ESSENTIALS OF DIAGNOSIS
Dyspnea, fatigue, chest pain, and syncope on exertion.
Narrow splitting of second heart sound with loud pulmonary component; findings of right ventricular hypertrophy and heart failure in advanced disease.
Electrocardiographic evidence of right ventricular strain or hypertrophy and right atrial enlargement.
Enlarged central pulmonary arteries on chest radiograph.
Elevated right ventricular systolic pressure on two-dimensional echocardiography with Doppler flow studies.
Pulmonary hypertension is a complex problem characterized by pathologic elevation in pulmonary arterial pressure. Normal pulmonary artery systolic pressure at rest is 15–30 mm Hg, with a mean pressure between 10 mm Hg and 18 mm Hg. The pulmonary circulation is a low-pressure, low-resistance system due to its large cross-sectional area, and it can accommodate significant increase in blood flow during exercise. The primary pathologic mechanism in pulmonary hypertension is an increase in pulmonary vascular resistance that leads to an increase in the pulmonary systolic pressure greater than 30 mm Hg or the mean pressure greater than 25 mm Hg.
The World Health Organization currently classifies pulmonary hypertension based on similarities in pathologic mechanisms and includes the following five groups.
Group 1 (pulmonary arterial hypertension secondary to various disorders): This group gathers diseases that localize directly to the pulmonary arteries leading to structural changes, smooth muscle hypertrophy, and endothelial dysfunction. This group includes idiopathic (formerly primary) pulmonary arterial hypertension, heritable pulmonary arterial hypertension, HIV infection, portal hypertension, drugs and toxins, connective tissue disorders, congenital heart disease, schistosomiasis, primary veno-occlusive disease, and pulmonary capillary hemangiomatosis.
Group 2 (pulmonary venous hypertension secondary to left heart disease): Often referred to as pulmonary venous hypertension or “post-capillary” pulmonary hypertension, this group includes left ventricular systolic or diastolic dysfunction and valvular heart disease.
Group 3 (pulmonary hypertension secondary to lung disease or hypoxemia): This group is caused by advanced obstructive and restrictive lung disease, including COPD, interstitial lung disease, pulmonary fibrosis, bronchiectasis, as well as other causes of chronic hypoxemia, such as sleep-disordered breathing, alveolar hypoventilation syndromes, and high-altitude exposure.
Group 4 (pulmonary hypertension secondary to chronic thromboembolism): This group consists of patients with pulmonary hypertension due to thromboembolic occlusion of the proximal and distal pulmonary arteries. (This classification no longer includes patients with non-thrombotic occlusion, such as tumors or foreign objects.)
Group 5 (pulmonary arterial hypertension secondary to hematologic, systemic, metabolic, or miscellaneous causes): These patients have pulmonary hypertension secondary to hematologic disorders (eg, chronic hemolytic anemia, myeloproliferative disorders, splenectomy), systemic disorders (eg, sarcoidosis, vasculitis, pulmonary Langerhans cell histiocytosis, neurofibromatosis type 1), metabolic disorders (eg, glycogen storage disease, Gaucher disease, thyroid disease), and miscellaneous causes (tumor embolization, external compression of the pulmonary vasculature, end-stage renal disease on dialysis).
The clinical severity of pulmonary hypertension is classified according to the New York Heart Association (NYHA) classification system, which was originally developed for heart failure but subsequently modified by the ...