The release of the surgical outcomes data last Friday was like a firework. There was a loud bang and a brief flash when people looked and then it disappeared into the darkness. In fact the story was more about the data that wasn't released than the data that was. Surgeons who defied the call for their data to be published were looked on with suspicion and outed at the behest of Jeremy Hunt, the Health Secretary. Once upon a time the only thing people talked about when it came to the assessment of quality in angioplasty was the number of procedures performed with high volume operators and centres regarded as the best. Part of this was because procedural volume was easy to measure whilst other quality markers were not. Today sees the publication of the coronary angioplasty data which has been collated by the British Cardiovascular Intervention Society (BCIS). The society has been collecting data on angioplasty since 1992 and presenting it as an annual audit on their website. In 2012 it became possible to link an individual angioplasty procedure to the GMC number of the consultant responsible and hence to produce the operator level data which has been published today. BCIS has tried to not turn this a beauty contest between interventional cardiologists and they have made it difficult, but not impossible, to compare the data. They rightly state that it is not possible to compare different cardiologist and this is true since the case mix of one will be different from another. There are some cardiologists who only perform only elective angioplasty on stable angina patients or who work in hospitals that don't perform primary angioplasty for acute heart attacks. These cardiologists should have very low death rates. BCIS have used a measure of self reported in-hospital death rate, stroke rate and requirement for emergency bypass surgery. From this they calculate a MACCE (major adverse cardiac and cerebrovascular event) rate for each interventional cardiologist. Then they calculate an expected MACCE rate and its 95% confidence interval based on patient factors including age, sex, history of stroke, urgency of procedure using a model developed by the North West Quality Improvement study (NWQIP). In a nutshell provided the cardiologist's MACCE rate is less than the 95% confidence interval then they are not regarded as an "outlier" and their practice is regarded as safe. So what determines MACCE? It is dependent on patient, interventional cardiologist and post-procedure factors. In most cases death, stroke and need for emergency bypass surgery are more dependent on the type of presentation, co-morbidity of the patient and severity of the coronary artery disease. The skill of the cardiologist might be better judged in terms of procedural complications such as vascular access site bleeding, the need for urgent repeat coronary intervention, the number of acute stent thrombosis or stent restenosis. These measures whilst more difficult to collect would provide a better estimate of quality. Measuring survival to hospital discharge as an outcome also leads to anomalies. Take this scenario, Cardiologist A treats an elective, stable patient with a stent and the patient is discharged only to be readmitted 48h later with an acute stent thrombosis causing an acute heart attack. This rare complication can sometimes be caused because of stent under-deployment. Cardiologist B is on call and treats the patient in the catheter lab to salvage the acutely blocked artery but sadly the patient dies. In the current analysis this death is recorded as belonging to Cardiologist B not Cardiologist A. A move to the measurement of 30 day mortality is needed but there will be difficulties in apportioning deaths when two cardiologists have treated the same patients. Another important skill, which is very difficult to measure, is that of case selection. Some cardiologists will attempt emergency angioplasty on almost all patients presenting with an acute myocardial infarction even if the chance of survival is very low. With the publication of this data it is likely that cardiologists will start to think twice before taking such patients to the catheter lab where the procedure may be futile, the outcome inevitable and the death counted on their angioplasty statistics. Interventional cardiologists have often been put in a position where an emergency patient has been turned down by a cardiothoracic surgeon because the risk of operation is deemed to high risk and they have then gone on to offer angioplasty. This behaviour may well change as interventional cardiologists are subject to increasing scrutiny. The other issue is training the next generation of interventional cardiologists. If the consultant is responsible for the procedure and the data is going to be published in a public forum how comfortable will they be allowing a fellow or registrar to be the first operator in a difficult case. If a mistake is made by the trainee cardiologist during the procedure this could affect the outcome. On the other hand if we don't train the interventional cardiologists of the future what hope will there be for us when we are old and need intervention ourselves. So what of the data released today. First we have to accept that some of it is missing as not all hospitals contributed so any conclusion drawn here are based on the data that is available. In 2012, 559 consultant cardiologists performed 83,121 angioplasty procedures. There were 22,426 primary angioplasties performed to treat acute ST elevation myocardial infarctions, 30,399 to treat acute coronary syndromes and 27,860 to treat stable angina. the rest were coded as other or unknown. The majority of angioplasty in the UK is used to treat emergency patients with only 34% of procedures for stable angina. This is very different from the data from other reports such as the New York State where 83% of PCI procedures were done for stable angina. Some hospitals perform a very large number of procedures. For example Liverpool Heart and Chest performed 2929 with the Freeman in Newcastle coming a close second with 2832 procedures. At the other end of the spectrum are the private hospitals which tend to perform mainly elective PCI usually, though not exclusively, by cardiologists who also work in NHS hospitals as well. Hospitals are supposed to perform 250 cases per year to remain viable, 17 hospitals reported completing less procedures than this. What can we learn from the individual data? BCIS have been careful to present the data in a way in which makes the comparison of different cardiologists very difficult. Each operator's data is presented separately on an individual webpage and so to make any direct comparison laborious. I suspect this was a deliberate measure but it does not make it impossible to abstract the data and to look at differences. Most surprisingly they also do not separate the outcome data into elective and non-elective cases. It is obvious that the MACCE rate for elective angioplasty will be low. Currently patients are quoted a 1% chance of heart attack, stroke, death or need for emergency bypass surgery when they sign the consent form. The actual MACCE rate for this procedure is probably around 0.2%. Compare this to the MACCE rate of more than 50% for a patient presenting with an acute myocardial infarction, cardiogenic shock and following an out of hospital cardiac arrest. No cardiologist had MACCE rate greater 95% of predicted so it appears that everyone is operating within the expect levels. I suspect this reflects the crude nature of the MACCE measurement and the NWQIP model which has been used. Looking at the high volume operators the predicted MACCE rates is running about twice as high as the actual MACCE rate suggesting that it does not predict particularly accurately a contemporary patient population. Statistically out of 559 operators one might expect at least 25 to lie above the 95% confidence interval simply by chance alone - none do, again questioning the accuracy of the risk prediction model and any conclusions regarding safety are dubious. BCIS recommend that interventional cardiologists should perform at least 75 PCI procedures per year in order to maintain competence. Nearly 20% of operators are apparently performing less than this with many of the interventional cardiologists working solely in the private sector doing very small numbers of cases each year. The median number of procedures per cardiologist is 138 although there are some cardiologists performing significantly larger numbers of procedures. Some cardiologists MACCE rates fall very close to the 95% confidence limit and some very far away. For example the largest volume operator in the UK who did 591 cases has a MACCE rate of only 0.17% (95% CI: 3.12%) although 62% of his patients were elective and only 5% primary PCI cases. At the other end of the procedural volume spectrum there is great difficulty in analysing data because of the small numbers. When a cardiologist has done only 25 procedures the confidence interval is so wide as to preclude any meaningful analysis. The publication of the angioplasty data by BCIS is a step in the right direction. Hopefully it will lead to an improvement in the quality of data collection and accuracy. What is sorely needed is the development of more accurate risk and quality control models as well as moving to measurement of 30 day mortality. We are at the beginning of a long and interesting journey and at the end we will see that quality in angioplasty is more than procedural volume. References: Grayson AD, Moore RK, Jackson M, et al. Multivariate prediction of major adverse cardiac events after 9914 percutaneous coronary interventions in the north west of England. Heart 2006 May;92(5):658-63. BCIS Individual Operator Level Data Website PCI in New York State Report 2008-2010
7 Comments
The debate over whether patients with 3 vessel coronary artery disease should be treated with multi-vessel stenting (PCI) or coronary bypass surgery (CABG) has raged for the last decade. Stenting only needed to be as good as surgery for it to become the treatment of choice since the procedure is less invasive and the recovery time quicker. Comparison of the two forms of treatment has been difficult because stents have been constantly improved meaning that every trial was out of date compared to currently available technology at the time the results were published. This week the final 5 year results of the SYNTAX trial were published in the Lancet. This trial randomised 1800 patients to stents or surgery. The average age of the patients was 65 years, 75% were men and 25% diabetic. The combined end point included all-cause mortality, stroke, myocardial infarction and repeat revascularisation. The results showed that 26·9% in the CABG group and 37·3% in the PCI group reached that endpoint (p<0·0001). Myocardial infarction was higher in the PCI group (9.7% vs 3·8%; p<0·0001), as was the need for repeat revascularisation (25·9% vs 13.7%; p<0·0001). All-cause death and stroke were not different. So what can we learn from this trial. First the CABG group appear to get continued benefit as time went on. One explanation for this is that since CABG bypasses, any disease progressing in the artery proximal to the insertion point of the bypass graft remains treated which is not the case if a stent has been implanted. This may not be the whole explanation since CABG did not show a benefit over PCI in the left main stem treatment group although there were only 222 patients in this group. Second, SYNTAX acknowledged that not all 3 vessel disease is the same with some patients have discrete, simple lesions and others having very complex disease. Embedded in this trial was a scoring system (www.syntaxscore.com) which allowed a measure of the severity of the coronary artery disease. Treatment of low score (22 or less) or an isolated left main stem stenosis with CABG did not appear to confer an advantage over stents. In contrast an intermediate or high SYNTAX score predicted a significantly worse outcome if treated with stents rather than CABG. The results indicate that patients with simple three vessel disease could reasonably be treated with stents rather than surgery although it is important to remember that the analysis of subgroups in clinical trials is only hypothesis generating. The subgroups do not have enough patients in them to be adequately powered to draw definitive conclusions. Calculation of the SYNTAX Score gives the cardiologist an estimate of the severity of disease and helps feed into the decision making process regarding the best means of revascularisation. The other issue is that of patient choice. More patients randomised to CABG withdrew from the trial compared to PCI. Faced with a decision regarding what treatment to have the patient will have views and these need to be informed by a discussion of the best available evidence. If a patient understands that stents may have a less good outcome they may still decide to have this treatment because it is less invasive than CABG. The SYNTAX trial also leaves open the question of how to manage much older patients where the risk of stroke and mortality is greater. Many patients we currently see are in their late 70s or 80s, often with severe coronary disease and they may be less included to undergo CABG. Also most of the participants in SYNTAX were male and therefore it is difficult to know whether the outcomes for women would be the same. The SYNTAX trial is an important landmark to inform how we should manage severe coronary artery disease. However we need to remember that as cardiologists we treat individual people and the results of the clinical trials present results from pooled groups of patients may not always be representative of the patient in front of us. Coronary artery bypass graft surgery versus percutaneous coronary intervention in patients with three-vessel disease and left main coronary disease: 5-year follow-up of the randomised, clinical SYNTAX trial It is the ultimate accolade for an inventor or manufacturer when their name becomes part of the language or is used as a verb to describe a action. Examples include Hoover, Xerox and Google. In cardiology the stent, which is used to treat patients with narrowed coronary arteries shares this unique position as a noun and a verb but where did the word stent come from and why are stents called stents? Mosby's medical dictionary defines a stent as "1. a compound used in making dental impressions and medical molds. 2. a mold or device made of stent, used in anchoring skin grafts and for supporting body parts and cavities during grafting of vessels and tubes of the body during surgical anastomosis." In 1856 Dr Charles Stent invented a material made of natural latex mixed with stearine, talc and red dye which resulted in a stable flexible material which could be used to make dental molds. Some years later the famous plastic surgeon Harold Gillies in his 1920 book Plastic Surgery of the Face, wrote "The dental composition used for this purpose is that put forward by Stent, and a mold composed of it, is known us a "Stent." This is probably the first use of Stent's name as a noun. The use of the word stent to describe a scaffold in the vascular system was by Dr Charles Dotter who in 1983 published his report on "Transluminal expandable nitinol coil stent grafting." The first coronary stent was implanted in 1986 by Jacques Puel in Toulouse and together with Ulrich Sigwart they were been credited with developing the concept of the coronary stent. This device is now used in more than 80% of angioplasty procedures and provides a scaffold for the local delivery of drugs to the artery to prevent re-narrowing at the site of implantation. Non flowing limiting mid LAD stenosis Most patients who present with an acute coronary syndrome (ACS) undergo coronary angiography and the majority are then treated with percutaneous coronary intervention (PCI). The remaining patients either have coronary artery disease which is not suitable for revascularisation or have lesions which do not appear to be angiographically flow limiting. ACS is thought to arise following rupture or erosion of thin-cap fibroatheroma (TCFA) on vulnerable plaques. When the angiogram shows non-flow limiting, but irregular and hazy lesions, some cardiologists feel uncomfortable treating the patient with medication alone. There is often discussion in the catheter laboratory about whether a coronary stent should be deployed with the rationale that this might "seal" or stabilise" the plaque and reduce the chance of future cardiac events. Advanced imaging with intravascular ultrasound-virtual histology (IVUS-VH) or optical coherence tomography (OCT) may help to identify TCFAs but there is no evidence that treating such lesions with bare metal or drug eluting stents reduces furture coronary events. Any potential benefit of stent treatment needs to be balanced against the risk of procedural complication, re-stenosis and stent thrombosis. A recent trial has sought to address the question of how to treat the vulnerable plaque. The SECRITT study published in Eurointervention in December 2012 investigated the effects of a stenting vulnerable plaque. 23 patients with high risk IVUS-VH and OCT proven TCFA and a non-flow limiting lesion proven with quantitative coronary angiography and FFR by pressure wire were randomised to treatment with a nitinol self-expanding vShield stent. This device has ultrathin 56 micron struts designed to reduce vessel damage and encourage laminar flow. The stent is self expanding and this avoids the need to deploy using conventional high pressure balloons. Following randomisation patient received either the vShield stent (n=13) or standard medical therapy (n=10). The baseline stenosis in the vShield group was 33.2±13.5% and the FFR 0.93±0.06. At six-month follow-up vShield patients had 18.7±16.9% stenosis and FFR was unchanged. The fibrous cap thickness at baseline was 48±12µm increasing to 201±168µm. No dissections occured and there were no plaque ruptures with the VShield. There were no device-related major adverse cardiovascular events (MACE) events at six-month follow-up. In the control group of 5 patients the % diameter stenosis, FFR were unchange at 6 months and there was no significant difference in late loss between the Vshield and medical treated groups. SECRITT is proof of principle study which has demonstrated that passivation and sealing of TCFA with a vShield self-expanding nitinol device appears feasible and safe. Whether treatment of vulerable plaque with conventional stents would have the same results is unknown. A comparison of the VShield with conventional balloon expandable stents has shown conventional stents result in a high proportion tissue prolapse or intra-stent dissection visible with OCT which are less frequently seen with the VShield stent. However, these vessel-wall injuries were not associated with in-hospital clinical events and currently it is difficult to know if OCT-detectable acute vessel-wall injury after stenting is associated with untoward clinical safety events. A long-term, larger randomised study is needed to evaluate the efficacy of stenting the vulnerable plaque is needed, until we have that data intensive medical therapy remains the standard treatment for non-flow limiting lesion. SECRITT Trial Slide Set Comparison of Acute Vessel Wall Injury After Self-Expanding Stent and Conventional Balloon-Expandable Stent Implantation: A Study with Optical Coherence Tomography |
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
August 2023
Categories
All
|