Secondary Pulmonary Hypertension

The blood goes from right to left side of the heart through the pulmonary circulation, which is low-resistance, low-pressure circulation. The mean pulmonary vascular pressure is normally between 10 to 18 mm Hg. During exercise, this low-pressure circulation can accommodate high blood flow. The resistance in the pulmonary vasculature depends on the pressure in the pulmonary arteries, left atrial pressure, and cardiac output.The increase in resistance due to any cause that leads to an abnormal increase in pressures in the pulmonary artery can lead to pulmonary hypertension. Pulmonary hypertension is a persistent increase in the mean pulmonary arterial pressure of more than 25 mm Hg at rest and greater than 30 mm Hg during exercise on cardiac catheterization.Pulmonary hypertension (PH) can be classified as idiopathic/primary when the cause is unknown. Secondary pulmonary hypertension occurs due to underlying diseases or known risk factors, underlying heart and lung disease being the most common.