The Prehospital Electrocardiogram Is the Cornerstone for Developing a Prehospital ST-elevation Myocardial Infarction System of Care
Pub Date: Wednesday, August 13, 2008
Author: Eric R. Bates, MD
Willem Einthoven, Sir Thomas Lewis, and Frank Wilson are widely regarded as the fathers of modern electrocardiography. Working in Leiden, Einthoven developed the string galvanometer in 1901 and used it to measure the human electrocardiogram (ECG), for which he was awarded the Nobel Prize in 1924. Lewis, working at the University College in London from 1908 to 1920, exploited this instrument to study the mechanisms of arrhythmias and spread of excitation. During the following 3 decades, at the University of Michigan, Wilson developed the physical and mathematical basis of the ECG, conceived the central terminal as an indifferent electrode, and introduced the unipolar precordial leads. He studied abnormalities of the waveforms including hypertrophy, bundle branch block, and myocardial infarction. The ability to operate the instrument and interpret the ECG first defined the cardiologist as a medical subspecialist. Although Einthoven's machine weighed 600 pounds and required five men to operate it, current technology permits the emergency portable recording of the ECG by an emergency medical technician and the prehospital diagnosis of ST-elevation myocardial infarction (STEMI). In the AHA scientific statement by Ting et al., the opportunities and challenges of implementing and integrating a prehospital ECG program into a STEMI system of care are explored.
We know that electrical defibrillation, reperfusion therapy, and antiplatelet and anticoagulant drugs dramatically decrease the complications of STEMI, including death. Time-to-treatment is the most critical variable in determining patient outcome, but major challenges exist in increasing the number of patients who activate the Emergency Medical Services (EMS) system and in reducing the time from symptom onset to first medical contact. Importantly, 30% of eligible patients are not receiving any reperfusion therapy, rescue percutaneous coronary intervention (PCI) is underutilized for fibrinolytic failures, a large proportion of patients are not given access to primary PCI, and half the patients receiving reperfusion therapy receive delayed treatment. Therefore, there has been increasing emphasis on building coordinated systems of care to improve timeliness of therapy and delivery of guideline-based therapy across the continuum of STEMI care from patient entry to hospital discharge. Important progress has been made in decreasing hospital door-to-needle and door-to-balloon times and coordinating the emergency department, the cardiac catheterization laboratory, and the coronary care unit into a hospital STEMI system of care. The next challenge is in coordinating EMS, referral hospitals, and receiving hospitals into a prehospital regional STEMI system of care, a necessary advance if primary PCI is to be made available to more patients.[6
Just as the ECG played a key role in the emergence of cardiology as a specialty, the prehospital ECG is the cornerstone for developing a prehospital STEMI system of care. The prehospital diagnosis of STEMI in a coordinated system of care enables a decision to be made regarding transport to the nearest facility or, if it does not have PCI capability, direct transport to a PCI-capable hospital (hospital bypass strategy). It also allows prehospital emergency department notification and activation of the cardiac catheterization laboratory and facilitates direct access to the lab (emergency department bypass strategy).
It is interesting to note that Einthoven used a telephone line to transmit the electrical impulses from the hearts of patients in the Academic Hospital to his physiology laboratory, almost a mile away, where they were recorded with the string galvanometer. More than a century later, there remain challenges in acquiring, interpreting, and communicating accurate ECG information between two different locations so that it can be integrated into the STEMI system of care. First, EMS systems have to purchase the appropriate equipment, and EMS providers have to be trained in recording high-quality tracings. Second, a choice has to be made between computer algorithm interpretation, paramedic interpretation, and wireless transmission for physician interpretation of the ECG. Third, EMS and the receiving hospital have to establish an organized system that will exploit prehospital diagnosis and decrease time-to-treatment. Finally, regional networks of hospitals have to establish systems of care that will facilitate prehospital triage or interhospital transfer for emergency STEMI care.
The 2004 American College of Cardiology/American Heart Association STEMI guidelines  list two recommendations related to the prehospital ECG. First, "it is reasonable that all advanced cardiac life support (ACLS) providers perform and evaluate 12-lead ECGs routinely on chest pain patients suspected of STEMI (Class IIa, LOE B)." Second, "if the ECG shows evidence of STEMI, it is reasonable that prehospital ACLS providers review a reperfusion 'checklist' and relay the ECG and checklist findings to a predetermined medical control facility and/or receiving hospital. (Class IIa, LOE C)." The 2007 focused update  states that "an underutilized but effective strategy for improving systems of care for STEMI patients is to expand the use of prehospital 12-lead electrocardiography programs by EMS that provide advanced life support," but offers no new recommendations. A stronger guideline endorsement of the prehospital ECG awaits the answers to a number of research questions detailed in the Scientific Statement.
There surely are staffing, training, technological, geographic, and financial barriers to implementing a successful prehospital ECG program. Moreover, increasing patient use of EMS and new reimbursement strategies will be required in an ideal system. However, even if a prehospital ECG program cannot be initiated in a given hospital, evaluating that possibility offers the hospital the opportunity to improve the existing system of care. Are there EMS destination and interhospital transfer protocols in place? Is there a reperfusion checklist? Are there standard pharmacological regimens and order sets? Have standard lines of communication been established between EMS, the emergency department, and interventional cardiology with single-call activation systems?
The American College of Cardiology-Door to Balloon (ACC-D2B) program has taught us that improving hospital systems of care is possible and results in improved patient outcomes. Now, the AHA Mission: Lifeline initiative is offering direction in improving our prehospital STEMI system of care. Hopefully, all of our health care systems will embrace this important initiative, because the next big reduction in adverse STEMI outcomes will come from more efficient and appropriate delivery of available treatments, rather than from new drug or device development. An important step in that direction would come from prehospital ECG diagnosis of STEMI, prehospital emergency department notification, and prehospital activation of the cardiac catheterization laboratory for primary PCI in communities with that capability. The feasibility of accomplishing this goal has been demonstrated.[9-15] The challenge is for individual communities to address their unique needs, resources, and barriers to implementing a STEMI system of care and to develop the best program possible that delivers excellent care to patients.
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-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --