A database analysis in New York found that the mitral valve case volume of individual surgeons had a significant impact on patient outcomes following surgery.

Surgeons who had more experience with the procedure had better repair rates, survival rates and reoperation rates compared with less experienced operators.

Lead researcher Joanna Chikwe, MD, of the Icahn School of Medicine at Mount Sinai and the Stony Brook University Hospital in New York, and colleagues published their results online May 2 in the Journal of the American College of Cardiology.

The findings were simultaneously presented at the American Association for Thoracic Surgery Centennial meeting in Boston.

“This study adds further clarity to the American Heart Association and American College of Cardiology guidelines which already recognize that patients with degenerative mitral valve disease should be referred to experienced mitral surgeons whenever feasible,” David H. Adams, MD, the study’s senior author from the Icahn School of Medicine at Mount Sinai, said in a news release. “Our study found for the first time that individual surgeon volume was directly linked to freedom from reoperation and survival after one year in patients operated on for degenerative mitral valve disease.”

Guidelines in the U.S. and Europe recommend valve repair instead of valve replacement when possible, according to the researchers, although they mentioned mitral valve replacement remains common in patients with degenerative valve disease.

This study included 5,475 adults who underwent primary mitral valve operations in New York between 2002 and 2013 and were part of the Statewide Planning and Research Cooperative System, an all-payer, administrative database. The researchers reviewed all of the patient data before the operation and followed up patients for at least 12 months after the procedure. They also identified 313 surgeons from 41 institutions who met their eligibility criteria.

Of the patients, 66.8 percent underwent mitral valve repair and 33.2 percent underwent mitral valve replacement. Meanwhile, the surgeons performed a median of 10 mitral valve operations per year, while the median annual institutional mitral valve volume was 59 mitral valve operations. Surgeons who had an annual surgeon volume of less than 25 operations carried out 25 percent of the operations.

Patients who saw surgeons with less than 25 operations in a year were significantly more likely to present as urgent admissions and were more likely to have congestive heart failure, chronic kidney disease or chronic airway disease compared with patients who were operated on by surgeons with higher total annual surgeon volumes.

After the researchers adjusted for multiple variables, they found that the total annual surgeon volume was independently associated with the probability of mitral valve repair. They mentioned the probability of repair increased by 13 percent for every 10-case increment in total annual surgeon volume. Patients who were operated on by surgeons with a total annual surgeon volume of more than 50 operations were more than three times as likely to undergo mitral valve repair compared with those who were operated on by surgeons with an annual surgeon volume of 10 or fewer operations.

They also found a significant association between low surgeon volume and increased risk of mitral valve reoperation within 12 months of follow-up after mitral valve repair. The cumulative incidence of reoperation at 12 months was 1.3 percent for patients operated on by a surgeon with a total annual surgeon volume of 25 or more operations compared with 3.6 percent for patients operated on by a surgeon with total annual surgeon volume of less than 25 operations.

Further, they mentioned that the total annual surgeon volume was independently associated with improved one-year survival in the degenerative disease cohort. The one-year survival rates were 97.8 percent for patients operated on by surgeons performing more than 50 operations per year and 94.1 percent for patients operated on by surgeons performing 10 or fewer operations per year.

Although mitral repair was significantly associated with better survival compared with mitral replacement, the total annual surgeon volume remained a significant independent predictor among patients undergoing mitral replacement, according to the researchers.

“Our data provide additional strong support to the calls for systematically focusing experience in mitral valve surgery,” the researchers wrote. “Encouraging targeted referral, with the goal of concentrating surgical volume, should help to address the wide variation in mitral valve repair rates described in the United States and elsewhere, a variation that persists despite the significant benefits of mitral valve repair over replacement.”

The researchers cited a few limitations of the study, including that they relied on an administrative database that could be subject to inaccurate coding of patients’ diagnoses and procedures. They also mentioned that ICD-9-CM codes do not perfectly distinguish degenerative from ischemic mitral valve disease, although they mentioned they created a method of identifying patients with degenerative disease with high specificity but at the expense of sensitivity. In addition, they did not analyze each surgeon’s cumulative experience, and they were unable to adjust for referral bias.

“Based on observations in the state of New York, a minimum surgeon annual volume of 25 mitral operations is a reasonable target to improve clinical outcomes in patients with degenerative mitral valve disease,” the researchers wrote. “Prospectively acquired national data in patients undergoing mitral surgery for degenerative disease is needed to further define estimates of minimum surgeon volume targets to improve repair rates and clinical outcomes.”