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Percutaneous coronary intervention. II: The procedure Drug eluting, coated stents Coated stents contain drugs that inhibit new tissue growth within the sub-intima and are a promising new option for preventing or treating in-stent restenosis. Sirolimus (an immunosuppressant used to prevent renal rejection which inhibits smooth muscle proliferation and reduces intimal thickening after vascular injury), paclitaxel (the active component of the anticancer drug taxol), everolimus, ABT-578, and tacrolimus are all being studied, as are other agents. Although long term data and cost benefit analyses are not yet available, it seems probable that coated stents will be commonly used in the near future. Occupation and driving Doctors may be asked to advise on whether a patient is “fit for work” or “recovered from an event” after percutaneous coronary intervention. “Fitness” depends on clinical factors (level of symptoms, extent and severity of coronary disease, left ventricular function, stress test result) and the nature of the occupation, as well as statutory and non-statutory fitness requirements. Advisory medical standards are in place for certain occupations, such as in the armed forces and police, railwaymen, and professional divers. Statutory requirements cover the road, marine, and aviation industries and some recreational pursuits such as driving and flying. Patients often ask when they may resume driving after percutaneous coronary intervention. In Britain, the Driver and Vehicle Licensing Agency recommends that group 1 (private motor car) licence holders should stop driving when anginal symptoms occur at rest or at the wheel. After percutaneous coronary intervention, they should not drive for a week. Drivers holding a group 2 licence (lorries or buses) will be disqualified from driving once the diagnosis of angina has been made, and for at least six weeks after percutaneous coronary intervention. Re-licensing may be permitted provided the exercise test requirement (satisfactory completion of nine minutes of the Bruce protocol while not taking
blockers) can be met and there is no other disqualifying condition. The diagram of the Angio-Seal device is used with permission of St Jude Medical, Minnetonka, Minnesota, USA. The angiogram showing the “candy wrapper” effect is reproduced with permission of R Waksman, Washington Hospital Center, and Martin Dunitz, London. Competing interests: None declared. Top left: four months after two stents (yellow lines) were deployed in the proximal and middle right coronary artery, severe diffuse in-stent restenosis has occurred with recurrent angina. Top right: two sirolimus coated Cypher stents (red lines) were deployed within the original stents. Bottom: after six months there was no recurrence of restenosis, and the 51 year old patient remained asymptomatic The incidence of restenosis is particularly high with percutaneous revascularisation of small vessels. A small diseased diagonal artery (arrows, top left) in a 58 year old patient with limiting angina was stented with a sirolimus coated Cypher stent (red line, top right). After six months, no restenosis was present (left), and the patient remained asymptomatic Further reading x Smith SC Jr, Dove JT, Jacobs AK, Kennedy JW, Kereiakes D, Kern MJ, et al. ACC/AHA guidelines of percutaneous coronary interventions (revision of the 1993 PTCA guidelines)—executive summary. A report of the American College of Cardiology/ American Heart Association Task Force on Practice Guidelines (committee to revise the 1993 guidelines for percutaneous transluminal coronary angioplasty). J Am Coll Cardiol 2001;37: 2215{39 x Morice MC, Serruys PW, Sousa JE, Fajadet J, Ban Hayashi E, Perin M, et al. A randomized comparison of a sirolimus-eluting stent with a standard stent for coronary revascularization. N Engl J Med 2002;346:1773-80 x Almond DG. Coronary stenting I: intracoronary stents—form, function future. In: Grech ED, Ramsdale DR, eds. Practical interventional cardiology. 2nd ed. London: Martin Dunitz, 2002:63-76 x Waksman R. Management of restenosis through radiation therapy. In: Grech ED, Ramsdale DR, eds. Practical interventional cardiology. 2nd ed. London: Martin Dunitz, 2002:295-305 x Kimmel SE, Berlin JA, Laskey WK. The relationship between coronary angioplasty procedure volume and major complications. JAMA 1995;274:1137-42 x Rensing BJ, Vos J, Smits PC, Foley DP, van den Brand MJ, van der Giessen WJ, et al. Coronary restenosis elimination with a sirolimus eluting stent. Eur Heart J 2001;22:2125-30 11 4 Chronic stable angina: treatment options Laurence O’Toole, Ever D Grech In patients with chronic stable angina, the factors influencing the choice of coronary revascularisation therapy (percutaneous coronary intervention or coronary artery bypass surgery) are varied and complex. The severity of symptoms, lifestyle, extent of objective ischaemia, and underlying risks must be weighed against the benefits of revascularisation and the patient’s preference, as well as local availability and expertise. Evidence from randomised trials and large revascularisation registers can guide these decisions, but the past decade has seen rapid change in medical treatment, bypass surgery, and percutaneous intervention. Therefore, thought must be given to whether older data still apply to contemporary practice. Patients with chronic stable angina have an average annual mortality of 2-3%, only twice that of age matched controls, and this relatively benign prognosis is an important consideration when determining the merits of revascularisation treatment. Certain patients, however, are at much higher risk. Predictors include poor exercise capacity with easily inducible ischaemia or a poor haemodynamic response to exercise, angina of recent onset, previous myocardial infarction, impaired left ventricular function, and the number of coronary vessels with significant stenoses, especially when disease affects the left main stem or proximal left anterior descending artery. Although the potential benefits of revascularisation must be weighed against adverse factors, those most at risk may have the most to gain. Major factors influencing risks and benefits of coronary revascularisation x x x x x x x Advanced age Female Severe angina Smoking Diabetes Obesity Hypertension x x x x x x x Multiple coronary vessels affected Coexisting valve disease Impaired left ventricular function Impaired renal function Cerebrovascular or peripheral vascular disease Recent acute coronary syndrome Chronic obstructive airways disease Left internal mammary artery with pedicle Saphenous vein graft Treatment strategies Medical treatment Anti-ischaemic drugs improve symptoms and quality of life, but have not been shown to reduce mortality or myocardial infarction.
blockers may improve survival in hypertension, in heart failure, and after myocardial infarction, and so are considered by many to be first line treatment. Nicorandil has recently been shown to reduce ischaemic events and need for hospital admission. Trials comparing medical treatment with revascularisation predate the widespread use of antiplatelet and cholesterol lowering drugs. These drugs reduce risk, both in patients treated with drugs only and in those undergoing revascularisation, and so may have altered the risk-benefit ratio for a particular revascularisation strategy in some patients. Coronary artery bypass graft surgery Coronary artery bypass surgery involves the placement of grafts to bypass stenosed native coronary arteries, while maintaining cerebral and peripheral circulation by cardiopulmonary bypass. The grafts are usually saphenous veins or arteries (principally the left internal mammary artery). Operative mortality is generally 1-3% but may be much higher in certain subsets of patients. Scoring systems can predict operative mortality based on clinical, investigational, and operative factors. Important developments that have occurred since trials of bypass surgery versus medical treatment were conducted include increased use of arterial grafts (which have much greater longevity than venous grafts), surgery without extracorporeal circulation (“off-pump” bypass), and minimal access surgery. 12 Top: Diagrams of saphenous vein and left internal mammary artery grafts for coronary artery bypass surgery. Bottom: Three completed grafts—(1) left internal mammary artery (LIMA) to left anterior descending artery (LAD), and saphenous vein grafts (SVG) to (2) diagonal artery (DG) and (3) obtuse marginal artery (OM) Risk score for assessing probable mortality from bypass surgery in patients with chronic stable angina Risk factor Age > 60 Female sex Chronic obstructive pulmonary disease Extracardiac arteriopathy Neurological dysfunction Previous cardiac surgery Serum creatinine > 200mol/l Reduced left ventricular ejection fraction Myocardial infarction in past 90 days Pulmonary artery systolic pressure > 60 mm Hg Major cardiac procedure as well as bypass surgery Emergency operation x Total score <2 predicts < 1% operative mortality x Total score of 3-5 predicts 3% operative mortality x Total score >6 predicts > 10% operative mortality Weighted score Score 1 for every 5 years over 1 1 2 2 3 2 1 for 30-50% 3 for < 30% 2 2 2 2 A more detailed assessment with logistic analysis is available at www.euroscore.org and is recommended for assessing high risk patients Chronic stable angina: treatment options Percutaneous coronary intervention The main advantages of percutaneous intervention over bypass surgery are the avoidance of the risks of general anaesthesia, uncomfortable sternotomy and saphenous wounds, and complications of major surgery (infections and pulmonary emboli). Only an overnight hospital stay is necessary (and many procedures can be performed as day cases), and the procedure can be easily repeated. The mortality is low (0.2%), and the most serious late complication is restenosis. Patient suitability is primarily determined by technical factors. A focal stenosis on a straight artery without proximal vessel tortuousness or involvement of major side branches is ideal for percutaneous intervention. Long, heavily calcified stenoses in tortuous vessels or at bifurcations and chronic total occlusions are less suitable. This must be borne in mind when interpreting data from trials of percutaneous intervention and bypass surgery, as only a minority of patients were suitable for both procedures. Nowadays, more and more patients undergo percutaneous intervention, and referral rates for bypass surgery are falling. Comparative studies of revascularisation strategies Coronary artery bypass surgery versus medical treatment In a meta-analysis of seven trials comparing bypass surgery with medical treatment, surgery conferred a survival advantage in patients with severe left main stem coronary disease, three vessel disease, or two vessel disease with severely affected proximal left anterior descending artery. The survival gain was more pronounced in patients with left ventricular dysfunction or a strongly positive exercise test. However, only 10% of trial patients received an internal mammary artery graft, only 25% received antiplatelet drugs, and the benefit of lipid lowering drugs on long term graft patency was not appreciated when these studies were carried out. Furthermore, 40% of the medically treated patients underwent bypass surgery during 10 years of follow up. Thus, these data may underestimate the benefits of surgery compared with medical treatment alone. In lower risk patients bypass surgery is indicated only for symptom relief and to improve quality of life when medical treatment has failed. Surgery does this effectively, with 95% of patients gaining immediate relief from angina and 75% remaining free from angina after five years. Unfortunately, venous grafts have a median life span of only seven years, and after 15 years only 15% of patients are free from recurrent angina or death or myocardial infarction. However, the increased use of internal mammary artery grafts, which have excellent long term patency (85% at 10 years), has increased postoperative survival and reduced long term symptoms. Subgroup analysis of mortality benefit from coronary artery bypass surgery compared with medical treatment at 10 years after randomisation for patients with chronic stable angina Subgroup Mean (1.96 SE) increased survival time (months) P value of difference 1.8 (3.0) 5.7 (3.6) 19.3 (13.7) 0.25 0.001 0.005 Vessel disease: 1 or 2 vessels 3 vessels Left main stem Left ventricular function: Normal Abnormal Exercise test: Normal Abnormal Severity of angina: CCS class 0, I, II CCS class III, IV 2.3 (2.4) 10.6 (6.1) 0.06 < 0.001 3.3 (4.4) 5.1 (3.3) 0.14 0.002 3.3 (2.7) 7.3 (4.8) 0.02 0.002 CCS=Canadian Cardiovascular Society Left: Angiogram of a 10 year old diseased venous graft to the obtuse marginal artery showing proximal aneurysmal dilatation (A) and severe stenosis in middle segment (B). Right: Removal of this graft after repeat bypass surgery shows its gross appearance (graft longitudinally opened in right image), with atherosclerosis in a thin walled aneurysm and a small residual lumen Old saphenous vein grafts may contain large amounts of necrotic clotted debris, friable laminated thrombus, and ulcerated atheromatous plaque and are unattractive for percutaneous intervention because of the high risk of distal embolisation. However, distal embolisation protection devices such as the FilterWire EX (far right) reduce this risk by trapping any material released. Such a device (far left, B) is positioned in the distal segment of a subtotally occluded saphenous vein graft of the left anterior descending artery (A) before it is dilated and stented (inner left, C) to restore blood flow (inner right) 13 ABC of Interventional Cardiology Percutaneous coronary intervention versus medical treatment Most percutaneous procedures are undertaken to treat single vessel or two vessel disease, but few randomised controlled trials have compared percutaneous intervention with medical treatment. These showed that patients undergoing the percutaneous procedure derived greater angina relief and took less drugs but required more subsequent procedures and had more complications (including non-fatal myocardial infarction), with no mortality difference. Patients with few symptoms did not derive benefit. Therefore, percutaneous intervention is suitable for low risk patients with one or two vessel disease and poor symptom control with drugs, at a cost of a slightly higher risk of non-fatal myocardial infarction. However, the procedure may not be indicated if symptoms are well controlled. Coronary angiogram showing a severe focal stenosis (arrow) in a large oblique marginal branch of the left circumflex artery (LCx), suitable for percutaneous coronary intervention. The left anterior descending artery (LAD) has no important disease Percutaneous intervention versus bypass surgery Single vessel disease In a meta-analysis by Pocock et al percutaneous intervention in patients with single vessel disease resulted in mortality similar to that found with bypass surgery (3.7% v 3.1% respectively) but a higher rate of non-fatal myocardial infarction (10.1% v 6.1%, P=0.04). Angina was well treated in both groups, but persistence of symptoms was slightly higher with percutaneous intervention. Rates of repeat revascularisation were much higher with percutaneous intervention than bypass surgery. Multivessel disease Since comparative trials could recruit only those patients who were suitable for either revascularisation strategy, only 3-7% of screened patients were included. These were predominantly “low risk” patients with two vessel disease and preserved left ventricular function—patients in whom bypass surgery has not been shown to improve survival—and thus it is unlikely that a positive effect in favour of percutaneous intervention would have been detected. The generally benign prognosis of chronic stable angina means that much larger trials would have been required to show significant differences in mortality. A meta-analysis of data available to the end of 2000 revealed similar rates of death and myocardial infarction with both procedures, but repeat revascularisation rates were higher with percutaneous intervention. The prevalence of appreciable angina was greater with percutaneous intervention at one year, but this difference disappeared at three years. The nature of percutaneous coronary intervention has changed considerably over the past 10 years, with important developments including stenting and improved antiplatelet drugs. The integrated use of these treatments clearly improves outcomes, but almost all of the revascularisation trials predate these developments. A more recent trial comparing percutaneous intervention and stenting with bypass surgery in multivessel disease confirmed similar rates of death, myocardial infarction, and stroke at one year, with much lower rates of repeat revascularisation after percutaneous intervention compared with earlier trials. There was also a cost benefit of nearly $3000 (£1875) per patient associated with percutaneous intervention at 12 months. The recent introduction of drug eluting (coated) stents, which seem to reduce substantially the problem of restenosis, is likely to extend the use of percutaneous intervention in multivessel disease over the next few years. Diabetes Bypass surgery confers a survival advantage in symptomatic diabetic patients with multivessel disease The BARI trial 14 Coronary angiograms of 70 year old woman with limiting angina. There were severe stenoses (arrows) in the proximal and middle left anterior descending artery (LAD, top) and in the distal right coronary artery (RCA, left). Because of the focal nature of these lesions, percutaneous coronary intervention was the preferred option Coronary angiograms of a 69 year old man with limiting angina and exertional breathlessness. There was severe proximal disease (arrows) of the left anterior descending (LAD) and left circumflex arteries (LCx) (top) and occlusion of the right coronary artery (RCA, left). The patient was referred for coronary artery bypass surgery on prognostic and symptomatic grounds Chronic stable angina: treatment options revealed a significant difference in five year mortality (21% with percutaneous intervention v 6% with bypass surgery). Similar trends have been found in other large trials. However, the recent RAVEL and SIRIUS studies, in which the sirolimus eluting Cypher stent was compared with the same stent uncoated, showed a remarkable reduction in restenosis rates within the stented segments in diabetic patients (0% v 42% and 18% v 51% respectively). Ongoing trials will investigate this issue further. Other study data Large registries of outcomes in patients undergoing revascularisation have the advantage of including all patients rather than the highly selected groups included in randomised trials. The registry data seem to agree with those from randomised trials: patients with more extensive disease fare better with bypass surgery, whereas percutaneous intervention is preferable in focal coronary artery disease. An unusual observation is that patients screened and considered suitable for inclusion in a trial fared slightly better if they refused to participate than did those who enrolled. The heterogeneous nature of coronary disease means that certain patient subsets will probably benefit more from one treatment than another. The better outcome in the patients who were suitable but not randomised may indicate that cardiologists and surgeons recognise which patients will benefit more from a particular strategy—subtleties that are lost in the randomisation process of controlled trials. Refractory coronary artery disease Increasing numbers of patients with coronary artery disease have angina that is unresponsive to both maximal drug treatment and revascularisation techniques. Many will have already undergone multiple percutaneous interventions or bypass surgery procedures, or have diffuse and distal coronary artery disease. In addition to functional limitations, their prognosis may be poor because of impaired ventricular function. Emerging treatments may provide alternative symptomatic improvement for some patients. There is also renewed interest in the potential anti-ischaemic effects of angiotensin converting enzyme inhibitors and the plaque stabilising properties of statins. The picture showing three completed coronary artery bypass grafts and the pictures of a 10 year old diseased venous graft to the obtuse marginal artery were provided by G Singh, consultant cardiothoracic surgeon, Heath Sciences Centre, Winnipeg, E Pascoe, consultant cardiothoracic surgeon, St Boniface Hospital, Winnipeg, and J Scatliff, consultant anaesthetist, St Boniface Hospital. The picture of the FilterWire EX distal embolisation protection device was provided by Boston Scientific Corporation, Minneapolis, USA. Competing interests: None declared. Names of trials x BARI—Bypass angioplasty revascularisation investigation x SIRIUS—Sirolimus-coated velocity stent in treatment of patients with de novo coronary artery lesions trial x RAVEL—Randomised study with the sirolimus-eluting velocity balloon-expandable stent in the treatment of patients with de novo native coronary artery lesions Emerging treatment options for refractory angina x Drugs—Analgesics, statins, angiotensin converting enzyme inhibitors, antiplatelet drugs x Neurostimulation—Interruption or modification of afferent nociceptive signals: transcutaneous electric nerve stimulation (TENS), spinal cord stimulation (SCS) x Enhanced external counterpulsation—Non-invasive pneumatic leg compression, improving coronary perfusion and decreasing left ventricular afterload x Laser revascularisation—Small myocardial channels created by laser beams: transmyocardial laser revascularisation (TMLR), percutaneous transmyocardial laser revascularisation (PTMLR) x Therapeutic angiogenesis—Cytokines, vascular endothelial growth factor, and fibroblast growth factor injected into ischaemic myocardium, or adenoviral vector for gene transport to promote neovascularisation x Percutaneous in situ coronary venous arterialisation (PICVA)—Flow redirection from diseased coronary artery into adjacent coronary vein, causing arterialisation of the vein and retroperfusion into ischaemic myocardium x Percutaneous in situ coronary artery bypass (PICAB)—Flow redirection from diseased artery into adjacent coronary vein and then rerouted back into the artery after the lesion x Heart transplantation—May be considered when all alternative treatments have failed Further reading x Yusuf S, Zucker D, Peduzzi P, Fisher LD, Takaro T, Kennedy JW, et al. Effect of coronary artery bypass graft surgery on survival; overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration. Lancet 1994; 344: 563-70 x Pocock SJ, Henderson RA, Rickards AF, Hampton JR, King SB 3rd, Hamm CW, et al. Meta-analysis of randomised trials comparing coronary angioplasty with bypass surgery. Lancet 1995;345:1184-9 x Raco DL, Yusuf S. Overview of randomised trials of percutaneous coronary intervention: comparison with medical and surgical therapy for chronic coronary artery disease. In: Grech ED, Ramsdale DR, eds. Practical interventional cardiology. 2nd ed. London: Martin Dunitz, 2002:263-77 x Serruys PW, Unger F, Sousa JE, Jatene A, Bonnier HJ, Schonberger JP, et al for the Arterial Revascularisation Therapies Study (ARTS) Group. Comparison of coronary-artery bypass surgery and stenting for multivessel disease. N Engl J Med 2001;344:1117-24 x Kim MC, Kini A, Sharma SK. Refractory angina pectoris. Mechanisms and therapeutic options. J Am Coll Cardiol 2002;39: 923-34 x Morice M-C, Serruys PW, Sousa JE, Fajadet J, Ban Hayashi E, Perin M, et al. A randomized comparison of a sirolimus-eluting stent with a standard stent for coronary revascularization. N Engl J Med 2002;346:1773-80 x Scottish Intercollegiate Guidelines Network. Coronary revascularisation in the management of stable angina pectoris. Edinburgh: SIGN, 1998 (SIGN Publication No 32) 15 5 Acute coronary syndrome: unstable angina and non-ST segment elevation myocardial infarction Ever D Grech, David R Ramsdale The term acute coronary syndrome refers to a range of acute myocardial ischaemic states. It encompasses unstable angina, non-ST segment elevation myocardial infarction (ST segment elevation generally absent), and ST segment elevation infarction (persistent ST segment elevation usually present). This article will focus on the role of percutaneous coronary intervention in the management of unstable angina and non-ST segment elevation myocardial infarction; the next article will address the role of percutaneous intervention in ST segment elevation infarction. Although there is no universally accepted definition of unstable angina, it has been described as a clinical syndrome between stable angina and acute myocardial infarction. This broad definition encompasses many patients presenting with varying histories and reflects the complex pathophysiological mechanisms operating at different times and with different outcomes. Three main presentations have been described— angina at rest, new onset angina, and increasing angina. Pathogenesis The process central to the initiation of an acute coronary syndrome is disruption of an atheromatous plaque. Fissuring or rupture of these plaques—and consequent exposure of core constituents such as lipid, smooth muscle, and foam cells—leads to the local generation of thrombin and deposition of fibrin. This in turn promotes platelet aggregation and adhesion and the formation of intracoronary thrombus. Unstable angina and non-ST segment elevation myocardial infarction are generally associated with white, platelet-rich, and only partially occlusive thrombus. Microthrombi can detach and embolise downstream, causing myocardial ischaemia and infarction. In contrast, ST segment elevation (or Q wave) myocardial infarction has red, fibrin-rich, and more stable occlusive thrombus. Plaque disruption or erosion Thrombus formation with or without embolisation Acute cardiac ischaemia No ST segment elevation ST segment elevation Markers of myocardial necrosis not elevated Elevated markers of myocardial necrosis Elevated markers of myocardial necrosis Unstable angina Non-ST segment elevation myocardial infarction (Q waves usually absent) ST segment elevation myocardial infarction (Q waves usually present) Acute coronary syndromes Spectrum of acute coronary syndromes according to electrocardiographic and biochemical markers of myocardial necrosis (troponin T, troponin I, and creatine kinase MB), in patients presenting with acute cardiac chest pain Three main presentations of unstable angina x Angina at rest—Also prolonged, usually > 20 minutes x Angina of new onset—At least CCS class III in severity x Angina increasing—Previously diagnosed angina that has become more frequent, longer in duration, or lower in threshold (change in severity by >1 CCS class to at least CCS class III) CCS=Canadian Cardiovascular Society Platelet-rich thrombus Activated platelets Key Epidemiology Collagen Intima Unstable angina and non-ST segment elevation myocardial infarction account for about 2.5 million hospital admissions worldwide and are a major cause of mortality and morbidity in Western countries. The prognosis is substantially worse than for chronic stable angina. In-hospital death and re-infarction affect 5-10%. Despite optimal treatment with anti-ischaemic and antithrombotic drugs, death and recurrent myocardial infarction occur in another 5-10% of patients in the month after an acute episode. Several studies indicate that these patients may have a higher long term risk of death and myocardial infarction than do patients with ST segment elevation. Diagnosis Unstable angina and non-ST segment elevation myocardial infarction are closely related conditions with clinical presentations that may be indistinguishable. Their distinction depends on whether the ischaemia is severe enough to cause myocardial damage and the release of detectable quantities of 16 Lumen Media Dividing smooth muscle cell Oxidised low density lipoprotein Lysosomes Adventitia Diagram of an unstable plaque with superimposed luminal thrombus Distal embolisation of a platelet-rich thrombus causing occlusion of intramyocardial arteriole (arrow). Such an event may result in micro-infarction and elevation of markers of myocardial necrosis Acute coronary syndrome: unstable angina and non-ST segment elevation myocardial infarction markers of myocyte necrosis. Cardiac troponin I and T are the preferred markers as they are more specific and reliable than creatine kinase or its isoenzyme creatine kinase MB. An electrocardiogram may be normal or show minor non{specific changes, ST segment depression, T wave inversion, bundle branch block, or transient ST segment elevation that resolves spontaneously or after nitrate is given. Physical examination may exclude important differential diagnoses such as pleuritis, pericarditis, or pneumothorax, as well as revealing evidence of ventricular failure and haemodynamic instability. I aVR V1 V4 II aVL V2 V5 III aVF V3 V6 Management Management has evolved considerably over the past decade. As platelet aggregation and thrombus formation play a key role in acute coronary syndrome, recent advances in treatment (such as the glycoprotein IIb/IIIa inhibitors, low molecular weight heparin, and clopidogrel) and the safer and more widespread use of percutaneous coronary intervention have raised questions about optimal management. As patients with unstable angina or non-ST segment elevation myocardial infarction represent a heterogeneous group with a wide spectrum of clinical outcomes, tailoring treatment to match risk not only ensures that patients who will benefit the most receive appropriate treatment, but also avoids potentially hazardous treatment in those with a good prognosis. Therefore, an accurate diagnosis and estimation of the risk of adverse outcome are prerequisites to selecting the most appropriate treatment. This should begin in the emergency department and continue throughout the hospital admission. Ideally, all patients should be assessed by a cardiologist on the day of presentation. II Electrocardiogram of a 48 year old woman with unstable angina (top). Note the acute ischaemic changes in leads V1 to V5 (arrows). Coronary angiography revealed a severe mid-left anterior descending coronary artery stenosis (arrow, bottom left), which was successfully stented (bottom right) Medical treatment Medical treatment includes bed rest, oxygen, opiate analgesics to relieve pain, and anti-ischaemic and antithrombotic drugs. These should be started at once on admission and continued in those with probable or confirmed unstable angina or non-ST segment elevation myocardial infarction. Anti-ischaemic drugs include intravenous, oral, or buccal nitroglycerin,
blockers, and calcium antagonists. Antithrombotic drugs include aspirin, clopidogrel, intravenous unfractionated heparin or low molecular weight heparin, and glycoprotein IIb/IIIa inhibitors. Conservative versus early invasive strategy “Conservative” treatment involves intensive medical management, followed by risk stratification by non-invasive means (usually by stress testing) to identify patients who may need coronary angiography. This approach is based on the results of two randomised trials (TIMI IIIB and VANQWISH), which showed no improvement in outcome when an “early invasive” strategy was used routinely, compared with a selective approach. These findings generated much controversy and have been superseded by more recent randomised trials (FRISC II, TACTICS-TIMI 18, and RITA 3), which have taken advantage of the benefits of glycoprotein IIb/IIIa inhibitors and stents. All three studies showed that an early invasive strategy (percutaneous coronary intervention or coronary artery bypass surgery) produced a better outcome than non-invasive management. TACTICS-TIMI 18 also showed that the benefit of early invasive treatment was greatest in higher risk patients with raised plasma concentrations of troponin T, whereas the outcomes for lower risk patients were similar with early invasive and non-invasive management. Right coronary artery angiogram in patient with non-ST segment elevation myocardial infarction (top left), showing hazy appearance of intraluminal thrombus overlying a severe stenosis (arrow). Abciximab was given before direct stenting (top right), with good angiographic outcome (bottom) Names of trials x TIMI IIIB—Thrombolysis in myocardial infarction IIIB x VANQWISH—Veterans affairs non-Q-wave infarction strategies in hospital x GUSTO IV ACS—Global use of strategies to open occluded arteries-IV in acute coronary syndromes x RITA 3—Randomised intervention treatment of angina x FRISC II—Fast revascularisation during instability in coronary artery disease x TACTICS-TIMI 18—Treat angina with Aggrastat and determine cost of therapy with an invasive or conservative strategy-thrombolysis in myocardial infarction 17 ABC of Interventional Cardiology The TIMI risk score Attempts have been made to formulate clinical factors into a user friendly model. Notably, Antman and colleagues identified seven independent prognostic risk factors for early death and myocardial infarction. Assigning a value of 1 for each risk factor present provides a simple scoring system for estimating risk, the TIMI risk score. It has the advantage of being easy to calculate and has broad applicability in the early assessment of patients. Applying this score to the results in the TACTICS-TIMI 18 study indicated that patients with a TIMI risk score of >3 benefited significantly from an early invasive strategy, whereas those with a score of <2 did not. Therefore, those with an initial TIMI score of >3 should be considered for early angiography (ideally within 24 hours), with a view to revascularisation by percutaneous intervention or bypass surgery. In addition, any patient with an elevated plasma concentration of troponin marker, ST segment changes, or haemodynamic instability should also undergo early angiography. Conclusion The diagnosis of unstable angina or non-ST segment elevation myocardial infarction demands urgent hospital admission and coronary monitoring. A clinical history and examination, 12 lead electrocardiography, and measurement of troponin concentration are the essential diagnostic tools. Bed rest, aspirin, clopidogrel, heparin, antianginal drugs, and opiate analgesics are the mainstay of initial treatment. Early risk stratification will help identify high risk patients, who may require early treatment with glycoprotein IIb/IIIa inhibitors, angiography, and coronary revascularisation. Those deemed suitable for percutaneous intervention should receive a glycoprotein IIb/IIIa inhibitor and stenting as appropriate. There seems to be little merit in prolonged stabilisation of patients before percutaneous intervention, and an early invasive strategy is generally preferable to a conservative one except for patients at low risk of further cardiac events. This approach will shorten hospital stays, improve acute and long term outcomes, and reduce the need for subsequent intervention. In the longer term, aggressive modification of risk factors is warranted. Smoking should be strongly discouraged, and statins should be used to lower blood lipid levels. Long term treatment with aspirin, clopidogrel (especially after stenting),
blockers, angiotensin converting enzyme inhibitors, and antihypertensive drugs should also be considered. Anti-ischaemic drugs may be stopped when ischaemia provocation tests are negative. The picture of a microthrombus occluding an intramyocardial arteriole was provided by K MacDonald, consultant histopathologist, St Boniface Hospital, Winnipeg. Competing interests: None declared. 18 The seven variables for the TIMI risk score x x x x x x x Age >65 years >3 risk factors for coronary artery disease >50% coronary stenosis on angiography ST segment change > 0.5 mm >2 anginal episodes in 24 hours before presentation Elevated serum concentration of cardiac markers Use of aspirin in 7 days before presentation Death or myocardial infarction at 14 days (%) Identifying higher risk patients Identifying patients at higher risk of death, myocardial infarction, and recurrent ischaemia allows aggressive antithrombotic treatment and early coronary angiography to be targeted to those who will benefit. The initial diagnosis is made on the basis of a patient’s history, electrocardiography, and the presence of elevated plasma concentrations of biochemical markers. The same information is used to assess the risk of an adverse outcome. It should be emphasised that risk assessment is a continuous process. Low risk 20 Higher risk 15 10 5 0 0 or 1 2 3 4 5 6 or 7 No of TIMI risk factors present Rates of death from all causes and non-fatal myocardial infarction at 14 days, by TIMI risk score. Note sharp rate increase when score >3 Unstable angina or non-ST segment elevation myocardial infarction TIMI risk assessment on presentation (aspirin, clopidogrel, heparin, nitrates, β blockers) Low risk (TIMI risk score 0-2, negative troponin test) Higher risk (TIMI risk score >3, positive troponin test, dynamic ST changes, or haemodynamically unstable) Conservative management Invasive management Stress test Possible glycoprotein IIb/IIIa inhibitor Negative Positive Coronary angiography Discharge Percutaneous coronary intervention plus glycoprotein IIb/IIIa inhibitor Coronary artery bypass surgery Medical treatment Simplified management pathway for patients with unstable angina or non-ST segment elevation myocardial infarction Further reading x Braunwald E, Antman EM, Beasley JW, Califf RM, Cheitlin MD, Hochman JS, et al. ACC/AHA 2002 guideline update for the management of patients with unstable angina and non-ST-segment elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association task force on practice guidelines. J Am Coll Cardiol 2002;40:1366-74 x Bertrand ME, Simoons ML, Fox KA, Wallentin LC, Hamm CW, McFadden E, et al. Management of acute coronary syndromes: acute coronary syndromes without persistent ST segment elevation. Recommendations of the Task Force of the European Society of Cardiology. Eur Heart J 2000;21:1406-32 x Antman EM, Cohen M, Bernink PJ, McCabe CH, Horacek T, Papuchis G, et al. The TIMI risk score for unstable angina/non-ST elevation MI: a method for prognostication and therapeutic decision making. JAMA 2000;284:835-42 x Ramsdale DR, Grech ED. Percutaneous coronary intervention unstable angina and non-Q-wave myocardial infarction. In: Grech ED, Ramsdale DR, eds. Practical interventional cardiology. 2nd ed. London: Martin Dunitz, 2002:165-87 6 Acute coronary syndrome: ST segment elevation myocardial infarction Ever D Grech, David R Ramsdale Acute ST segment elevation myocardial infarction usually occurs when thrombus forms on a ruptured atheromatous plaque and occludes an epicardial coronary artery. Patient survival depends on several factors, the most important being restoration of brisk antegrade coronary flow, the time taken to achieve this, and the sustained patency of the affected artery. Recanalisation There are two main methods of re-opening an occluded artery: administering a thrombolytic agent or primary percutaneous transluminal coronary angioplasty. Although thrombolysis is the commonest form of treatment for acute myocardial infarction, it has important limitations: a rate of recanalisation (restoring normal flow) in 90 minutes of only 55% with streptokinase or 60% with accelerated alteplase; a 5-15% risk of early or late reocclusion leading to acute myocardial infarction, worsening ventricular function, or death; a 1-2% risk of intracranial haemorrhage, with 40% mortality; and 15-20% of patients with a contraindication to thrombolysis. Primary angioplasty (also called direct angioplasty) mechanically disrupts the occlusive thrombus and compresses the underlying stenosis, rapidly restoring blood flow. It offers a superior alternative to thrombolysis in the immediate treatment of ST segment elevation myocardial infarction. This differs from sequential angioplasty, when angioplasty is performed after thrombolysis. After early trials of thrombolytic drugs, there was much interest in “adjunctive” angioplasty (angioplasty used as a supplement to successful thrombolysis) as this was expected to reduce recurrent ischaemia and re-infarction. Later studies, however, not only failed to show any advantage, but found higher rates of major haemorrhage and emergency bypass surgery. In contrast, “rescue” (also known as “salvage”) angioplasty, which is performed if thrombolysis fails to restore patency after one to two hours, may confer benefit. Pros and cons of primary angioplasty Incidence (%) Advantages Large randomised studies have shown that thrombolysis significantly reduces mortality compared with placebo, and this effect is maintained long term. Primary angioplasty confers 15 Mortality 3 Cerebrovascular events Histological appearance of a ruptured atheromatous plaque (bottom arrow) and occlusive thrombus (top arrow) resulting in acute myocardial infarction Acute ST segment elevation myocardial infarction Thrombolytic treatment Primary angioplasty Infarct artery not recanalised Infarct artery recanalised, but significant residual stenosis Rescue angioplasty (1-2 hours after failed thrombolysis) Elective angioplasty (if continued ischaemia) Adjunctive angioplasty Deferred angioplasty (1-7 days after thrombolysis) Methods of recanalisation for acute myocardial infarction Comparison of methods of recanalisation Thrombolysis Time from admission to recanalisation Recanalisation with brisk antegrade flow Systemic fibrinolysis Staff and catheter laboratory “burden” Cost of procedure 8 Rescue Primary angioplasty angioplasty 1-3 hours after start of thrombolysis 55-60% Time to start of thrombolysis plus 2 hours 85% 20-60 minutes +++ − +++ + − +++ + +++ +++ 95% Re-infarction P<0.0001 P<0.0001 P=0.0002 10 P=0.0004 4 P<0.0001 5 6 2 1 2 0 9 studies (n=58 600)* 23 studies (n=7437)✝ 0 * FTT Collaborative Group, Lancet 1994;343:311-22 ✝ Keeley et al, Lancet 2003;361:13-20 9 studies (n=58 600)* 23 studies (n=6271)✝ Controls 0 23 studies (n=6497)✝ Thrombolytic PCI Effects of treatment with placebo, thrombolytic drugs, or primary percutaneous coronary intervention (PCI) on mortality, incidence of cerebrovascular events, and incidence of non-fatal re-infarction after acute myocardial infarction in randomised studies. Of the 1% incidence of cerebrovascular events in patients undergoing primary percutaneous intervention, only 0.05% were haemorrhagic. In contrast patients receiving thrombolytic drugs had a 1% incidence of haemorrhagic cerebrovascular events (P<0.0001) and an overall 2% incidence of cerebrovascular events (P=0.0004) 19 ABC of Interventional Cardiology extra benefits in terms of substantial reductions in rates of death, cerebrovascular events, and re-infarction. The information provided by immediate coronary angiography is valuable in determining subsequent management. Patients with severe three vessel disease, severe left main coronary artery stenosis, or occluded vessels unsuitable for angioplasty can be referred for bypass surgery. Conversely, patients whose arteries are found to have spontaneously recanalised or who have an insignificant infarct related artery may be selected for medical treatment, and thus avoid unnecessary thrombolytic treatment. Disadvantages The morbidity and mortality associated with primary angioplasty is operator dependent, varying with the skill and experience of the interventionist, and it should be considered only for patients presenting early ( < 12 hours after acute myocardial infarction). Procedural complications are more common than with elective angioplasty for chronic angina, and, even though it is usual to deal only with the occluded vessel, procedures may be prolonged. Ventricular arrhythmias are not unusual on recanalisation, but these generally occur while the patient is still in the catheterisation laboratory and can be promptly treated by intravenous drugs or electrical cardioversion. Right coronary artery procedures are often associated with sinus arrest, atrioventricular block, idioventricular rhythm, and severe hypotension. Up to 5% of patients initially referred for primary angioplasty require urgent coronary artery bypass surgery, so surgical backup is essential if risks are to be minimised. There are logistical hurdles in delivering a full 24 hour service. Primary angioplasty can be performed only when adequate facilities and experienced staff are available. The time from admission to recanalisation should be less than 60 minutes, which may not be possible if staff are on call from home. However, recent evidence suggests that, even with longer delays, primary angioplasty may still be superior to thrombolysis. A catheterisation laboratory requires large initial capital expenditure and has substantial running costs. However, in an existing, fully supported laboratory operating at high volume, primary angioplasty is at least as cost effective as thrombolysis. Severe distal left main stem stenosis (arrow 1) and partially occluded mid-left anterior descending artery due to thrombus (arrow 2). In view of the severity of the lesion salvage angioplasty was contraindicated. An intra-aortic balloon pump was used to augment blood pressure and coronary flow before successful bypass surgery Pros and cons of primary angioplasty* compared with thrombolysis Advantages x High patency rates ( > 90%) with brisk, antegrade flow x Lower mortality x Better residual left ventricular function x More rapid electrocardiographic normalisation x Less recurrent ischaemia (angina, reinfarction, exercise induced ischaemia) x No systemic fibrinolysis, therefore bleeding problems avoided x Improved risk stratification by angiography with identification of patients suitable for coronary artery bypass surgery Disadvantages x Higher procedural cost than streptokinase or alteplase (although long term costs lower) x Can be performed only when cardiac catheterisation facilities and experienced staff available x Recanalisation more rapid than thrombolysis only if 24 hour on-call team available x Risks and complications of cardiac catheterisation and percutaneous intervention x Reperfusion arrhythmias probably more common because of more rapid recanalisation *With or without stenting Primary angioplasty and coronary stents Although early randomised studies of primary angioplasty showed its clinical effectiveness, outcomes were marred by high rates of recurrent ischaemia (10-15% of patients) and early reinfarction of the affected artery (up to 5%). Consequently, haemodynamic and arrhythmic complications arose, with the need for repeat catheterisation and revascularisation, prolonged hospital stay, and increased costs. Furthermore, restenosis rates in the first six months remained disappointingly high (25-45%), and a fifth of patients required revascularisation. Although stenting the lesion seemed an attractive answer, it was initially thought that deploying a stent in the presence of thrombus over a ruptured plaque would provoke further thrombosis. However, improvements in stent deployment and advances in adjunctive pharmacotherapy have led to greater technical success. Recent studies comparing primary stenting with balloon angioplasty alone have shown that stented patients have significantly less recurrent ischaemia, reinfarction, and subsequent need for further angioplasty. Economic analysis has shown that, as expected, the initial costs were higher but were offset by lower follow up costs after a year. 20 Anterior myocardial infarction of 4 hours’ duration and severe hypotension, caused by a totally occluded proximal left anterior descending artery (arrow, top left). After treatment with abciximab, a stent was positioned. Initial inflation showed “waisting” of the balloon (top right), due to fibrous lesion resistance, which resolved on higher inflation (bottom left). Successful recanalisation resulted in brisk flow (bottom right), and the 15 minute procedure completely resolved the patient’s chest pain