Eligibility for intravenous thrombolysis in suspected acute myocardial infarction

Impact of the troponin standard on the prevalence of acute myocardial infarction

BACKGROUND

Recent recommendations are that troponin should replace creatine kinase (CK)-MB as the diagnostic standard for myocardial infarction (MI). The impact of this change has not been well described. Our objective was to determine the impact of a troponin standard on the prevalence of acute non-ST-elevation MI.

METHODS

The current study was a retrospective analysis of consecutive patients without ST-segment elevation admitted for exclusion of myocardial ischemia to an inner city urban tertiary care center. All patients underwent serial marker sampling (CK, CK-MB, and cardiac troponin I [cTnI]). Patients with ST elevation consistent with acute MI (n = 130) or who did not have an 8 hour cTnI (n = 124) were excluded. The impact of 3 different cTnI diagnostic values were examined in 2181 patients: the lower limit of detectability (LLD); an optimal diagnostic value (OPT), chosen using receiver operator characteristic curve analysis; and the manufacturer's suggested upper reference level (URL), when compared to a gold standard CK-MB MI definition. In addition, MI prevalence was assessed using different CK-MB MI definitions and evaluated in patients with ischemic changes only.

RESULTS

The prevalence CK-MB MI was 7.8%. Using the various cTnI diagnostic values, the incidence of MI increased the prevalence by 28% to 195%. Using the optimal diagnostic value for cTnI, patients with cTnI elevations not meeting CK-MB MI criteria had an intermediate 30-day mortality (5.4%) compared to those with CK-MB MI (7.1%). Grouping the cTnI positive, CK-MB MI negative patients with the CK-MB MI patients rather than the non-CK-MB MI patients reduced mortality for both the MI (to 5.9%) and non-MI groups (from 1.9% to 1.6%).

CONCLUSIONS

Changing to a troponin standard will have a substantial impact on the number of patients diagnosed with MI. The revised definition for MI will have important clinical and health care implications.

Predictors of myocardial damage prior to hospital admission among patients with acute chest pain or other symptoms raising a suspicion of acute coronary syndrome

AIM

To evaluate factors which, prior to hospital admission, predict the development of acute coronary syndrome or acute myocardial infarction among patients who call for an ambulance due to suspected acute coronary syndrome.

DESIGN

Prospective observational study.

METHODS

All the patients who called for an ambulance due to suspected acute coronary syndrome in South Hospital's catchment area in Stockholm and in the Municipality of Göteborg between January and November 2000, were included. On arrival of the ambulance crew, a blood sample was drawn for bedside analysis of serum myoglobin, creatine kinase (CK)MB and troponin-I. A 12-lead electrocardiogram (ECG) was simultaneously recorded.

RESULTS

In all, 538 patients took part in the survey. Their mean age was 69 years and 58% were men. In all, 307 patients (57.3%) had acute coronary syndrome and 158 (29.5%) had acute myocardial infarction. Independent predictors of the development of acute coronary syndrome were a history of myocardial infarction (P=0.006), angina pectoris (P=0.005) or hypertension (P=0.017), ECG changes with ST elevation (P<0.0001), ST depression (P<0.0001) or T-wave inversion (P=0.012) and the elevation of CKMB (P=0.005). Predictors of acute myocardial infarction were being a man (P=0.011), ECG changes with ST elevation (P<0.0001) or ST depression (P<0.0001), the elevation of CKMB (P<0.0001) and a short interval between the onset of symptoms and blood sampling (P=0.010).

CONCLUSION

Among patients transported by ambulance due to suspected acute coronary syndrome, predictors of myocardial damage can be defined prior to hospital admission on the basis of previous history, sex, ECG changes, the elevation of biochemical markers and the interval from the onset of symptoms until the ambulance reaches the patient.

Prognosis after acute myocardial infarction continues to improve in the reperfusion era in the community of Göteborg

BACKGROUND

The objective of this study was to compare the prognosis of nonselected patients who had an acute myocardial infarction (AMI) during 2 time periods in the thrombolytic era and to describe coronary heart disease (CHD) mortality rates in the community of Göteborg during 1990 to 1995.

METHODS

Patients aged <75 years who were hospitalized in the community of Göteborg for AMI during 1990 to 1991 (period 1) and 1995 to 1996 (period 2) were compared in terms of history, treatment for AMI, and outcome. Information on CHD mortality rates in the community of Göteborg was gathered from the National Registry of Deaths.

RESULTS

The numbers of patients in the 2 cohorts were 926 and 861, respectively. The incidence rate for AMI per 100,000 inhabitants and year was 200 for period 1 and 183 during period 2. During period 2, there was an increased use of percutaneous transluminal coronary angioplasty, coronary artery bypass grafting, angiotensin-converting enzyme inhibitors, heparin, and intravenous nitroglycerin. On the other hand, there was a decreased use of thrombolytic agents, diuretic agents, digitalis, long-acting nitrates, calcium-channel blockers, and lidocaine. The hospital case-fatality rates were 9.4% during period 1 and 6.0% during period 2 (P =.01). The adjusted risk ratio for period 2 versus period 1 was 0.65, with 95% confidence limits of 0.45 to 0.94. The mortality rate over a period of 3 years was 26.5% during period 1 and 17.8% during period 2 (P <.0001). The adjusted risk ratio for period 2 versus period 1 was 0.67, with 95% confidence limits of 0.54 to 0.82. Among inhabitants aged 30 to 74 years in the community of Göteborg, the CHD mortality rate decreased in 1995 as compared with 1990 (age-adjusted odds ratio 0.79, 95% confidence limits 0.68 to 0.92).

CONCLUSIONS

For consecutive patients aged <75 years who were hospitalized for AMI in the community of Göteborg, we found that in the thrombolytic era, major changes in medical and nonmedical treatment still took place associated with a continuing decrease in mortality rates during 3 years of follow-up. A similar reduction of CHD mortality rates was seen in the same age group within the community of Göteborg.

Incidence of high-risk acute coronary syndromes and eligibility for glycoprotein IIb/IIIa inhibitors among patients admitted for possible myocardial ischemia

OBJECTIVE

Recent studies have demonstrated that glycoprotein (GP) IIb/IIIa inhibitors can reduce cardiac events in patients with acute coronary syndromes (ACS). However, little is known about how many patients are actually eligible for treatment. Our purpose was to determine how many patients admitted for possible myocardial infarction (MI) meet GP IIb/IIIa inhibitor treatment criteria.

METHODS

Patients admitted for possible MI who underwent a standard protocol that included serial sampling of total creatine kinase (CK), CK-MB, and troponin I (TnI) were retrospectively assigned to different treatment algorithms on the basis of criteria from GP IIb/IIIa inhibitor trials: an electrocardiogram (ECG) consistent with acute MI or ischemia, and myocardial marker elevations. Elevated CK-MB was considered diagnostic of MI. High-risk ACS was defined as ischemic ECG changes or troponin elevations without CK-MB elevations.

RESULTS

A total of 2179 patients were admitted for MI exclusion. MI was identified in 304 patients (14.0%) (123 ST-elevation, 49 ischemic ECG, 132 nonischemic ECG). Another 273 patients (12.5%) without CK-MB criteria for MI met high-risk ACS criteria (172 ischemic ECG, 120 TnI elevations). Ischemic ECGs or elevated myocardial markers identified 454 (21%) patients as eligible for treatment. Inclusion of patients with ST elevation increased eligibility to 26.5%. Of the 454 non-ST-elevation ACS patients, 340 (74%) were identified early by the ECG or the initial markers.

CONCLUSIONS

A large proportion of patients admitted for possible MI met criteria for treatment with GP IIb/IIIa inhibitors. The non-ST-elevation ACS group was >3 times larger than the ST-elevation MI group. These findings have important implications for treatment of patients with ACS.

Primary angioplasty for acute myocardial infarction in the elderly

Elderly patients with acute myocardial infarction present a formidable therapeutic challenge. Although there appears to be a survival benefit from thrombolytic therapy for the eligible elderly patient, persistent concerns regarding the risk of intracranial hemorrhage impedes utilization in this age group. Primary or direct angioplasty of the infarct artery has been proven to be an effective modality for reperfusion. Randomized comparisons suggest an advantage over thrombolysis in terms of achieving superior patency and mitigating recurrent ischemic events. Primary angioplasty expands the reperfusion population by including many patients ineligible for thrombolysis and is more effective for treating patients at high risk, such as those with cardiogenic shock. Acute angiography accumulates important prognostic and decision-facilitating information. The benefits of primary angioplasty are more impressive for the aging patient. The survival gain and reduction in intracranial hemorrhage may combine to magnify the advantages of performing angioplasty on patients in this group. Emerging evidence concerning the aging population validates continued examination of this invasive reperfusion approach.

Five-year mortality after acute myocardial infarction in relation to previous history, level of initial care, complications in hospital, and medication at discharge

The purpose of this study was to describe the prognosis during 5 years of follow-up in a consecutive population of patients discharged from hospital after acute myocardial infarction (AMI) in relation to clinical history, level of initial care, complications during hospitalization, and medication at discharge. All patients admitted to a single hospital from February 15, 1986 to November 9, 1987 due to AMI, regardless of age and whether or not they were treated in the coronary care unit, and who were discharged alive from hospital were included in the study. There were 862 patients with AMI, 740 of whom were discharged alive. Information on medication at discharge was available in 713 patients (96%). In a multivariate analysis taking into account age, sex, history of cardiovascular diseases, whether patients were admitted to coronary care unit or not, complications during hospitalization, and medication at discharge, the following factors appeared to be independent predictors of mortality: age (p < 0.001), history of AMI (p < 0.001), congestive heart failure in hospital (p < 0.001), whether beta-blockers had been prescribed at discharge (p < 0.01), and a history of diabetes (p < 0.01). This study indicates that in consecutive patients surviving the hospital phase of AMI, the development of complications while in hospital and the manner in which medication was prescribed at discharge independently influenced their long-term prognosis, but age was the most important factor in long-term prognosis.

The outcome of patients with acute myocardial infarction ineligible for thrombolytic therapy. Israeli Thrombolytic Survey Group

PURPOSE

The aim of this study was to determine the proportion of patients with acute myocardial infarction (AMI) excluded from thrombolytic therapy on a national basis and to evaluate the prognosis of these patients by reasons of ineligibility and according to the alternative therapies that they received during hospitalization.

PATIENTS AND METHODS

During a national survey, 1,014 consecutive patients with AMI were hospitalized in all the 25 coronary care units operating in Israel.

RESULTS

Three hundred and eighty-three patients (38%) were treated with a thrombolytic agent and included in the GUSTO study. Ineligible patients for GUSTO were treated: (1) without any reperfusion therapy (n = 449), (2) by mechanical revascularization (n = 97), or (3) given 1.5 million units of streptokinase (n = 85) outside of the GUSTO protocol. The inhospital and 1-year post-discharge mortality rates were 6% and 2% in patients included in the GUSTO study; 6% and 5% in those mechanically reperfused; 15% and 10% in those treated with thromoblysis despite ineligibility for the GUSTO trial, and 15% and 13% among patients not treated with any reperfusion therapy.

CONCLUSIONS

Ineligibility for thrombolysis among patients with AMI remains high. Patients ineligible for thrombolysis according to the GUSTO criteria, but nevertheless treated with a thrombolytic agent were exposed to an increased risk.

Primary angioplasty and thrombolysis for acute myocardial infarction: an evidence summary

Coronary angioplasty is being increasingly used as the primary treatment for patients with acute myocardial infarction, but controversy remains over its potential adoption in preference to thrombolysis as standard care. This report summarizes the published evidence on health outcomes after primary angioplasty compared with thrombolysis or no intervention for patients with acute myocardial infarction. The data tables presented provide the scientific groundwork to assist physicians and other policy-makers in deciding which interventions to provide for broad populations of patients.

Early intravenous thrombolysis in acute myocardial infarction: the Jerusalem experience

Myocardial damage in acute myocardial infarction is a time-dependent process. We examined the influence of very early thrombolytic therapy, comparing prehospital to hospital administration, in a consecutive group of patients with myocardial infarction on mortality, complications and the preservation of left ventricular function. Seven hundred sixty patients received early thrombolytic therapy: 114 at home (time delay to treatment 1.4 +/- 0.8 h) and 646 in hospital (2.1 +/- 1.0 h). Sixteen patients died in hospital and significant hemorrhage occurred in 15 (including three patients with hemorrhagic stroke). There was no difference between groups in hospital mortality or rate of complications. The duration of ischemia was shorter in patients with prehospital therapy (pain duration: 3.3 +/- 2.1 vs. 4.0 +/- 2.2; P < 0.05, and time to recovery of the ST segment in the electrocardiogram: 4.3 +/- 3.3 vs. 6.6 +/- 6.3; P < 0.002). Peak plasma creatine kinase was earlier in patients with prehospital therapy (11.2 +/- 5.0 vs. 13.0 +/- 5.8; P < 0.002), although there was no difference between groups in the absolute peak plasma level. Left ventricular function was assessed by contrast ventriculography 1 week after admission (616 patients). Ventricular function was better in patients with prehospital therapy: (ejection fraction of 58 +/- 13% vs. 54 +/- 15%; P < 0.05 and a left ventricular dysfunction index of 534 +/- 515 vs. 691 +/- 519 units; P < 0.05). We conclude that prehospital thrombolytic therapy is feasible and safe. Reperfusion is achieved earlier and more myocardium can be salvaged using this strategy without increasing the rate of complications.

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.

The earliest diagnosis of acute myocardial infarction

Acute myocardial infarction results from the cessation of myocardial blood flow caused by thrombotic occlusion of a coronary artery. Rapid restoration of blood flow to the ischemic myocardium minimizes cardiac damage and improves early and long-term morbidity and mortality. Chest pain is the first symptom of myocardial infarction, but in some patients with silent ischemia, the disease can be diagnosed only in retrospect. In symptomatic patients, myocardial infarction should be accurately and promptly diagnosed so that reperfusion therapy can begin immediately. Electrocardiography is the simplest diagnostic modality. Although regional ST-segment elevation is specific, it is not sensitive. In contrast, new computerized algorithms for electrocardiographic analysis and serial monitoring increase sensitivity without decreasing specificity. In the emergency room, echocardiography is used to diagnose patients with no prior history of coronary artery disease whose electrocardiograms proved nondiagnostic. Time-consuming perfusion nuclear studies are inferior to echocardiography but may nevertheless enable physicians to diagnose myocardial infarction in the emergency room. Although the presence of excess creatine kinase is a sign of myocardial necrosis, its increase is delayed for a few hours after coronary occlusion. Doctors can diagnose myocardial infarction as early as two hours after coronary occlusion with the help of simpler automatic assays of MB-creatine kinase mass that use monoclonal antibodies. Other investigational markers of myocardial necrosis include myoglobin and troponin. Elevation of a circulating protein marker also signifies established necrosis, but physicians hope to achieve reperfusion through therapy before irreversible damage occurs.

Use of composite endpoints in thrombolysis trials of acute myocardial infarction

Although preventing early mortality following acute myocardial infarction (MI) is the most important goal of thrombolytic therapy, insistence on its use as the only or principal endpoint in trials of acute MI will limit the number of new thrombolytic-antithrombotic regimens that can be tested, and thus may inhibit future progress of this important area of cardiovascular therapeutics. Trials of thrombolytic therapy over the past decade, as discussed in this article, have demonstrated that: (1) thrombolytic therapy improves both mortality and intermediate endpoints, and (2) intermediate nonfatal endpoints are strongly linked to long-term mortality. Taken together, these facts provide strong evidence that intermediate nonfatal events can be used as valid endpoints in future trials of thrombolytic therapy. The unsatisfactory outcome composite endpoint, which incorporates mortality and important intermediate endpoints, will make it possible to compare innovative new regimens in much smaller trials. Ultimately, both of these approaches (i.e., megatrials using a mortality endpoint and smaller trials utilizing a composite unsatisfactory outcome endpoint) can be used in a complementary fashion. A new regimen could first be tested using the unsatisfactory outcome endpoint; if it showed particular promise, it could then become a candidate for testing in a megatrial. Conversely, if it did not prove better than standard regimens, futile research in tens of thousands of patients might be prevented. Thus, the use of composite endpoints will expand the number of new thrombolytic-antithrombotic regimens that can be tested and, it is hoped, accelerate progress in the treatment of acute MI.

Expediting the early hospital care of the adult patient with nontraumatic chest pain: impact of a modified ED triage protocol

A prospective study that compared a traditional emergency department (ED) triage protocol with an expedited protocol was conducted to determine if minimizing the subjectivity of nursing triage would result in more efficient management of adult patients presenting with nontraumatic chest pain. The traditional protocol triaged 382 patients into 1 of 5 categories of acuity. The expedited study group (418 patients) were triaged as usual but subsequently were treated as if they were triage category 1 or 2 (medical evaluation within 15 minutes of arrival). Traditional triage led to 40% of acute myocardial infarction (AMI) patients being triaged into inappropriately low-acuity categories. The expedited protocol resulted in significant improvement in the following intervals: ED arrival to triage, triage to cubicle, ED arrival to cubicle, ED arrival to electrocardiogram (ECG) ordered, ED arrival to ECG available, ED arrival to physician evaluation, and ED arrival to decision to thrombolyse. Study patients with non-AMI cardiac chest pain and AMI cardiac chest pain were evaluated by a physician an average of 12 minutes and 8 minutes after ED arrival, respectively. Delays in interdepartmental processes, such as ECG-technician responsiveness, thrombolysis protocol fulfillment and thrombolytic agent delivery, negated benefits derived from improvements in internal processes. Effective coordination of the numerous processes involved in the initial ED management of adult patients with nontraumatic chest pain is required to make thrombolytic therapy for AMI within 30 minutes of patient arrival a routinely achievable goal.

Primary coronary angioplasty for acute myocardial infarction with contraindication to thrombolysis

Patients with acute myocardial infarction (AMI) and contraindication to thrombolysis have a high mortality and morbidity with conventional medical treatment. Among 226 consecutive patients hospitalized within 6 hours of the onset of Q-wave AMI, 45 (20%) had contraindications to thrombolysis. All were treated by emergent primary angioplasty. Mean age of the 45 patients was 60 +/- 11 years and 8 (18%) were > or = 70 years old; 17 (38%) had multivessel disease and 5 (11%) presented with cardiogenic shock. Successful angioplasty was achieved in 42 of the 45 patients (93%) 52 +/- 27 minutes after admission and 238 +/- 100 minutes after the onset of pain. Overall in-hospital mortality was 9% (4 of 45). Neither major bleeding nor stroke occurred. There was 1 case of early symptomatic reocclusion, treated with emergent repeat angioplasty without reinfarction. Predischarge angiography in 33 patients showed only 1 silent reocclusion (3%). Ejection fraction at discharge was 46 +/- 13%. Repeat catheterization at 6 months in 19 patients showed 4 restenoses (21%) and 4 reocclusions (21%) of the infarct-related artery. There were 3 late deaths (2 noncardiac), which gave survival rates of 87 and 85% at 1 and 3 years, respectively, and event-free survival rates of 71 and 69% including in-hospital deaths. There were no cases of late reinfarction. Consequently, in this series, primary coronary angioplasty proved safe and highly effective in rapidly restoring sustained infarct-vessel patency during AMI, and led to a greater improvement in early and late outcomes than that reported in the literature for medically treated subjects in this high-risk subset for which thrombolytic therapy is contraindicated.

Thrombolytic treatment of an acute anterior myocardial infarction based upon echocardiography and in the absence of electrocardiographic criteria

Tissue plasminogen activator was administered intravenously to a patient with clinical features of, but without electrocardiographic criteria for, an acute myocardial infarction. The ultimate treatment decision was based upon echocardiographic findings diagnostic for an anteroseptal myocardial infarction. Subsequent coronary angiography demonstrated a severe proximal, but patent left anterior descending stenosis. The patient is now asymptomatic 3 months following thrombolytic therapy and coronary angioplasty.

Goals of thrombolytic therapy

In the past decade, mortality associated with acute myocardial infarction has been reduced to between 5% and 9% in selected groups of patients, largely due to use of early reperfusion. Thrombolytics combined with aggressive mechanical revascularization reduce the likelihood of death both during hospitalization and in the ensuing several years. Overall morbidity is also lessened, although salvage of patients with severe left ventricular dysfunction may make this difficult to demonstrate. Foremost among issues remaining unresolved is the relationship between patency of the infarct vessel and survival. Survival associated with reperfusion is limited primarily to patients with successful reperfusion. Myocardial salvage is more likely in these patients, but the correlation between myocardial salvage and mortality reduction is not determined. Late spontaneous reperfusion occurs in greater than 50% of patients who do not receive a thrombolytic; survival seems to be greater when vessels undergo spontaneous reperfusion. Only a minority of patients can be treated within the first hour after chest pain onset. It is not clear that the time window in which early reperfusion can be accomplished allows benefit to be clinically evident. Resources need to be directed toward agents to augment the rate of lysis and toward improvement of delivery. Mortality is highest in the first 24 hours after thrombolytic administration. Understanding of the underlying mechanisms may promote further reductions in mortality. Intravenous thrombolytic therapy can be given on average 2-3 hours after pain onset. If the myocardial salvage versus time curve is steepest immediately after occlusion, early administration of thrombolytics, such as by paramedics in the field, may be indicated.(ABSTRACT TRUNCATED AT 250 WORDS)