Chapter 427 Pulmonary Hypertension
427.1 Primary Pulmonary Hypertension
Pathophysiology
Primary pulmonary hypertension is characterized by pulmonary vascular obstructive disease and right-sided heart failure. It occurs at any age, although in pediatric patients the diagnosis is usually made in adolescence. In older patients, females outnumber males 1.7 : 1; in younger patients, both genders are represented equally. Some patients have evidence of either an immunologic disorder or a hypercoagulable state. Mutations in the gene for bone morphogenetic protein receptor-2 (BMPR-2, a member of the transforming growth factor-β receptor family) on chromosome 2q33 have been identified in patients with autosomal dominant familial primary pulmonary hypertension (known as PPH1). This genetic variant demonstrates a female preponderance and is found in 60% of patients with a family history and up to 25% of patients with sporadic disease. Other potential disease causing genes have been identified, including chromosome 2q31 (PPH2) and 12q13 (ALK1). Viral infection, such as with the vasculotropic human herpesvirus 8 (HHV8), has been suggested as a trigger factor in many patients. Diet pills, particularly fenfluramine, have also been implicated. Pulmonary hypertension is a common complication of sickle cell anemia and other hemolytic anemias. Pulmonary hypertension is associated with precapillary obstruction of the pulmonary vascular bed as a result of hyperplasia of the muscular and elastic tissues and a thickened intima of the small pulmonary arteries and arterioles. Atherosclerotic changes may be found in the larger pulmonary arteries as well. In children, pulmonary veno-occlusive disease may account for some cases of primary pulmonary hypertension. Before a diagnosis of primary pulmonary hypertension can be made, other causes of elevated pulmonary arterial pressure must be eliminated (chronic pulmonary parenchymal disease, persistent obstruction of the upper airway, congenital cardiac malformations, recurrent pulmonary emboli, alveolar capillary dysplasia, liver disease, autoimmune disease, and moyamoya disease). A classification system is noted in Table 427-1. Pulmonary hypertension places an afterload burden on the right ventricle, which results in right ventricular hypertrophy. Dilatation of the pulmonary artery is present, and pulmonary valve insufficiency may occur. In the later stages of the disease, the right ventricle dilates, tricuspid insufficiency develops, and cardiac output is decreased. Arrhythmias, syncope, and sudden death are common.
Table 427-1 REVISED WHO CLASSIFICATION OF PH
From ACCF/AHA: 2009 Expert consensus document on pulmonary hypertension: a report of the American College of Cardiology Foundation Task Force on Expert Consensus Documents and the American Heart Association developed in collaboration with the American College of Chest Physicians; American Thoracic Society, Inc.; and the Pulmonary Hypertension Association, J Am Coll Cardiol 53:1573–1619, 2009.
Diagnosis
Chest roentgenograms reveal a prominent pulmonary artery and right ventricle (Fig. 427-1). The pulmonary vascularity in the hilar areas may be prominent, in contrast to the peripheral lung fields in which pulmonary markings are decreased. The electrocardiogram shows right ventricular hypertrophy, often with spiked P waves. Echocardiography is used to screen for any congenital cardiac malformations. Doppler evaluation of the tricuspid valve, if insufficiency is present, will allow estimation of the right ventricular (and hence pulmonary arterial) systolic pressure.
