CJEM Articles: acute myocardial infarction

Objective: Timely reperfusion therapy for ST-elevation myocardial infarction (STEMI) is an important determinant of outcome, yet targets for time to treatment are frequently unmet in North America. Prehospital strategies can reduce time to reperfusion. We sought to determine the extent to which emergency medical services (EMS) use these strategies in Canada.
Methods: We carried out a cross-sectional survey in 2007 of ground EMS operators in British Columbia, Alberta, Ontario, Quebec and Nova Scotia. We focused on the use of 4 prehospital strategies: 1) 12-lead electrocardiogram (ECG), 2) routine expedited emergency department (ED) transfer of STEMI patients (from a referring ED to a percutaneous coronary intervention [PCI] centre), 3) prehospital bypass (ambulance bypass of local EDs to transport patients directly to PCI centres) and 4) prehospital fibrinolysis.
Results: Ninety-seven ambulance operators were surveyed, representing 15 681 paramedics serving 97% of the combined provincial populations. Of the operators surveyed, 68% (95% confidence interval [CI] 59%-77%) had ambulances equipped with 12-lead ECGs, ranging from 40% in Quebec to 100% in Alberta and Nova Scotia. Overall, 47% (95% CI 46%-48%) of paramedics were trained in ECG acquisition and 40% (95% CI 39%-41%) were trained in ECG interpretation. Only 18% (95% CI 10%-25%) of operators had prehospital bypass protocols; 45% (95% CI 35%-55%) had protocols for expedited ED transfer. Prehospital fibrinolysis was available only in Alberta. All EMS operators in British Columbia, Alberta and Nova Scotia used at least 1 of the 4 prehospital strategies, and one-third of operators in Ontario and Quebec used 0 of 4. In major urban centres, at least 1 of the 3 prehospital strategies 12-lead ECG acquisition, bypass or expedited transfer was used, but there was considerable variation within and across provinces.
Conclusion: The implementation of widely recommended prehospital STEMI strategies varies substantially across the 5 provinces studied, and relatively simple existing technologies, such as prehospital ECGs, are underused in many regions. Substantial improvements in prehospital services and better integration with hospital-based care will be necessary in many regions of Canada if optimal times to reperfusion, and associated outcomes, are to be achieved.

Objective: Acute myocardial infarction (AMI) remains a major cause of death and β-blockers are known to reduce long-term mortality in post-AMI patients. We sought to determine whether patients receiving β-blockers acutely (within 72 h) following AMI had a lower mortality rate at 6 weeks than patients receiving placebo.

Methods: We conducted a systematic review of randomized controlled clinical trials that assessed 6-week mortality and compared β-blockers with placebo in patients randomized within the first 72 hours following AMI. We searched these databases: MEDLINE (1966-2006), EMBASE (1980-2007), Cochrane Central Register of Controlled Trials, Health Star (1966-2007), Cochrane Database for Systematic Reviews, ACP Journal Club (1991-2007), Database of Abstracts of Reviews of Effect (< 1st quarter 2007) and Conference Papers Index (1984-2007). Two blinded reviewers extracted the data and rated study quality using the Jadad score and the adequacy of allocation concealment score, which was adopted by the Cochrane group. We calculated pooled odds ratios (ORs) using a random effect model and performed sensitivity analyses to explore the stability of the overall treatment effect.

Results: We included 18 studies (13 were rated high-quality) with 74 643 enrolled participants and had 5095 deaths. Compared with placebo, adding β-blockers to other interventions within 72 hours after AMI did not result in a statistically significant reduction in 6-week mortality (OR 0.95, 95% confidence interval [CI] 0.90-1.01). When restricted to high quality studies, the OR for 6-week mortality reduction was 0.96 (95% CI 0.91-1.02). We found similar results including studies that enrolled patients within 24 hours after AMI. However, a subgroup analysis that excluded high-risk patients with Killip class III and above showed that β-blockers resulted in a significant reduction in short-term mortality (OR 0.93, 95% CI 0.88-0.99).

Conclusion: Acute intervention with β-blockers does not result in a statistically significant short-term survival benefit following AMI but may be beneficial for low-risk (Killip class I) patients.

Objective: Acetylsalicylic acid (ASA) is a simple and cost-effective treatment for acute coronary syndromes (ACS). Our objectives were to determine the frequency of ASA administration in the emergency department (ED) for patients with acute myocardial infarction or unstable angina, and to identify patient characteristics associated with its administration.

Methods: This is a retrospective chart review of patients discharged with a final diagnosis of ACS. Data on age, gender, mode of presentation, presence of chest pain at triage, administration of ASA or not in the ED, dosage and form of ASA received, timing of administration, presence of contraindications to ASA and use of regular ASA prior to ED presentation were recorded.

Results: Six hundred and one charts were analyzed. Five hundred and fifty patients (91.5%) received ASA. Only 444 (73.9%) of these 550 patients were administered the ASA appropriately, according to the American Heart Association / American College of Cardiology (AHA/ACC) guidelines. Univariate analysis showed that chart notes "Transport by ambulance," "Allergy to ASA" and "Gastrointestinal bleed" were associated with a lower probability of the patient being administered ASA. If a patient was noted as taking ASA regularly, it increased the chance of this patient being administered ASA in the ED.

Conclusion: Although the study ED performed well, administering ASA to 91.5% of patients with ACS, only 73.9% of the patients who received ASA were administered the ASA appropriately, as recommended in the AHA/ACC guidelines. Educational strategies and system changes are necessary to increase the proportion of eligible ACS patients who receive appropriate ASA therapy.