Minimally invasive vs conventional sternotomy for mitral valve repair surgery: An expertise based multicentre randomised controlled trial (UK Mini Mitral)
The definitive end of an ERA?
Reported from ACC 2023 / WCC
Edoardo Zancanaro provides his take on this clinical trial presented by Enoch Akowuah at the American College of Cardiology Scientific Session (ACC.23/WCC).
Why this study? – the rationale/objective
Mitral valve repair has been considered the gold standard for the treatment of mitral valve regurgitation (MR) for more than 20 years now.
Different techniques have been invented over the course of time, and still today many surgeons are finding new ways to repair efficiently the valve.
In the last decades, the big changes have been represented by the surgical approaches to repairing the valve. The more “classic” way has been represented by the medial sternotomy. The “new” way is represented, instead, by the right anterior thoracotomy (RAMT) (direct vision or endoscopic). A great debate has come up between surgeons on the real efficacy of this new surgical approach and many data have been presented over years 1.
The UK Mini Mitral (Minimally Invasive Versus Conventional Sternotomy For Mitral Valve Repair Surgery: An Expertise Based Multicentre Randomised Controlled Trial) aimed to answer millions of surgeons on which approach can be preferred and if RAMT has the same or better results compared to the “classic” median sternotomy.
How was it executed? – the methodology
The UK Mini Mitral trial is a multicenter randomized controlled trial that randomized patients to either medial sternotomy or RAMT. They used expertise-based randomization to remove the impact of the learning curve and assure patients that, regardless of which study arm they were assigned to, they would receive a high-quality procedure performed by an expert.
A total of 330 patients (average age 67,3% women) were treated at 10 centres in the U.K. All patients suffered from severe MR in which 96% had Type II MR, 65% isolated P2 prolapse, and 23% had bi-leaflets prolapse.
- Primary endpoint: Change in patients’ physical functioning and ability to return to usual activities at 12 weeks after the operation. Changes were assessed via periodic questionnaires and with a Fitbit-like device that patients wore on their wrists.
- Secondary endpoints: Patient deaths at one year; surgical outcomes such as hospitalization for heart failure and the need for repeat mitral valve surgery; echocardiogram findings, including mitral valve leakage; adverse events, including stroke; length of hospital stay; and patient quality of life.
What is the main result?
The study randomized more than 330 patients suffering from severe MR enrolled at 10 Centers in the UK (United Kingdom).
The main baseline characteristics were similar between the two groups. Concerning operative data, in RAMT (right anterior mini-thoracotomy) group there were higher cross-clamp time (11 minutes), Circulatory Pulmonary Bypass (30 minutes), and length of procedural time (44 minutes), compared to ST group (STernotomy Group).
- For the primary endpoint at 12 weeks, recovery of physical function levels compared to pre-surgery levels was similar in both groups. However, at six weeks, patients in the mini-thoracotomy group had recovered physical function compared to pre-surgery levels whereas patients in the sternotomy group had not. Moreover, at six weeks mini-thoracotomy patients were spending more time doing moderate to vigorous physical activity such as walking, running, and cycling. Sleep efficiency was also higher in the mini-thoracotomy group.
- Concerning the secondary endpoint, at 1-year rates of death, hospitalization for heart failure, repeat mitral valve surgery, adverse events (including stroke), and quality of life were not significantly different in the two groups. Also, Mini-thoracotomy patients were in the hospital for a median of five days (compared with a median of six days for sternotomy patients) and were twice as likely to be discharged home within four days of surgery.
Interestingly enough the repair rate was high in both groups (96%) with excellent 1-year results (93% with MR<2).
Critical reading and the relevance for clinical practice
First and foremost, it is important to highlight that this trial means a historical landmark in the field of mitral valve repair, as it represents the first randomized data that compare the two more debated surgical approaches in this field.
We have learnt that:
- RAMT is safe and effective as a sternotomy for mitral valve repair (MVr) in case of degenerative MR.
- Recovery from the baseline to 6 weeks is better with RAMT.
- At 12 weeks the mean change in physical activity function from baseline is the same.
- In both groups the repair rate is excellent.
This trial represents an important milestone in a very debated topic. We have seen multiple studies that showed excellent results for MVr with a minimally invasive approach2, also comparing the sternotomy3. Nevertheless, the cardiac surgery world was still not convinced of the real difference between these two approaches, in particular, there was still the idea that a longer cross-clamp time and a longer intervention can negatively influence the outcome; on the other side, the audience was very worried on the rate of repair and the effective improvement in patients Quality of Life (QoL). It’s clear that with this new trial, the left-behind doubts can be once and for all closed.
A very important aspect that this trial is embracing, is the clear benefit on the patient’s daily activities and quality of life. This is a very important aspect since the final goal of this type of surgery is the long-term benefit in terms of repair and wellness for the patients treated.
This trial can finally encourage the still sceptical cardiac surgeons that prefer the median sternotomy, to bring their surgery to a different level, for the benefit of their patients. There is an important need of creating a real “academy” to teach a totally different approach to a very standardized procedure.
Finally, this first randomized data in the field of mitral valve repair gives us the important message, that minimally invasive approach represents a valid alternative to median sternotomy showing non-inferiority results and a better QoL to the patient treated.
The next step is the 5-year outcomes since the trial will continue to enroll in order to give still more strong evidence. Let’s see what the future brings…
Reference
- Reser D, Holubec T, Yilmaz M, Guidotti A, Maisano F. Right lateral mini-thoracotomy for mitral valve surgery. Multimed Man Cardiothorac Surg. 2015 Oct 26;2015:mmv031. doi: 10.1093/mmcts/mmv031. PMID: 26507363.
- Van Praet KM, Stamm C, Sündermann SH, Meyer A, Unbehaun A, Montagner M, Nazari Shafti TZ, Jacobs S, Falk V, Kempfert J. Minimally Invasive Surgical Mitral Valve Repair: State of the Art Review. Interv Cardiol. 2018 Jan;13(1):14-19. doi: 10.15420/icr.2017:30:1. Erratum in: Interv Cardiol. 2018 May;13(2):99. PMID: 29593831; PMCID: PMC5872370.
- á MPBO, Van den Eynde J, Cavalcanti LRP, Kadyraliev B, Enginoev S, Zhigalov K, Ruhparwar A, Weymann A, Dreyfus G. Mitral valve repair with minimally invasive approaches vs sternotomy: A meta-analysis of early and late results in randomized and matched observational studies. J Card Surg. 2020 Sep;35(9):2307-2323. doi: 10.1111/jocs.14799. Epub 2020 Jul 15. PMID: 32668091.
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