The acute vasodilator test should be performed in a hospital with experience in drug application and interpretation of results. A positive test is defined as a decrease in mean pulmonary artery pressure of at least 10 mmHg to an absolute value of 40 mmHg or less without a decrease in cardiac output. Patients who respond well to an acute vasodilator test may be treated with a calcium channel blocker. This is because calcium channel blockers are usually very effective in patients with a positive vasodilator test. They are orally administered and much less expensive than other drugs. However, calcium antagonists should not be used lightly and should always be used under the supervision of a pulmonary vascular specialist. After taking calcium antagonists, if they are effective, it is recommended to gradually increase the dosage of the drug according to blood pressure and heart rate and cardiac function. About three months or so can be seen in the pulmonary circulation specialist clinic.