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 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. 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