treatment of pulmonary hypertension is determined by whether the ph is arterial, venous, hypoxic, thromboembolic, or miscellaneous. if it is caused by left heart disease, the treatment is to optimize left ventricular function by the use of medication or to repair/replace the mitral valve or aortic valve. patients with left heart failure or hypoxemic lung diseases (groups ii or iii pulmonary hypertension) should not routinely be treated with vasoactive agents including prostanoids, phosphodiesterase inhibitors, or endothelin antagonists, as these are approved for the different condition called primary pulmonary arterial hypertension. to make the distinction, doctors at a minimum will conduct cardiac catheterization of the right heart, echocardiography, chest ct, a six-minute walk test, and pulmonary function testing. using treatments for other kinds of pulmonary hypertension in patients with these conditions can harm the patient and wastes substantial medical resources.