In both the rare primary form and the more common secondary form, a resting systolic pulmonary artery pressure (PAP) greater than 30 mm Hg and a mean PAP greater than 18 mm Hg indicates pulmonary hypertension.
Primary or idiopathic pulmonary hypertension is characterized by increased PAP and increased pulmonary vascular resistance, both without an obvious cause. This form is most common in women between ages 20 and 40 and is usually fatal within 3 to 4 years; mortality is highest in pregnant women.
Secondary pulmonary hypertension results from existing cardiac or pulmonary disease or both. The prognosis in secondary pulmonary hypertension depends on the severity of the underlying disorder.
The cause of primary pulmonary hypertension is unknown, but the tendency for the disease to occur in families points to a hereditary defect. It also occurs more commonly in those with collagen disease and is thought to result from altered immune mechanisms.
Signs and Symptoms
The signs and symptoms of pulmonary hypertension are subtle in the early stages of the disease and may not be apparent for months or even years. As the disease progresses, signs and symptoms become more noticeable. They include:
Arterial blood gas (ABG) studies reveal hypoxemia (decreased partial pressure of arterial oxygen).
Electrocardiography, in right ventricular hypertrophy, shows right axis deviation and tall or peaked P waves in inferior leads.
Cardiac catheterization discloses increased PAP, with a systolic pressure greater than 30 mm Hg. It may also show an increased pulmonary artery wedge pressure (PAWP) if the underlying cause is left atrier myxoma, mitral stenosis, or left ventricular failureotherwise, PAWP is normal.
Pulmonary angiography reveals filling defects in pulmonary vasculature such as those that develop with pulmonary emboli. Pulmonary function tests may show decreased flow rates and increased residual volume in underlying obstructive disease; in underlying restrictive disease, they may show reduced total lung capacity.
Radionuclide imaging allows assessment of right and left ventricular functioning, and open lung biopsy may be used to determine the type of disorder.
Echocardiography allows the assessment of ventricular wall motion and possible valvular dysfunction. It can also demonstrate right ventricular enlargement, abnormal septal configuration consistent with right ventricular pressure overload, and a reduction in left ventricular cavity size.
Perfusion lung scan may produce normal or abnormal results, with multiple patchy and diffuse filling defects that don't suggest pulmonary thrombo-embolism.
Oxygen therapy decreases hypoxemia and resulting pulmonary vascular resistance. For patients with right ventricular failure, treatment also includes fluid restriction, digitalis glycosides to increase cardiac output, and diuretics to decrease intravascular volume and extravascular fluid accumulation. Vasodilators and calcium channel blockers can reduce myocardial work load and oxygen consumption. Bronchodilators and beta-adrenergic agents may also be prescribed. A patient with primary pulmonary hypertension usually respond to epoprostenol (PGl2) as a continuous home infusion.
For a patient with secondary pulmonary hypertension, treatment must also aim to correct the underlying cause. If that isn't possible and the disease progresses, the patient may need a heart-lung transplant.
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