Minimally invasive thoracoscopically-guided right minithoracotomy versus conventional sternotomy for mitral valve repair: the UK Mini Mitral multicentre RCT

Background The safety, effectiveness and cost-effectiveness of mitral valve repair via thoracoscopically guided minithoracotomy compared with conventional median sternotomy (Sternotomy) in patients with degenerative mitral valve regurgitation is uncertain and widely debated. Objectives To determine if Mini was more effective than Sternotomy in terms of physical functioning and associated return to usual activities and was cost-effective compared with Sternotomy. Design A pragmatic, multicentre, expertise-based, superiority, randomised trial. Participants Adults with degenerative mitral valve regurgitation undergoing mitral valve repair surgery. Setting Ten tertiary care institutions in the United Kingdom. Intervention Mini or Sternotomy mitral valve repair performed by an expert surgeon. Blinding Primary outcome measure [Short Form 36-item Health Survey, version 2 (SF-36v2) physical functioning score] was measured by an independent assessor, blinded to allocation. Echocardiographic findings were measured in a core laboratory, blinded to allocation. Outcome Measures Primary outcomes were physical functioning and associated return to usual activities measured by change from baseline in SF-36v2 physical function domain at 12 weeks following index surgery. The primary economic measure was incremental cost per quality-adjusted life-year over the year following surgery. Secondary outcomes included recurrent mitral regurgitation grade, physical activity and quality of life measured at time points to 1 year. Safety outcomes included death, repeat mitral valve surgery or heart failure hospitalisation up to 1 year. Results Between November 2016 and January 2021, 330 participants were randomised; 166 to Mini and 164 to Sternotomy. Of these, 309 underwent surgery and 294 reported the primary outcome. Thirty per cent were female. At 12 weeks, mean difference between groups in the change in SF-36v2 physical function T -scores was 0.68 (95% confidence interval −1.89 to 3.26). Valve repair rates (96%) were similar in both groups. Echocardiography demonstrated mitral regurgitation severity as none or mild for 92% of participants at 1 year in both groups. The composite safety outcome occurred in 5.4% (9/166) of Mini and 6.1% (10/163) of Sternotomy participants at 1 year. On average, Mini was more costly £29,424 (95% confidence interval 26,909 to 31,940) versus £27,397 (95% confidence interval 25,172 to 29,620) and more effective 0.81 quality-adjusted life-years (95% confidence interval 0.78 to 0.84) versus 0.78 (95% confidence interval 0.75 to 0.81) than Sternotomy. The adjusted incremental cost-effectiveness ratio was £74,863 per quality-adjusted life-year for the comparison between Mini and Sternotomy. Mini has a probability of < 50% of being cost-effective at the range of willingness-to-pay values considered. Limitations To minimise bias, SF-36v2 and all echocardiographic measures were independently assessed by personnel blinded to allocation. Expertise-based randomisation was important to address the limitations of previous studies; however, it is possible that it may have introduced potential confounders. Conclusions Mini is not superior to Sternotomy in recovery of physical function at 12 weeks. Mini achieves high rates and quality of valve repair and has similar safety outcomes at 1 year to Sternotomy. The balance of probabilities favoured Sternotomy as the preferred surgical procedure in the base-case analysis over the range of willingness-to-pay values society might consider worthwhile for a quality-adjusted life-year. Nevertheless, additional factors such as equity or patient preferences for one procedure over another may need to also be taken into account . Results provide high-quality evidence to inform shared decision-making and treatment guidelines. Future work Work is ongoing to disseminate findings and influence guidelines; patients have consented to longer-term follow-up. From an economics perspective, the currently available evidence shows that further research into patient preferences is important to inform the choice of surgical procedure. Trial registration This trial is registered as ISRCTN 13930454. Funding This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: 14/192/110) and is published in full in Health Technology Assessment ; Vol. 29, No. 55. See the NIHR Funding and Awards website for further award information.