Authors' objectives: 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. 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. Mitral regurgitation (MR) is a condition of one of the valves in the heart where the valve becomes leaky, allowing blood to flow the wrong way. The most common type of MR is degenerative mitral valve regurgitation (DMR). Patients usually become short of breath, and when it becomes severe, the best treatment is heart surgery to repair the valve. Conventional mitral valve repair (MVr) surgery via median sternotomy (Sternotomy) is routinely performed via full sternotomy where the surgeon cuts through the breastbone (sternum), enabling easy access to the heart, flexibility in myocardial protection strategies, multiple ways of accessing the mitral valve and eases de-airing to prevent air emboli that cause cerebrovascular accidents. The sternum is immobilised using wires, bands or plates to allow sternal union around 12 weeks after surgery. The invasiveness of this approach limits physical activity, delays a rapid return to pre-surgery physical function levels and increases the risk of postoperative complications. A video-assisted thoracoscopically guided, minimally invasive approach to mitral repair (Mini), performed via a 4- to 7-cm lateral thoracotomy, completely avoiding sternotomy, is increasingly demanded by patients who believe that it accelerates recovery and improves cosmesis. Surgeons who favour this approach argue that it reduces the time taken to recover physical function after surgery, postoperative complications and costs by reducing hospital stay. Uptake of Mini is low worldwide, though there are a few countries who have higher rates of uptake. The main reason is the lack of clear and definitive evidence from robustly designed and adequately powered trials confirming equivalent or superior benefits of this approach relative to sternotomy; in a review of the literature performed prior to the trial, only one single-centre randomised trial, including 140 participants, was identified. There are concerns that the relative complexity of Mini may increase the risk of adverse events (AEs), particularly vascular injuries and stroke, and uncertainty around the ability to repair complex valve lesions through the Mini incision. Consequently, the best surgical approach for MVr is widely debated. A consensus document from the International Society of Minimally Invasive Cardiac Surgery and guidelines have recommended a multicentre randomised controlled trial (RCT) to assess the effectiveness and safety of Mini versus Sternotomy MVr. The UK Mini Mitral Trial compared the benefits and risks of the two procedures and specifically aimed to determine if the physical functioning (PF) and associated return to usual activities were superior after the Mini approach and if the Mini approach was cost-effective compared with Sternotomy. The main objective was to determine if minimally invasive surgery was more effective than conventional sternotomy in terms of PF and associated return to usual activities, measured by the change in the Short Form 36-item Health Survey, version 2 (SF-36v2) PF scale 12 weeks following surgery. The primary economic objective was to understand if the minimally invasive surgery was more cost-effective than the conventional sternotomy measured in incremental cost per quality-adjusted life-year (QALY) over the year following surgery.

Authors' results and conclusions: 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. 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. From November 2016 to January 2021, 1167 patients were screened, of whom 330 were enrolled and randomised to Mini (n = 166) or Sternotomy (n = 164). Of these, 309 (94%) participants underwent surgery in the trial; 147 of 163 (90%) participants were randomised to Sternotomy and 162 of 166 (98%) were randomised to Mini. The two groups were well matched for demographic, clinical and echocardiographic characteristics at the baseline. Mean age was 67 years and 100 (30%) were women. Mini and Sternotomy surgeons had performed a median of 86 and 162 procedures, respectively, prior to enrolling participants; all met the expertise criteria. The MVr was performed in 296 of 309 participants; repair rates were similar in both groups (95.6% in Mini and 97.3% in Sternotomy) and were higher than the current national repair rate of 60%, most likely due to the expertise of the surgeons. Average CBP and aortic cross-clamp times were longer in the Mini than in the Sternotomy (32.9 minutes longer 95% CI 19.46 to 46.34 and 11.42 minutes longer 95% CI 5.21 to 17.63, respectively). These differences were expected, given the additional complexity of the Mini procedure, and did not result in differences in complications, including death, reoperation, hospitalisation for heart failure or stroke to 1 year. Primary outcome The primary analysis did not demonstrate superiority of Mini versus Sternotomy with a mean difference in SF-36v2 PF T-scores 0.68 (95% CI −1.89 to 3.26) between groups. These results were consistent across the per-protocol and as-treated analyses and also the sensitivity analyses for the imputation of missing data. The change from baseline in SF-36v2 PF T-scores at 12 weeks was 7.62 (95% CI 5.49 to 9.78) in the Mini group and 7.20 (95% CI 5.04 to 9.35) in the Sternotomy group. The change from baseline in the SF-36v2 PF percentage scale at 12 weeks was 14.97 (95% CI 10.79 to 19.23) in the Mini group and 14.14 (95% CI 9.90 to 18.37) in the Sternotomy group. The primary outcome was reanalysed on the percentage scale and the results were consistent with the standardised T-score. We also found no evidence of any interactions in any subgroup analyses. This multicentre, expertise-based RCT of Mini versus Sternotomy MVr demonstrated no difference between the groups for the primary outcome of mean change in SF-36v2 PF T-score from baseline to 12 weeks. There was no evidence of differences across all pre-specified subgroup and sensitivity analyses. The cost-effectiveness analysis found that, on average, Mini was more costly and more effective compared with Sternotomy. Mini had < 50% chance of being cost-effective at all values for society’s WTP for a QALY considered. These results were consistent across sensitivity analysis, although results were sensitive to changes in the assumptions made around the cost parameter. Although repair techniques were at the discretion of the operating surgeons and differed in the two procedures, high rates of valve repair and low rates of recurrent MR were observed in both groups, providing important information to a clinical community concerned about repair rates and durability of repair using the Mini approach. CPB times were longer with Mini, but postoperative complications and AEs were similar. There was no difference between the two groups with respect to the safety outcomes to 1 year. Time spent undertaking MVPA was higher among participants receiving Mini at 6 weeks, although the treatment effect was small and with no evidence of a difference at 12 weeks. There was also no evidence of differences in serial QoL scores and PF T-scores. Reduced length of hospital stay and increased likelihood of early discharge in the Mini group are important findings for patients who often prefer to return home and also for the NHS, as this increases the capacity to treat other patients. This trial confirms for the first time in a multicentre RCT that Mini MVr achieves high-quality and durable valve repair up to 1 year with similar safety outcomes to Sternotomy, but at 12 weeks, the change in physical function from baseline was not significantly different. Although the balance of probabilities favours sternotomy over Mini over the follow-up additional factors, such as equity or patient, preferences for one procedure over another may also need to be taken into account when choosing which surgery to offer a patient.

Authors' methods: A pragmatic, multicentre, expertise-based, superiority, randomised trial. Adults with degenerative mitral valve regurgitation undergoing mitral valve repair surgery. Ten tertiary care institutions in the United Kingdom. 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. The UK Mini Mitral was a multicentre, superiority, expertise-based RCT of Mini (intervention) versus Sternotomy (control) in patients undergoing MVr, conducted across 10 UK NHS centres. Participants were adults aged ≥ 18 years, having DMR requiring MVr. All participants’ conditions were discussed by a mitral valve heart team, where the diagnosis of DMR was made and suitability for MVr was confirmed. Participants were included if they provided written consent and were suitable for surgery and cardiopulmonary bypass (CPB); concomitant surgery for atrial fibrillation (AF) or tricuspid valve repair was allowed. Exclusions included concomitant coronary or aortic valve surgery and redo surgery, planned mitral valve replacement, acute infective endocarditis or impaired mobility that would preclude SF-36v2 completion. Eligible participants were randomised in a 1 : 1 ratio to MVr via Mini or Sternotomy. A minimisation scheme accounted for the baseline SF-36v2 PF score, presence of AF and presence and severity of tricuspid regurgitation. The primary outcomes were PF and associated return to usual activities measured by the change from baseline in SF-36v2 PF scale at 12 weeks following index surgery. The primary economic outcome was cost-effectiveness at 1 year, measured as incremental cost per QALY derived from responses to the EuroQol-5 Dimensions, five-level version (EQ-5D-5L). Secondary outcomes included recurrent MR, physical activity and quality of life (QoL; including the EQ-5D-5L) and death, repeat mitral valve surgery or heart failure hospitalisation. All secondary outcomes were measured to 1 year, with participants undertaking trial visits at 6, 12, 18, 24 and 36 weeks and 1 year following surgery. The sample size was calculated using the SF-36v2 PF at 12 weeks and a minimal clinically important change of 10 points on the percentage scale with a standard deviation (SD) of 30. Given these assumptions, 382 participants (191 in each arm) were required to achieve 90% power at a two-sided significance level of 5% in the absence of correlation between baseline and 12 weeks. Due to challenges with recruitment, and to assess our assumptions, a blinded sample size re-estimation using baseline SF-36v2 PF scale data from 177 trial patients was performed. Using the re-estimated SD of 26.3 with 90% power, 288 participants were required. The final sample size was therefore reduced to 330, which included attrition. The primary analysis of the primary outcome was performed according to the modified intention-to-treat (mITT) principle, and it included all trial participants who underwent randomisation, received surgery and contributed data on the primary outcome at 12 weeks. The primary outcome of the SF-36v2 PF T-score was analysed using a linear mixed-effects model that adjusted for the minimisation factors except for baseline SF-36v2 PF score, which was included as part of the outcome to calculate the change from baseline. Conversion from the percentage scale to T-scores was recommended and described in the SF-36v2 user manual and was described in the Statistical Analysis Plan. Treatment effect estimates were expressed as mean differences with 95% confidence intervals (CIs) and p-values. Secondary outcomes were analysed using all available data in the mITT cohort with linear mixed-effects models for continuous variables. A within-trial analysis was conducted to assess the incremental cost per QALY gained. The economic evaluation took the perspective of the UK NHS and Personal Social Services and all costs were reported using 2022 values. Costs were based on detailed micro-costing of the interventions and on the use of primary and community care, secondary care and social care services over the 1-year trial period. QALYs were derived from responses to the EQ-5D-5L scores which were mapped to the E5-5D-3L descriptive system in order to generate the utility values. A longer-term model was conducted to extrapolate the mean costs and QALYs based on the results of the trial. Surgeon expertise Individual expert surgeons performed only one type of operation. Before performing surgery within the trial, each surgeon completed a minimum of 50 procedures; the Trial Steering Committee reviewed records for each surgeon and agreed to their participation. Depending on allocation, participants were required to move to another surgeon following randomisation.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hta/14/192/110

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hta/PKOT2391

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/PKOT2391

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk