The human body has two parallel blood circulation systems. Systemic circulation supplies blood to the entire body and pulmonary circulation supplies blood to the lungs. Pulmonary circulation is normally a low-pressure zone and the mean pulmonary artery pressure is 15mmHg in contrast to 70-110mmHg of systemic mean pressure.
Pulmonary Hypertension is said to exist when mean pulmonary artery pressure(mPAP) is more than 25mmHg. Pulmonary Hypertension(PH) can be caused by various mechanisms. Broadly it can be classified as:
- Pre-Capillary PH: is said to be present when the left heart is normal and PH occurs due to conditions like Primary Pulmonary Hypertension or Chronic Pulmonary Thromboembolism.
- Post –Capillary PH: is said to exist when PH is secondary to left heart disease.
PH was said to be an orphan disease and was largely unnoticed by the medical science. However since mid 20th-century lot of research has thrown light into the mechanism of disease, its clinical significance and many treatment options are now available.
It is now grouped into 5 groups.
GROUP 1 includes :
- Primary pulmonary hypertension
- Drug-induced pulmonary hypertension
- Pulmonary hypertension associated with connective tissue diseases
- Pulmonary hypertension associated with HIV
- Pulmonary hypertension associated with portal hypertension
- Pulmonary hypertension associated with congenital heart disease
GROUP 2: Pulmonary Hypertension caused by left-sided heart disease.
GROUP 3: Pulmonary Hypertension caused by respiratory diseases
GROUP 4: Pulmonary hypertension caused by Chronic Thromboembolism
GROUP 5: Pulmonary hypertension with unknown cause
Pulmonary hypertension usually presents with the sensation of breathlessness or chest pain. It can mostly be diagnosed by noninvasive investigations like ECG and Echocardiography, however, at times, Right Heart Catheterization is required.
Pulmonary Hypertension whenever presents, it implies worse prognosis. Many drugs have been developed for treatment like Calcium channel blockers, Prostanoids, Endothelin receptor antagonists, Phosphodiesterase inhibitors and recently soluble guanylate cyclase stimulators. However, none of the agents alter the course of the disease.