Ans. is 'c' i.e., alpha blockers Pulmonary hypertension General managementDiuretic therapy may be useful as it relieves pulmonary edema.Anticoagulant therapy is advocated for all patients.Specific managementCalcium channel blockersPatients who have substantial reductions in pulmonary arterial pressure in response to short acting vasodilators at the time of cardiac catheterization should be initially treated with calcium channel blockers.Endothelin receptor antagonistBostenan is a non-selective endothelium receptor antagonist, is an approved t/t for patients who are NYHA functional classes III and IV.Phosphodiesterase-5 inhibitorsSlidenafil is used for patients who are NYHA functional classes II and III.ProstacyclinsIloprost is a prostacyclin analogue used in PAH patients who are NYHA functional classes III and IV.Pulmonary circulation is unique in that it accommodates a blood flow that is almost equal to that of all the other organs of body but still maintains low pressure.The factors responsible for low pressure in pulmonary circulation (even with large volume of blood) are:-Larger diameter of pulmonary vessels due to thin wall of pulmonary artery and arterioles.Greater compliance (distensibility) of pulmonary vessels.Humoral factors responsible for maintaining pulmonary circulation:- NormallyNO causes vasodilation and | proliferation of smooth muscles by |in the cone, of cGMP - this increases the diameter of pulmonary vessels.PGI2 causes vasodilation and decreased proliferation of smooth muscles by increasing the cone, of cAMP -increase in the diameter of pulmonary vessels. Prostaglandin also decreases coagulation.Endothelin causes vasoconstriction and increase smooth muscle proliferation -| lumen of pulmonary vessels.- Normally the vasodilators and antiproliferative effects of NO and PGI2dominateIn Pulmonary hypertensionThere is | production of NO (and cGMP) and PGI2 (and cAMP), | vasoconstriction and proliferation of smooth muscles, | lumen of pulmonary vessel. Decreased production of PGI2 also causes increased coagulation.There is | production of endothelin, | vasoconstriction and smooth muscle proliferation, | lumen.Drug therapy in pulmonary hypertension is targeted at these growth factor pathways which are involved in the pathogenesis of pulmonary hypertension;Endothelium receptor antagonistBostenan is an endothelin receptor antagonist. It prevents endothelin mediated contraction of vessels. Phosphodiesterase-5 inhibitorsNitric oxide mediates its action through increasing cGMP concentration. Increased cGMP relaxes the vessels. cGMP is degraded by an enzyme phosphodiesterase-5 (PDE-5).- Sildenafil is a phosphodiesterase 5 inhibitor. It reduces the degradation of cGMP, thus causing vascular relaxation and reducing pulmonary hypertension.ProstacyclinsIn pulmonary hypertension, the level of prostacyclin is reduced.This causes pulmonary constriction as prostacyclin causes dilatation of pulmonary vessels.