KB-2023-001134 - [2025] EWHC 2121 (KB)

Preliminary Issue 1(a) surgical planning/preparation and risk mitigation

By the time of trial, the core allegation in respect of surgical planning and preparation was that the Defendant was negligent in failing to expose suitable femoral/groin vessels and failing to prepare those vessels (including by slinging them) in advance of the sternotomy to facilitate the establishment of more rapid cardiopulmonary bypass in the event of injury to the aorta. Further, it was alleged that taking such steps would have allowed the surgeon to check that the vessels were appropriate for cannulation, that the right size cannula was selected in advance for the vessel, and would have rendered the vessels easier to handle and to cannulate in the event of emergency. The Claimant’s case was that such steps were the minimum mitigating measures which were appropriate given the significant risks of injury to the aorta arising from the proximity of the aorta to the rear of the sternum.

Mr Elgot confirmed in closing that allegations relating to the alleged failure to carry out CT scanning of the groin vessels (as opposed to ultrasound) and allegations of a failure to establish whether the vessels were “pristine” were not pursued.

It was also alleged that there was a failure, in advance of commencing the sternotomy, to agree and note the size of the femoral cannula that would be needed. Mr Nassar’s evidence was that there was the usual “huddle” to discuss such matters and that the agreed estimated cannula size would have been marked on a board in the theatre. I accept Mr Nassar’s evidence that matters such as cannula size would have been agreed in advance. Insofar as this allegation remained in issue and was not formally abandoned, I am satisfied that there was no failure to agree on the size of femoral cannula which would be required in the event of an emergency bypass.

Mr Nassar’s evidence was that he reviewed the most recent CT angiogram from January 2022, prior to the operation. The experts agreed that “all scans and data” should be reviewed for the purpose of the risk assessment (including the 2016 scans), albeit that both accepted that the most recent imagery was likely to be the most relevant and informative. There was no evidence before me to suggest that the 2016 scan would have revealed any material information which was not available from the 2022 scan. I do not consider that any failure to review the 2016 scan is material in any way.

Mr Nassar did not comment in his first witness statement on his calculation from the CT imaging of the distance between the posterior table of the sternum and the distended aorta.

His oral evidence was more detailed. He explained that in the Claimant’s case he did not expect the aorta to be adherent to the sternum. He said that, when reviewing scans, he sometimes uses a measuring tool to assist in establishing distances, but does not recall if he measured the distance from the back of the sternum to the aorta in the case of the Claimant. He also explained that his technique of performing the sternotomy meant that he could assess whether the aorta was adherent before he used the saw as he progressed in 5cm sections up the sternum.

As to his decision not to expose the femoral vessels in advance, he explained that there was a balancing exercise of different factors, with particular reference to how difficult the surgeon considered the entry to the chest would be based on the CT imaging. His decision not to expose the femoral vessels was based, he says, on three factors: (a) he had carefully reviewed the CT imaging and “it was not anticipated to be any more difficult than other re-do patients”; (b) given the congenital nature of the Claimant’s heart issues, he was not keen to expose the groin vessels as he wanted to avoid any unnecessary risk of damaging those vessels as they may be required for use in future surgery; and (c) he wanted to avoid the risks of infection by creating an additional wound given that the risks of infection are heightened in a patient undergoing multiple concomitant cardiac interventions.

Mr Nassar’s oral evidence was that if his review of the 2022 CT scans had led him to conclude that the aorta was adherent to the sternum then the chances of damaging the aorta would be “extremely high” and, in such circumstances, he would have exposed the groin vessels in advance of the sternotomy in order to reduce the time taken to establish cardiopulmonary bypass in the event of injury to the aorta. However, Mr Nassar did also accept in cross-examination that the proximity of the aorta to the rear of the sternum increased the risk of aortic injury. He stated that if he had exposed the vessels in advance, it was not his practice to sling the vessels as this could cause injury and bleeding and interfere with distal leg perfusion in case of artery and venous drainage.

During his oral evidence, Mr Nassar sought to counter Mr Yap’s assessment as to the proximity of the aorta to the rear of the sternum, which Mr Yap had illustrated by two stills taken from the CT imaging. Mr Nassar produced copies of four slides taken from the CT imaging to explain that imaging can be adjusted for contrast/brightness and that depending on the adjustments made, one can obtain a clearer image of the position of the external wall of the aorta. He said that his images gave a more accurate presentation of the position of the aorta and showed a larger gap between the rear of the sternum and the outer surface of the aorta wall than the slides produced by Mr Yap.

The risks posed by the surgery: The experts agreed that, using the Euroscore system, the risk of mortality was 6%-9%. Some time was spent in cross-examination and in submissions on whether the Euroscore system (risk of mortality of 6%-9%) adequately reflected the true risks posed in congenital cases (as compared, in particular, to an alternative assessment model known as “PEACH”) and/or in cases in which the aorta is close to the rear of the sternum. Whilst the risk of mortality is clearly of relevance to the advice given to the Claimant in terms of the risks of the procedure, and provides an important context to the magnitude of the risks involved, the critical risk in question in relation to mitigation steps was the risk of injury to the aorta as opposed to the risk of mortality per se.

In his report Mr Yap states that “a 3^rd time re-sternotomy is inherently risky. The presence of a closely applied ascending aortic aneurysm to the back of the sternum increases the risk of injury significantly…. If the aorta is closely applied to the back of the sternum, the chances of injury to the aorta is predictably high. This was the case with [the Claimant]”.

Mr Yap reproduced a still from the 2016 CT scan showing, in his view, that, at least in one place, the gap between the aorta and the back of the sternum was only 1.46mm to 2.23mm, but that one needed to allow for the thickness of the wall of the aorta which could be between 1.5mm and 3.5mm, accounting for the entirety of that 1.46mm to 2.23mm. Mr Yap concluded that: “This would suggest that there was no tissue plane between the aorta and the sternum in this case. It is reasonable to say that the aorta would predictably be breached by the saw when the sternum was opened”.

Mr Roberts did not directly address the CT scans or the proximity of the aorta to the sternum in his report nor, therefore, the specific risks arising from the sternotomy having regard to the CT scans. This is surprising given that he concluded that there was no need for Mr Nassar to take any greater mitigating measures (including exposing the femoral vessels) than he had in fact taken.

In their joint statement the experts agreed that “the aorta was closely applied to the sternum on the CT scan. The experts agreed that based on measurement on the CT Contrast scan, the aorta was within 3mm of the sternum.” The experts also agreed that “a tissue plane is space between two structures filled with body tissue” and that “if two structures are adherent then there would be no tissue plane” and that “if the structures are not adherent there would be a tissue plane (space) between them”.

Mr Yap considered that “the risk of aortic injury should have been considered medium to high as it was a 3^rd re-sternotomy and the CT scan showed the aorta was adherent to the back of the sternum… an adherent pressurised aorta to the back of the sternum would almost inevitably result in the aorta being opened”. In his oral evidence he was clear that even if the aorta was not in fact adherent, it was still extremely close to the sternum in places. This should therefore be considered to be a case of a medium to high risk of aortic injury as the risk must be assessed by reference to where the aorta is closest to the sternum as that will give rise to the greatest risk, not the average distance between the aorta and the sternum. The thrust of his evidence was that his CT still demonstrated that, in places, the aorta was too close to the sternum to enable a surgeon to be confident that there was any real tissue plane. Mr Nassar’s four stills did not change his assessment in this regard.

Mr Roberts, conversely, considered that “the risk assessment made by the operating surgeon (low to medium) was reasonable given the information he had, the review of the CT scan, and in relation to his particular technique as described in the supplementary witness statement … and the high volume of redo surgery he performs as a congenital surgeon”.

Mr Roberts agreed, however, that on the CT image used by Mr Yap as an illustration in his report, and on the contrast selected, it was reasonable to say that there appeared to be only a 1.4mm gap between the wall of the aorta and the rear of the sternum, although this was only one image and it would be necessary to review the totality of the imagery. The experts disagreed on whether the aorta was adherent to the back of the sternum. Mr Yap considered that it was adherent when one took into account the expected aortic wall thickness. Mr Roberts considered that there was “some space” between the aorta and sternum.

The steps required to mitigate the risk of aortic injury: In his report, Mr Yap says this:

“[43] With the significant risk of injury to the aorta on sternotomy, all reasonably competent and logical surgeons would have prepared for this risk with mitigating actions. … There were a range of options that could have been considered. Mr Nasser’s [sic] action of marking the sites for the femoral vessels with ultrasound and no further was completely inadequate considering the predictably extreme risk of aortic injury….

…

[45] When an injury to an important underlying organ happens, the time it takes to establish cardiopulmonary bypass equates to the time it takes to perfuse the brain and other vital organs. So, time is of the essence. With such a high predictable risk of aortic injury in this case, no reasonably competent surgeon approaching this issue logically would have failed to at least expose the peripheral vessels for emergency cannulation.

[46] Exposure of the femoral artery and vein in an elective setting is a very safe and straightforward procedure. This simple procedure allows the surgeon to cannulate and establish cardiopulmonary bypass quickly and safely when required in an emergency setting… I have no statement as to the difficulty that Mr DeVita [sic] faced. I could not ascertain whether the cannulation was done by Seldringer’s technique or direct cannulation with x clamps. Trying to expose the femoral vessels and to also cannulate them in an emergency with stress and adrenaline surge made the procedure very challenging. If the femoral vessels were exposed and slung [in advance], these actions would have allowed the operator to examine the quality and calibre of the exposed femoral vessels. This would allow the operator to match the size of the cannula to the vessel. Cannulating a femoral artery with an oversized cannula can result in a dissection especially in an emergency setting with stress and urgency. The detrimental effect of stress on technical and non-technical (decision making, situation awareness) skills during surgical procedures are well established (ref: “The effects of stress on surgical performance: a systematic review Adam Tan et al, Surgical Endoscopy (2025) 39: 77-98.)

[47] In this case Mr Nasser [sic] failed in his duty to consider the CT scan findings and the severe risk of injury to the aorta and did not take the necessary steps to minimise the time for brain hypoxia by the delay in establishing cardiopulmonary bypass…

…

[49]Even in moderate risk of injury, the Mayo group recommended preparation for cardiopulmonary bypass on re-sternotomy by exposing and preparing the femoral vessels…. The Mayo clinic group’s chart is the reasonable course of action.

[50] In this case if Mr Nasser [sic] had at least prepared [the Claimant’s] femoral vessels for cannulation, he would have been able to assess the vessels directly and consider their suitability for cannulation. We do not know from Mr DeVita [sic] what problems he faced when cannulating the left femoral artery in the emergency resulting in a dissection.

[51] The Mayo Clinic group had recommended at least the exposure of the femoral vessels even in a moderate risk case. This was not done in [the Claimant’s] case. The time saved in establishing cardiopulmonary bypass with the preparation of the femoral vessels would be related to the time it took Mr DeVita [sic] to expose the vessel and cannulate. The brain is very sensitive to hypoxia and many factors may play a role in brain injury. Any logical and competent cardiac surgeon would always act to minimise brain hypoxic time.”

In cross-examination, Mr Yap put the matter more succinctly. He summarised the position by saying that that injury to the aorta is a recognised risk of a sternotomy and the fact that the aorta was, on any view, very close to the rear of the sternum meant that any surgeons would need a plan for “how do I get out of this if it [injury to the aorta] happens?”. His answer to that question was that it was going to be necessary to expose the femoral vessels in advance so as to reduce the risks of hypoxia in the event of injury to the aorta.

His references, at paragraphs 49 to 51 of his report, quoted above, to the recommendations of the Mayo Clinic Group, are to a paper entitled “High-risk reoperative sternotomy – How we do it, How we teach it” by Siddharth Pahwa et al, World Journal for Pediatric and Congenital Heart Surgery, Vol 11, issue 4, July 2020, p459. This recommends preparation for cardiopulmonary bypass on re-sternotomy by exposing and preparing the femoral vessels even in moderate risk cases. The authors explain that exposing and preparing the vessels in advance means that “Bypass can then be instituted quickly in the event of iatrogenic injury…”. As noted above, in his report Mr Yap stated that this was “the” reasonable course to take. He conceded in cross-examination, however, that it was “a” reasonable course of action rather than “the” (only) reasonable course of action.

Mr Roberts disagrees with Mr Yap. His position was that:

“[2.5.7] The strategy to mark the groin vessels to allow immediate cannulation if required, in my opinion, would be supported by a reasonable and responsible body of cardiac surgeons.

[2.5.8] The options available to a surgeon are to image the vessel and mark the skin only, percutaneously wire the vessel and place a sheath prior to resternotomy, there is an option of opening the groin and slinging the vessels to be ready to cannulate without giving Heparin should an emergency occur or there is the option of opening the groin and cannulating the vessel – this requires full Heparinisation and having the ability to establish cardiopulmonary bypass straight away in this scenario. It is my summary opinion that each surgeon makes a risk assessment in each case and decides which strategy to use. It is absolutely not the case that every redo sternotomy procedure has femoral vessels opened and slung.

[2.5.9] I note Mr Nassar’s statement which outlines his strategy. I do not identify any breach of duty in his approach. It is logical and reasonable.”

As noted above, however, Mr Roberts offered this opinion notwithstanding the absence of any discussion in his report as to the risks posed in this case having regard to the CT scans and the proximity of the distended aorta to the sternum.

The critical evidence on this issue was set out in the joint statement. The experts agreed that Mr Nassar’s planning of the sternotomy was “within the practice of a reasonable body of cardiac surgeons IF the court accepts that the level of risk of aortic injury was low”; but they are agreed that the precautions taken were not acceptable if the risk of aortic injury was high.

Mr Yap’s position, as set out in the joint statement, was that “if the court accepts that the aortic risk was “medium to high” – then slinging the groin vessels was the minimum level of mitigation required in this case taking into consideration the presence of significant aortic regurgitation but agrees that many reasonably competent surgeons would use a higher level of mitigation such as commencing cardiopulmonary bypass before sternotomy”.

Mr Roberts’s position is that if the court finds that the risk of aortic injury was high then just exposing and slinging the groin vessels would not have been sufficient. He did not expressly deal, in writing, with the position if the risk of aortic injury was properly to be assessed as “medium to high”. Mr Roberts, in cross examination, described the decision as to whether to expose the femoral vessels in advance as a “small decision”. He said that the “big decision” was whether to establish the Claimant on cardiopulmonary bypass prior to undertaking the sternotomy, and it was common ground between Mr Yap and him that in the Claimant’s case Mr Nassar could not be criticised for deciding against establishing bypass at the outset.

Mr Roberts expressed the view that “a few extra minutes were taken to open the groin which is quick and easy to do…. 3-5 minutes might have been saved.” In his view, however, most of the time lapse which occurred in the event was due to “the second unforeseen event which was the dissection of the femoral artery, which could not have been foreseen by pre operative imaging…”. Mr Yap takes the view that “if the peripheral vessels … were exposed and prepared for cannulation, this would reduce the time to commence cardiopulmonary bypass. The time required to expose femoral artery [sic] can be unpredictable depending on the size of the vessels, the patient’s body habitus and the competency of the surgeon. The dissection of the femoral artery during cannulation by the surgeon on probability [sic] would not have happened if the femoral artery was exposed and ready”.

Mr Yap is an aortic surgeon and I am satisfied that he is very familiar with assessing the risks posed to atypical aortas by surgical procedures, including sternotomies and re-do sternotomies. Mr Roberts clearly also has relevant experience, but he candidly accepted in cross-examination that his experience of re-do sternotomies involving enlarged/distended aortas is more limited; he said this: “it [i.e. relevant experience] is there, but a handful of cases”.

The evidence before me does not demonstrate that the aorta was adherent to the inner wall of the posterior table of the sternum. However, I am satisfied that the wall of the enlarged aorta was in close proximity to the inner surface of the posterior table of the sternum. I recognise Mr Nassar’s point that adjusting the contrast/brightness of the CT scan imagery may enable a more accurate understanding of the position of the exterior wall of the aorta than is apparent from the single CT still in Mr Yap’s report, but this does not detract from the agreed evidence of the experts that the wall of the aorta was “closely applied to the sternum” and was, at least in places, “within 3mm of the sternum”. That description does not exclude the possibility that, in places, the distance may have been smaller than 3mm – meaning that there might be very little by way of a tissue plane.

Given that I am not satisfied that the aorta was adherent, I consider that Mr Yap’s assertion in his report that a sternotomy would “almost inevitably result in the aorta being opened” overstates the position. As Ms Power pointed out in cross-examination, if that were the reality then the balance would tip in favour of establishing the Claimant on cardiopulmonary bypass prior to opening the sternum whereas Mr Yap did not criticise Mr Nassar for failing to take this mitigating step.

Nevertheless, I do accept the general thrust of Mr Yap’s evidence that even if the aorta was not adherent to the rear of the sternum, it was sufficiently close to the rear of the sternum, at least in places, to mean that no surgeon could be confident, in a re-do sternotomy, of being able to open the sternum without causing injury to the enlarged aorta. Mr Yap’s oral evidence on this was clear: “When you have an aorta that is applied so intimately to the back [of the sternum], we are not sensitive enough to just cut the bone layer and not get beyond”.

I accept Mr Yap’s assessment, as an experienced aortic surgeon, that even if the aorta was not actually adherent to the rear of the sternum, it was in close enough proximity to the sternum, at least in places, that the risk of injury to the enlarged aorta on this third re-do sternotomy, with attendant risks of variations in the thickness of the sternum and risks of adhesions, should properly be classified as “medium to high” rather than “low to medium”.

The approach of the experts in the joint statement, namely that one must first determine the nature of the risks of aortic injury before determining the appropriateness of the decision as to whether to expose the femoral vessels, is the logical and correct approach. Mr Yap was clear in the joint statement and in his oral evidence that exposing and preparing the femoral vessels was the minimum level of mitigation required if the risk of aortic injury was “medium to high”.

It is notable, in my judgment, that Mr Roberts, clearly a careful and thorough surgeon, did not directly address the question of the proximity of the aorta to the sternum in the case of the Claimant in his report despite offering the opinion that Mr Nassar’s approach to the surgery, including his decision not to expose the femoral vessels, was reasonable and logical. It seems to me that an expert cannot properly give evidence as to whether Mr Nassar’s approach accorded with a practice accepted as proper by a responsible body of surgeons without considering the particular risks posed by the proximity of the enlarge aorta to the rear of the sternum in the Claimant’s case.

In the joint statement, Mr Roberts set out his view as to the appropriate action if the risk of aortic injury was high (cardio-pulmonary bypass would have been required from the outset) and if it was “low to medium” (marking the femoral vessels would have been appropriate). It is unfortunate that he did not set out his opinion as to the steps which should have been taken (i.e., whether femoral vessels should have been exposed and prepared) if the risk of aortic injury was properly assessed as “medium to high”.

Mr Roberts suggested that there may have been complications arising from “vessel spasm” if the femoral vessels had been exposed in advance. Mr Yap’s evidence was that steps could have been taken to mitigate any issues in relation to vessel spasm and that he did not consider this to be a valid reason for not exposing the vessels in advance. In any event, I was unpersuaded by Mr Roberts’ concerns about vessel spasm in circumstances in which both experts were agreed that if the risk of aortic injury was “high” then the femoral vessels should have been exposed and prepared in advance, presumably notwithstanding any risks of vessel spasm.

I take on board the fact that Mr Nassar considered that his surgical technique (see [87] above) enabled him to progress in a staged progress and satisfy himself that the aorta was not adherent to the sternum prior to sawing through the next section of the sternum, but the evidence was that this technique still left the surgeon largely “blind” (as Mr Nassar himself accepted, see [127] below) as to the precise location of the aorta in relation to the rear of the sternum when using the saw.

Given the “medium to high” risk of injury, I am satisfied that Mr Yap is correct to say that exposing and preparing the relevant groin vessels as a preparatory step in case emergency bypass can properly be characterised as the minimum level of mitigation required in this case.

To the extent that Mr Roberts disagreed with Mr Yap’s clear evidence that proper practice (within the meaning of the professional practice test) required the femoral vessels to be exposed if the risk of aortic injury should properly have been assessed as “medium to high”, then the basis of any such disagreement was not set out in his written report nor the joint statement and nor was it adequately explained and justified. Further, and in any event, I do not consider that Mr Roberts’s evidence can be said to amount to evidence that a responsible body of cardiac or congenital surgeons would accept the mere marking of the femoral vessels as proper practice in the event that the risk of aortic injury was properly assessed as being “medium to high”. Nor do I consider that there was adequate evidence to establish that any such practice would be capable of withstanding analysis in accordance with Bolitho.

I accept that exposing and preparing the peripheral vessels might only have saved a few minutes (a point considered in more detail below), but, as Mr Yap explained, time is of the essence when it comes to establishing full cardiopulmonary bypass in the event of a catastrophic haemorrhage of the aorta. I address the issue as to whether the risk of dissection of the femoral artery might have been mitigated had the vessels been exposed and prepared in advance at paragraphs [154] to [161] below.

It follows that I do not accept that there was any valid basis for Mr Nassar’s evidence that he did not consider that exposing and preparing the femoral vessels in advance was necessary because he did not anticipate that the Claimant’s re-do sternotomy was likely to be “any more difficult than other re-do patients”. Indeed, Mr Nassar accepted in cross-examination that the Claimant’s aorta was “close” to the sternum (but not adherent) and that the closer the aorta is to the sternum, the higher the risks of the surgery. As Mr Yap explained, the surgical procedure of the sternotomy is simply not sensitive enough to enable the surgeon to be confident of cutting through only the bone layer without risking injury to an enlarged aorta which is so closely applied. This is consistent with the evidence given by Mr Nassar in his third statement when explaining the complexities of the procedure and the difficulties in judging how deeply one is cutting when using the oscillating saw (see [127] below).

For the reasons set out above, in my judgment, Mr Nassar fell below the requisite standard of care in not taking the step of exposing and preparing the femoral vessels in advance of the sternotomy having regard to the medium to high risk of aortic injury posed by this third re-do sternotomy in circumstances in which the Claimant’s enlarged aorta was closely proximate to the rear of the sternum.