Mitral Valve Surgery Volume vs. Outcomes

Study Questions:

For patients with degenerative mitral regurgitation, is there a relationship between surgeon case volume and repair rates and clinical outcomes?

Methods:

A mandatory New York State database was used to identify (by a process of excluding patients with infective endocarditis, rheumatic disease, congenital disease, coronary artery disease/myocardial infarction, and cardiomyopathy) 5,475 patients with presumed degenerative disease who underwent mitral valve surgery between 2002 and 2013. Mitral repair rates, mitral reoperations within 12 months of repair, and survival were analyzed using multivariable Cox modeling and restricted cubic spline function.

Results:

Median annual surgeon volume of any mitral cases was 10 (range 1-230), with a mean repair rate in the whole cohort of 55% (n = 20,797 of 38,128). In the subgroup of patients with presumed degenerative mitral valve disease, the mean repair rate was 67% (n = 3,660 of 5,475), ranging from 48% (n = 179 of 370) for surgeons with total annual volumes ≤10 mitral cases to 77% (n = 1,710 of 2,216) for surgeons with total annual volumes ≥51 mitral cases (p < 0.001). Higher total annual surgeon volume was associated with increased degenerative mitral repair rates (adjusted odds ratio [OR], 1.13 for every additional 10 mitral cases; 95% confidence interval [CI], 1.10-1.17, p < 0.001); a steady decrease in reoperation risk up to 25 total mitral cases annually; and improved 1-year survival (adjusted hazard ratio, 0.95 for every additional 10 cases; 95% CI, 0.92-0.98; p = 0.001). For surgeons with total annual volume ≤25 mitral cases, repair rates were higher (63.4%, n = 180 of 282) if they operated in the same institution as a surgeon with total annual mitral volumes ≥50 and degenerative mitral repair rates ≥70%, compared with those operating in the other institutions (51.3%, n = 580 of 1,130; adjusted OR, 1.79; 95% CI, 1.24-2.60; p < 0.001).

Conclusions:

The authors concluded that individual surgeon volume is a determinant of not only mitral repair rates, but also freedom from reoperation and survival; and that these data support the guideline recommendation of referral of mitral surgery in order to improve outcomes in patients with degenerative mitral disease.

Perspective:

Repair rates of degenerative mitral regurgitation are highly variable. This study, derived from a large administrative database (and with all the associated limitations), again suggests that surgeon volume of mitral valve cases influences repair rates and clinical outcomes. Establishing reference centers for mitral valve intervention, in order to “concentrate” patients and allow higher per-surgeon volumes, probably is in the best medical interest of patients.


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