Heart surgery for aortic valve replacement through a small incision versus the standard full incision at the front of the chest

What question were we trying to answer?

We reviewed the evidence on the effect of a smaller "keyhole"-type cut (instead of the usual full cut down the breastbone) on aortic valve replacement surgery in adults. We wanted to see if both were as safe and effective as each other.

Why is this important?

The aortic valve prevents blood from flowing backwards from the body back into the heart. Aortic valve disease is a common condition that is treated best with heart surgery. The usual way of performing this is by splitting the entire breastbone lengthways to gain access to the heart, but this is thought to be painful and disruptive. For nearly 20 years, some surgeons have been doing the operation through a smaller hole, cutting part of the breastbone instead of the whole length. Doing it this way makes the scar smaller, but can also make the operation more challenging because it is more difficult to see and reach the heart. This might make the operation longer and less safe, even though it looks smaller from the outside.

Which studies were included in this review?

We checked scientific databases to find published and unpublished studies that compared fully opening the breastbone (called "median sternotomy") for aortic valve replacement against opening just part of the breastbone (called "minimally invasive" or "partial" sternotomy) for the same operation. We searched all records up to July 2016 and found seven studies that answered this question that had 511 participants in them.

How were the studies designed?

The studies came from countries in Europe and North Africa. There were 511 participants, with a mixture of different conditions needing aortic valve replacement. Most of these people were 60 to 70 years old and approximately half were male. The participants in each group were similar. One of the studies was funded by a company that makes equipment for doing minimally invasive surgery.

What did the studies show?

There was no difference between the groups in the number of people who died as a result of having surgery. If 23 out of every 1000 people who had the full-size cut in their breastbone died after the operation, around 24 (somewhere between eight and 66) in every 1000 would die using the "keyhole" operation. Because that range goes from three times less to three times more, it is difficult to say whether the operation is definitely better or worse.

The amount of time that surgeons needed to use a heart-lung machine to support the heart while doing the operation was also not different. Neither was the amount of time that the heart was completely stopped to do the operation.

There was little difference in the amount of time participants were on the ventilator or in hospital, although the time spent on the intensive care unit was less by about half a day in the group with the smaller incision. None of the important problems that occur after heart surgery were more common in either group (infections around the heart, irregular heart rhythms or the need for an urgent reoperation because of bleeding). Participants bled slightly less after having minimally invasive surgery. In the operation with the smaller cut, the average blood loss was 158 mL less.

Quality of evidence

The quality of evidence ranged from very low to moderate. One of the main problems with the studies was that they were small and may not have picked up subtle differences between the groups. Because problems after heart surgery are rare, we need to assess lots of people having operations in order to spot small changes. Another problem is that surgeons tend to have lots of slightly different ways in which they do operations. There were also differences in practice, meaning that measurements might not have been taken at the same times, using the same ways. We need to be careful about making conclusions about which differences in the groups in this review were due to the smaller incision and which were due to other factors.

Authors' conclusions: 

The evidence in this review was assessed as generally low to moderate quality. The study sample sizes were small and underpowered to demonstrate differences in outcomes with low event rates. Clinical heterogeneity both between and within studies is a relatively fixed feature of surgical trials, and this also contributed to the need for caution in interpreting results.

Considering these limitations, there was uncertainty of the effect on mortality or extracorporeal support times with upper hemi-sternotomy for aortic valve replacement compared to full median sternotomy. The evidence to support a reduction in total hospital length of stay or intensive care stay was low in quality. There was also uncertainty of any difference in the rates of other, secondary outcome measures or adverse events with minimally invasive limited sternotomy approaches to aortic valve replacement.

There appears to be uncertainty between minimally invasive aortic valve replacement via upper hemi-sternotomy and conventional aortic valve replacement via a full median sternotomy. Before widespread adoption of the minimally invasive approach can be recommended, there is a need for a well-designed and adequately powered prospective randomised controlled trial. Such a study would benefit from performing a robust cost analysis. Growing patient preference for minimally invasive techniques merits thorough quality-of-life analyses to be included as end points, as well as quantitative measures of physiological reserve.

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Background: 

Aortic valve disease is a common condition that is easily treatable with cardiac surgery. This is conventionally performed by opening the sternum longitudinally down the centre ("median sternotomy") and replacing the valve under cardiopulmonary bypass. Median sternotomy is generally well tolerated, but as less invasive options have become available, the efficacy of limited incisions has been called into question. In particular, the effects of reducing the visibility and surgical access has raised safety concerns with regards to the placement of cannulae, venting of the heart, epicardial wire placement, and de-airing of the heart at the end of the procedure. These difficulties may increase operating times, affecting outcome. The benefits of smaller incisions are thought to include decreased pain; improved respiratory mechanics; reductions in wound infections, bleeding, and need for transfusion; shorter intensive care stay; better cosmesis; and a quicker return to normal activity.

Objectives: 

To assess the effects of minimally invasive aortic valve replacement via a limited sternotomy versus conventional aortic valve replacement via median sternotomy in people with aortic valve disease requiring surgical replacement.

Search strategy: 

We performed searches of CENTRAL, MEDLINE, Embase, clinical trials registries, and manufacturers' websites from inception to July 2016, with no language limitations. We reviewed references of identified papers to identify any further studies of relevance.

Selection criteria: 

Randomised controlled trials comparing aortic valve replacement via a median sternotomy versus aortic valve replacement via a limited sternotomy. We excluded trials that performed other minimally invasive incisions such as mini-thoracotomies, port access, trans-apical, trans-femoral or robotic procedures. Although some well-conducted prospective and retrospective case-control and cohort studies exist, these were not included in this review.

Data collection and analysis: 

Two review authors independently assessed trial papers to extract data, assess quality, and identify risk of bias. A third review author provided arbitration where required. The quality of evidence was determined using the GRADE methodology and results of patient-relevant outcomes were summarised in a 'Summary of findings' table.

Main results: 

The review included seven trials with 511 participants. These included adults from centres in Austria, Spain, Italy, Germany, France, and Egypt. We performed 12 comparisons investigating the effects of minimally invasive limited upper hemi-sternotomy on aortic valve replacement as compared to surgery performed via full median sternotomy.

There was no evidence of any effect of upper hemi-sternotomy on mortality versus full median sternotomy (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.36 to 2.82; participants = 511; studies = 7; moderate quality). There was no evidence of an increase in cardiopulmonary bypass time with aortic valve replacement performed via an upper hemi-sternotomy (mean difference (MD) 3.02 minutes, 95% CI -4.10 to 10.14; participants = 311; studies = 5; low quality). There was no evidence of an increase in aortic cross-clamp time (MD 0.95 minutes, 95% CI -3.45 to 5.35; participants = 391; studies = 6; low quality). None of the included studies reported major adverse cardiac and cerebrovascular events as a composite end point.

There was no evidence of an effect on length of hospital stay through limited hemi-sternotomy (MD -1.31 days, 95% CI -2.63 to 0.01; participants = 297; studies = 5; I2 = 89%; very low quality). Postoperative blood loss was lower in the upper hemi-sternotomy group (MD -158.00 mL, 95% CI -303.24 to -12.76; participants = 297; studies = 5; moderate quality). The evidence did not support a reduction in deep sternal wound infections (RR 0.71, 95% CI 0.22 to 2.30; participants = 511; studies = 7; moderate quality) or re-exploration (RR 1.01, 95% CI 0.48 to 2.13; participants = 511; studies = 7; moderate quality). There was no change in pain scores by upper hemi-sternotomy (standardised mean difference (SMD) -0.33, 95% CI -0.85 to 0.20; participants = 197; studies = 3; I2 = 70%; very low quality), but there was a small increase in postoperative pulmonary function tests with minimally invasive limited sternotomy (MD 1.98 % predicted FEV1, 95% CI 0.62 to 3.33; participants = 257; studies = 4; I2 = 28%; low quality). There was a small reduction in length of intensive care unit stays as a result of the minimally invasive upper hemi-sternotomy (MD -0.57 days, 95% CI -0.93 to -0.20; participants = 297; studies = 5; low quality). Postoperative atrial fibrillation was not reduced with minimally invasive aortic valve replacement through limited compared to full sternotomy (RR 0.60, 95% CI 0.07 to 4.89; participants = 240; studies = 3; moderate quality), neither were postoperative ventilation times (MD -1.12 hours, 95% CI -3.43 to 1.19; participants = 297; studies = 5; low quality). None of the included studies reported cost analyses.

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