Lowering Pulmonary Blood Pressure Linked to Better Survival in Study

Vanda Pinto, PhD avatar

by Vanda Pinto, PhD |

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A mean pulmonary artery pressure (mPAP) — blood pressure in the lungs — of less than 40 mmHg (millimeters of mercury) significantly increases the survival rate of patients with different subsets of pulmonary arterial hypertension (PAH), a study suggests.

The successful outcome was achieved with an intensive therapeutic approach and early intervention.

“To the best of our knowledge, this is the first report of the success of PAH treatment aimed at lowering mPAP with improvement of survival,” the researchers wrote.

The study, “Outcome of mean pulmonary arterial pressure-based intensive treatment for patients with pulmonary arterial hypertension,” was published in the Journal of Cardiology.

PAH is defined as a mPAP of 25 mmHg or higher, measured by right heart catheterization — a method that evaluates how well the heart is pumping and determines pressure in the heart and lungs.

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The disease can be caused by many other conditions, including viral infections, heart defects, liver disease, connective tissue diseases such as scleroderma and lupus, and certain medications, or it can be inherited (hPAH). When no apparent cause has been found, the disease is called idiopathic PAH (iPAH).

Despite the development of many therapies for PAH, the five-year survival rate is still only about 60% and better treatment strategies are needed to improve prognosis.

Researchers in Japan previously showed that the 10-year survival rate was 100% for treated patients with iPAH/hPAH who had a mPAP level lower than 42.5 mmHg. mPAP is also a known predictive biomarker of chronic thromboembolic pulmonary hypertension, a condition caused by blood clots forming in the blood vessels of the lungs.

The same research team assessed whether an intensive treatment regimen to lower mPAP to under 40 mmHg can improve the survival of patients with any PAH subtype.

A total of 43 PAH patients who were untreated or were receiving treatment for less than three months (median age, 63 years; 81% women) were recruited from September 2014 to August 2019.

The treatment strategy was based on the World Health Organization (WHO) functional class (a higher WHO functional class level indicates more severe symptoms), mPAP, and percent predicted diffusing capacity of the lung for carbon monoxide (%DLco) — which assesses the lungs’ capacity to transfer oxygen to blood cells.

Participants with an mPAP level lower than 40 mmHg and WHO functional class II received oral monotherapy. Those with an mPAP of 50 mmHg or higher or with WHO functional class IV were given combination therapy including parenteral (injection) prostacyclin. The remaining patients received oral combination therapy.

Those who did not respond well enough to the initial treatment within three months had their therapies upgraded — those on oral monotherapy started combination therapy and those on combination therapy were also given prostacyclin.

In the study, 19 patients had iPAH/hPAH and 12 had scleroderma, also called systemic sclerosis (SSc) — an autoimmune disease marked by scar tissue buildup in the skin and several internal organs. Seven patients had a connective tissue disease other than SSc, two had congenital heart disease, and three had portopulmonary hypertension, which is marked by PAH with elevated pressure in the portal vein that directs blood from the gastrointestinal tract to the liver. About 80% of patients were WHO functional class III or IV, the two most severe stages.

Treatment was started right after the PAH diagnosis. Mean follow-up period was 2.6 years and by the last visit, 10 patients were on oral monotherapy, 21 were on oral combination therapy, and 12 were on combination therapy as well as prostacyclin. No serious side effects caused by the PAH treatments were reported.

Findings showed that mPAP levels significantly improved from 45 mmHg to 24 mmHg and that 86% of patients reached an mPAP value of less than 40 mmHg. Also, mPAP dropped to under 25 mmHg in 47% of patients.

Reductions in mPAP were greater among those undergoing combination therapy with prostacyclin. Importantly, the cardiac index — an indicator of how well the heart is working — continued stable despite mPAP lowering.

Further analysis showed the 1-, 3-, and 5-year survival rates of all patients was 90.7%. Those who reached an mPAP of less than 40 mmHg had a significantly better survival rate than those who did not reach this goal (97.3% vs. 50%). No differences were found in survival rate between the several treatment regimens.

Having an mPAP level of less than 40 mmHg at follow-up was the independent predictor of survival, the researchers noted.

“This study demonstrated that PAH treatment aiming to achieve mPAP [under] 40 mmHg succeeded in most cases and resulted in excellent outcome of PAH patients,” the researchers wrote. “Early initiation of appropriate therapy depending on the baseline hemodynamics [blood flow] of each patient would be a key to achieve the therapeutic goal.”

The researchers said a multi-center study is needed to confirm the robustness of their treatment strategy and outcomes.