How is pulmonary hypertension classified?

Etiology: primary vs. secondary. Primary pulmonary hypertension is not associated with any of the known causes of pulmonary hypertension. Secondary pulmonary hypertension is due to an underlying disease.

Location: precapillary vs. post-capillary. Precapillary pulmonary hypertension is caused by increased resistance to flow in the pulmonary arteries and arterioles. Post-pulmonary hypertension is caused by back pressure from the left heart and/or increased resistance to flow in the pulmonary veins.

Duration: acute vs. chronic. Acute pulmonary hypertension is caused by such things as thromboembolism or adult respiratory distress syndrome. Most other forms of pulmonary hypertension are chronic.

Histopathology: plexiform vs. thrombotic. The plexiform lesion is characterized by focal medial disruption and aneurysmal dilatation, with formation of a complex proliferative tuft of intimal cells and channels. Thrombotic histopathology is characterized by intravascular thrombus.

What should the clinical evaluation for possible pulmonary hypertension include?

As always, the evaluation begins with a thorough history and physical examination. Possible causes of secondary pulmonary hypertension, as listed in the accompanying figure, should be addressed in the history. In addition, travel to or residence in an area endemic for shistosomiasis should be considered. All patients should receive a basic initial screening evaluation, consisting of chest x-ray, electrocardiogram, and echocardiogram.

Patients with no clues to the etiology on history or physical examination are given a broad detailed evaluation; patients with a suspected secondary cause receive a focused evaluation to verify that etiology, followed by the broad evaluation if necessary. In addition to these tests, arterial blood gases and pulmonary angiography may be indicated. If undertaken, pulmonary angiography should be performed by someone experience in working with pulmonary hypertension patients. See figure.

List some causes of secondary pulmonary hypertension:

Recurrent pulmonary emboli Chronic exposure to high altitude Chronic lung diseases, especially COPD Sleep apnea

Obesity with hypoventilation Sickle cell disease Schistosomiasis Left heart failure

Mitral valve disease, especially stenosis Pulmonary veno-occlusive disease Collagen vascular disease.

How is pulmonary hypertension classified? Photo Gallery

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