Selection factors for the use of thrombolytic treatment in acute myocardial infarction: a population based study of current practice in the United Kingdom. The European Secondary Prevention Study Group

Acute ST-segment elevation myocardial infarction and prior stroke: an analysis from the Magnesium in Coronaries (MAGIC) trial

BACKGROUND

Patients with prior stroke represent a substantial proportion of patients presenting with acute ST-segment elevation myocardial infarction (STEMI). However, the impact of prior stroke on prognosis has not been rigorously examined in the reperfusion era.

METHODS

The baseline characteristics, treatments, and clinical outcomes of patients with prior stroke enrolled in the Magnesium in Coronaries (MAGIC) trial were evaluated and compared to those of patients without prior stroke.

RESULTS

MAGIC enrolled 6213 patients with STEMI, of whom 558 (9.0%) had prior stroke. Patients with prior stroke were more likely to have a history of hypertension (88.0% vs 70.3%), diabetes (19.9% vs 14.5%), myocardial infarction (38.2% vs 25.1%), and congestive heart failure (15.6% vs 9.7%). The mean Thrombolysis in Myocardial Infarction Risk Score was higher in patients with prior stroke compared to those without prior stroke (4.37 vs 3.93, P < .0001). Patients with prior stroke were less likely to receive reperfusion therapy, even among those considered eligible at presentation (66.3% vs 80.6%, P < .0001). Compared to patients without prior stroke, inhospital stroke (3.0% vs 1.0%, P < .0001), severe congestive heart failure (23.3% vs 18.2%, P = .003), and 30-day mortality (21.0% vs 14.7%, P < .0001) were higher among patients with prior stroke. On multivariable analysis, prior stroke was independently associated with a significantly higher risk of death at 30 days (odds ratio 1.44, P = .0023).

CONCLUSIONS

Patients with prior stroke who present with STEMI are at very high risk for short-term morbidity and mortality. Aggressive treatment of these patients appears warranted.

Use of thrombolytic therapy for acute myocardial infarction: effects of gender and age on treatment rates

BACKGROUND

Although there have been efforts to increase the utilization of thrombolytic therapy, there are still many patients who might benefit from this treatment who do not receive it. Women and the elderly have been particularly undertreated, despite evidence that their survival can be improved with thrombolysis. This study was undertaken to determine the relative rates of treatment of women vs. men and the elderly vs. younger subjects and to examine factors that might explain differences in treatment frequency.

METHODS AND RESULTS

This is a retrospective study of patients who presented to the Emergency Departments of four local hospitals in 1993 and 1994 with evidence for acute ST-elevation myocardial infarction. Demographic data, past medical history, information on co-morbid illnesses, and times to hospital arrival, first electrocardiogram, physician notification, and thrombolytic therapy were recorded as was survival to hospital discharge. Data for patients who did or did not receive thrombolytic therapy were compared. Men were treated more frequently in both tertiary and community hospitals. Women were older, but within each age bracket, men were treated more often. The time of arrival was similar for men and women, but men who arrived within 6 hours or 6-12 hours after pain onset were treated at a higher rate than women. For patients without contraindications, treatment was not affected by gender or age. However, treatment rates decreased with increased prevalence of exclusionary factors, and since both women and the elderly tended to have more such factors, elderly women were treated at a markedly lower rate. The single clinical factor that increased thrombolytic usage in women compared to men was a history of prior myocardial infarction.

CONCLUSION

Despite convincing evidence that thrombolytic therapy is beneficial in women and the elderly, these groups have been relatively neglected unless attention is called to clinical risk, for example, by history of prior myocardial infarction.

Value of the ECG in suspected acute myocardial infarction with left bundle branch block

Uncomplicated left bundle branch block (LBBB) is characterized by true ST-segment shifts resulting from delayed repolarization in the left ventricle with respect to the right ventricle. When acute coronary occlusions develop in the setting of previous or new LBBB, 12-lead eCG manifestations of injury may also appear. They consist of a more pronounced ST-segment elevation, of ST-segment deviations opposite to those of uncomplicated LBBB, or both. We have reported that the only 3 independent ECG signs of acute MI during LBBB among patients with chest pain or history of coronary disease are: ST elevation > or = 1 mm in leads with a positive QRS, ST-depression > or = 1 mm in V1 to V3, and ST elevation > or = 5 mm in leads with a negative QRS. In our study, the clinical prediction rule score values of these signs were 5; 3; and 2, respectively. A score > or = 3 made a diagnosis of MI with a 90% specificity and a score of 2 with > 80%, specificity. Recent validation studies have confirmed that the presence of any of these ECG signs is associated with a sensitivity of 44 to 79% and a specificity of 93 to 100%. Sensitivity increases if serial or previous ECGs are available for comparison. Interobserver agreement is very high. While current practice guidelines recommend thrombolysis for all patients with chest pain and LBBB, concern among physicians about hemorrhagic stroke prevents many of these patients from receiving timely treatment. In a population with LBBB and chest pain where our proposed ECG criteria were not ascertained, only 73% of eligible patients received thrombolysis; on the other hand, 48% of patients with no biochemical evidence of MI were thrombolyzed. For the latter group, the clinical prediction rule had a score of 0. Instead, 79% of patients with confirmed acute MI had a prediction rule score > or =2. Similar values applied to a subgroup of patients with serial ECGs. We propose that thrombolysis among patients with chest pain and LBBB be decided on the basis of a systematic ECG review to "rule patients in". This provision may result in both a significant reduction in the number of patients without infarction who receive thrombolysis and in timely treatment of those who do have MI.

Suspected myocardial infarction and left bundle branch block: electrocardiographic indicators of acute ischaemia

OBJECTIVES

To examine the use of thrombolytic treatment in patients with suspected acute myocardial infarction (AMI) and left bundle branch block (LBBB). To evaluate electrocardiographic criteria for the identification of AMI in the presence of LBBB, and examine the implications of using these criteria in the clinical setting.

METHODS

A retrospective study over two years, based in two Sheffield teaching hospitals. Patients presenting with LBBB and suspected AMI were studied by analysis of an AMI database. The proportion of patients with LBBB and AMI receiving thrombolysis, and the in-hospital delay before the start of treatment, were used as indicators of current performance. Three predictive criteria were applied to the electrocardiograms (ECGs) retrospectively, and their ability to identify acute ischaemic change assessed. The implications of using the predictive criteria in the clinical setting were explored.

RESULT

Twenty three per cent (5/22) of patients with LBBB and AMI did not receive thrombolysis, in the absence of documented contraindications. The mean in-hospital treatment delay for thrombolysed patients was 154 minutes. Forty eight per cent (16/33) of those thrombolysed did not have a final clinical diagnosis of AMI. In the majority of cases (8/12), the decision not to administer thrombolysis was based on a single ECG recording. The presence of any of the predictive electrocardiographic criteria was associated with a diagnosis of AMI, with a sensitivity of 0.79 (95% confidence interval 0.63 to 0.95), specificity 1, positive predictive value 1, and negative predictive value 0.79. The kappa scores between four independent observers showed either substantial or near perfect agreement.

CONCLUSION

Currently, thrombolytic treatment is under-utilised in patients with LBBB and AMI, and those who are thrombolysed endure lengthy delays before treatment. Patients with any of the predictive criteria should be thrombolysed immediately. When the diagnosis is in doubt, serial ECGs may demonstrate evolving ischaemic change.

Body-surface map models for early diagnosis of acute myocardial infarction

The standard 12-lead ECG is only 50% sensitive for the detection of acute myocardial infarction (AMI). The majority of leads for optimal classification of AMI probably lie outside the area covered by the 6 precordial leads. Thus, body-surface mapping (BSM) may be more helpful, as a larger thoracic area is sampled. We recorded 64-lead anterior BSMs in 635 patients with chest pain suggestive of AMI and abnormal electrocardiograms (ECGs), and 125 controls without chest pain. Of the 635 patients, 325 had AMI according to World Health Organization (WHO) criteria (203 presenting with ST segment elevation, and 122 with nondiagnostic ECG), and 310 had an "abnormal ECG but not AMI." QRS and ST-T isointegrals and variables describing map shape were derived. Subjects were randomly allocated to a training set (63 controls, 321 patients) and a validation set (62 controls, 314 patients). Multiple logistic regression was used in the training set to identify which variables gave best discrimination between groups. A model with these variables was then tested prospectively in the validation set. In stage 1 (all subjects), controls were compared with patients. In the training set, a model containing 21 variables classified 58/63 controls (specificity 92%) and 316/321 patients (sensitivity 98%). In the validation set, the model classified 48/62 controls (specificity 77.4%) and 302/314 patients (sensitivity 96%). In stage 2 (studying patients only), patients with AMI were compared with patients who had an abnormal ECG-not AMI. In the training set, a model containing 28 variables classified 132/165 patients (sensitivity 80%) with AMI and 134/156 patients (specificity 86%) with an abnormal ECG-not AMI. In the validation set, the model classified 123/160 patients (sensitivity 77%) with AMI and 131/154 patients (specificity 85%) with an abnormal ECG-not AMI. Combining results of both stages in a two-step algorithm gave an overall classification in the training set of controls 92%, abnormal ECG-not AMI 84%, AMI 80%, and in the validation set of controls 77%, abnormal ECG-not AMI 82%, AMI 74%. Thus, in conclusion, when compared with the 12-lead ECG, BSM models results in higher sensitivity and specificity for detection of AMI, particularly in patients presenting with chest pain and nondiagnostic ECG changes. The use of BSM models in such patients, may lead to the earlier detection of AMI and appropriate administration of fibrinolytic therapy and/or anti-platelet agents.

Trends in the treatment of patients with myocardial infarction and coronary revascularization procedures in Finland during 1986-92: the FINMONICA Myocardial Infarction Register Study

OBJECTIVES

To investigate changes in the medical treatment of patients with myocardial infarction and the trends in revascularization procedures in Finland.

DESIGN

A population-based myocardial infarction (MI) register study.

SETTING

Populations, aged 25-64 years, of the three geographical areas of Finland, provinces of North Karelia and Kuopio in eastern Finland and the Turku-Loimaa area in south-western Finland.

MAIN OUTCOME MEASURES

Medical treatment administered prior to the coronary event, during the hospitalization and at discharge from hospital to all patients hospitalized due to suspected myocardial infarction and all CAD deaths occurring during three separate 4-month periods in 1986, 1989 and 1992. Data on coronary bypass surgery and percutaneous coronary angioplasty in the study areas for 1986-92.

RESULTS

The most marked change in the medical treatment of hospitalized myocardial infarction patients was the significant increase in the use of thrombolytic treatment (5% of patients in 1986 and 24% in 1992, P < 0.001 for trend). The use of antiplatelet agents increased from 1986 to 1992 prior to the coronary event, during the hospitalization and at discharge. The use of beta-blockers and intravenous nitrates increased and the use of calcium-channel blockers declined significantly in hospitalized patients during the study period. Hospitalized male myocardial infarction patients were treated more often with beta-blockers, nitrates, antiplatelet agents and thrombolytic agents than female patients, suggesting less intensive medical treatment in women.

CONCLUSION

The results of the large clinical trials regarding the medical treatment of myocardial infarction patients were adopted in the clinical practice rapidly and the treatment of myocardial infarction patients and the number of revascularization procedures changed markedly from 1986 to 1992 in Finland. These changes may in part explain the favourable changes in mortality from CAD in Finland.

Utilisation of thrombolytic therapy in older patients with myocardial infarction

Empirical evidence from many countries, obtained from sampling populations of patients admitted to hospital with acute myocardial infarction, has confirmed that elderly patients are significantly less likely to receive thrombolytic therapy. This difference persists after controlling for confounding factors such as admission delay and contraindications to thrombolysis. However, evidence supporting the efficacy of thrombolysis in reducing mortality after acute myocardial infarction is less clear cut in patients aged 75 years or above than in younger patients. These older patients are substantially under-represented in the clinical trials although they constitute one third of the clinical population. Observational studies indicate that older patients are at slightly higher risk than younger patients of experiencing haemorrhagic stroke after thrombolysis. It is, however, unlikely that efficacy and tolerability considerations alone account for the low use of thrombolytics in the elderly as similar trends are seen for other modalities of treatment of acute myocardial infarction. Since older patients have the highest mortality risk after myocardial infarction, they have the greatest potential gain from thrombolytic treatment, assuming a uniform treatment effect across age. The estimated cost effectiveness (cost per quality-adjusted life-year gained) improves with increasing age. It is concluded that patient age should not influence the treatment decision concerning thrombolysis. To ensure that elderly patients receive maximum benefit from this therapeutic advance requires attention to referral patterns from the community, speed of assessment in hospital and a clear treatment policy without age constraints. The effectiveness of these measures should be routinely audited.

Incidence and mortality from early stroke associated with acute myocardial infarction in the prethrombolytic and thrombolytic eras. Secondary Prevention Reinfarction Israeli Nifedipine Trial (SPRINT) and Israeli Thrombolytic Survey Groups

OBJECTIVES

This study sought to compare the incidence of early cerebrovascular events and subsequent mortality in two cohorts of consecutive patients with acute myocardial infarction (AMI), admitted to coronary care units (CCUs) in Israel, in the prethrombolytic and thrombolytic eras.

BACKGROUND

During the past decade, substantial changes have occurred in the medical treatment of AMI, and important new therapies have been introduced that could all affect stroke risk and type by diverse mechanisms. Yet the overall impact of these new therapeutic modalities on the incidence of stroke complicating AMI is not clear.

METHODS

We compared the incidence and mortality rates of cerebrovascular events complicating AMI within CCUs among 5,839 consecutive patients admitted in the period 1981 to 1983 versus 2,012 patients from two prospective nationwide surveys conducted in all CCUs operating in Israel in 1992 and 1994.

RESULTS

The demographic and clinical characteristics of patients with AMI in both periods were comparable. Patients admitted in the period 1981 to 1983 did not receive thrombolysis and reperfusion therapy; those admitted in 1992 and 1994 received thrombolysis (45%) and coronary angioplasty or coronary artery bypass graft surgery (14%), and antiplatelet and anticoagulant treatments were more frequently used. The incidence of early cerebrovascular events was 0.74% (43 of 5,839) in 1981 to 1983 versus 0.75% (15 of 2,012) in the 1992 to 1994 cohort. Patients with an AMI who experienced a cerebrovascular event were somewhat older in both groups and had a high rate of previous cerebrovascular events, congestive heart failure and atrial and ventricular arrhythmias during the hospital period. Mortality declined by one-third between the two periods. However, the mortality rate of patients with AMI who sustained a cerebrovascular event remained high (> or =40% for 30 days, 60% for 1 year).

CONCLUSIONS

The overall incidence of early cerebrovascular events complicating AMI remained similar (0.75%) in the prethrombolytic and thrombolytic eras. Mortality rates of patients with an AMI but no cerebrovascular events decreased substantially over the past decade but not in patients with AMI with a cerebrovascular event.