Pulmonary hypertension (PH) is the common broad term used to describe the elevated level of blood pressure in the lungs. PH is a pathophysiologic condition with various possible causes and this condition often accompanies severe heart or lung diseases. The symptoms of PH include shortness of breath, exhaustion, chest pain, shivers, pain, poor appetite, dizziness, fainting or syncope, swelling, and cyanosis. Earlier it is grouped as primary pulmonary hypertension and secondary pulmonary hypertension. If the cause of the disease is known, it is referred as primary pulmonary hypertension and if unknown, it is referred to as secondary. More often the secondary is identified as idiopathic pulmonary hypertension. Now, the classification is extended to five groups, according to WHO. Among the groups, group I is referred as Pulmonary Arterial Hypertension (PAH).
Is PAH The Same as Pulmonary Hypertension?
Pulmonary hypertension (PH) is different from the term Pulmonary Arterial Hypertension (PAH). PAH is a chronic and sporadic form of disease; and a group of pulmonary hypertension (PH). Precisely, it is referred as group I according to WHO. It is the disease of arteries of the lungs and may cause alteration in the function of right heart. It ultimately leads to death if not treated at earlier. Precisely, it is characterized by right-heart catheterization (RHC) presenting precapillary pulmonary hypertension with a mean pulmonary artery pressure (mPAP) of > 25 mmHg and a normal pulmonary artery wedge pressure (PCWP) of <15 mmHg. It is also characterized by vascular obstruction leading to progressive increase in vascular resistance.
Pulmonary Arterial Hypertension (PAH) is idiopathic i.e. the cause of the condition is unknown. It is an incurable disease that causes narrowed arteries. As a consequences, the flow of the blood is interrupted. Typically, it is an additional stress for the heart function. The heart function harder because of inability to pump the blood to the lungs because of narrowed arteries. The arteries tighten and heart becomes enlarged and inflexible. Many diseases like HIV infection, heart problems, high blood pressure in the hepatocytes, sickle cell anemia, certain nematode and parasite infection (Schistosomiasis), and connective tissue disorder (scleroderma, CREST syndrome, and lupus) can able to cause PAH. Sometimes rare disorder like pulmonary capillary hemangiomatosis and persistent pulmonary hypertension of the newborn can also be responsible. They do not respond to treatment and organ transplantation is the best choice.
Congenital heart disease (CHD) has significant part in triggering PAH and the prevalence of PAH associated with congenital systemic-to-pulmonary shunts in North America has been estimated between 1.6 and 12.5 cases per million adults Among these cases, 25 to 50% of this population affected by Eisenmenger’s syndrome (congenital cardiac defect).
Aminorex, dexfenfluramine, toxic rapeseed oil, benfluorex, dasatinib, st. john’s wort flower, pergolide, oral contraceptives, estrogen therapy, cigarette smoking are some of the drugs and toxins which can able to cause PAH. Among these, Aminorex, fenfluramine derivatives and toxic rapeseed oil represent the only identified “definite” risk factors for PAH. At present, methamphetamine use is measured as “very likely” risk factor for the development of PAH.
PAH is a serious genetic disorder that may pass to children. Heritable factor is relatively uncommon and only a less percentage of people carry this PAH gene. BMPR2, ALK1, SMAD9, caveolin 1, KCNK3 mutations, and EIF2AK4 mutations are some of the gene that promotes the function of pulmonary arterial endothelial cells. Any dysfunction or inhibition of these genes can cause abnormal rise in pulmonary arterial pressure.
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