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Date: November 22, 2023

Reference: Stopyra et al. Delayed First Medical Contact to Reperfusion Time Increases Mortality in Rural EMS Patients with STEMI. AEM November 2023.

Guest Skeptic: Dr. Lauren Westafer an Assistant Professor in the Department of Emergency Medicine at the University of Massachusetts Medical School – Baystate. She is the cofounder of FOAMcast and a pulmonary embolism and implementation science researcher. Dr. Westafer serves as the Social Media Editor and a research methodology editor for Annals of Emergency Medicine.

Case: A 72-year-old man with a history of high blood pressure and diabetes calls emergency medical services (EMS) for chest pressure and dyspnea that started 1 hour ago. Upon EMS arrival, they find the patient is sweaty with normal vital signs. A 12-lead electrocardiogram (ECG) demonstrates ST elevations in leads II, III, and aVF with ST depressions in leads I and aVL and the team begins transport to the nearest percutaneous coronary intervention (PCI) capable hospital.

Background: We have covered the issue of heart attacks several times on the SGEM. These include looking at the HEART score, troponin testing and cardiovascular disease in women. One aspect we have not addressed is rural.

  • SGEM#151: Groove is in the HEART Pathway
  • SGEM#160: Oh Baby, You’re Too Sensitive – High Sensitivity Troponin
  • SGEM#280: This Old Heart of Mine and Troponin Testing
  • SGEM#370: Listen to your HEART (Score)
  • SGEM#400: A Little Bit of Heart and Sport and Sports Related Sudden Cardiac Arrest in Women
  • SGEM Xtra: Unbreak My Heart – Women and Cardiovascular Disease

Current guidelines target a time between first medical contact (FMC) like EMS on-scene and stent or balloon deployment (PCI) of 90 minutes or less. If time from FMC to PCI is anticipated to be greater than 120 minutes, the guidelines recommend systemic thrombolysis rather than PCI [1].

I’ve published on this issue with a project we called “barn door-to-needle time” [2]. We looked at 101 STEMI patients from two rural EDs. The median door-to-ECG time was 6 minutes, door-to-physician time was 8 minutes and DTN time was 27 minutes; 58% of patients received thrombolytics within 30 minutes.

Regional systems of care have been designed to rapidly recognize patients with STEMI and direct STEMI patients to timely reperfusion. Many hospitals do not provide PCI, prolonging transportation times, which disproportionately affects rural patients. There are several distinct time intervals in the care of patients with STEMI and it is unclear which steps in pre-PCI care of patients contribute to avoidable delays.

Clinical Question: Is there an association between in-hospital mortality and time between first medical contact and primary percutaneous coronary intervention in rural patients who present with a STEMI?

Reference: Stopyra et al. Delayed First Medical Contact to Reperfusion Time Increases Mortality in Rural EMS Patients with STEMI. AEM November 2023.

  • Population: Patients ≥ 18 years of age who were transported to one of three tertiary care hospitals by a rural EMS agency and received primary percutaneous coronary intervention (PCI) for STEMI. Rural agency was defined by US census codes (2014)
    • Excluded: Patients <18, those who had prehospital cardiac arrest, and those who were transferred between hospitals
  • Exposure: 90-minute first medical contact to PCI goal (defined as time between the time recorded as EMS personnel arrival on scene and the time the angioplasty or stent was deployed
  • Comparison: Greater than 90 minute first medical contact to PCI
  • Outcome:
    • Primary Outcome: All-cause in-hospital mortality during the index hospitalization
    • Secondary Outcomes: Prehospital time intervals stratified by index hospitalization mortality.
  • Type of Study: A retrospective cohort study from eight rural North Carolina EMS agencies between January 2016 to March 2020.

Dr. Michael Supples

This is an SGEMHOP episode, and it is my pleasure to introduce Dr. Michael Supples. He is an assistant professor of emergency medicine and faculty within the emergency medical services fellowship at Wake Forest School of Medicine in North Carolina. He is double boarded in EM and EMS and focuses on prehospital research. Responds

Authors’ Conclusions: “Death among rural patients with STEMI was four times more likely when they did not receive PCI within 90 minutes.”

Quality Checklist for Observational Study:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Yes
  3. Was the cohort recruited in an acceptable way? Yes
  4. Was the exposure accurately measured to minimize bias? Yes
  5. Was the outcome accurately measured to minimize bias? Yes
  6. Have the authors identified all-important confounding factors? Unsure
  7. Was the follow up of subjects complete enough? Yes
  8. How precise are the results? Not very precise.
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Unsure
  11. Do the results of this study fit with other available evidence? Yes
  12. Funding of the Study? Grant from the National Center For Advancing Translational Sciences of the National Institutes of Health

Results: There was a total of 365 rural patients with STEMIs included in the study. The mean age was 63 years of age, 70% were male, 46% smoked, 69% had hypertension, 61% had hypercholesterolemia and 29% had diabetes. PCI was performed <90 minutes 61% of the time and <120 minutes in 89%. The overall in-hospital mortality was 3% (11/365)

Key Results: Patients receiving PCI within 90 minutes were associated with less in-hospital mortality.

  • Primary Outcome: All-cause in-hospital mortality during the index hospitalization
    • 1.4% (3/221) if treated <90 min vs 5.6% (8/144) if treated >90 min p= 0.03 (95% CI; 0.3% to 8.8%)
    • Meeting the 90-min time goal yielded a 98.6% (95% CI; 96.1% to 99.7%) negative predictive value (NPV)
    • A 78-min FMC to PCI time was the optimal cut point for rural STEMI patients, yielding a NPV of 99.3% (95% CI; 96.1% to 100%) for index death
    • Area under the receiver operating curve (AUC) = 0.752 (95%CI: 0.581, 0.922)
  • Secondary Outcomes: Prehospital time intervals stratified by index hospitalization mortality.

This is an observational study so we can only make conclusions of associations. We also already mentioned there were only 11 deaths which gives wide 95% confidence intervals. Have a listen to the podcast to hear Michael answer our five nerdy questions.

1) Confounding – According to Table 1, the patients who experienced in-hospital mortality were older by about a decade and more patients had key cardiovascular comorbidities (hypertension, hypercholesterolemia, diabetes, and prior MI or CABG). A confounder is a variable that it is associated with the primary exposure of interest and the disease outcome of interest. Can you discuss the decision to adjust/not adjust for potential confounders in this study?

2) Causal Inference – It seems like the bulk of the first medical contact time to PCI time between those who lived and those who died in-hospital was in the door to PCI time. This differed by 30 minutes between groups, whereas most other time points (e.g. dispatch time, response time, scene time etc.) only differed by a median of 0-1 minutes. Activation time was longer in the group that died, but by a shorter length of time. To me, this suggests that there is something about the presentation of the patient or delivery of in-hospital care that is different or more complicated. What are your thoughts on this and the role of prehospital transport?

3) Clustering – Clusters are common in medicine – EMS agencies that treat patients, the hospital to which a patient presents, or even the treating clinician. The outcome of interest may vary less within the cluster than it does in the entire dataset. Can you tell us more about your (appropriate) decision to adjust for clusters?

4) Generalizability – In this study, the median response time was 9 minutes, the median transport time was 27 minutes, and the median total EMS time was 41 minutes. Thus, although these patients were classified as rural, access to a PCI center was relatively timely (i.e. not remote rural locations). How do you think this could impact results?

5) Selection Bias – This study included individuals who had a STEMI and received PCI. There may be circumstances in which a patient has an occlusive myocardial infarction (including STEMI) but does not receive PCI (e.g. patient died – possibility for immortal time bias) [3]. How do you think this could impact results?

Comment on Authors’ Conclusion Compared to SGEM Conclusion: Timely care of patients with occlusive myocardial infarction is imperative and geographic disparities likely exist. However, there are likely several patient-level confounders that also influence time to PCI.

SGEM Bottom Line: Higher in-hospital mortality for rural STEMI patients is associated with longer time from first medical contact to percutaneous coronary intervention.

Case Resolution: EMS activates the local STEMI pathway immediately the patient is given aspirin and nitroglycerin and transported to the nearest PCI-capable hospital.

Dr. Lauren Westafer

Clinical Application: Decreasing unnecessary delays in the prehospital and emergency department settings are important in the care of patients with occlusive myocardial infarction. There is likely potential in rural settings to optimize care to meet recommended benchmarks or provide alternative therapy when necessary.

What Do I Tell My Patient? You are having a heart attack. We are bypassing the closest hospital and transporting you to the nearest hospital that will be able to relieve the blockage in your heart. Things will move very quickly to take the best care of you.

Keener Kontest: Last weeks’ winner was Amanda dos Santos. She knew “wet read” refers to when plain films were developed in liquid solutions. The preliminarily read would sometime be done when the film was wet and still drying.

Listen to this weeks’ show to hear the keener contest question. If you think you know the answer then send an email to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

SGEMHOP: Now it is your turn SGEMers. What do you think of this study of rural STEMI patients? Tweet your comments using #SGEMHOP. What questions do you have for Michael and his team? Ask them on the SGEM blog. The best social media feedback will be published in AEM.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References:

  1. O’Gara PT, Kushner FG, Ascheim DD, et al. ACCF/AHA guideline for the management of ST-elevation myocardial infarction: a re- port of the American College of Cardiology Foundation/American Heart Association TASk Force on Practice Guidelines. Circulation. 2013;127(4):e362-e425. doi:10.1161/CIR.0b013e3182742cf6
  2. Vlahaki D, Fiaani M, Milne WK. A door-to-needle time of 30 minutes or less for myocardial infarction thrombolysis is possible in rural emergency departments. CJEM. 2008 Sep;10(5):429-33. doi: 10.1017/s1481803500010502. PMID: 18826730.
  3. Yadav K, Lewis RJ. Immortal Time Bias in Observational Studies. JAMA. 2021;325(7):686–687. doi:10.1001/jama.2020.9151