Importantly, right ventricular remodeling is associated with increased apoptosis; this is in contrast to pulmonary vascular remodeling which involves inhibition of apoptosis. Diagnosis
In terms of the diagnosis of pulmonary hypertension, it has five major types, and a series of tests must be performed to distinguish pulmonary arterial hypertension from venous, hypoxic, thromboembolic, or unclear multifactorial varieties. PAH is diagnosed after exclusion of other possible causes of pulmonary hypertension. Physical examination
A physical examination is performed to look for typical signs of pulmonary hypertension (described above), and a detailed family history is established to determine whether the disease might be heritable. A history of exposure to drugs such as benfluorex (a fenfluramine derivative), dasatinib, cocaine, methamphetamine, ethanol leading to cirrhosis, and tobacco leading to emphysema is considered significant. Use of selective serotonin reuptake inhibitors during pregnancy (particularly late pregnancy) is associated with an increased risk of the baby developing persistent pulmonary hypertension of the newborn. Echocardiography
If pulmonary hypertension is suspected based on the above assessments, echocardiography is performed as the next step. A meta-analysis of Doppler echocardiography for predicting the results of right heart catheterization reported a sensitivity and specificity of 88% and 56%, respectively. Thus, Doppler echocardiography can suggest the presence of pulmonary hypertension, but right heart catheterization (described below) remains the gold standard for diagnosis of PAH. Echocardiography can also help to detect congenital heart disease as a cause of pulmonary hypertension.
Instead, the left heart fails to pump blood efficiently, leading to pooling of blood in the lungs and back pressure within the pulmonary system. This causes pulmonary edema and pleural effusions. In the absence of pulmonary blood vessel narrowing, the increased back pressure is described as isolated post-capillary pulmonary hypertension (older terms include passive or proportionate pulmonary hypertension or pulmonary venous hypertension). However, in some patients, the raised pressure in the pulmonary vessels triggers a superimposed component of vessel narrowing, which further increases the workload of the right side of the heart. This is referred to as post-capillary pulmonary hypertension with a pre-capillary component or combined post-capillary and pre-capillary pulmonary hypertension (older terms include reactive or out-of-proportion pulmonary hypertension).In pulmonary hypertension due to lung diseases and/or hypoxia (WHO Group III), low levels of oxygen in the alveoli (due to respiratory disease or living at high altitude) cause constriction of the pulmonary arteries. This phenomenon is called hypoxic pulmonary vasoconstriction and it is initially a protective response designed to stop too much blood flowing to areas of the lung that are damaged and do not contain oxygen. When the alveolar hypoxia is widespread and prolonged, this hypoxia-mediated vasoconstriction occurs across a large portion of the pulmonary vascular bed and leads to an increase in pulmonary arterial pressure, with thickening of the pulmonary vessel walls contributing to the development of sustained pulmonary hypertension.