Conclusion
This study evaluated characteristics associated with mitral valve repair rates and 30-day mortality for degenerative MR, focussing on the impact of procedural caseload. It conclusively demonstrates that within the Australian cohort, annual surgeon caseload was strongly associated with repair rate, with hospital caseload less strongly but also associated with higher repair rate. Surgeons with an annual volume of >20 demonstrated the highest odds of repair, approximately four times that of surgeons performing ≤5/year. Repair rate for these higher volume surgeons was approximately 80%, compared with approximately 57% in the lowest volume category. A threshold of >10 procedures/year per surgeon was defined as a statistically significant cut-off to improve the odds of repair, though above this threshold, greater volume was generally associated with higher odds of repair, particularly >20/annum. For hospitals, the same threshold of >10 procedures was statistically significant for improving the odds of repair, though the caseload above this cut-off did not appear to matter. Repair rate for hospital caseload ≤10/annum was 52%, climbing to approximately 71% for hospitals above this threshold. This study, therefore, demonstrated that to maximise the likelihood of repair for degenerative MR, individual hospitals and surgeons should be performing more than 10 such procedures annually.
Additionally, this study demonstrated that in the Australian cohort, wherein unadjusted 30-day mortality rate for repair was 1.18% and 2.75% for replacement, mitral valve repair conferred a significant 30-day survival advantage when adjusting for age, gender and procedural volume. Although mortality was not significantly affected by surgeon and hospital procedural volume, unadjusted data nonetheless suggests that higher volumes may reduce mortality rates.
Finally, this data provided support for the consideration of mitral valve surgery as a subspecialty within cardiac surgery. Both for higher-complexity degenerative pathology, as well as for the asymptomatic patient in whom the guideline expected likelihood of durable repair must be high or in excess of 95% [2,3] such patients should be considered for referral to higher volume surgeons. This may therefore require surgeon inter-referral, as well as encouragement of such referral patterns by Cardiologists to mitral subspecialist surgeons.