate RV coronary blood flow. The onset of RV failure, often manifest by peripheral edema, is associated with a poor outcome.

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Diagnosis

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The most common symptom attributable to pulmonary hypertension is exertional dyspnea. Other common symptoms are fatigue, angina pectoris, syncope, near syncope, and peripheral edema.

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The physical examination typically reveals increased jugular venous pressure, a reduced carotid pulse, and a palpable RV impulse. Most patients have an increased pulmonic component of the second heart sound, a right-sided fourth heart sound, and tricuspid regurgitation (Chap. 227). Peripheral cyanosis and/or edema tend to occur in later stages of the disease.

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Laboratory Findings

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(Fig. 250-1) The chest x-ray generally shows enlarged central pulmonary arteries. The lung fields may reveal other pathology. The electrocardiogram usually shows right axis deviation and RV hypertrophy. The echocardiogram commonly demonstrates RV and right atrial enlargement, a reduction in left ventricular (LV) cavity size, and a tricuspid regurgitant jet that can be used to estimate RV systolic pressure by Doppler. Pulmonary function tests are helpful in documenting underlying obstructive airways disease, whereas high-resolution chest computed tomography (CT) is preferred to diagnose restrictive lung disease. Hypoxemia and an abnormal diffusing capacity for carbon monoxide occur with pulmonary hypertension of many causes. A perfusion lung scan is almost always abnormal in patients with thromboembolic pulmonary hypertension (Chap. 262). However, diffuse defects of a nonsegmental nature often can be seen in long-standing pulmonary hypertension in the absence of thromboemboli. Laboratory tests should include antinuclear antibody and ...

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