MTG8 The VeriQ system: Mr Peter O'Keefe, Consultant Cardiothoracic Surgeon and Dr Peter Groves, Consultant Cardiologist
Dr Peter Groves, vice chair of the Medical Technologies Advisory Committee and Mr Peter O’Keefe, expert adviser to that committee, discuss implementing the recommendations of this guidance and related practical issues.
This podcast was added on 18 Nov 2011
Interviewer: Hello and welcome to this NICE podcast about the NICE medical technology guidance on the VeriQ system for assessing graft flow during coronary artery bypass graft surgery. In particular this podcast will be focusing on implementing the recommendations in the guidance.
I am Katie Worrall, Implementation adviser at NICE and with me are Dr Peter Groves, Consultant Cardiologist and Mr Peter O’Keefe, Consultant Cardiothoracic Surgeon. Both are based at Cardiff and Vale NHS Trust. Dr Groves is the vice chair of the NICE medical technologies advisory committee who developed this guidance and Mr O’Keefe provided expert advice to that committee during the development of this guidance.
Interviewer: Mr O’Keefe, what is Coronary artery bypass graft surgery?
POK: Coronary artery bypass graft surgery sometimes referred to as CABG is a surgical technique to improve the blood supply to the heart. It can take a number of forms. It can be use of arterial grafts or venous grafts, it can be used to treat chronic angina which is not adequately controlled by medical means or it can be used to treat patients with acute coronary problems where we know their prognosis is improved by revascularisation. There are many different ways of performing the operation using cardiopulmonary bypass machines, using stabilisers with off pump techniques and the bypass grafts themselves whilst most commonly placed in isolation can also be used in conjunction with other aspects of cardiac surgery. So for instance a valve replacement or repair, bypass grafts as well.
PG: Peter, can you describe to us exactly how the graft improves the circulation to the heart muscle?
POK: The principle behind coronary artery surgery is to provide blood flow beyond a flow limiting stenosis in a native coronary artery. We recognise that the process of atherosclerosis, of hardening of the arteries, reduces blood flow through the arteries and when it becomes critical that turns into ischemia of the heart muscle beyond the narrowing. By taking a bypass graft which is a blood vessel, be it an artery or a vein which is able to be removed from its native site because other vessels will take that role on, and using that either by connecting it to the aorta and then subsequently to the coronary artery beyond the narrowing, or in the case of some arteries preserving their natural in flow and just taking the distal end and then anatomising it to an artery beyond the narrowing, we provide a new source of blood flow. By taking that blood beyond where the narrowing is we don’t have the need to interfere with the narrowing we can just revascularise the territory beyond where the narrowing is affecting it.
PG: So, in a sense the operation is quite literally by-passing blood around the narrowing but because of that the important thing is that the flow through the graft must be good and must be substantially better than through the narrowed artery to produce the clinical benefits?
POK: Very much so, and obviously putting a patient through the acute physiological disturbance which is any type of cardiac surgery but then failing to adequately improve the blood supply, as intended, would leave patients susceptible to adverse consequences of the intervention.
PG: So, the improvement in graft blood flow is fundamental to the success of the operation?
POK: Yes in the short, medium and long term. Both in terms of guarding the patients safety during and immediately after surgery and also in what is going to happen to their quality of life and their need for further interventions as time goes by.
Interviewer: Thank you very much. I understand that it is important to assess the graft flow during the surgery, why is this?
POK: We know that when graft flow is inadequate it can lead to early failure of the grafts and when that happens in the immediate perioperative period that is associated with worse outcome for the patients. Sometimes that can be death, more commonly it can be use of drugs to support their heart, inotropes or mechanical circulatory support. When coronary artery surgery was first developed the grafts were often screened in the cath lab, some point after surgery. But until relatively recently there has not been an easy way to assess graft performance in the operating room, which obviously gives surgeons the opportunity to take a decision on whether they need to revise that graft at the time.
Interviewer: Thank you very much and commonly how is the graft assessed at the moment?
POK: Well in most circumstances the assessment of the graft, at the moment in the operating room, is a very subjective thing and there are a number of different techniques that surgeons use. Depending on how the operation is conducted the sort of things that might happen would be injecting blood or a saline solution into the graft once the distal anastomosis has been conducted or constructed and then by feel, by subjective assessment, deciding whether that run off is good or bad or indifferent. In some cases when the graft has been completely constructed the surgeon will milk the graft. By which I mean they will use their thumb and forefinger to occlude the graft proximally, empty the graft by pushing their other thumb and forefinger along it, and then release their proximal clamp to see how quickly the graft fills. (and) Obviously, also if the graft has been constructed and the heart is not performing adequately at the time of surgery the question will be raised as to whether or not one or more of the grafts are inadequate in terms of providing blood flow to the myocardium.
Interviewer: Brilliant thank you and what is the VeriQ system?
POK: The VeriQ system is a system of measuring transit time volume using probes placed around the graft. It is non invasive and it uses ultrasound and it measures a number of parameters to asses graft blood flow and patency. During the procedure the probes are applied to the grafts and different sized probes are available to correlate with the different sizes of blood vessels that are used to construct bypass grafts. The ultrasound beam from the probe goes across the vessel and it measures literally the time taken for blood cells to pass through its range and this enables the construction of a flow curve which is a real time estimate of flow and allows constructed or deducted values on the adequacy of the graft and the patency of the graph to be devised. This gives the surgeon a range of values within which he or she would decide that graft flow was adequate or not.
Interviewer: Thank you. Dr Groves, in which situations does the NICE guidance recommend the VeriQ system is used?
PG: Well Katie, the committee considered that the available clinical and cost evidence supported the case for adopting the VeriQ system in the NHS. (and) We considered that its use in routine clinical practice was important. (so) The committee would recommend that the VeriQ be used in routine practice in all patients undergoing coronary artery bypass grafting, and that every graft that is constructed by the surgeon is assessed with a VeriQ system. (and) The reason for that as we have heard from Mr O’Keefe is that the current rather subjective clinical assessment, while being tried and tested in some regards in clinical care by very experienced and very skilled surgeons, still has the potential to miss the odd graft in which the construction and blood flow to the heart muscle is not quite perfect. (and) Therefore, in which by use of the VeriQ that can be recognised and then by reconstructing the graft and improving its flow characteristics, the blood flow to the heart muscle can be improved. So our feeling was that its use in all grafts was therefore best practice. (and) Our guidance is very much in line with recent guidelines that have been published by the European Society of Cardiology and also the European Association for Cardiac and Thoracic Surgery, who together have recommended that evaluation of graft blood flow should be performed as routine clinical practice.
PG: I think one important point to establish and the committee thought this was crucial was that by recommending the use of this technology what we are talking about is an adjunct technique, something in other words that is not designed to replace current clinical practice but is more used as a refinement in order to improve clinical practice. So in other words we know that cardiac surgeons are very good and experienced at assessing graft flow in other regards, and you have talked about the details of how that is done both manually and the use of indirect techniques such as transoesophageal echocardiography to look at heart function. So the guidance is very much an adjunct to established techniques and something to add on and to refine current practice and in no way to replace what is essentially well established clinical procedures.
POK: I think that is an extremely important point, if a graft insufficiency is detected in whatever way shape or form there is no need to wait for the veriQ to confirm it at the end of the operation. Similarly, to my mind one of the great advantages of using objective quality assessment is it will detect the unexpected failures or impending failure and gives the surgeon an opportunity to address it before it translates into a poor clinical outcome. (and) That is a relative straight forward thing to do in the operating room during the course of the operation. (and) As many of us are aware to address that in a patient who has become acutely unwell in the few hours after surgery it is far more dangerous and far more expensive both in terms of patient quality of life and outcome and in terms of resources to the NHS.
PG: Indeed, I think it was also clear from the evidence that we looked at that clinical outcomes, it has to be said, for patients undergoing cardiac surgery and coronary artery bypass surgery in the UK are extremely good and compare very favourably with other parts of Europe and the world. But with the implementation of this type of new technology, what we are trying to aspire to is improving what are already excellent results. So it has to be said that this is something that will add potentially to what are already excellent clinical outcomes in the UK.
POK: I hope that is going to be shown to be the case. Cardiac surgeons in the United Kingdom have grasped the nettle of performance management and the realistic benefits that have been seen for care of patients having cardiac surgery in the United Kingdom are now in the public domain. They are there for us all to see and when we are benchmarked in the United Kingdom against other countries our global performance is extremely good. What we can’t do is rest on our laurels and just say we were good then. We have to continue to strive to improve and I think this is a simple straight forward cost effective way to take another step forward in improving the outcomes for patients in the United Kingdom.
Interviewer: That is brilliant thank you. Can we just dig a little bit deeper into what the real benefits of this system are to patients and to the NHS?
POK: Sometimes grafts have technical failures within them. Sometimes a clot can form within the vessels that the surgeon is not aware of. Sometimes the graft can be placed inadvertently prior to an important stenosis rather than beyond it and the surgeon will not necessarily be aware of any of these failings simply by looking at the graft at the time of surgery. If a surgeon has constructed a graft which he or she feels is technically completely adequate and then gets information from using the VeriQ which says the flow down the graft is poor, the pulsitility index is high, which would indicate there is an obstruction to flow of some sort, then that graft being revised at that time is likely to result in better blood flow to the territory of the myocardium that the graft was intending. (and) That is going to save from problems absolutely no doubt at all. So there is a clinical judgement around the use of the information but unexpected poor graft performance detected intra-operatively and then corrected, I think is the single strongest reason for using this technology and it is something we just can’t do at the moment unless we use a quality control method objectively.
PG: In terms of the wider benefit to the NHS, the committee considered as part of their evidence a very detailed assessment of the potential cost benefit analysis of the implementation of this technology. (and) The conclusions of the cost analysis are that by using this procedure, this technique in all cases and in all grafts potentially could save the NHS between £100 and £150 per patient treated.
Interviewer: Wow, that is brilliant thank you.
Interviewer: Mr O’Keefe, I understand that you have used this system how much additional time do you think using this device would add to the length of surgery, what advice would you give to your colleagues who are looking to implement these recommendations in practice?
POK: It does not take very long at all. It is a very straightforward technical exercise. Probes come in a number of different sizes. It is important that the size of the probe is well matched to the size of the bypass graft. If the patients grafts are made only for instance of long saphenous veins or of mammary arteries then a particular size probe will be used throughout the case but it may well be, and it is for most cases for coronary surgery in isolation, more than one probe size needs to be selected. If the probe that was initially selected appears to be lose or tight choose another one and use it. (because) The information will vary depending upon how well the probe fits to the vessel, and from the surgeons perspective the single most important aspect of applying the probe is to make sure it is the right size. Also to ensure that if the information on the screen is not what was expected that the probe application has not inadvertently led to a displacement or kink of the graft and to be sure that the probe is lying square on to the graft and it is not producing, by virtue of the way it has been applied, an artefactal discordance. That is another important tip I think. (and) It is quite useful to make sure that the contact between the probe and the graft is wet, it is moist, just by dousing it in saline at the time that the measurement is about to be made. Sometimes with pedicle mammary grafts it can be challenging to identify a segment where the measurement is going to happen. With skeletonised mammary grafts that is not a problem and it may be that surgeons would want to identify a point where they are going to apply the probe at the end of the case and prepare the vessel accordingly. The time it takes to add objective flow measurement to a patient with three or four grafts is two or three minutes at most. It really does not take very long. (and) It obviously requires an operator of the consol who is not part of the scrubbed team as well as the surgeon themselves to undertake the exercise.
POK: I would suggest that within the team who work in the operating room at the time of surgery the individuals who are going to operate the consol are identified. There is a training need, it is very simple, it is very straight forward but it is something that they do need to address. Obviously before rolling out a new technology there is a requirement for the operators to understand how to use the consol and how to store the information, because all this information can be archived and it is accessible at any point in the future. From the point of view of delivering the quality control in practice there is a school of thought that says it is only useful when you know that there is a problem. I think personally that being familiar with the technology, being comfortable with the techniques of use through the use in every single patient is going to mean that when there is a clinical issue or problem you can rely on the information that you are being provided with but similarly you will pick up cases that you were not expecting to have a problem in.
PG: Peter, this is an important change in clinical practice for many of your colleagues and it is quite difficult sometimes to implement changes in practice that has been well established over many years. How long do you think it would take for a surgeon to become familiar with the use of this technology in day to day clinical practice? Is there much implication for learning the technique and training?
POK: Actually, I think it is remarkably straight forward. I can’t see that there are many barriers at all in terms of the technical exercise of applying the probe and the probe needs to be applied anywhere on the graft, it does not need to be down where the graft is applied to the coronary artery. It can be applied where the graft comes off the aorta or where it is easy to access. So in patients where the off pump techniques are being used or, as it has to be when cardiopulmonary bypass has been weaned, there is no need to displace the heart to access a graft to measure it. It is a very technically straight forward exercise.
Interviewer: Brilliant thank you and NICE have also developed a slide set which presents key points from the guidance and a costing template which can be used to support business cases so these can be used to help implement the guidance in practice as well.
Interviewer: Thank you both very much. We hope that you will find the information in this podcast useful in helping you implement this NICE guidance in practice. For more information about the NICE medical technology guidance on the VeriQ system, including the NICE implementation tools which can all be adapted for local use, please visit our website, www.nice.org.uk/MT.
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This page was last updated: 19 September 2012