People often ask me how long will a coronary stent last? When counselling patients about a stent procedure I usually warn them about the risk of restenosis but there is no easy answer to the question of how long a coronary stent will last. Some last for as long as we have been following patients up (20 years) but in others restenosis occurs. The greatest value of the stent was to solve the problem of acute vessel closure in the first few hours after balloon angioplasty. This saved many patients from immediate coronary bypass surgery but the bare metal stent was associated with a high rate of restenosis almost comparable to that of balloon angioplasty. Fortunately the restenosis problem has been tackled by the introduction of drug-eluting stents coated with agents that inhibit cell proliferation. In-stent restenosis usually occurs within the first 200 days after an angioplasty. It can be symptomatic (clinical restenosis) or silent (angiographic restenosis). The practice of performing a routine check angiogram after stenting has nowadays largely ceased however two recently published papers, where routine check angiography has been performed, give important information about this topic. From 1998 to 2009 routine angiography was performed 6-9 months after coronary stenting. In the first 4 years bare metal stents were used then first, subsequently second generation drug eluting stents. Restenosis was defined simply as the presence of ≥50% lumen diameter stenosis at follow-up angiography. Data from 10 004 patients (15 004 lesions) are presented with 4649 treated with bare metal stents (6521 lesions) and 5355 with drug eluting stents (8483 lesions). With the bare metal stents 30.1% of patients had angiographic re-stenosis. The effectiveness of drug eluting stents is seen in terms of reduced re-stenosis falling to 14.6% for first and 12.2% for second generation drug eluting stents. What predicts restenosis? For bare metal stents it was small vessel size, long lesion and long stented length and of course type 2 diabetes. For drug eluting stents it was these same factors but the different anti-restenotic potency of the stent also made a difference with the lowest re-stenosis rates seen with Xience and Resolute stents at around 10%. But does re-stenosis matter; does it affect prognosis? From the same study comes a second paper looking at this question. 5% of patients presented with an acute coronary syndrome, 43.2% with stable angina pectoris and 51.8% were asymptomatic. Restenosis was independently associated with a 23% increase in 4-year mortality. Of the 5185 asymptomatic patients 18.4% had restenosis: of these 40.7% underwent further stenting but this did not impact on 4-year-mortality. There were 300 deaths among asymptomatic patients during the 4-year follow-up, 73 occurred in patients with restenosis and 227 in patients without restenosis. In patients with restenosis the decision to perform a further stenting procedure did not impact on 4-year-mortality risk. It is widely recognised that routine angiography after PCI leads to higher rates of repeat intervention and there is no clear advantages when compared with a surveillance strategy in which repeat angiography is reserved for the evaluation of recurrent symptoms or objective signs of myocardial ischaemia. It is interesting then that in the era of drug eluting stents when 90% of patients do not have restenosis that so many people were being exposed to an invasive procedure outside of a clinical trial simply because of an institutional policy. One wonders if for these institutions in Germany this practice was more important for income generation than for improvement of clinical outcomes. However the data generated has given some important real world data. It seems however that angiography after PCI should be restricted to patients with recurrent symptoms or signs of ischaemia and although the presence of asymptomatic restenosis detected at routine control angiography provides additional clinically relevant information concerning long-term mortality risk although it does not indicate that routine angiography is a predictor of long-term mortality.
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Anatomy is important but it tells you very little about the functioning of the human body. Galen, who studied the anatomy of the human body in the first century proposed that blood moved around the body by diffusion and he did not regard the heart as a pump. His theory, completely wrong, dominated medial opinion for nearly 15 centuries. There was no idea of the circulation of blood until the publication of William Harvey's Du Moto Cordis. After this the great physiologists of the 19th and 20th centuries defined the very purpose of the organs of the body and allow us come to a point of understanding how the body worked. It seems so simple now. How could anyone seriously have believed the Galenic theory? What seemed so right was in fact so wrong. If Galen had studied physiology he would have realised this but his anatomy only told him about structure not function and it needed physiology to understand the circulation. If anatomy is so limited in understanding function why are cardiologists today still so attached to anatomical assessment of coronary arteries using angiography. If you are trying to decide whether a coronary stenosis is significant or not, and therefore whether to recommend a stent or a bypass graft, the assessment of whether the lesion is flow limiting or not is vital. Can anatomy really tell you that. Is the percentage stenosis a good marker? When I started training in cardiology nearly 20 years ago it was often said in the catheter laboratory about an angiogram: "Do a intravascular ultrasound if you want to put a stent in, do a pressure wire study if you don't." Cardiologists were so attached to their visual assessments of coronary artery disease they forgot that with intermediate stenosis of 40-70% it was impossible to determine the physiological significance by angiography. That didn't stop them of course. Many patients around the world have had bypass grafting and stenting of non-flow limiting lesions and medial therapy for significant ones. We are now reaching a mature evolution of our speciality of interventional cardiology and it's time to call into question the role of diagnostic coronary angiography. First performed by Mason Sones in 1958 we may ask whether in 2014 assessment of anatomy alone is good enough to make decisions about revascularisation? I teach my fellows that for intermediate stenosis you might as well flip a coin to decide whether a lesion is flow limiting or not - you simply cannot tell and the quicker cardiologist wake up and admit this the better. The pressure wire and measurement of fractional flow reserve (FFR) has been on the shelf in the catheter laboratory since about 1996. The technology hasn't changed but our attitude to it has. I have always been in favour of this technology but there more evidence that is collected about its utility the more I like it. In recent years cardiologists have begun to use it more and more frequently with data from BCIS showed that in 2008 there were about 5,000 pressure wire studies rising to over 13,000 in 2013. Before the publication of COURAGE, FAME and DEFER there was a scepticism about the device amongst many interventional cardiologists. They "assumed" that stenting worked and that it was good for patients and they weren't going to have their clinical and anatomical judgement of lesion severity changed by a pressure wire. They were used to the angiogram and when the lesion looked severe and then a pressure wire told them it was not haemodynamically significant it must be the pressure wire that was wrong. Post COURAGE it looked like stents did not affect prognosis and the FAME and DEFER studies showed that lesions that were not haemodynamically significant could be safely treated medically and not stented or bypassed. Sadly for the interventional cardiologist wedded to the angiogram coronary physiology is complex and the significance of a lesion is not simply based on the percentage stenosis. It depends on multiple factors including the size of the vessel, the length of the lesion, the size of the territory subtended by the artery and the presence of collaterals. Often colleagues look shocked when I say I don't know whether an angiographic lesion is flow limiting. They expect the interventional cardiologist to know the answer to something as simple as this. But of course it is not simple for the reasons described above. There are people who are willing to give a firm opinion one way or the other about the functional significance of a lesion but I fear their assessment is based on hubris rather than objective evidence. We need to face up and admit that diagnostic angiography is a useful test but that it is certainly not the gold standard everyone assumes it is. A recent paper in JACC with a meta-analysis of FFR data has shown how the pressure wire assessment not only leads to better decisions regarding revascularisation it make the revascularisation safer, associated with less angina and better outcomes. For patients the question to ask your cardiologist is have you assessed my coronary arteries with a pressure wire and if not, why not? I was at the autumn meeting of the British Cardiovascular Intervention Society (BCIS) today in Blackpool. One of the speakers raised this question. There wasn’t much debate or discussion and I guess this might be because the audience was full of interventional cardiologists. But the speaker was thinking forward to future not so far away when this question might asked more and more. The coronary angiogram was once seen as the gold standard for the assessment of coronary artery stenosis. NICE chest pain guidelines recommend angiography as the first line investigation where the likelihood of coronary artery disease us high and this results in about 250,000 angiograms being performed every year in the UK. Of course we all know, or should know, that an angiogram is not done to make a diagnosis of angina. That diagnosis based on the clinical history, rather the angiogram is done to define the pattern of coronary artery disease and to make recommendations regarding potential revascularisation or further management. So if the reason for doing the angiogram is to plan further management is it reasonable that this procedure should only be done by cardiologists with a specialist interest in coronary artery disease management namely interventional cardiologists? In 2013 about a quarter of a million angiograms were performed in the UK, many of these by non-interventional cardiologists and cardiology trainees. At present the trainees have to learn how to do a coronary angiogram and be signed off as competent to perform this procedure independently. The number of procedures requires is not stated and the assessment based on competency. Once they become a consultant many cardiologists like to continue performing angiography as it is a commonly requested test and they wish to continue performing the procedure in the private sector. I think that is necessary to carry out at least 100 angiograms per year to maintain competency and less than this the skill level probably declines. There was once a time that the junior registrars performed all of the angiography in a hospital with the consultants getting on with the intervention. Fortunately this has changed and in my practice I directly supervise and teach all my trainees in the catheter laboratory and every case is attended and reported by myself. Having personally performed more than 5000 coronary angiograms and interventional procedures I firmly believe that procedural experience enables the cardiologist to undertake the procedures safely, rapidly and to be able to deal with all eventualities. It is rare for experienced operators to fail in vascular access or to be able to complete the procedure successfully. The fact that the interventional cardiologists can proceed to angioplasty may also improve patient safety if a complication occurs especially if the angiogram is taking place on a site where they are the only cardiologist present. But there is more to my argument that just operator experience or safety. Interventional cardiologists have woken up to the realisation that eyeballing a coronary angiogram might not be the best way to assess the significance of a narrowing. For years we have had the idea that the percentage stenosis is so important. Is the lesion 50% or 70%? This terminology should be abandoned and replaced by description of whether the lesion is significant (i.e. flow-limiting) or non-significant, at least with respect to the need for interventional treatment of stable angina. This leads us to the growing body of data derived from functional assessments using pressure wires which prove that the “Wire is mightier than the eye”. In the RIPCORD study, the recommendation for medication, angioplasty or cardiac surgery changed in 30% of cases when pressure wire data was available in addition to the angiogram. This is of huge important if you’re the patient and your cardiologist has just told you that you should have coronary bypass surgery. What if their eyeball assessment was wrong and actually all you needed was a stent or worse still just some medication? Although the RIPCORD study is not a randomised trial and it doesn’t have clinical outcome data it does illustrate vividly the importance of functional assessment of coronary lesions in making an accurate diagnosis.The argument then follows that if there is a need for pressure wire assessment shouldn’t the diagnostic angiogram be carried out by an interventional cardiologist who is trained to make these measurements. An interventional cardiologist has been trained to pass wires down the coronary arteries safely and therefore should be the person performing the procedure. Patients currently being treated by non-interventional cardiologists might have this important assessment denied to them by lack of training, experience or an outdated reliance on the eye-ball assessment of coronary disease. It is also possible that because interventional cardiologists are performing intervention that they in fact be better at lesion assessment. This could include the use of non-traditional views to assess difficult things such as ostial disease. Also having performed many pressure wire measurements the interventional cardiologist has an inbuilt feedback which may in fact improve their calibration and eyeball assessment of coronary lesions. The interventional cardiologist also has a better idea of whether revascularisation is possible and the potential pitfalls. One patients three vessel disease is not the same as another patients and should not immediately lead to a reflex surgical referral especially if the Syntax score is low. Importantly the patient treated by an interventional cardiologist has the option to proceed to coronary intervention at the same time as the angiography. This might be if there is an urgent clinical situation or a catheter induced complication or more commonly if the patient prefers to have definitive treatment on the same occasion as the diagnostic test. Although ad hoc angioplasty is discouraged by the European Society of Cardiology in some situations where the patient has ongoing angina, a positive stress test, is already on 2 anti-anginal medicines and has a type A critical stenosis in one single vessel there is little to discuss and proceeding at the same time as performing the angiogram saves the patient from having two invasive procedures. The interventional cardiologist also provides the patient with continuity of care for both diagnostic and interventional procedures and their expert knowledge and practical experience of the pros and cons of different methods of revascularisation is likely to be greater. It may be that non-interventional cardiologists have a bias to recommend medical therapy rather than angioplasty, which may not always be appropriate. Interventional cardiologists may also tend to be more up-to date with new techniques such as the use of the radial rather than the femoral artery, the management of chronic total occlusions and therefore be in a position to offer the patient treatments which non-interventional cardiologists are not familiar with. The decision about the scope of a doctor’s practice often resides with their employing institution or them as an individual. However I believe patients should be better informed about the doctors that are treating them. I have put a lot of detailed information about my practice on the web including information about volumes and my views on angiography and angioplasty. I don’t see that very often from other cardiologists and until very recently with the publication of the BCIS angioplasty data by individual operator gaining any specific information about a cardiologists practice as a member of the public was virtually impossible. It is often surprising how rarely patients ask the question: How many of these procedure have you done? What is your success rate? What is you complication rate? There is an assumption that if you are doing the procedure you know what you are doing. I would welcome your comments on this. As we move towards more functional assessment and a debate about whether pressure wire assessment should be incorporated into diagnostic coronary angiography this question is going to be raised more and more. |
Dr Richard BogleThe opinions expressed in this blog are strictly those of the author and should not be construed as the opinion or policy of my employers nor recommendations for your care or anyone else's. Always seek professional guidance instead. Archives
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