CHICAGO – A total annual surgeon volume of fewer than 25 operations was associated with increased 1-year mortality and reoperation rates, according to a study presented at the 2017 American Association for Thoracic Surgery Centennial.

Improvements in repair rates, survival, and freedom from reoperation increased with increasing surgeon case volumes, Joanna Chikwe, MD , and her colleagues at the Icahn School of Medicine at Mount Sinai, New York, stated.

The study analyzed 5,475 adult patients who underwent primary mitral valve operations (replacement or repair) in New York state between Jan. 1, 2002, and Dec. 31, 2013. Patients in the Statewide Planning and Research Cooperative System were identified using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedure codes 35.23 and 35.24 for replacement and ICD-9-CM codes 35.12 and 35.33 for repair.

The researchers compared repair rates, long-term survival, and risk of postrepair reoperation in patients with degenerative disease according to total annual surgeon volume, which was defined as any mitral valve operation for any cause during the study period. The study was simultaneously published in the Journal of the American College of Cardiology ( 2017 May 16;69[19]:2397-406 ).

Mitral valve repair is the preferred treatment, compared with valve replacement, for the treatment of severe mitral valve regurgitation in patients who have degenerative valve disease with mitral valve prolapse, and both U.S. and European guidelines strongly recommend valve repair whenever possible, according to Dr. Chikwe and her colleagues.

But, “mitral valve replacement unfortunately remains relatively common in patients with degenerative valve disease,” they stated.

A total of 313 surgeons from 41 institutions met the study eligibility criteria, according to the researchers. They performed a median of 10 mitral valve operations per year (range, 1-230). The median annual institutional mitral valve volume was 59 mitral valve operations, ranging from a minimum of 6 to a maximum of 310 operations. Repair rates for primary mitral valve operations for any cause at all 41 institutions varied from 15% to 83%, and repair rates for degenerative mitral valve operations varied from 25% to 100%.

In the study cohort, surgeons with a total annual volume of less than 25 operations carried out 25% of procedures.

After multivariable adjustment, total annual surgeon volume was independently associated with the probability of mitral valve repair. The chance of repair increased significantly by 13% for every 10-case increment in total annual surgeon volume (P less than .001).

In addition, compared with patients operated on by surgeons with a total annual surgeon volume of 10 or fewer operations, patients operated on by surgeons with a total annual surgeon volume of greater than 50 operations were more than three times as likely to undergo mitral valve repair rather than replacement.

A total annual surgeon volume of less than 25 operations was associated with lower mitral valve repair rates and with increased 1-year mortality and mitral valve reoperation rates. Improvements in repair rates, survival, and freedom from reoperation increased with increasing surgeon case volumes.

After 1 year of repair or replacement, the actuarial survival of patients with degenerative mitral valve disease who were operated on by surgeons performing greater than 50 operations per year was 97.8%, compared with 94.1% for patients operated on by surgeons performing less than or equal to 10 operations a year.

Compared with replacement, mitral repair was significantly associated with better survival, but total annual surgeon volume still remained a significant independent predictor (P less than .001). In addition, for those patients who underwent mitral valve repair, total annual surgeon volume was a significant independent predictor of late death.

The results are important, the investigators noted, given that the median number of mitral valve operations performed annually by individual surgeons in the United States was five, according to an analysis of the Society of Thoracic Surgeons database – and that, in New York state, most surgeons actually performed less than one mitral operation per month.

There were significant differences seen in the patient characteristics across surgeons’ case volume groups. The prevalence of congestive heart failure was significantly higher in patients operated on by surgeons with lower volumes, and the proportion of patients undergoing urgent surgery was also significantly higher for lower-volume surgeons.

“This leads to a double jeopardy, where sicker patients are adversely affected by the lower repair rates and poorer outcomes seen with lower-volume surgeons, and it underscores the need to refer the highest-risk patients to high-volume surgeons,” said Dr. Chickwe and her colleagues.

However, “even among high-volume surgeons, there was an observed variability of degenerative disease repair rates, ranging from 19% to nearly 100%,” they added. “This finding reflects that surgeon volume is not the only factor for better outcomes, and it emphasizes the need for more transparency of surgeon-related factors and outcomes of degenerative mitral valve surgery for patients and referring cardiologists.

“Considering that there was an incremental improvement in survival and probability of repair with increasing volume over 25 operations, one could make the argument that a minimum volume target of 50, or even more, operations would be optimal,” the researchers noted. “Developing more very high-volume surgeons experienced in mitral valve repair would likely be particularly beneficial for patients with complex but repairable mitral valve disease, and for asymptomatic patients whose repair feasibility would optimally approach 100%.”

Dr. David Adams is the national coprincipal investigator of the Core Valve United States Pivotal Trial, supported by Medtronic. Dr. Chikwe received speaker honoraria from Edwards Lifesciences. The other coauthors had no disclosures to report.