ACC 2017: Aortic valve surgery underutilized in patients with chronic kidney disease

March 17, 2017 – Chronic kidney disease is independently associated with reduced utilization of aortic valve replacement in patients meeting criteria for the surgery, DCRI researchers find.

A large retrospective study involving over 78,000 patients, presented at the 2017 Scientific Sessions of the American College of Cardiology (ACC) by researchers from the DCRI, aimed to analyze the utilization of aortic valve replacement (AVR) in patients with chronic kidney disease (CKD).

“Valvular problems such as aortic stenosis happen more often in those with kidney disease than those who don’t have the dysfunction,” said Zainab Samad, MD, associate professor of medicine, assistant director for research, Duke Echocardiography Lab and lead author of the study.

To treat stenosis or abnormal narrowing of the aortic valve, surgical valve replacement is required. Although less invasive approaches such as a catheter procedure are possible in some cases, surgical aortic valve replacement is the gold-standard treatment for aortic stenosis, Samad said. Researchers analyzed data from the Duke Echo Lab database and linked it to hospital administrative billing and coding databases.

“The Duke Echo Lab database is one of the largest imaging databases in the world,” said Eric Velazquez, MD, professor of medicine and director of Echocardiography Labs and Cardiovascular Imaging at Duke (pictured). “It is unique in its depth of clinical data and outcomes, which allows us to look at clinical outcomes and find relationships with other labs and imaging tests,” he said.

Using the linked datasets, investigators compared patients with CKD who were indicated to get surgery for severe aortic stenosis with patients who did not have CKD but still were indicated to get surgery for aortic stenosis. They used statistical adjustment to nullify the differences in patient characteristics, such as comorbidities, to compare these patients.

The study found that out of 78,059 patients, 890 had severe aortic stenosis of which 84 percent met the criteria to receive aortic valve replacement. Of these patients, more than half had CKD. However, it was found that valve replacement surgery was performed more often in patients without CKD as compared to patients with CKD.

Patients who underwent aortic valve replacement were found to be older and had higher left ventricular ejection fraction as compared to those who did not undergo the surgery. They also had a lower euroSCORE – a risk model which allows the calculation of the probability of death after a heart operation. Even after the team adjusted for comorbidities, patients who had CKD underwent surgery less often than those who did not.

“The findings support what we see clinically, which is that physicians are less likely to refer patients with severe aortic stenosis for valve disease if they have underlying chronic kidney disease,” Velazquez said.

Even though it is known that fixing the aortic valve reduces mortality in patients with kidney disease, who already have a high rate of aortic stenosis, more in-depth analysis is needed to assess whether benefit of surgery outweighs the risks in these patients.

The study was partially funded by the Duke O’Brien Center for Kidney Research.

In addition to the DCRI’s Velazquez and Samad, other researchers included Joseph Sivak and Matthew Phelan of Duke University and Phillip Schulte of Mayo Clinic.