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Prospective evaluation of eligibility for thrombolytic therapy in acute myocardial infarction
J K French1, B F Williams, H H Hart
1Coronary Care Unit, Green Lane Hospital, Auckland, New Zealand.
Insights
About half of acute myocardial infarction patients are eligible for thrombolytic therapy. Few have contraindications, yet treatment rates remain suboptimal, with high mortality persisting.
Area of Science:
- Cardiology
- Emergency Medicine
Background:
- Acute myocardial infarction (AMI) is a leading cause of mortality worldwide.
- Thrombolytic therapy is a crucial reperfusion strategy for AMI.
- Assessing eligibility for thrombolysis is vital for timely patient management.
Purpose of the Study:
- To determine the proportion of patients with acute myocardial infarction eligible for thrombolytic therapy.
- To identify contraindications to thrombolysis in this patient population.
- To analyze treatment rates and outcomes among eligible patients.
Main Methods:
- A cohort follow-up study was conducted in four coronary care units in Auckland, New Zealand.
- 3014 patients presenting with suspected myocardial infarction in 1993 were analyzed.
- Eligibility criteria included symptom onset within 12 hours, specific ECG changes (ST elevation or new left bundle branch block).
Main Results:
- Of 1081 patients with definite or probable myocardial infarction, 53.3% were eligible for reperfusion.
- Only 3.6% (39/1081) had definite contraindications to thrombolysis.
- Ultimately, 49.7% of eligible patients received thrombolytic therapy, with hospital mortality rates of 11.7% for treated and 17.0% for untreated patients.
Conclusions:
- Approximately half of AMI patients admitted to coronary care units meet current criteria for thrombolytic therapy.
- Definite contraindications to thrombolysis are uncommon in eligible patients.
- Despite eligibility, thrombolytic treatment rates are suboptimal, and overall mortality for myocardial infarction remains high.
Objectives:
To determine the proportion of patients presenting with acute myocardial infarction who are eligible for thrombolytic therapy.
Design:
Cohort follow up study.
Setting:
The four coronary care units in Auckland, New Zealand.
Subjects:
All 3014 patients presenting to the units with suspected myocardial infarction in 1993.
Main Outcome Measures:
Eligibility for reperfusion with thrombolytic therapy (presentation within 12 hours of the onset of ischaemic chest pain with ST elevation > or = 2 mm in leads V1-V3, ST elevation > or = 1 mm in any other two contiguous leads, or new left bundle branch block); proportions of (a) patients eligible for reperfusion and (b) patients with contraindications to thrombolysis; death (including causes); definite myocardial infarction.
Results:
948 patients had definite myocardial infarction, 124 probable myocardial infarction, and nine ST elevation but no infarction; 1274 patients had unstable angina and 659 chest pain of other causes. Of patients with definite or probable myocardial infarction, 576 (53.3%) were eligible for reperfusion, 39 had definite contraindications to thrombolysis (risk of bleeding). Hence 49.7% of patients (537/1081) were eligible for thrombolysis and 43.5% (470) received this treatment. Hospital mortality among patients eligible for reperfusion was 11.7% (55/470 cases) among those who received thrombolysis and 17.0% (18/106) among those who did not.
Conclusions:
On current criteria about half of patients admitted to coronary care units with definite or probable myocardial infarction are eligible for thrombolytic therapy. Few eligible patients have definite contraindications to thrombolytic therapy. Mortality for all community admissions for myocardial infarction remains high.