The evolution of aortic root surgery for Marfan syndrome

In the development of a complex process with multiple iterations, a point may be reached when the next best step is simplification. The pre-emptive management of the Marfan aortic root, which has the single goal of preventing fatal dissection, may be an example. In the light of our report in Interactive CardioVascular and Thoracic Surgery[1] is it time to ask if, with progress in imaging and computer aided design, we might be approaching a point where simplification is the next best step in the elective management of the aortic root in the early uncomplicated Marfan patient? Pepper et al. report the technical realisation of a concept of individualised external aortic root support (EARS) [1] which was proposed and developed by the design engineer Golesworthy [2]. He inherited and has expressed the Marfan gene with all of its characteristic manifestations including dilatation of his aortic root. While undergoing regular echo measurements to see if the aortic root was enlarging, to the point where he met existing criteria for a root replacement, he instigated a radical rethink on our surgical approach. While aware of the work of the surgeon Robicsek and the engineer Thubrikar [3], Golesworthy postulated that surgeons had thus far failed to take advantage of the techniques of computer aided design. He proposed that we use the very high-resolution spatial data made available by modern imaging to make an exact, customised support for the Marfan aortic root. The anatomical requirements were explored in collaboration with Treasure et al. [4] and Golesworthy himself was the recipient of the first implant [2]. The Bentall operation can be performed at low risk in expert hands and valve-sparing versions, with all their advantages, are now available [5, 6]. During training in the 1970s the situation was very different. The Bentall operation had not long been described [7] and aortic root surgery was a technical challenge, not to be undertaken unless the clinical indications were compelling – but for Marfan patients the very high risk of fatal dissection at young age constituted a compelling argument. For a young surgeon in the early 1980s it was evident that there was much to learn and the writer spent a month in January 1985 in Houston, Texas observing aortic surgery on a daily basis in the operating rooms of the doyens of aortic surgery, the late Stanley Crawford and Denton Cooley (Fig. 1 ). An aortic root replacement for chronic ascending aortic dissection in Houston, Texas 1985 (with permission). The drawings and notes were made by the author (a) and the surgeon demonstrates the completed operation (b). As a point of technical interest, exposure details (aperture and shutter speed) were recorded, but more noteworthy are the operative data. The distal anastomosis was made during an 8 min period of total circulatory arrest at a nadir of 21 °C and the myocardial ischaemic time was 20 min with hypothermia as the means of myocardial protection. From around that time elective Marfan root surgery could be undertaken at lower and lower risk and was therefore justifiable at progressively earlier stages in the process of dilatation [8]. The focus of our own research was into evaluation of the risk related to the absolute dimensions and their rate of change to make individualised clinical decisions concerning the timing of surgery [9]. It was not just the risk of the surgery itself that had to be considered on the down side, but also the loss of the native aortic valve, and the need for anticoagulation, which were implicit at that time. Amongst the advantages of EARS are that no cardiopulmonary bypass or myocardial ischaemia are required; the valve is conserved but better supported; and no change is made to the interface between the blood and the aortic endothelium [1]. Root replacement is now well established including the use of tissue valves and valve sparing variants [5]. It is worth reflecting on how we arrived at where we are today. The negative aspects of the original Bentall operation have been overcome stepwise. The original grafts had to be preclotted; we were spared that by the successive introduction of collagen and gelatine sealed grafts. We originally had to sew the valve into the tube but soon manufacturers provided us with valved conduits (Fig. 2 ). The coronary anastamoses were the Achilles' heel of the operation: the ostia were originally sutured en face into the tube graft and the aorta wrapped around the graft and yet perigraft leaks and pseudoaneurysm formation were not infrequent. The button technique, with surgical skill and practice, largely overcame those problems. The need for life-long warfarin was avoided by the development of valve sparing versions of the operation [5]. Notwithstanding the iterative solving of previous problems and reported low mortality in the hands of world experts, the Society of Thoracic Surgeons (STS) data show mortality of the order of 10% for root reconstruction [10] and it should be remembered that highly developed versions of root replacement offer no protection to any other part of the aorta – a limitation they share with EARS. In Bentall's original operation, and as performed by the author in the 1980s, the valve was sewn into the tube graft by hand. The tube had to be preclotted. An inclusion technique with a wrap was usual. Another way of considering the question is to reflect on historical examples of natural evolution and of human design. The nobel prize winning scientist Peter Medawar postulated that the dinosaurs were an ‘end product’ and might be seen as an evolutionary cul de sac. Mammals including ourselves were not a product of further evolution, but a step back to an earlier evolutionary branch. Similarly, with the Zeppelin: even though problems of conflagration might have been overcome, in the event the development of modern aviation took a quite different route. This is not to denigrate in any way the highly evolved valve sparing versions of Bentall's operation but just to remind ourselves the eventual solution is not always reached by relentlessly solving the problems of the previous design. David's operation is in its sixth version and although the authors themselves write that they provide excellent clinical outcomes, there are deaths and problems, early and late [6], and can the best of these outcomes be replicated in less brilliant hands [10]? An alternative is to reframe the question in the light of opportunities offered by new technology. What matters to the Marfan patient is maximising life and minimising risk and fear. The non-ablative tissue sparing solution offered by EARS may allow very early low-risk pre-emptive surgery, safeguarding many Marfan patients at an earlier stage in their rather hazardous lives. What will be the ultimate solution for the fibrillin deficient ascending aorta? Gene therapy perhaps. Meanwhile Golesworthy's operation merits attention [1].