A higher volume of mitral valve repair procedures is associated with lower mortality rates

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Vinay Badhwar

US national hospital- and surgeon-level inverse volume–outcome associations were observed for 30-day and one-year mortality after mitral valve surgery for primary mitral regurgitation, according to a study published in JAMA Cardiology. Authors Vinay Badhwar (Department of Cardiovascular and Thoracic Surgery, West Virginia University, Morgantown, USA) and colleagues say the findings may help to define access to experienced centres and surgeons for the management of primary mitral regurgitation.

The investigators explain that surgery for severe primary degenerative mitral regurgitation is recommended even in asymptomatic patients, provided optimal outcomes are achievable. However, say Badhwar et al, “despite recent advances in surgical and transcatheter mitral therapy, the contemporary volume–outcome association in mitral valve surgery has not been assessed nationally, nor have rigorous data been provided to assist in defining a mitral reference center. This important information has the potential to shape quality improvement, patient-physician referral patterns, and resource allocation regarding the management of primary mitral regurgitation.”

The multicentre cross-sectional observational study aimed to assess national 30-day and 1-year outcomes of mitral valve surgery, and define the hospital- and surgeon-level volume–outcome association with mitral valve repair or replacement (MVRR) in patients with primary mitral regurgitation. The researchers used the Society of Thoracic Surgeons Adult Cardiac Surgery Database to identify patients undergoing isolated MVRR for primary mitral regurgitation in the USA. Operative data were collected from 1 July 2011 to 31 December 2016, and analysed from 1 March to 1 July 2019, with data linked to the Centers for Medicare and Medicaid Services.

The primary outcome was 30-day in-hospital operative mortality after isolated MVRR for primary mitral regurgitation. Secondary outcomes were 30-day composite mortality plus morbidity (any occurrence of bleeding, stroke, prolonged ventilation, renal failure, or deep wound infection), rate of successful mitral valve repair of primary mitral regurgitation (residual mitral regurgitation of mild [1+] or better), and one-year mortality, reoperation, and rehospitalisation for heart failure.

In all, 55, 311 patients, 1,094 hospitals, and 2,410 surgeons were identified. Increasing hospital and surgeon volumes were associated with lower risk-adjusted 30-day mortality, lower 30-day composite mortality plus morbidity, and a higher rate of successful repair. The lowest versus highest hospital volume quartile had higher one-year risk-adjusted mortality (hazard ratio [HR] 1.61, 95% confidence interval [CI] 1.31–1.98), but not mitral reoperation (odds ratio [OR] 1.51, 95% CI 0.81–2.78) or hospitalisation for heart failure (HR 1.25, 95% CI 0.96-1.64). The surgeon-level one-year volume-outcome associations were similar for mortality (HR 1.6, 95% CI 1.32–1.94) but not significant for mitral reoperation (HR 1.14, 95% CI 0.6–2.18) or hospitalisation for heart failure (HR 1.17, 95% CI 0.91–1.5).

The authors write: “For the surgical management of primary mitral regurgitation, this national clinical registry analysis provides … documentation that hospital and surgeon volume–outcome associations exist for rates of successful mitral valve repair and one-year mortality, but not for one-year mitral valve reoperation or one-year hospitalisation for heart failure. These findings may assist efforts to define access to experienced centres and surgeons for primary MR or complex primary MV disease.”

They add: “The data generated from this analysis may provide further support for efforts to regionalise mitral valve surgery for primary mitral regurgitation, especially for patients who may be asymptomatic but meet guideline criteria for mitral valve repair, in whom the pathology may be deemed complex, or for patients seeking innovative mitral valve repair approaches, such as minimally invasive or robotic surgery. Such cases may be better suited to experienced mitral valve surgeons and centres based on volume. But importantly, higher volumes centres and surgeons in the United States are far more accessible than previously recognized.”

Badhwar et al concede the “inherent limitations of any analysis of a large clinical registry”, and that the “ascertainment of aetiology may be imprecise”. In addition, they say, the surgeon volume thresholds reported may be conservative.


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