Pulmonary hypertension (PH) and the more severe pulmonary arterial hypertension (PAH) refers to an increase in the blood pressure in the lung vasculature. The narrowing of pulmonary arteries increases vasoconstriction and vascular resistance which causes increased pressure on the right side of the heart for pumping blood into the lungs efficiently and providing the required oxygen supply. If left untreated, it can lead to failure of the right side of the heart.
PAH and Scleroderma:
PAH is a late complication in 8-10% of Scleroderma (SSc) cases. People with cutaneous scleroderma are at greater risk of developing PAH than those with diffused cutaneous scleroderma. In both types, endothelial cells in the inner lining of the blood vessels are injured and the connective tissue is laid down inside the walls of these blood vessels. These tissues outgrow and constrict the walls of pulmonary vasculature which outgrow and constrict blood-flow. Microangiopathy with sclerosis is the key to PAH in Scleroderma. Patients with hepatic scleroderma have scarred lung tissues which reduces blood flow and consequently the oxygen levels – which increase pressure in the pulmonary arteries as a reflex.
The development of PAH in SSc patients can occur between 5 to 10 years after onset of SSc symptoms. In many cases, people who develop SSc at a later stage are affected with a more severe PAH.
Prognosis and Assessment:
Assessing the nature of PAH depends on the cardiopulmonary hemodynamic parameters of the patient. The mean pulmonary arterial pressure (mPAP), left ventricular end diastolic pressure, cardiac output, and pulmonary vascular resistance (PVR) should be measured accurately to detect the severity of the condition.
Shortness of breath, chest pain and dyspnea are the common symptoms of PAH with SSc. However the symptoms are generic, non-specific and may denote any cardiopulmonary complication, including pulmonary veno-occlusive disease, with similar effects. Differential and systematic diagnosis is very important. Early diagnosis is vital to decrease the chances of progression.
Pulmonary Function Tests (PFT) which measures the diffusing capacity of the lungs (ability of oxygen to move through the lungs and walls of the blood vessels and diffuse into the bloodstream) can be a vital indicator of PAH. Low values of 50-60% or less, indicate the need for further examination and possible right heart catheterization. Imaging techniques like pulmonary echocardiograms, chest x-rays, and non invasive tomography scans are accessory techniques which could help in zeroing in on PAH. Further confirmations towards a case of PAH can be had from the following hemodynamic values: mPaP of > 25 mmHg, a Tricuspid Regurgitant Jet (TRJ) value of > 3.4 m/s and Pulmonary Artery Systolic Pressure (PASP) of > 50 mmHg.
Clinical trials are underway to determine a fixed and systematic approach to a step-wise assessment of PAH, by eliminating other similar complications. Also, selective biomarkers are being accessed for possible therapeutic intervention. The new knowledge may help detect PAH development at earlier stages. One such biomarker is CXCL4, which is secreted by the Plasmacytoid dendritic cells (pDCs) circulating in blood during SSc.
Currently, no blood tests for CXCL4 detection exists. Screening and early detection of PAH may one day improve the current survival rate of one to three years.
Mortality associated with SSc with PAH is more in comparison with Idiopathic Pulmonary Arterial Hypertension (IPAH) because of the difference in severity of the two conditions and associated comorbidities with the former.
Treatment options specific to PAH include vasodilators that include prostacyclin analogs such as epoprostenol and treprostinil; phosphodiesterase 5 inhibitors, and endothelin receptor analogs that include bosentan and macitentan. The therapies have led to increased median survival rate by as much as 70% to 80%.
Further research into screening for biomarkers could help in better prognosis and treatment options at the early stage of the disease.