The trial, which was first presented earlier this year at the American College of Cardiology meeting, showed that minimally invasive mitral valve repair does not improve physical function at 12 weeks compared with sternotomy, but outcomes at 1 year show minimally invasive repair is as safe and effective as sternotomy for degenerative mitral regurgitation.
The authors, led by Enoch Akowuah, MD, South Tees Hospitals NHS Foundation Trust, Middlesbrough, United Kingdom, explain that mitral valve repair surgery is the preferred treatment for patients with degenerative mitral regurgitation, and is routinely performed via full sternotomy, enabling easy access to the heart, flexibility in myocardial protection strategies, and multiple ways of accessing the mitral valve and easing de-airing to prevent air emboli, which cause cerebrovascular accidents.
However, the invasiveness of sternotomy is associated with delayed return to presurgery physical function levels and an increase in postoperative complications.
An alternative new video-guided minimally invasive approach involving a 4- to 7-cm lateral thoracotomy, completely avoiding sternotomy, has been developed, with the hope that it should speed physical recovery function after surgery, and reduce postoperative complications and costs by reducing hospital stay.
Akowuah et al note that uptake of minithoracotomy is variable, with low rates in the United States and the United Kingdom but high rates in Germany. They say that this variation is attributable to the absence of high-quality evidence from randomized trials demonstrating equivalent or superior benefits compared with sternotomy, and there are also concerns that the increased technical complexity of minithoracotomy may impair the ability to repair complex valve lesions or increase perioperative complications, particularly vascular injuries and stroke.
The UK Mini Mitral trial was therefore conducted to compare the effectiveness and safety of minithoracotomy versus sternotomy mitral valve repair.
For the trial, 330 patients with degenerative mitral regurgitation were randomized to receive either minithoracotomy or sternotomy mitral valve repair performed by an expert surgeon.
The primary outcome was physical functioning and associated return to usual activities measured by change from baseline in the 36-Item Short Form Health Survey (SF-36) physical functioning scale 12 weeks after the surgery.
This failed to show superiority of minithoracotomy, with a mean difference of 0.68 (95% confidence interval, −1.89 to 3.26) between the two groups.
Analysis of secondary outcomes demonstrated that time spent undertaking moderate to vigorous physical activity was higher among participants receiving minithoracotomy at 6 weeks, although the treatment effect was small at an average of 9 minutes and was not different at 12 weeks.
Postoperative length of hospital stay was reduced after minithoracotomy by 1 day, with a median of 5 days compared with 6 days after sternotomy.
Although repair techniques were at the discretion of the surgeons and differed between the two procedures, high rates of valve repair and low rates of recurrent mitral regurgitation were observed in both groups. Cardiopulmonary bypass times were longer with minithoracotomy, but postoperative complications and adverse events were similar.
There was no difference between the two groups with respect to the prespecified safety outcome of death, repeat mitral valve surgery, or heart failure hospitalization up to 1 year, which occurred in 5.4% of patients undergoing minithoracotomy and 6.1% of those undergoing sternotomy.