Is volume an accurate measure of success when it comes to mitral valve surgery?

Nearly 93% of the U.S. population lives in a hospital referral region with at least one medical center that performs 25 or more mitral valve repairs or replacements (MVRRs) each year, according to work published in JAMA Cardiology—but MVRR centers continue to suffer from significant geographical and patient-level disparities.

Volume is often regarded in healthcare as an important measure of an institution’s expertise, first author Sreekanth Vemulapalli, MD, an assistant professor of medicine at Duke University School of Medicine, and colleagues wrote, yet researchers have raised concerns that it might not be the most accurate measure of success.

Vemulapalli et al. said previous analyses and guidelines have suggested that operator and institutional metrics should both be implemented to ensure high-quality outcomes after mitral valve surgery—and that includes volume thresholds. But “implementation of volume requirements may decrease access to MV surgery to underserved populations,” the authors wrote.

The team undertook a cross-sectional, observational study of patients in the Society of Thoracic Surgeons Adult Cardiac Surgery Database who underwent any surgical MVRR procedure in the U.S. between July 2014 and June 2018. They looked at volume distribution of MVRR by both hospital and hospital referral region.

A total of 165,405 MVVRs were performed across 1,802 centers during the study period, 52.3% of which were MV repairs. A little over half of centers (53.1%) performed 25 or more MVRRs each year, and the geographic distribution of those centers differed greatly from centers that performed fewer than 25 MVRRs per year. Of 304 designated hospital referral regions in the U.S., 77.3% included at least one center that performed at least 25 MVRRs per year, representing accessibility to one or more higher-volume center for 296.4 million of 320.1 million U.S. residents.

Centers with the highest MVRR volume—those that logged at least 40 MVRRs annually—were accessible in 55.3% of hospital referral regions, representing accessibility to such centers for 259.8 million of 317.9 million of the U.S. population.

Vemulapalli and colleagues reported that more black and Hispanic patients received MVRRs in centers that performed 25 or more procedures per year versus lower-volume centers (22,984 patients vs. 3,227 patients, respectively), but the proportion was higher in lower-volume centers (15.5% of patients vs. 19% of patients, respectively). A lower percentage of Medicare and Medicaid patients received an MVRR at low-volume centers than higher-volume centers (0.3% vs. 32.3%, respectively), and the same was true for patients from rural zip codes.

 “To quantify the potential outcome of volume-based quality metrics or specialized center designations, this study presents the first data describing national hospital and patient demographics by institutional MVRR volume,” Vemulapalli and co-authors wrote, noting that while 92.6% and 81.7% of U.S. residents live within a referral region of at least one center that performs 25 or more or 40 or more MVRRs a year, major gaps still exist when it comes to patient race, rurality, geography and insurance status.

“This is consistent with prior literature for other common surgical procedures and suggests a balance must be struck between access and efforts to improve quality by instituting volume-based designations.”