(Reuters Health) - Patients who need blockages cleared in their carotid arteries to reduce the risk of stroke may want to seek hospitals and doctors who do a lot of these procedures, a new research review suggests.

These delicate procedures on a major artery carrying blood to the brain carry a high risk for complications. The analysis found that hospitals and doctors with higher volumes had roughly half the rate of patient deaths and strokes compared to those with lower volumes.

The review, published in Annals of Surgery, pooled data from studies of carotid endarterectomy, in which surgeons remove plaque from the carotid artery, and carotid stenting, in which a mesh tube is placed in the artery to prop it open.

“Hundreds of thousands of both procedures are performed worldwide each year,” said senior author Dr. Gert de Borst, head of vascular surgery at University Medical Center in Utrecht, The Netherlands.

Several studies have used operator and hospital volume as reflections of quality of care, but reported associations between volume and outcomes have been inconsistent, de Borst said by email.

In this systematic review and meta-analysis, de Borst and colleagues analyzed studies comparing high- and low-volume hospitals and surgeons on the basis of patient deaths or strokes within 30 days of the procedures.

For carotid endarterectomy, the researchers looked at operator volume in 40 studies with more than 1.2 million patients and hospital volume in 49 studies with more than 4.2 million patients. High operator volume reduced the risk of death or stroke by about 50 percent. Similarly, high hospital volume reduced the risk by 38 percent.

For carotid artery stenting, they looked at operator volume in 11 studies with 103,000 procedures and hospital volume in 15 studies with 178,000 procedures. High operator volume reduced the risk of death or stroke by 57 percent, and high hospital volume reduced the risk by 54 percent.

There are several potential explanations, de Borst and colleagues note. One is that “practice-makes-perfect,” and more experience leads to fewer adverse events. Another theory holds that more patients may be referred to surgeons and hospitals with better outcomes, giving them higher volumes. Doctors and hospitals might also choose lower-risk patients, resulting in better outcomes.

“The relationship between operator volume and outcome may be just as much about selecting the right patients for the right therapy as it is about perfecting the technical aspects of the procedure or the care after the procedure,” said Dr. Herbert Aronow of the Lifespan Cardiovascular Institute in Providence, Rhode Island, who wasn’t involved in the analysis.

“Higher volume does not always mean higher quality,” he said by email. “It is possible to do something more often but still do it less well.”

The analysis lacked information about operator or hospital experience over time and about other factors that can influence outcomes. Also, definitions of high and low volumes varied in the studies, so researchers could only compare high versus low, not assess the volume at which outcomes began to diverge.

“It is not surprising that the study authors identified a relationship between volume and outcome,” Aronow added. However, “there was no particular volume threshold above which outcomes were better.”

Aronow suggested that operators and centers participate in national registries that monitor quality and volume, such as the American College of Cardiology Peripheral Vascular Intervention Registry and the Society for Vascular Surgery’s Vascular Quality Initiative.

“Patients should (ask about) procedural outcomes and patient experience when choosing an operator or hospital,” he said. “It is important not to focus solely on volume.”

SOURCE: bit.ly/2XX67sg Annals of Surgery, online March 14, 2019.