Boston, Mass. – Chronic kidney disease (CKD) is common among people newly diagnosed with pulmonary hypertension (PH), and kidney function may continue to decline as PH progresses, according to a large study.
Researchers found that several measures of abnormal blood flow and pressure in the heart and lungs were associated with poorer kidney function. However, elevated pressure on the right side of the heart emerged as the measure most consistently associated with reduced kidney function and the development of CKD over time.
Because CKD can affect outcomes for people with PH, the findings underscore the importance of routinely monitoring kidney function in these patients. According to the researchers, closer monitoring may also help clinicians identify opportunities to preserve kidney function and slow the progression of kidney disease.
The study, “Association Between Invasive Cardiac Hemodynamics and Kidney Function in Patients with Pulmonary Hypertension,” was published in Kidney360 by researchers in Germany and the U.S.
PH and kidney disease are closely connected
Pulmonary hypertension encompasses a group of disorders characterized by abnormally high blood pressure in the pulmonary arteries, which carry blood from the heart to the lungs. Over time, this increased pressure places additional strain on the right side of the heart and can eventually contribute to right-heart failure.
People with PH may also develop CKD, a progressive condition in which the kidneys lose their ability to adequately filter waste and excess fluid from the blood.
Previous research has shown that the combination of PH and CKD is associated with an increased risk of death. However, the factors that contribute to the development and progression of kidney disease in people with PH have remained poorly understood.
To investigate those factors, researchers analyzed data from COMPERA, a large registry of people with pulmonary hypertension. Their goal was to determine whether measurements of blood pressure and blood flow in the heart and lungs — collectively known as hemodynamic measures — were associated with kidney function and the subsequent development of CKD.
Study included more than 9,000 people with PH
The analysis included 9,195 people who had been diagnosed with PH within six months of enrolling in the registry. Their median age was 70, and slightly more than half were women.
About 52% had pulmonary arterial hypertension, although patients representing all PH groups were included.
During a median follow-up period of 2.5 years, approximately 44% of the patients died.
Overall, patients showed elevated pressure in the pulmonary arteries and increased resistance to blood flow through the lungs. They also had moderately reduced cardiac index, a measure of how much blood the heart pumps relative to a person’s body size.
Most participants had substantial limitations in physical activity. About 71% were classified as World Health Organization (WHO) functional class III, while 15% were in class IV. Patients in class IV experience severe limitations and may have PH symptoms even while at rest.
Reduced kidney function was already common at diagnosis
Kidney impairment was widespread at the beginning of the study.
About 45% of patients had mild to moderate kidney dysfunction, defined as an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m². The eGFR is a standard measure used to estimate how effectively the kidneys filter the blood.
Another 23% had more severe kidney impairment, with an eGFR below 45 mL/min/1.73 m².
Several abnormal hemodynamic measures were associated with a higher prevalence of CKD. These included higher pressure in the heart’s upper-right chamber, or right atrium; higher pulmonary artery pressure; greater resistance to blood flow through the lungs; and a lower cardiac index.
These findings suggested that more severe cardiovascular abnormalities in PH tended to occur alongside poorer kidney function.
Higher right-heart pressure emerged as key predictor
Kidney disease continued to develop during follow-up. A total of 1,859 patients developed stage 3a CKD, while 1,905 developed stage 3b CKD.
The incidence of stage 3a CKD was 16.3 cases per 100 patient-years, while stage 3b occurred at a rate of 10.9 cases per 100 patient-years. Put another way, among 100 similar patients followed for one year, about 16 would be expected to develop stage 3a CKD and approximately 11 would develop stage 3b disease.
In general, worse hemodynamic measurements were associated with lower eGFR values and therefore poorer kidney function.
However, when the researchers considered the different measurements together, higher pressure on the right side of the heart remained the factor most consistently associated with reduced kidney function and the development of CKD.
For every 5 mmHg increase in right-heart pressure, the risk of developing CKD increased by about 12%.
Congestion may help explain kidney decline
The researchers suggested that the relationship between elevated right-heart pressure and kidney dysfunction may be related to venous congestion and fluid buildup.
When pressure rises on the right side of the heart, blood can back up in the body’s veins, increasing pressure in organs such as the kidneys. This congestion may interfere with the kidneys’ ability to filter blood effectively and could contribute to progressive loss of kidney function.
The findings reinforce earlier research connecting elevated right atrial pressure and congestion with lower eGFR and a greater risk of CKD.
Understanding why kidney function declines in people with PH could ultimately help clinicians identify patients at greater risk and develop strategies to prevent or slow the progression of kidney disease.
The researchers emphasized that monitoring kidney function may therefore be particularly important in patients with elevated right-heart pressures.
They also cautioned that the study cannot establish that elevated right-heart pressure directly causes CKD. COMPERA is an observational registry, meaning unmeasured factors could have influenced the results. Differences in PH treatments and other aspects of patient care may also have affected kidney outcomes.
Even with these limitations, the findings highlight a strong relationship between right-heart pressure and kidney health in people with pulmonary hypertension and suggest that kidney function should be closely followed throughout the course of the disease.