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The Role of Emergency Medical Systems in the Pre-Hospital Management of STEMI 

For over two decades, scientific evidence has proven that early coronary reperfusion reduces morbidity and mortality in patients with acute ST - segment elevation myocardial infarction (STEMI). Emergency Primary coronary intervention (PPCI) has become the dominant reperfusion strategy, being superior to fibrinolysis in reducing mortality, reinfarction and cerebral apoplexy. We also know that with earlier intervention the greater the benefit. After 12 hours, there is no significant reperfusion benefit and the risk of complications can increase.


STEMI Chain of Survival


The STEMI chain of survival was adapted by the American Heart Association (AHA) and it summarizes the four most important components (links) to achieve early reperfusion (see figure below):

  • The time the patient seeks medical help or calls 9-1-1,

  • Time of evaluation and treatment by the Emergency Medical System (EMS)

  • The time it takes for the Emergency Department (ED) to diagnose STEMI and

  • The time needed by the hospital to perform reperfusion.
















Each link is critical, and if one fails it can be harmful and fatal for the patient.


Importance of the Emergency Medical System


The EMS is a very important component in this chain of survival, especially if used optimally and not merely as a transport service. There are multiple benefits of an efficient transport by EMS, with the potential to save lives: by providing therapeutic interventions such as aspirin, oxygen, nitroglycerin, morphine; having the possibility of initiating advanced cardiovascular resuscitation in case of cardiac arrest; by facilitating early diagnosis of STEMI with the ability to do a 12-lead electrocardiogram (ECG); and by choosing a PCI Center as the destination hospital once STEMI is confirmed. Thus, with an early ECG diagnosis of STEMI this helps direct the patient to the nearest hospital with PPCI capability and to alert and activate the catheterization team (STEMI alert), so when the patient arrives, he may bypass the ED straight to the catheterization laboratory.


For these processes to occur and function efficiently plenty of planning and coordination between EMS and the community hospitals is required. The guidelines of the American College of Cardiology (ACC) and the AHA suggest and promote each community develop its own STEMI systems, adapting strategies that have proven to reduce reperfusion times. It is important that hospitals incapable of PPCI (referring hospitals) have defined protocols, transfer criteria and agreements with hospitals with PPCI capacity (receiving hospitals). The EMS should also respond and participate in these inter-hospital transports.


One of the pillars of the PRINCE initiative (Puerto Rico Infarction National Collaborative Experience) is the integration of EMS in this STEMI system of care. This project works with the 9-1-1 system, the state EMS (CEM-PR), municipal EMS and private agencies, in collaboration with PPCI hospitals, to improve the management and survival of patients suffering from acute heart attack in Puerto Rico.




We must educate the community to recognize symptoms of an acute heart attack and to call 9-1-1 as soon as possible. An optimal EMS allows the diagnosis of STEMI with prehospital ECG; transports the patient with STEMI to hospitals with PPCI capability; alert and activate the catheterization team prior to hospital arrival; and potentially may bypass the ED and direct the patient into the catheterization laboratory for quicker intervention. This strategy not only has proven to reduce reperfusion time but also patient mortality. For this reason, it is imperative to improve and standardize the prehospital management of EMS with the use of 12-lead ECG equipment and transmission capacity in order to make it a stronger link in the STEMI Chain of Survival.



By: Jose Escabí-Mendoza, MD, FACC  

Invasive Cardiologist

Director, Chest Pain Center & Coronary Care Unit

VA Caribbean Healthcare System, San Juan, Puerto Rico 

PRINCE Initiative EMS Liaison

Spanish translation of this document 

Telephone contact list for referral to STEMI PCI Centers 

Suggested hospital destination selection criteria for EMS in confirmed STEMI cases 

Fourth Symposium of the Academy of "Cuerpo de Emergencias Médicas-Puerto Rico".

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