Potentiating minimal access surgery for treating aortic valve disease is likely to develop in the coming years with sutureless valves playing an important role. The drive to minimise sternal trauma is furthered by the enhancement of transcatheter aortic valve implantation (TAVI). The recent expansion of risk-categories encompassed by TAVI treatment [6] continues to provide a significant alternative to all forms of surgical AVR, by avoiding sternal trauma altogether. However, the challenges associated with TAVI (poor femoral vessel access, multi-valve surgery and severe mitral annular calcification) as well as higher complications of paravaulvular leak and heart block, necessitates constant development in surgical approaches, and indeed, the above challenges can at times contraindicate patients for TAVI treatment altogether.
Only a few studies provide comparative data between the outcomes of sutureless valves in combination with mini-sternotomy versus conventional access [2, 8, 9]. The additive effect of sutureless technology to mini-sternotomy access can potentially circumvent the technical challenge of reduced operative space, hence limiting the increased operative time usually associated with mini-AVR. Our study has found equivocal operating times between conventional and mini-sternotomy, which contrasts with many studies that found longer cross clamp times in mini-AVR with sutured valves. Furthermore, the rates of short-term complications were similar between both cohorts, which is also echoed by our results.
Benefits of sutureless valves
Rapid deployment valve technology has been a primary innovation in surgical AVR in the last two decades based on the design of transcatheter valves [10]. The self-expandable, stentless and sutureless Perceval S (Sorin Group Italia Srl, Saluggia, Italy) and the balloon-expandable, stented Intuity valve (Edwards Lifesciences, Irvine, CA) are the most frequently implanted sutureless valves worldwide for AVR.
The technology exhibited by sutureless valves afford it two main recognised benefits: (1) ergonomic implantation (particular effective in minimally invasive surgery) and (2) favourable valve hemodynamics (particularly with Perceval) [3, 11]. The valve design eliminates the need for sutures to be placed in the aortic annulus (aside from 3 guiding stitches), which can typically take 15–20 min. This added benefit reduces cardiopulmonary bypass time and its associated complications, especially in high-risk patient groups.
Numerous studies have compared the outcomes of sutureless valves with conventionally implanted AVRs. Postoperative bleeding and blood transfusion requirements have also been reported to diminish, which likely reflects the shorter time on the CPB machine [12,13,14]. There has also been reported reductions in ventilation time [12, 13], reduced incidence of acute kidney injury [13, 14], shorter intensive care stay [12] and shorter hospital stay [12].
Many studies have reported a higher rate of permanent pacemaker (PPM) insertion after Perceval valve implantation [13,14,15,16]. A recent meta-analysis by Sohn and colleagues (21 studies, n = 2785) reaffirmed the higher rate of PPM insertion in sutureless valves compared to conventional prostheses (relative risk 2.08; 95% CI, 1.49–2.90) [17].
When compared to TAVI, Santarpino and colleagues [18] conducted a propensity matched analysis (n = TAVI 538 vs sutureless 385) and showed that sutureless valves resulted in better long-term outcomes compared to TAVI, despite the increased need for blood transfusions in the short term. Furthermore, one randomised trial of TAVI with an early-generation valve in 280 patients demonstrated that TAVI was not inferior to surgery with more than 5 years of follow-up [19]. In addition to this, a meta-analysis found that sutureless valves result in improved perioperative survival compared to TAVI, albeit with only 6 studies analysed, adding further weight to case of sutureless valves as a viable option, especially for minimally invasive approaches [20].
Enhanced recovery with sutureless via minimal access
In the present study, mini-sternotomy was found to be a strong predictor of shorter ICU stay (p = 0.024), which concords with similar large studies. A recent multi-centre study based on propensity matched data from the STS registry [21] compared 1,341 AVR patients in two cohorts: conventional sternotomy vs mini-AVR (either through partial sternotomy or right mini-thoracotomy). Mini-AVR demonstrated enhanced recovery through decreased ventilator time (5 vs 6 h; p = 0.04) and earlier discharge (15.2% vs 4.8% in ≤ 4 days; p < 0.001). The study also found a lower rate of blood transfusion which was not seen in our patients. Interestingly, we found the rate of new onset atrial fibrillation (AF) post-surgery in mini-AVR to be almost half of that in the sternotomy cohort (24% vs 42%) although this did not reach significance (p = 0.250).
On the other hand, studies reporting non-superiority of MIS compared to sternotomy with regards to enhanced recovery have also been published. A recent RCT led by Papworth (UK), (Mini-Stern trial) (N = 118 MS vs N = 118 MIS, all conventional sutured prostheses in both cohorts) [22] found no added benefits offered by mini-sternotomy for recovery time, rather minimal access resulted in longer CPB and cross clamp times. This perhaps gives precedent for the use of operative adjuncts, such as sutureless valves, to augment the benefit of minimal access surgery.
Early myocardial remodelling
The present study has also demonstrated a significant positive impact of mini-AVR on left ventricular dimensions by 6 months. This could reflect the reduced myocardial handling intra-operatively and improved patient pain profile, leading early cardiovascular recovery and rehabilitation, allowing the myocardium to adapt to the haemodynamic changes affected by the treated aortic valve [23]. This contrasts with other reports in the literature [3]: the study by Dalen and colleagues, compared mini-sternotomy patients with median sternotomy (all receiving isolated Perceval AVR—like the present study), and the most notable finding was a significantly higher post-operative transvalvular gradient (28.1 vs 23.3 mmHg, p = 0.026) in the mini-AVR group.
Limitations
The main drawback of the present study is the small sample size, which limits the power of our conclusions (e.g. shorter ICU/hospital stay). Whilst the outcomes for our unit was very positive for major short-term complication (zero incidence of mortality and stroke) this may also reflect the underpowered cohorts, which limits their ability to detect potential differences. This is particularly the case for post-operative AF, where the lower incidence in the mini-AVR group, although non-significant, may provide clinical relevance in a larger patient group. Although our follow-up time is limited to one year, the echocardiographic findings we have provided are unique and warrant further exploration in a larger patient group over a longer period. Indeed, long-term echocardiographic results for the Perceval valve, whilst mostly promising, has raised questions over the durability of its nitinol frame after a few years. This could also be correlated with patient functional outcome, which the present study did not analyse.