Surgeons performing lower volumes of mitral valve operations each year are significantly more likely to replace, rather than repair, mitral valves in patients with degenerative disease compared to those who perform higher volumes, according to research presented May 2 at the American Association for Thoracic Surgery's annual meeting in Boston, MA, and simultaneously published in the Journal of the American College of Cardiology.

Joanna Chikwe, MD, and colleagues examined 5,475 patients with degenerative disease who underwent primary mitral surgery between 2002 and 2013. A total of 3,660 (66.8 percent) patients underwent mitral valve repair and 1,815 patients (33.2 percent) underwent mitral valve replacement. Median follow-up time was 6.8 years. Surgeons included in the study performed a median of 10 mitral valve operations per year.

Results showed that the repair rate for primary mitral procedures for any cause was 55 percent. In the degenerative subgroup, the mean repair rate was 66.8 percent, ranging from 48.4 percent for surgeons with total annual volumes less than 11 mitral cases to 77.2 percent for surgeons with total annual volumes of more than 50 mitral cases. After multivariable adjustment, total annual surgeon volume was independently associated with the probability of mitral repair; the chance of repair increased by 13 percent for every 10-case increment in total annual surgeon volume. Compared with patients operated on by surgeons with a total annual surgeon volume of 10 cases or less, patients operated on by surgeons with a total annual surgeon volume of more than 50 cases were more than three times as likely to undergo mitral repair. There were improved mitral repair rates and survival in the patients of lower-volume surgeons if they operated at institutions where there was a surgeon performing more than 50 total mitral cases annually with a >70 percent degenerative repair rate.

The researchers conclude that a total annual surgeon volume less than 25 cases was not only associated with lower mitral valve repair rates, but also was associated with increased one-year mortality and mitral valve reoperation, and that improvements in repair rates, survival and freedom from reoperation continued with increasing surgeon case volume. They write that the data provides strong support to the calls for systematically focusing experience in mitral valve surgery. They conclude that encouraging targeted referral, with the goal of concentrating surgical volume, should help to address the wide variation in mitral repair rates.

"With this important study, Chikwe et al., address the who and where in the treatment of degenerative mitral valve disease," write Marc Gillinov, MD, and colleagues in an accompanying editorial comment. "Surgeons (ideally, teams of surgeons) with a special focus, who have developed expertise via training and operative volume, should operate on patients with degenerative mitral valve disease in hospitals with appropriate infrastructure. This tenet should apply even to the 'simple' P2 prolapse. We recognize that this statement will generate controversy, as it challenges the status quo."

Keywords: Cardiac Surgical Procedures, Follow-Up Studies, Goals, Heart Valve Diseases, Mitral Valve, Probability, Prolapse, Referral and Consultation, Reoperation, Research, Research Personnel, Surgeons, Thoracic Surgery

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