Percutaneous transluminal coronary angioplasty after thrombolytic therapy: a prospective controlled randomized trial

Design and Execution of Clinical Trials in the Cardiac Intensive Care Unit

Clinical practice in the contemporary cardiac intensive care unit (CICU) has evolved significantly over the last several decades. With more frequent multisystem organ failure, increasing use of advanced respiratory support, and the advent of new mechanical circulatory support platforms, clinicians in the CICU are increasingly managing patients with complex comorbid disease in addition to their high-acuity cardiovascular illnesses. Here, the authors discuss challenges associated with traditional trial design in the CICU setting and review novel clinical trial designs that may facilitate better evidence generation in the CICU.

Multivessel vs. culprit-lesion only percutaneous coronary intervention in ST-elevation myocardial infarction

The optimal treatment of non-infarct-related coronary arteries in patients presenting with ST-elevation myocardial infarction (STEMI) has been a subject of debate for many years. Earlier medium-sized randomized controlled trials reported a benefit of multivessel percutaneous coronary intervention (PCI) primarily due to a reduction of subsequent revascularizations. Recently, the well-powered COMPLETE trial showed a reduction in the composite endpoint of cardiovascular mortality and myocardial reinfarction through complete revascularization. The present review summarizes the current evidence regarding revascularization strategies in STEMI patients.

Adjunctive Pharmacotherapy for Thrombotic Coronary Lesions

Patients with unstable coronary syndromes are often found to have intracoronary thrombus on angiography. Despite advancements in catheter-based treatments for coronary disease, these lesions remain challenging, as percutaneous coronary intervention of thrombus-containing lesions may be associated with worse outcomes. This article reviews the literature on adjunctive pharmacotherapy in the treatment of thrombotic coronary lesions with special focus on ST-segment elevation myocardial infarction, lesions with high thrombus burden, and saphenous vein graft intervention.

An early invasive strategy versus ischemia-guided management after fibrinolytic therapy for ST-segment elevation myocardial infarction: a meta-analysis of contemporary randomized controlled trials

BACKGROUND

Although the use of an early invasive strategy among patients with ST-segment elevation myocardial infarctions (STEMI) who are treated initially with fibrinolytic therapy is common, the safety and efficacy of this approach remains uncertain. We performed a meta-analysis to best estimate the benefits and harms of an early invasive strategy in STEMI patients treated initially with full-dose intravenous fibrinolytic therapy, as compared to a traditional strategy of ischemia-guided management.

METHODS

We included contemporary randomized controlled trials, defined a priori as those with >50% stent use during percutaneous coronary intervention (PCI). Outcomes extracted from the published results of eligible trials included all-cause mortality, reinfarction, stroke, and in-hospital major bleeding.

RESULTS

We identified 5 contemporary trials enrolling 1,235 patients who met our inclusion criteria. Of the patients randomized to an early invasive strategy, 86% underwent PCI with 87% receiving stents. Follow-up duration ranged from 30 days to 1 year. An early invasive strategy was associated with significant reductions in mortality (odds ratio [OR] 0.55, 95% CI 0.34-0.90) and reinfarction (OR 0.53, 95% CI 0.33-0.86) compared with ischemia-guided management. There were no significant differences in the risk of stroke (OR 1.31, 95% CI 0.42-4.10) or major bleeding (OR 1.41, 95% CI 0.74-2.69).

CONCLUSIONS

An early invasive strategy after fibrinolytic therapy is associated with significant reductions in mortality and reinfarction. Our results suggest a potentially important role for this strategy in the management of STEMI patients but should be confirmed by large randomized trials.

Overview of contemporary reperfusion strategies in acute ST-elevation myocardial infarction

The rupture of an atherosclerotic plaque in an epicardial coronary artery with subsequent occlusive coronary thrombosis has been established as the decisive event in the pathogenesis of an acute coronary syndrome, which encompasses the clinical entities of unstable angina, non-ST- and ST-elevation myocardial infarction. This article focuses on contemporary treatment strategies for patients with acute ST-elevation myocardial infarction and reviews the role of pharmacologic thrombolysis and mechanical reperfusion by percutaneous transluminal approaches. Statements of the latest guidelines for the treatment of ST-elevation myocardial infarction are included, as well as some recently distributed information not covered by the guideline publications. Finally, some future perspectives for the treatment of acute ST-elevation myocardial infarction are outlined.

Early and long-term outcome of elective stenting of the infarct-related artery in patients with viability in the infarct-area: Rationale and design of the Viability-guided Angioplasty after acute Myocardial Infarction-trial (The VIAMI-trial)

Background

Although percutaneous coronary intervention (PCI) is becoming the standard therapy in ST-segment elevation myocardial infarction (STEMI), to date most patients, even in developed countries, are reperfused with intravenous thrombolysis or do not receive a reperfusion therapy at all. In the post-lysis period these patients are at high risk for recurrent ischemic events. Early identification of these patients is mandatory as this subgroup could possibly benefit from an angioplasty of the infarct-related artery.

Since viability seems to be related to ischemic adverse events, we initiated a clinical trial to investigate the benefits of PCI with stenting of the infarct-related artery in patients with viability detected early after acute myocardial infarction.

Methods

The VIAMI-study is designed as a prospective, multicenter, randomized, controlled clinical trial. Patients who are hospitalized with an acute myocardial infarction and who did not have primary or rescue PCI, undergo viability testing by low-dose dobutamine echocardiography (LDDE) within 3 days of admission. Consequently, patients with demonstrated viability are randomized to an invasive or conservative strategy. In the invasive strategy patients undergo coronary angiography with the intention to perform PCI with stenting of the infarct-related coronary artery and concomitant use of abciximab. In the conservative group an ischemia-guided approach is adopted (standard optimal care).

The primary end point is the composite of death from any cause, reinfarction and unstable angina during a follow-up period of three years.

Conclusion

The primary objective of the VIAMI-trial is to demonstrate that angioplasty of the infarct-related coronary artery with stenting and concomitant use of abciximab results in a clinically important risk reduction of future cardiac events in patients with viability in the infarct-area, detected early after myocardial infarction.

Reappraising the role of immediate intervention following thrombolytic recanalization in acute myocardial infarction

Early studies indicated that after successful thrombolytic recanalization, adjunctive percutaneous transluminal coronary angioplasty (PTCA) was not appropriate, even when a significant residual stenosis was present. The aim of this study was to assess in-hospital clinical outcomes of patients with acute myocardial infarction (AMI) who underwent successful recanalization after thrombolytic therapy. The relation between repeat AMI/unstable angina and the severity of the stenosis, as well as other angiographic and clinical features was also examined. One hundred patients with AMI of <10 hours underwent coronary angiography 2 hours after receiving thrombolytic therapy. Salvage PTCA +/- stenting was performed if recanalization was unsuccessful (Thrombolysis In Myocardial Infarction [TIMI] trial grade 0 to 2), and no PTCA was undertaken if there was brisk anterograde flow (TIMI 3). Angiographic analysis was performed to assess the severity of the residual lesion, as well as the presence or absence of thrombus. Forty patients had unsuccessful recanalization, and of these, 36 underwent attempted PTCA. Of the 60 patients with TIMI 3 flow, 15 required repeat angiography and PTCA after repeat AMI (n = 13) or unstable angina (n = 2) within 5 days. Receiver-operating characteristic analysis indicated an optimum percent diameter stenosis predictor of 85% for repeat AMI/unstable angina. There was no additional relation to age, gender, time to thrombolysis, the infarct-related artery, or the presence of culprit lesion thrombus. After recanalization, a high-grade stenosis >85% is common (n = 25, 42.4%). This is associated with a 54% repeat AMI/unstable angina risk-a ninefold increase in the incidence of such events than in patients with lesions <85%. Thus, patients with narrowings >85% may benefit from early intervention rather than a conservative approach. Narrowings <85% have a 94% probability of no repeat AMI/unstable angina and do not require early intervention.

[The practical clinical guidelines of the Sociedad Española de Cardiología on coronary surgery]

Surgery in coronary disease, including myocardial revascularization and the surgery of mechanical complications of acute myocardial infarction, has shown to improve the symptoms, quality of life and/or prognosis in certain groups of patients. The expected benefit in each patient depend on many well-known factors among which the appropriateness of the indication for surgery is fundamental. The objective of these guidelines is to review current indications for cardiac surgery in patients with coronary heart disease through an evaluation of the degree of evidence of effectiveness in the light of current knowledge (systematic review of bibliography) and expert opinion gathered from various reports. Indications and the degree of recommendation for conventional coronary artery bypass grafting have been established for each of the most frequent anatomo-clinical situations defined by clinical symptoms (stable angina, unstable angina and acute myocardial infarction) as well as by left ventricular function and extend of coronary disease. Furthermore, the subgroups with the greatest surgical risk and stratification models are described to aid the decision making process. Also we analyse the rational basis and indication for the new surgical techniques such as minimally invasive coronary surgery and total arterial revascularization. Finally, the indication and timing of surgery in patients with mechanical complications of acute myocardial infarction are considered.

Rescue PTCA Following Failed Thrombolysis and Primary PTCA: A Retrospective Study of Angiographic and Clinical Outcome

Evidence is increasing that a patent culprit artery improves the prognosis of patients with acute myocardial infarction (AMI). Primary percutaneous transluminal coronary angioplasty (PTCA) has shown to be more effective than thrombolytic therapy alone. How effective is rescue PTCA after failed thrombolytic treatment? In a retrospective analysis, 176 consecutive patients with AMI and TIMI 0 or 1 perfusion grade were included. Patients had either rescue PTCA after failed thrombolysis (100 patients) or primary PTCA (76 patients). Angiographic data and in-hospital and 1-year outcome were analyzed. Comparison of baseline data of the two groups showed a higher proportion of long-standing angina and use of nitrates and aspirin in the primary PTCA group. Also, the delay between the onset of pain and PTCA was not significantly different, with a mean of 222 minutes for rescue PTCA and 245 minutes for primary PTCA (p = 0.52). The angiographic outcomes in the rescue PTCA group and the primary PTCA group were identical: The intervention was successful (TIMI 3 flow and residual stenosis <50%) in 86.0% and 85.5%, respectively. Complication rates of the procedure were also similar, except for bleeding complications. Blood transfusion was only needed after rescue PTCA in 3.0% versus 0.0% in primary PTCA patients. Clinical outcomes during hospital stay in terms of death rate (4.0% and 6.6%), reinfarction (6.0% and 3.9%), recurrent angina (16.0% and 11.8%), and repeat interventions were comparable, as was the first-year outcome. Failed PTCA was the most important predictor of a poor 1-year outcome; 28.0% died after failed PTCA versus 4.6% after successful PTCA (p < 0.001). In this retrospective analysis of 176 AMI patients, angiographic and clinical outcome, including a 1-year follow-up in patients who had rescue PTCA after failed thrombolysis, were of the same magnitude of patients in whom primary PTCA was performed. These findings suggest that in this subset the outcome of patients with rescue PTCA because of failed thrombolysis is good and is comparable with patients who underwent primary PTCA.

Coronary microembolization--its role in acute coronary syndromes and interventions

The diagnosis coronary artery disease is classically based on patient's symptoms and morphology, as analyzed by angiography. The importance of risk factors for the development of coronary atherosclerosis and disturbance of coronary vasomotion is clearly established. However, microembolization of the coronary circulation has also to be taken into account. Microembolization may occur as a single or as multiple, repetitive events, and it may induce inflammatory responses. Spontaneous microembolization may occur, when the fibrous cap of an atheroma or fibroatheroma (Stary i.v. and Va) ruptures and the lipid pool with or without additional thrombus formation is washed out of the atheroma into the microcirculation. Such events with progressive thrombus formation are known as cyclic flow variations. Plaque rupture occurs more frequently than previously assumed, i.e. in 9% of patients without known heart disease suffering a traffic accident and in 22% of patients with hypertension and diabetes. Also, in patients dying from sudden death microembolization is frequently found. Patients with stable and unstable angina show not only signs of coronary plaque rupture and thrombus formation, but also microemboli and microinfarcts, the only difference between those with stable and unstable angina being the number of events. Appreciation of microembolization may help to better understand the pathogenesis of ischemic cardiomyopathy, diabetic cardiomyopathy and acute coronary syndromes, in particular in patients with normal coronary angiograms, but plaque rupture detected by intravascular ultrasound. Also, the benefit from glycoprotein IIb/IIIa receptor antagonist is better understood, when not only the prevention of thrombus formation in the epicardial atherosclerotic plaque, but also that of microemboli is taken into account. Microembolization also occurs during PTCA, inducing elevations of troponin T and I and elevations of the ST segment in the EKG. Elevated baseline coronary blood flow velocity, as a potential consequence of reactive hyperemia in myocardium surrounding areas of microembolization, is more frequent in patients with high frequency rotablation than in patients with stenting and in patients with PTCA. The hypothesis of iafrogenic microembolization during coronary interventions is now supported by the use of aspiration and filtration devices, where particles with a size of up to 700 microns have been retrieved. In the experiment, microembolization is characterized by perfusion-contraction mismatch, as the proportionate reduction of flow and function seen with an epicardial stenosis is lost and replaced by contractile dysfunction in the absence of reduced flow. The analysis of the coronary microcirculation, in addition to that of the morphology and function of epicardial coronary arteries, and in particular appreciation of the concept of microembolization will further improve the understanding of the pathophysiology and clinical symptoms of coronary artery disease.

Protection of acutely ischemic myocardium by controlled reperfusion

The goal of revascularization after acute occlusion of a coronary artery is the return of contractile function and the reduction of mortality. Although reperfusion of ischemic myocardium is a prerequisite for return of function, it may, in itself, cause further injury. Controlled blood cardioplegic reperfusion reduces this "reperfusion injury" and provides maximal myocardial protection. In this article, we review recent advances in surgically controlled reperfusion and speculate on future prospects for myocardial protective techniques in patients with acute coronary artery occlusion.

The role of coronary angioplasty and stenting in acute myocardial infarction

Despite the improvements in the pharmacological treatment of acute myocardial infarction, it is recognised that thrombolysis fails to reproduce reperfusion in a significant proportion of patients. Coronary interventional techniques have been shown to offer an alternative reperfusion strategy. There is increasing evidence that mechanical reperfusion may offer significant advantages over established thrombolytic therapy.

[Non-invasive methods for evaluating reperfusion in acute myocardial infarct: enzymes and MIBI-SPECT cardiac gammagraphy]

INTRODUCTION

Several studies point out the importance of what is called rescue angioplasty or fibrinolysis when thrombolysis has been ineffective in acute myocardial infarction. Therefore, it is necessary to make use of new non-invasive methods to asses reperfusion and to safely establish that such a treatment has not been effective.

PATIENTS AND METHOD

We present a work which is based on the assessment of patients with acute myocardial infarction treated with or without fibrinolysis. After determining cardiac enzymatic profiles of creatine kinase and MB isoform (time course, peak, appearance rate constant time-activity: K1). With cardiac imaging gammagraphies 99mTc-isonitrile-single-photon emission computed tomography pre and post treatment after to calculating myocardium at risk, salvage and relationship.

RESULTS

In patients treated with fibrinolysis, the salvage myocardium was higher (8.3% vs 3.0%; p < 0.05). Considering that an improvement in perfusion defect (salvaged myocardium/myocardium at risk) higher than 30% can be viewed as an effective reperfusion, we can see that the percentage in the group treated with fibrinolysis being 45.8%, and the percentage in the group under conventional treatment being just 6.7%. Patients with acute myocardial infarction treated with fibrinolysis show much shorter start of rise-peak time and pain-peak time, all this with very significant differences for the creatine kinase (p < 0.0001) as well as for the MB (p < 0.001). Patients with reperfusion show a rapid increase in activity enzymatic, as demonstrated by the pain-peak time variable and the appearance rate constant time-activity (K1), with very significant differences in the latter (p < 0.0001). In relation with gammagraphy, values of K1 higher or equal to 0.19 for the creatine kinase and 0.14 for the MB isoform, achieved a sensibility of 83% and 91%, and a specificity of 85% and 80% respectively, to asses reperfusion.

CONCLUSION

We think that cardiac imaging gammagraphy with isonitriles as well as as determination of the appearance rate enzymatic constant time-activity, can be useful in monitoring treatment with fibrinolysis in infarction patients. New studies are needed to assess these same aspects, with a lesser number of enzymatic determinations.

Basic and clinical aspects of myocardial stunning

Although the pathogenesis of myocardial stunning has not been definitively established, the two major hypotheses are that it is caused by the generation of oxygen-derived free radicals on reperfusion and by a loss of sensitivity of contractile filaments to calcium. These hypotheses are not mutually exclusive and are likely to represent different facets of the same pathophysiological cascade. For example, a burst of free radical generation after reperfusion could alter contractile filaments in a manner that renders them less responsive to calcium. Increased free radical formation could also cause cellular calcium overload, which would damage the contractile apparatus of the myocytes. There is now considerable evidence that myocardial stunning occurs clinically in various situations in which the heart is exposed to transient ischemia, such as unstable angina, acute myocardial infarction with early reperfusion, exercise-induced ischemia, cardiac surgery, and cardiac transplantation. Recognition of myocardial stunning is clinically important and may impact patient treatment. Although no ideal diagnostic technique for myocardial stunning has yet been developed, thallium-201 scintigraphy or dobutamine echocardiography are available and can be useful to identify viable myocardium with reversible wall motion abnormalities. An intriguing possibility is that so-called chronic hibernation may in fact be the result of repetitive episodes of stunning, which have a cumulative effect and cause protracted postischemic left ventricular dysfunction. A better understanding of myocardial stunning will expand our knowledge of the pathophysiology of myocardial ischemia and provide a rationale for developing new therapeutic strategies designed to prevent postischemic dysfunction.

Delayed percutaneous transluminal coronary angioplasty after acute myocardial infarction

The value of delayed percutaneous transluminal coronary angioplasty (> 12 h from admission or after thrombolytic therapy) following acute myocardial infarction is controversial. We compared the short- and long-term prognosis of 1940 consecutive patients after acute myocardial infarction, of whom 188 underwent delayed percutaneous transluminal coronary angioplasty. Delayed percutaneous transluminal coronary angioplasty was more frequently done in patients treated with thrombolysis (12%) than among patients excluded from thrombolytic therapy (8%; P=0.005). Patients in the delayed percutaneous transluminal coronary angioplasty group were younger, included more men and smokers and had less in-hospital complications in comparison to patients who did not undergo delayed percutaneous transluminal coronary angioplasty. The crude 30-day and 1-year mortality rates were 3 and 6% among patients who underwent percutaneous transluminal coronary angioplasty vs. 14 and 21% (P<0.01 for each) among those without percutaneous transluminal coronary angioplasty, respectively. After multivariate analysis adjusted for confounding factors, delayed percutaneous transluminal coronary angioplasty was associated with 65 (RR=0.35; 90% CI 0.14-0.88) and 50% (RR=0.50; 90% CI 0.27-0.92) mortality risk reduction after 30 days and 1 year, respectively. In conclusion, delayed percutaneous transluminal coronary angioplasty applied to selected post-myocardial infarction patients upon clinical indication is safe and beneficial for the treatment of acute myocardial infarction in the community.

Sum of ST-segment elevations on admission electrocardiograms in acute myocardial infarction predicts left ventricular dilation

In summary, ST-segment elevations on the admission electrocardiogram not only diagnose acute myocardial infarction but also provide predictive information with respect to developing infarct size and left ventricular remodeling as well as survival.

Protection of evolving myocardial infarction and failed PTCA

Acute myocardial infarction is caused by acute coronary occlusion and is the major cause of death in Europe and the United States. In-hospital mortality is due principally to cardiogenic shock because of extensive ischemic muscle damage. Previous surgical results of coronary artery bypass grafting for left ventricular power failure have been disappointing because intraoperative ischemic injury is superimposed on severe damage already sustained by the myocardium. Surgical revascularization has, in general, been restricted to patients with acute occlusion after elective percutaneous transluminal coronary angioplasty with or without thrombolytic therapy. During the last years new knowledge has been gained in the pathophysiology of acute coronary occlusion on ischemic and nonischemic (remote) myocardium that has evolved in a new surgical strategy for revascularization of patients with evolving myocardial infarctions and failed percutaneous transluminal coronary angioplasty. Studies of the natural history of acute regional ischemia have shown that acute occlusion of a coronary artery not only affects the ischemic myocardium but causes structural, functional, and metabolic alterations in the remote and adjacent myocardium. These changes in the remote myocardium are even more severe if the remote myocardium is supplied by a stenotic coronary artery. Furthermore, many experimental and clinical studies have shown that normal blood reperfusion of myocardium injured previously by ischemia leads to additional damage (reperfusion injury).(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement of global and regional left ventricular function by percutaneous transluminal coronary angioplasty after myocardial infarction

OBJECTIVES

This study was designed to evaluate how elective percutaneous transluminal coronary angioplasty of the infarct-related vessel after acute myocardial infarction affects global ejection fraction and regional wall function.

BACKGROUND

The severity of the residual stenosis of the infarct-related artery after thrombolysis is an important predictor of changes in left ventricular function; however, the optimal time to restore complete perfusion in the infarct area has not been determined.

METHODS

We prospectively evaluated patients with a first myocardial infarction, postinfarction ischemia and residual high grade stenosis with reduced flow in the infarct-related artery who underwent successful coronary angioplasty. The group comprised 74 patients (61 men, 13 women with a mean age +/- SD of 55.9 +/- 9.9 years). Global ejection fraction and infarct region function (expressed as area ejection fraction) were angiographically measured before coronary angioplasty (3.9 +/- 2.1 weeks after infarction) and on routine follow-up study 6 +/- 1 months after angioplasty.

RESULTS

Restenosis with reduced flow occurred in 15 patients (20%). The global ejection fraction in patients with complete flow at follow-up increased significantly from 56.8% +/- 12% to 62.3% +/- 12.5% (p < 0.001). Regional wall motion of the infarct area increased from 12.1% to 22.5% (p = 0.001) in patients with anterior wall infarction and from 20.4% to 28.5% (p = 0.002) in those with inferior wall infarction. In patients with restenosis there was no difference at follow-up either in global ejection fraction (from 47.7% +/- 7.7% to 47.1% +/- 12.7%, p = 0.57) or in regional wall motion of the infarct area.

CONCLUSIONS

Global and regional myocardial dysfunction due to postinfarction ischemia lessens significantly after successful coronary angioplasty of the infarct-related coronary artery with long-term sustained normal, complete flow. In contrast, restenosis with reduced flow prevents long-term improvement of left ventricular function.

Restenosis after delayed coronary angioplasty of the culprit vessel in patients with a recent myocardial infarction treated by thrombolysis

BACKGROUND

Clinical follow-up after percutaneous transluminal coronary angioplasty (PTCA) of an infarct-related lesion has demonstrated a low incidence of recurrent symptoms and repeated revascularization. In the absence of systematic angiographic follow-up, this low rate of clinical restenosis may reflect either a truly lower incidence of anatomic restenosis or the lack of recurrent symptoms in patients with extensive infarction in the territory of the restenotic vessel.

METHODS AND RESULTS

We studied 300 consecutive patients who, after a thrombolysis for myocardial infarction, underwent delayed (10.5 +/- 6 days after the myocardial infarction) PTCA of the infarct-related lesion. Procedural success was obtained in 253 patients (84%), and angiographic follow-up was performed in 205 of this group (81%) at a mean of 7.3 +/- 1.9 months. Restenosis (defined as the recurrence of > 50% stenosis) was present in 105 patients (51%). Only 34 of the 105 patients (32%) with angiographic restenosis were symptomatic; the other 68% had clinically silent restenosis. Of these 105 patients, 27 (13% of the total population undergoing follow-up angiography) had reocclusion at the dilated site at follow-up. The severity of the stenosis at follow-up and the late loss in minimal lumen diameter followed a nearly Gaussian distribution if the lesions that were totally occluded at follow-up were excluded. By multivariate analysis, two independent predictors of reocclusion were identified: a small reference diameter (P < .0005) and the presence of collateral vessels before the procedure (P < .01). Only one factor was associated with restenosis in the 178 patients who did not have reocclusion at follow-up; a Thrombolysis in Myocardial Infarction grade < or = 2 before the procedure (P < .0001). At follow-up, there was a significantly (P < .01) higher ejection fraction in patients without restenosis (56.1 +/- 13.4%) and in patients with restenosis without total occlusion (56.0 +/- 13.8%) than in patients with reocclusion (46.4 +/- 13.0%).

CONCLUSIONS

Despite a satisfactory clinical outcome, delayed PTCA of an infarct-related lesion is associated with a high rate of angiographic recurrence. Two distinct mechanisms account for recurrent stenosis: progressive luminal renarrowing as documented after angioplasty of stable lesions and reocclusion of the infarct-related lesion. Only reocclusion is associated with a deterioration in left ventricular function at follow-up.

Does PTCA in acute myocardial infarction affect mortality and reinfarction rates? A quantitative overview (meta-analysis) of the randomized clinical trials

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) is often performed after acute myocardial infarction (AMI) either as an adjuvant to thrombolytic therapy or instead of thrombolysis. The effect of PTCA in AMI on mortality and reinfarction has remained unclear, with the available randomized trials indicating inconsistent results.

METHODS AND RESULTS

A systematic overview (meta-analysis) of the randomized trials was conducted to assess the effect of PTCA in AMI on mortality and reinfarction rates. Data from 7 trials in which primary PTCA was evaluated and 16 trials in which PTCA after thrombolysis was studied were included in this overview, comprising a total of 8496 patient. The trials represented different approaches to the timing of PTCA after AMI. The trials of PTCA after thrombolytic therapy were also categorized according to the different protocols with respect to the routine or elective character of PTCA in the invasive group. A reduction in short-term (6 week) mortality (odds ratio, 0.56; 95% CI, 0.33, 0.94) and in the combined outcome of short-term mortality and nonfatal reinfarction (odds ratio, 0.53; 95% CI, 0.35, 0.80) was observed in the trials comparing primary PTCA with thrombolytic therapy. In contrast, in trials in which an approach of thrombolysis and PTCA was compared with thrombolytic therapy alone, there was no important difference in early mortality, with an apparent reduction in mortality between 6 and 52 weeks. The lower mortality between 6 and 52 weeks among 6-week survivors seemed to be restricted to the subgroup of trials in which PTCA was used as a routine strategy (odds ratio, 0.58; 95% CI, 0.39, 0.87).

CONCLUSIONS

Although the analyses of the various categories of trials suggest that primary PTCA may be more beneficial than thrombolytic therapy in AMI, these data should be interpreted cautiously unless confirmed by larger studies. In contrast, the addition of various other strategies of PTCA to thrombolytic therapy does not convincingly indicate a clinically different outcome than if a more conservative strategy is followed, in which PTCA is used only if clinically indicated. Some specific strategies, however, such as rescue PTCA in high-risk patients with occluded arteries, may be of benefit.

Limitation of infarct size and preservation of left ventricular function after primary coronary angioplasty compared with intravenous streptokinase in acute myocardial infarction

BACKGROUND

Early and effective flow through the infarct-related vessel is probably of paramount importance for limitation of infarct size and preservation of left ventricular function in patients with acute myocardial infarction. Primary coronary angioplasty may offer advantages in these respects compared with thrombolytic therapy. The purpose of the present study was to assess the effects on estimated enzymatic infarct size and left ventricular function in patients with acute myocardial infarction randomly assigned to undergo primary angioplasty or to receive intravenous streptokinase.

METHODS AND RESULTS

We evaluated 301 patients with signs of acute myocardial infarction and without contraindications for thrombolysis who presented within 6 hours after onset of symptoms or between 6 and 24 hours if there was evidence of ongoing ischemia. One hundred fifty-two patients were randomly assigned to undergo primary angioplasty, and 149 patients were assigned to receive treatment with streptokinase (1.5 million U i.v.). Infarct size was estimated from enzyme release. Global left ventricular ejection fraction and regional wall motion, if possible in combination with exercise testing, were evaluated by radionuclide ventriculography before discharge. Thrombolysis in Myocardial Infarction (TIMI) flow grade 3 through the infarct-related vessel within 120 minutes after admission was achieved in 92% of all patients assigned to receive primary angioplasty therapy. Myocardial infarct size was 23% smaller in the angioplasty group compared with patients assigned to receive streptokinase (1003 +/- 784 versus 1310 +/- 1198 U/L, P = .012). Global left ventricular ejection fraction (50 +/- 9% versus 45 +/- 11%, P < .001) and regional wall motion in the infarct-related zones (42 +/- 14% versus 34 +/- 13%, P < .001) were better in the angioplasty group, which could mainly be contributed to myocardial salvage in the infarct-related areas. The observed differences were more pronounced in patients with an anterior wall myocardial infarction, although patients with a nonanterior infarct location also showed a beneficial effect of primary coronary angioplasty on left ventricular function compared with streptokinase therapy. Furthermore, the observed differences appeared to be more pronounced in patients presenting relatively early (within 2 hours) after onset of symptoms.

CONCLUSIONS

In patients with acute myocardial infarction, primary angioplasty results in a smaller infarct size and a better preserved myocardial function compared with patients randomized to receive treatment with intravenous streptokinase. This is probably due to early and optimal blood flow through the infarct-related vessel, as can be accomplished in a very high percentage of patients undergoing primary coronary angioplasty.

Coronary angioplasty in acute myocardial infarction: primary, immediate adjunctive, rescue, or deferred adjunctive approach?

OBJECTIVE

To address the current clinical applications, outcomes, and limitations of coronary angioplasty in the setting of acute myocardial infarction.

DESIGN

We review the results of several large trials in which various strategies of thrombolysis and primary, immediate adjunctive, rescue, or deferred adjunctive coronary angioplasty were used in patients with acute myocardial infarction.

MATERIAL AND METHODS

Four strategies for the utilization of angioplasty in myocardial infarction have been developed and are based on the timing and concurrent use of thrombolytic therapy.

RESULTS

Primary coronary angioplasty without prior thrombolytic therapy is as effective as thrombolytic therapy for salvaging myocardium. Results of a meta-analysis of recent trials suggest potential benefits of increased survival and decreased reinfarction in comparison with the results of thrombolysis in recent trials. Immediate adjunctive angioplasty after thrombolytic therapy has been tested in three large, randomized trials. The results suggest that this strategy is associated with increased risks without benefits of increased survival or improved left ventricular function. Rescue angioplasty may be helpful after failed thrombolytic therapy. Ongoing randomized trials might further clarify the benefits of rescue angioplasty. Because of the inherent difficulty in the noninvasive identification of patients with persistent reocclusion, diagnostic coronary angiography early after thrombolytic therapy may be necessary. Deferred adjunctive angioplasty during the weeks after infarction to prevent recurrent ischemia was not shown to decrease mortality or reinfarction in two large trials.

CONCLUSION

Primary coronary angioplasty is the treatment of choice for patients with contraindications to thrombolytic therapy. Certain high-risk subgroups may also benefit from primary angioplasty.

Frequency of inclusion of patients with cardiogenic shock in trials of thrombolytic therapy

The purpose of this study was to determine the extent to which patients with cardiogenic shock have participated in trials of thrombolytic therapy, to examine factors associated with their exclusion from these trials, and to summarize data on the efficacy of thrombolysis in these patients. Previous publications were searched for all randomized, controlled studies involving the use of thrombolytic medications used in the treatment of acute myocardial infarction. Data were abstracted for year of trial publication, performance location, sample size, maximal allowable delay between symptom onset and treatment, and exclusion criteria. Of the 94 trials included in the analysis, 22% included patients with cardiogenic shock, 37% excluded them, and the remainder contained no information on their inclusion or exclusion. Only 2 trials provided data on the efficacy of thrombolytic therapy in patients with cardiogenic shock. Multivariate analysis revealed that studies conducted exclusively in the U.S. were significantly more likely to exclude patients in cardiogenic shock than those conducted outside of the U.S., as were studies that excluded patients with a previous myocardial infarction, studies published more recently, and smaller trials. Patients with cardiogenic shock have frequently been excluded from clinical trials of thrombolytic agents. As a result, data on the efficacy of thrombolytic agents in these patients is extremely limited.

Long-term follow-up of global and regional left ventricular function by two-dimensional echocardiography after thrombolytic therapy in acute myocardial infarction

In order to evaluate changes in left ventricular volumes and regional left ventricular function after thrombolytic therapy in acute myocardial infarction serial two-dimensional echocardiography was performed during a follow-up of 2 years in 206 consecutive patients treated with streptokinase and adjunctive angioplasty in a randomized group of patients. Unexpected progressive left ventricular enlargement was detected both with and without angioplasty. In anterior wall infarction, end-diastolic volume index increased from 55 +/- 14 to 91 +/- 28 ml/m2 (+65%, P < 0.01) and end-systolic volume index increased from 31 +/- 11 to 55 +/- 23 ml/m2 (+79%, P < 0.01), whereas ejection fraction decreased from 45 +/- 9 to 41 +/- 7% (-9%, P = NS). Averaged regional anterior wall motion improved during the first 4 weeks (11 +/- 10 to 16 +/- 12%), but subsequently deteriorated (16 +/- 12 to 10 +/- 6, P < 0.05). The number of segments with pathological wall motion increased. Similar volumetric and regional wall motion data were demonstrated in inferior wall infarction. We believe this reflects a chronic ventricular remodelling phenomenon. This process takes place predominantly during the first 3 months, but continues over the whole follow-up period. Forty percent of the patients suffered symptoms of heart failure on long-term follow-up. Attenuation of progressive ventricular enlargement remains a therapeutic challenge in the long-term care of these patients. Angiotensin-converting enzyme inhibitors are promising agents in this regard.

Retreatment with alteplase for early signs of reocclusion after thrombolysis. The European Cooperative Study Group

Recurrent chest pain with new ST-segment elevation was observed in 26 of 652 patients (4%) with myocardial infarction in a clinical trial of alteplase (recombinant tissue-type plasminogen activator; 100 mg) and aspirin with or without heparin. Clinical and electrocardiographic signs of reocclusion were treated with a second dose of alteplase: 50 mg in 20 patients with signs of reocclusion < or = 24 hours after initial therapy, and 100 mg in 5 patients with signs between 24 and 77 hours, and in 1 patient with early signs of reocclusion. Pain and ST changes disappeared within 100 minutes (median 50). D-dimer determinations in 15 patients were increased, indicating activation of the coagulation system. Signs of reocclusion occurred despite adequate anticoagulation with heparin in 5 of 11 patients in whom coagulation measurements were available. No excess bleeding was observed in patients who received a second dose of alteplase. Retreatment with alteplase is feasible and provides an alternative for angioplasty in patients with clinical and electrocardiographic signs of reocclusion early after thrombolytic therapy.

Invasive versus conservative strategy after thrombolytic therapy for acute myocardial infarction in patients with antecedent angina. A report from Thrombolysis in Myocardial Infarction Phase II (TIMI II)

OBJECTIVES

This study was designed to assess the possibility that a subgroup of patients at high risk for recurrent ischemia and reinfarction after thrombolytic therapy might benefit from early intervention.

BACKGROUND

The Thrombolysis in Myocardial Infarction Phase II (TIMI II) study recently concluded that an obligatory invasive strategy after thrombolytic therapy offered no advantage over a more conservative strategy.

METHODS

Data from the 3,534 patients enrolled in the TIMI II trial were analyzed to determine whether a history of antecedent angina before myocardial infarction identifies patients at high risk for subsequent ischemia and whether these patients might benefit from an invasive strategy.

RESULTS

Within the TIMI II population, antecedent angina identified patients at increased risk for recurrent chest pain in the hospital (32.3% vs. 22.1%, p < 0.001) and recurrent infarction during the 1st year of follow-up (11.2% vs. 7.9%, p = 0.001) compared with that of patients without antecedent angina. Among patients assigned to the invasive strategy, coronary arteriography revealed that those with antecedent angina had a more severe residual stenosis of the infarct-related artery after thrombolytic therapy (77.1 +/- 0.7% vs. 73.0 +/- 0.9%, p < 0.001) and more multivessel disease (37.9% vs. 26.4%, p < 0.001). The clinical outcome of the patients with antecedent angina assigned randomly to either the invasive or the conservative strategy were compared. The invasive strategy patients had a slightly lesser incidence of recurrent chest pain in the hospital (29.9% vs. 34.8%, p = 0.13) and more negative (normal) findings on exercise tolerance tests (24.7 vs. 18.9%, p = 0.003), but there was no difference between the treatment strategies in the end point variable of recurrent myocardial infarction or death.

CONCLUSIONS

These data demonstrate that antecedent angina identifies patients at increased risk for recurrent ischemic events after thrombolytic therapy. However, similar to the results for the overall population, the invasive strategy does not alter the risk of reinfarction or death compared with the conservative approach.

Recombinant tissue-type plasminogen activator and immediate angioplasty in acute myocardial infarction. One-year follow-up. The European Cooperative Study Group

BACKGROUND

The European Cooperative Study Group conducted two randomized trials in patients with suspected myocardial infarction to assess the effect of 100 mg single-chain recombinant tissue-type plasminogen activator (rt-PA, alteplase) on enzymatic infarct size, left ventricular function, morbidity and mortality relative to placebo (alteplase/placebo trial) and to assess the effect of immediate percutaneous transluminal coronary angioplasty (PTCA) in addition to alteplase (alteplase/PTCA trial). One-year follow-up results are reported.

METHODS AND RESULTS

In the alteplase/placebo trial, 721 patients with chest pain of less than 5 hours and extensive ST-segment elevation were allocated at random to 100 mg alteplase or placebo (double-blind) over 3 hours. In the alteplase/PTCA trial, 367 similar patients received alteplase and subsequently were allocated at random to immediate coronary angiography and angioplasty of the infarct-related vessel or control. All patients received aspirin and intravenous heparin. In the alteplase/placebo trial, mortality during the first year was reduced by 36% with alteplase (from 9.3% to 5.6%; difference, -3.7%; 95% confidence interval, -7.5% to 0.2%). Revascularization was performed more frequently after alteplase, and more patients in the alteplase group were in New York Heart Association functional class I or II. Reinfarction tended to occur more frequently after alteplase than after placebo. In the alteplase/PTCA trial, reinfarction was less common after immediate PTCA, and revascularization procedures were less frequent. However, this benefit was offset by a high rate of immediate reocclusion and early recurrent ischemia and by higher mortality at 1 year (9.3% versus 5.4%; difference, 3.9%; 95% confidence interval, -1.5% to 9.2%) in the invasive group. In a multivariate analysis of 1,043 hospital survivors, mortality after discharge was related to coronary anatomy, left ventricular function, age, and previous infarction but not to initial treatment allocation. Reinfarction after hospital discharge tended to be more common after alteplase and related to coronary anatomy.

CONCLUSIONS

Benefit from treatment with alteplase, heparin, and aspirin is not diminished at 1 year. Routine immediate PTCA does not confer additional benefit. Prognosis after hospital discharge mainly is determined by coronary anatomy and residual left ventricular function and is unrelated to initial treatment assignment.

The intracoronary administration of urokinase following direct PTCA for acute myocardial infarction reduces early restenosis

Early restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) without antecedent thrombolytic therapy in patients with acute myocardial infarction (AMI) was assessed by performing in-hospital cardiac catheterization in 62 (88%) of 70 consecutive patients. Specific attention was focused on the effectiveness of the intracoronary administration of urokinase in cases with angiographic residual thrombus after successful direct PTCA. The following two treatment regimens were used: PTCA alone (43 patients) and PTCA followed by the intracoronary infusion of urokinase (27 patients). The rate of early restenosis was higher after successful direct PTCA alone (28%) than after direct PTCA followed by intracoronary urokinase (5%). Bleeding complications were no different between the two groups. These findings suggest that intracoronary urokinase can be effective in reducing early restenosis in patients with angiographic residual thrombus after successful direct PTCA. Therefore early restenosis may be related to residual intracoronary thrombus.

Intraaortic balloon pumping as the postangioplasty strategy in acute myocardial infarction

To assess the usefulness of intraaortic balloon pumping (IABP) in acute myocardial infarction (AMI), 114 patients with anterior AMI undergoing emergency percutaneous transluminal coronary angioplasty (PTCA) for total occlusion of the left anterior descending artery were studied. After successful PTCA 66 patients were treated with conventional therapy (group I), and 48 patients were treated with IABP for 25 +/- 8 hours (group II). The reocclusion rate was significantly lower in group II (2.4% vs 17.7% p less than 0.05). An increase in ejection fraction in group II compared with group I was marginally significant (4.5 +/- 12.2% vs 9.2 +/- 13.0%, p = 0.08). Vascular complications occurred in two patients, but there were no deaths from IABP. These results suggest that after successful PTCA for acute myocardial infarction, IABP prevents reocclusion and may add strength to reperfusion in the improvement of left ventricular function.

SWIFT trial of delayed elective intervention v conservative treatment after thrombolysis with anistreplase in acute myocardial infarction. SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group

OBJECTIVE

To see whether early elective angiography with a view to coronary angioplasty or bypass grafting of a stenosed infarct related vessel would improve outcome in acute myocardial infarction treated by thrombolysis with anistreplase.

DESIGN

Randomised study of two treatment strategies with analysis of results over 12 months.

SETTING

21 district hospitals and regional cardiac centres in Britain and Ireland.

SUBJECTS

800 of 993 patients presenting with clinical and electrocardiographic features of acute myocardial infarction up to three hours after the onset of major symptoms. TREATMENT STRATEGIES: Intravenous anistreplase 30 units followed by a standard regimen of heparin, warfarin, and timolol and (in patients so randomised) early angiography plus appropriate intervention.

MAIN OUTCOME MEASURE

Death or reinfarction within 12 months.

RESULTS

397 patients were randomised to receive early angiography plus appropriate intervention (coronary angioplasty in 169 cases, coronary grafting in 59) and 403 patients to receive conservative care (of these, 12 had angioplasty and seven bypass grafting during the initial admission). By 12 months mortality (5.8% (23 patients) in the intervention group v 5.0% (20) in the conservative care group; p = 0.6) and rates of reinfarction (15.1% (60 patients) v 12.9% (52); p = 0.4) were similar in the two groups. No significant differences in rates of angina or rest pain were found at 12 months. Left ventricular ejection fraction at three and 12 months was the same in both groups. Median hospital stay was longer in the intervention group (11 days v 10 days; p less than 0.0001).

CONCLUSION

For most patients given thrombolytic treatment for acute myocardial infarction a strategy of angiography and intervention is appropriate only when required for clinical indications.

Prediction of degree of residual stenosis in coronary thrombolysis

In order to predict the residual stenosis in coronary thrombolysis, the factors easily obtained from clinical history--age, gender, history of angina before acute myocardial infarction (AMI), family history, hypertension, diabetes, hypercholesterolemia, smoking, and interval between onset of AMI and recanalization--were observed in 114 patients with successful coronary thrombolysis. In 55 patients with angina before AMI, 29 patients had residual stenosis greater than or equal to 75% and 26 patients had residual stenosis less than 75%. In 59 patients without angina before AMI, 15 patients had residual stenosis greater than or equal to 75%, and 44 patients had residual stenosis less than 75%. The presence or absence of angina before AMI was the main variable that discriminated the groups of residual stenosis of more or less than 75%, which was the only significant independent variable to predict the residual stenosis. These data suggest that the presence of angina pectoris before AMI is likely to be associated with a significant degree of residual stenosis after thrombolysis.

Reasons for the lack of benefit of immediate angioplasty during recombinant tissue plasminogen activator therapy for acute myocardial infarction: a regional wall motion analysis. European Cooperative Study Group

Regional ventricular wall motion analysis utilizing three different methods was performed on predischarge left ventriculograms from 291 of 367 patients enrolled in a randomized trial of single chain recombinant tissue-type plasminogen activator (rt-PA), aspirin and heparin with and without immediate angioplasty in patients with acute myocardial infarction. With univariate analysis, no difference in regional wall motion variables between the two treatment groups was observed. However, with individual baseline risk assessment by multivariate linear regression analysis using baseline characteristics known to be related to left ventricular function after thrombolytic therapy or outcome of coronary angioplasty, or both, an excess of high risk patients in the invasive treatment group was detected. To adjust for this unequal distribution of baseline risk, multivariate linear regression analysis was performed. No benefit of immediate coronary angioplasty was observed after adjustment. Reocclusion or reinfarction, or both, occurred more frequently in the invasive than in the noninvasive treatment group (18% versus 13%, respectively). Among patients with a patent infarct-related vessel on angiography between days 10 and 22 and without reinfarction before angiography, there was a trend toward benefit from the invasive strategy, indicating that reocclusion and reinfarction might be responsible for the lack of benefit of the invasive strategy. This implies that immediate coronary angioplasty may be beneficial in selected patients, provided that these complications can be prevented.

Critically ischemic myocardium in clinically stable patients following thrombolytic therapy for acute myocardial infarction: potential implications for early coronary angioplasty in selected patients

The utility of post-thrombolysis, rest-redistribution thallium (TI)-201 scintigraphy was studied in 32 patients with a first myocardial infarction who were clinically stable following reperfusion. Day 1 scintigraphy obtained 5 +/- 4 hours (range 1 to 16) after thrombolysis revealed an average perfusion defect of 6.5 +/- 2.6 segments (range 1 to 11). There was a total of 208 abnormal segments, 137 of which were nonreversible at 4 hours, 50 of which were fully or partially reversible, and 21 of which had a reverse redistribution pattern. Repeat TI-201 scintigraphy on day 10 revealed significantly smaller perfusion defects of 4.9 +/- 2.4 segments (range 0 to 9) with improvement predominantly of the day 1 reversible segments, and the improvement in segmental perfusion correlated with better regional left ventricular function. Twenty-nine (58%) of the 50 reversible segments normalized by day 10, and 11 (22%) improved, whereas only 16 (12%) of 137 nonreversible segments had normalized by day 10, only 9 had (6%) improved and 112 (82%) were unchanged (p less than 0.001 reversible versus nonreversible). There was no significant change in segments with a pattern of reverse redistribution. The improvement of reversible segments was greater in the 16 patients who underwent coronary angioplasty (PTCA) during the interval between the two scintigrams than in the 16 who did not. All 24 reversible segments in the PTCA group improved or normalized by day 10 compared with 16 (62%) of 26 reversible segments in the No PTCA group (p less than 0.001). Furthermore, 8 of the 10 reversible segments in the No PTCA group that did not improve actually deteriorated and became nonreversible by day 10. The minor improvement of nonreversible segments was not related to PTCA. Consistent with the findings in individual segments, the 19 patients with a reversible component on the day 1 TI-201 scintigram had significantly greater improvement in perfusion defect by day 10 than the 13 patients without a reversible component (37 +/- 33% versus 7 +/- 22% decrease in perfusion defect severity, p less than 0.05), and this improvement was greatest in the 10 patients with a reversible component who underwent PTCA. In contrast, PTCA had no impact on the perfusion defect in the 13 patients without a reversible component. Our data suggest that following thrombolytic therapy for acute myocardial infarction, viable myocardium in the reperfused zone may remain ischemic, as manifested by a reversible pattern of TI-201 redistribution at rest, and thus may be in jeopardy of gradual progression to necrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Management of the patient following coronary thrombolysis

Myocardial salvage can be maximized by the early institution of thrombolytic therapy and aspirin. Certain patients may benefit from the administration of intravenous heparin, beta blockers, or nitroglycerin. The routine use of percutaneous transluminal coronary angioplasty (PTCA) or calcium-channel blockers does not appear to be warranted. Recurrent myocardial ischemia should be vigorously treated with medical therapy and there may be value in cardiac catheterization, followed by PTCA or bypass surgery, depending upon the extent of myocardium at risk and the underlying coronary anatomy. Long-term morbidity and mortality may be reduced by instituting aspirin and beta blockers as well as by modifying risk factors. There is no evidence for the long-term benefit from any calcium-channel blocker. Oral anticoagulation may be warranted in those patients with a mural thrombus, congestive heart failure, or atrial fibrillation. ACE inhibitors may be of value in the presence of left ventricular dysfunction and certainly in the presence of symptomatic congestive heart failure. Antiarrhythmic therapy is generally indicated only for symptomatic or life-threatening arrhythmias. Residual myocardial ischemia should be sought by exercise testing, and those patients with poor exercise tolerance generally warrant cardiac catheterization in consideration for revascularization.

Cardiac rupture, mortality and the timing of thrombolytic therapy: a meta-analysis

This study examined the relation between the risk of cardiac rupture and the timing of thrombolytic therapy for acute myocardial infarction. To test the hypothesis that cardiac rupture is prevented by early thrombolytic therapy but is promoted by late treatment, randomized controlled trials of thrombolytic agents for myocardial infarction were pooled. A logistic regression model including 58 cases of cardiac rupture among 1,638 patients from four trials showed that the odds ratio (treated/control) of cardiac rupture was directly correlated with time to treatment (p = 0.01); at 7 h, the odds ratio was 0.4 (95% confidence limits 0.17 to 0.93); at 11 h, it was 0.93 (0.53 to 1.60) and at 17 h, it was 3.21 (1.10 to 10.1). Analysis of data from the Gruppo Italiano per lo Studio della Streptochinasi nell'Infarto Miocardico (GISSI) trial independently confirmed the relation between time to thrombolytic therapy and risk of cardiac rupture (p = 0.03). Analysis of 4,692 deaths in 44,346 patients demonstrated that the odds ratio of death was also directly correlated with time to treatment (p = 0.006); at 3 h, the odds ratio for death was 0.72 (0.67 to 0.77); at 14 h, it was 0.88 (0.77 to 1.00) and at 21 h, it was 1 (0.82 to 1.37). Thrombolytic therapy early after acute myocardial infarction improves survival and decreases the risk of cardiac rupture. Late administration of thrombolytic therapy also appears to improve survival but may increase the risk of cardiac rupture.

Comparison of immediate invasive, delayed invasive, and conservative strategies after tissue-type plasminogen activator. Results of the Thrombolysis in Myocardial Infarction (TIMI) Phase II-A trial

To assess the value and timing of percutaneous transluminal coronary angioplasty (PTCA) after thrombolytic therapy for acute myocardial infarction (AMI), 586 patients in the Thrombolysis in Myocardial Infarction Study Phase II-A were randomized among three treatment strategies, one using immediate coronary arteriography followed by PTCA if appropriate (immediate invasive strategy group, n = 195), a second that deferred angiography and PTCA for 18-48 hours (delayed invasive strategy group, n = 194), and a third, more conservative, approach in which PTCA was used only if ischemia occurred spontaneously or at the time of predischarge exercise testing (conservative strategy group, n = 197). Predischarge contrast left ventricular ejection fraction, the primary study end point, was similar among the patients in all three treatment groups and averaged 49.3%. The finding of a patent infarct-related artery at the time of predischarge arteriography was equally common among the patients in the three groups (mean, 83.7%); however, the mean residual infarct artery stenosis was greater in the patients in the conservative strategy group (67.2%) as compared with the patients in the immediate invasive (50.6%) and the delayed invasive strategy groups (47.8%) (p less than 0.001). Immediate invasive strategy led to a higher rate of coronary artery bypass graft surgery (CABG) after PTCA (7.7%) than did delayed invasive and conservative strategies (2.1% and 2.5%, respectively; p less than 0.01). Furthermore, among patients not undergoing CABG during the first 21 days, blood transfusion of more than 1 unit was used in 13.8% of the patients in the immediate invasive strategy group, 3.1% of the patients in the delayed invasive strategy group, and 2.0% of the patients in the conservative strategy group (p less than 0.001). At 1-year follow-up, the three treatment groups had similar cumulative rates of mortality (8.7%, pooled over all groups), fatal and nonfatal reinfarction (8.5%), combined death and reinfarction (14.5%), and CABG (17.2%), although the cumulative performance rate of PTCA remained higher in the invasive groups (immediate invasive strategy group, 75.8%; delayed invasive strategy group, 64.3%; and conservative strategy group, 23.9%; p less than 0.001). Thus, because conservative strategy achieves equally good short- and long-term outcome with less morbidity and a lower use of PTCA, it seems to be the preferred initial management strategy.

Value of immediate angioplasty after intravenous streptokinase in acute myocardial infarction

To improve reperfusion, immediate percutaneous transluminal coronary angioplasty (PTCA) was considered after intravenous streptokinase (0.75 to 1.5 million U) was administered to 98 patients with acute myocardial infarction less than 4 hours after the onset of chest pain. Thirty-four culprit arteries were occluded (group A); 42 arteries were patent with residual stenosis of more than 70% (group B). Twenty-two patients had residual stenosis of less than 70% (group C); eight of these had severe disease of the remaining vessels. Group C patients were either treated conservatively or underwent bypass surgery. Immediate PTCA was attempted in 74 patients (32 in group A, 42 in group B) and was successful in 68 (92%). Emergency bypass surgery for acute occlusion after PTCA was required in two patients. Follow-up averaged 23 months (range, 16 to 47 months). Asymptomatic occlusion recurred in three patients. Restenosis occurred in five patients: four had early restenosis (one in group A, three in group B) and one had late restenosis (group B). These arteries were successfully redilated. Late reinfarction occurred in two patients. They were treated with intravenous urokinase and repeat PTCA. Elective bypass surgery was performed in three patients because of recurrent angina. They had severe three-vessel disease as revealed by control angiography. The mortality rate was 2.7% (two patients; one in group B had early reinfarction, and one patient in group A died suddenly after 17 months). Eighty-five percent of patients treated with PTCA alone remain free of symptoms. This approach has a high success rate and low morbidity and mortality rates. Long-term results are superior to thrombolysis alone.

Distal embolization during mechanical thrombolysis: rotational thrombectomy vs. balloon angioplasty

To determine the incidence and extent of distal embolization during percutaneous transluminal balloon angioplasty (PTA) and rotational thrombectomy (PRT), we collected, filtered, and weighed the distal effluent of acute thrombotically occluded canine arteries following mechanical thrombolysis. PRT (n = 11) and PTA (n = 10) were equally effective in recanalizing occluded vessels (91% vs. 90%) and reduced percent diameter stenosis to a similar degree (97 +/- 6% to 8 +/- 11% and 100 +/- 0% to 17 +/- 23%, respectively). Distal embolization following mechanical intervention was observed in 10 of 10 and 8 of 9 arteries recanalized with PRT and PTA, respectively. The mean weights of collected emboli were similar between the two groups (18 +/- 24 mg vs. 37 +/- 79 mg, PRT vs. PTA, P = NS), although the range of size and weight of thromboemboli was larger in the PTA group (0-206 mg vs. 2-51 mg, PRT). Angiographically defined residual thrombus was significantly less frequent in arteries recanalized with PRT as compared with PTA (10% vs. 55%, P = 0.03). In summary, PRT and PTA are equally effective in recanalizing acutely occluded canine arteries and result in similar reductions in percent diameter stenosis. Each intervention results in distal embolization of thrombi. PRT is associated with a reduced incidence of angiographically evident residual thrombus at the site of arterial injury and may avoid embolization of large fragments occasionally produced by PTA. Thus PRT may serve as a useful alternative to coronary angioplasty during acute myocardial infarction.

Coronary angioplasty after intravenous streptokinase in acute myocardial infarction: influence of restenosis on clinical outcome and left ventricular function

The importance of recurrence of stenosis on clinical outcome and left ventricular function was studied in a consecutive series of patients with acute evolving myocardial infarction (maximal duration of pain 4 h) and thrombolysis (1.5 x 10(6) units of streptokinase intravenously over 60 min) with recanalized single-vessel disease and subsequent successful coronary angioplasty. Coronary angioplasty was performed in 76 patients between 24 hours and 8 days (mean interval 3.3 days) after thrombolysis and was successful in 86% (65/76). The in-hospital reinfarction rate was 5.2% (2 acute and 2 in-hospital reinfarctions). Repeat angiography after a mean interval of 5.9 months revealed a 39% (24/62) restenosis rate (21 restenoses, 3 reocclusions). Restenoses were associated with significantly more clinical complaints (21% vs. 62%; p less than 0.001). Left ventricular function analysis showed significant improvement in the mean global ejection fraction (6.6 +/- 6.0%; p less than 0.001) and mean regional wall motion of the infarct zone (6.2 +/- 8.2%; p less than 0.01) only in patients without restenosis. Recovery of left ventricular function was more evident in inferior than in anterior wall infarctions. In contrast, patients with restenosis had no change in left ventricular function. Thus, the present study demonstrates the adverse influence of restenosis on recovery of left ventricular function and clinical outcome.

Practice guidelines and professional autonomy in a universal health insurance system: the case of tissue plasminogen activator in Ontario

Ontario's universal health insurance system has placed few constraints on the clinical and economic autonomy of medical doctors. Although fees are standardized, most physicians remain in private fee-for-service practice and thereby retain control of the mix and volume of services. Utilization review is minimal. While organized medicine has argued that health care is 'under-funded', the government is pressing for better use of extant resources through firmer management of the medical services sector. The Ontario Medical Association (OMA), the major bargaining agent for doctors in the province, has accordingly sought to protect professional autonomy by developing voluntary self-regulatory approaches that obviate the need for external controls over physician practice patterns. Part of this strategy is promulgation of practice guidelines. Tissue plasminogen activator (t-PA), a clot-lysing drug for myocardial infarction, was released in late 1987, and, at C$2950 per treatment, constituted an unforeseen add-on cost for hospitals. The OMA subsequently convened an expert panel to develop guidelines for thrombolysis in myocardial infarction. Among the unanticipated results was the conclusion that insufficient evidence had accumulated to recommend routine use of t-PA instead of streptokinase, an older drug costing C$290. The OMA panel's guidelines were approved by the OMA executive, and led the government to reject special add-on funding for hospitals purchasing t-PA. The OMA's position and government decision provoked negative reactions from the OMA's own cardiology section. Indicative of clinicians' feelings, a follow-up survey of cardiologists and internists showed that only 28% of respondents were indifferent between t-PA and streptokinase, while 64% preferred t-PA. On the other hand, 74% supported clinical policy development by the OMA, while 94% opposed direct government involvement in guideline-setting. The case of the OMA thrombolysis guidelines illustrates a strategic conundrum facing Canadian organized medicine. Professional activism in guideline-setting may in theory protect the individual practitioner's autonomy by offering a voluntary alternative to utilization management by government, and is likely to strengthen the collective influence of organized medicine. However, among the risks are alienation of practitioners who see professional guidelines and government control as two sides of the same regulatory coin, and the transmogrification of voluntary guidelines into parameters for cost control and utilization management by government or hospitals. Future initiatives will depend on how these benefits and risks are weighed.