Pre-Hospital ECG for STEMI Cath Lab Activation

May 2010

Pre-Hospital ECG for STEMI Cath Lab Activation

Search Strategy: .You perform three PubMed searches the terms “prehospital 12 lead ECG”, “paramedic STEMI” and “EMS myocardial infarction angioplasty” yielding a combined 127 hits. You eliminate the non-English articles and select the following:

You are sitting in the resident’s area outside of the EMS section offices when you overhear Dr. Levine and Dr. Gilmore discussing the 12 lead ECG project for Saint Louis Fire Department. Dr. Gilmore is discussing with Dr. Levine whether Paramedics can effectively obtain and interpret 12-lead ECGs in the field and activate the cardiac catheterization lab directly from the prehospital setting. You scratch your head as the endless bantering continues and quickly pull up PubMed on the computer to find an article to quiet them so that you can finish your follow-ups for Dr. Char.


PICO Question

Population: Prehospital patients with suspected STEMI

Intervention: Prehospital 12-lead ECG program

Control: Standard prehospital chest pain treatment

Outcome: Sensitivity, specificity, likelihood ratio, reliability, availability, time-to-diagnosis, adverse effects of one diagnostic strategy over another


Years

First years: Impact of the prehospital ECG on door-to-balloon time in ST elevation myocardial infarction. Catheter Cardiovasc Interv 2010; 75: 174-178. (http://pmid.us/19806636)

Second years: Can paramedics read ST-segment elevation myocardial infarction on prehospital 12-lead electrocardiograms? Prehosp Emerg Care 2009;13: 207-214. (http://pmid.us/19291559)

Third years: A comparison of door-to-balloon times and false-positive activations between emergency department and out-of-hospital activation of the coronary catheterization team. Acad Emerg Med 2008; 15: 784-787. (http://pmid.us/18638030)

Fourth years: Real-time paramedic compared with blinded physician identification of ST-segment elevation myocardial infarction: results of an observational study. Am J Emerg Med 2005; 23: 443-448. (http://pmid.us/16032608)


Articles

Article 1: Impact of the Pre-hospital ECG on Door-to-Balloon Time in ST Elevation Myocardial Infarction, Catheterization and Cardiovascular Interventions 2010; 75:174–178
ANSWER KEY

Article 2: CAN PARAMEDICS READ ST-SEGMENT ELEVATION MYOCARDIAL INFARCTION ON PREHOSPITAL 12-LEAD ELECTROCARDIOGRAMS? PREHOSPITAL EMERGENCY CARE 2009; 13:207-214
ANSWER KEY

Article 3: A Comparison of Door-to-balloon Times and False-positive Activations between Emergency Department and Out-of-hospital Activation of the Coronary Catheterization Team, Acad Emerg Med 2008; 15:784-787
ANSWER KEY

Article 4: Real-time paramedic compared with blinded physician identification of ST-segment elevation myocardial infarction: results of an observational study, Am J Emerg Med 2005; 23:443–448
ANSWER KEY


Bottom Line

Door-to-balloon times may soon change to initial contact (EMS) to balloon times in an attempt to further reduce the myocardial ischemia time. Pre-hospital ECG-based activation of cardiac cath labs makes intuitive sense in settings where prolonged transport times exist, but the diagnostic and therapeutic impact of this expensive, labor-intensive technology remains uncertain (clinical equipoise). The disadvantages/barriers of a pre-hospital ECG program include:

  • Expense — $25,000 with institutional discount + transmission fees + maintenance
  • Cath lab (Interventional Cardiology) acceptance with an ill-defined false-positive rate
  • Quality assurance training & maintaining EMS ECG skill sets
  • Medicare does not reimburse EMS for pre-hospital ECG’s

At Barnes Jewish Hospital the median transport time is 20-minutes. Locally, Christian Northeast EMS has been empowered to activate the cath lab based upon their EMS interpretation of ECG’s with a goal false-positive rate of <10%. Thus far, they have attained an 8.8% false-positive activation rate. In this setting, we analyzed the best-available evidence to define the diagnostic accuracy and clinical outcomes from pre-hospital based ECG protocols to activate the cath lab.

Note that we’d looked at this topic once before (April 2006) and concluded that

“Several small studies of heterogeneous design demonstrate no significant transport delays and a probable reduction in door-to-needle times by using pre-hospital ECG for AMI in both rural and urban settings of 20-30 minutes. Acknowledging the accepted view that “time is myocardium” and the limited impact of health care providers on presentation delays, maximizing efficiency by concurrently activating the cardiac catheterization team while transportation is occurring is logical. Future trials should assess the impact of pre-hospital ECG on cost-effectiveness and patient-important outcomes such as cardiovascular mortality, post-MI functional status, and adverse outcomes from appropriate and inappropriate use of in-hospital reperfusion based upon the electrocardiograms in a variety of pre-hospital systems.”

A paper-based survey of Connecticut paramedics using typical and atypical ACS patients, demonstrated that recently ECG trained non-volunteer ALS EMS personnel who work > 1 shift/month can accurately diagnose STEMI (93% sensitive, 85% specific) and activate the cath lab (88% sensitive, 88% specific) in pre-hospital settings independent of their level of experience, extra-curricular ECG training, or patient’s symptom characteristics. Of course, future trials will need to verify this accuracy in actual field situations complicated by heterogeneous ECG quality, competing distracters and variably trained/motivated pre-hospital providers. The PGY-IV paper did analyze some of these questions prospectively comparing pre-hospital ECG accuracy (in selected patients suspected of AMI without left bundle branch block or pacemaker) with EM physician and Cardiologist’s interpretation noting equivalent specificity (97% EMS vs. 96% EM and 96% Cardiologist) and good sensitivity (80% EMS vs. 80% EM physician vs. 92% Cardiologist) for detecting STEMI.

The PGY-I paper, a non-randomized, unadjusted, three-center analysis suggests that a pre-hosp ECG transmitted to ED physician (vs. ED-obtained ECG) can reduce DTB times by 30-minutes and stabilize door-to-balloon times during off-hours. The PGY-III paper, a single-center (UCLA-Harbor) quality improvement data-based retrospective analysis of confirmed STEMI patients suggests that pre-hospital ECG’s in paramedics trained to obtain (but not interpret) ECG’s — and not empowered to activate the cath lab — produce significantly more false-positive cath lab activations than ED activation protocols without reducing door-to-balloon times. In order to understand the costs and non-financial barriers to minimizing the initial medical contact to balloon times, future research should establish acceptable false-positive cath lab activation rates and better define barriers (EMS training, cath lab acceptance) to the initiation of pre-hosp cath lab activation.

Therefore, pending as yet unreported clinical trial data pre-hospital ECG protocols seem logical if the following criteria are met.

  1. Interventional Cardiology will act upon the pre-hospital ECG with an accepted false-positive cath lab activation rate.
  2. Somebody (hospital, pre-hospital company) will purchase & maintain the transmission equipment.
  3. EMS medical officers are committed to a robust quality control program including training and periodic ECG performance reviews.
  4. The time-saving benefits outweigh the delay in obtaining an ECG and likely increased false-positive cardiac cath lab activation rates.

A quick review of clinicaltrials.gov reveals several industry and non-industry trials underway to further assess these questions including:

So stay tuned for more data…

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