that the effect of beta‐blockers in reducing arrhythmic events is equally offset by an increase in development of cardiogenic shock, and survival is similar regardless of early administration of intravenous beta‐blockers [43]. Current AHA/ACC recommendations for administration of intravenous beta‐blockers in the setting of STEMI are limited to patients who are hypertensive or have ongoing ischemia with no contraindications to their use [16]. On balance, the guidelines suggest that the need for prehospital administration of beta‐blockers to patients with STEMI is limited.
Prehospital fibrinolysis
Since fibrinolytics were introduced to emergency cardiac care in the mid‐1980s, some have proposed initiating the drug in the prehospital setting. Several studies published in the early 1990s showed that the strategy was feasible and that it could decrease mortality from STEMI in settings that had relatively long EMS response and/or transport intervals [44, 45]. Additional studies reinforced the original findings. A meta‐analysis of pooled results from six randomized trials enrolling more than 6,000 subjects concluded that prehospital initiation of fibrinolytics decreased all‐cause mortality by shortening initiation of fibrinolytics by 58 minutes [46].
Prehospital fibrinolysis has not been used commonly in the United States compared to Europe, where there are often physician‐staffed ambulances [47]. However, even in Europe prehospital fibrinolysis has been replaced by primary PCI for treatment of STEMI. In a prospective observational cohort study of 26,205 consecutive patients with STEMI in Sweden, representing about 95% of the population of STEMI patients in the country, those who were treated with primary PCI had lower 30‐day mortality than those treated with fibrinolytics in the hospital (4.9% versus 11.4%) [48]. Primary PCI patients also had lower mortality than those treated with prehospital fibrinolytics (4.9% versus 7.6%).
Several large clinical trials examined the strategy of transferring patients to PCI‐capable institutions from local hospitals compared with administration of fibrinolytics at the local hospitals [49, 50]. For situations in which transfer directly to a center capable of primary PCI is not possible in a timely fashion, a strategy of fibrinolysis at a non‐PCI hospital followed by transport to a regional PCI center may be necessary.
Systems of care for STEMI
The EMS system plays a key role in shortening the process of caring for patients with STEMI. Patients who are transported by EMS have shorter treatment intervals than those patients who arrive at the hospital by other means [51]. Patients can be encouraged to use EMS appropriately. A community intervention to shorten the time interval from symptom onset to ED arrival was shown to increase the proportion of ACS patients who used EMS for transport to the ED, though no effect was seen on the time interval of interest [52].
Prehospital notification/field cardiac catheterization laboratory
Activation
A key benefit of a prehospital 12‐lead ECG is notification of the receiving facility of an impending STEMI patient’s arrival. Shortening door‐to‐balloon time by 30 minutes reduces in‐hospital mortality from STEMI by about 1% [53]. Implementation of a prehospital 12‐lead ECG program with prehospital notification shortened door‐to‐balloon times by about 60 minutes in San Diego [54]. An evaluation of a large patient registry revealed that prehospital notification and subsequent ED activation of the catheterization team, before patient arrival at the hospital, shortened door‐to‐balloon time by approximately 15 minutes [55].
Occasional false‐positive activation of the PCI team is a necessary by‐product of an aggressive field approach to alerting hospitals about patients with suspected STEMI. One report suggests that up to 15%–20% of team activations may not result in any intervention [56]. The rate of false‐positive activations depends on the pretest probability of finding a STEMI. If EMS clinicians perform 12‐lead ECGs broadly (e.g., everyone over the age of 30 with any of the following characteristics: chest pain, shortness of breath, abdominal pain, diabetes, or cardiac history), the prevalence of actual STEMI is between 0.5% and 5%. The positive predictive value of a “STEMI positive” prehospital 12‐lead ECG may approximate 50% [57]. Such an approach could result in more false positive than true positive activations of the PCI team.
When patients have a reasonable likelihood of STEMI based on their clinical presentations and 12‐lead ECG findings, prehospital cardiac catheterization PCI team activation has consistently been shown to shorten the time to definitive treatment. For example, Nestler et al. showed that prehospital activation of the catheterization laboratory reduced the median door‐to‐balloon times from 59 to 32 minutes [58]. Cone et al. found that field activation of the catheterization laboratory was associated with 37‐ and 35‐minute shorter door‐to‐balloon times than ED activation for walk‐in STEMI patients or STEMI patients arriving by EMS without field activation, respectively [59]. In addition, field activation of the catheterization laboratory was associated with improved performance relative to 90‐minute STEMI treatment benchmarks. Finally, Horvath et al. found similar reductions in the door‐to‐balloon times (44 vs. 57 minutes) in EMS‐transported STEMI patients who had prehospital activation of the cardiac catheterization laboratory compared to those who had the laboratory activated after ED arrival [60].
Field activation of the cardiac catheterization laboratory when a prehospital ECG shows evidence of STEMI is strongly supported by published data. However, in one published study of 27,840 patients with STEMI, where field activation could have occurred, only 41% of the time did field activation happen [61]. EMS systems should work with their PCI‐capable hospitals to establish and promote cardiac catheterization laboratory prehospital STEMI activation protocols and quality improvement monitoring.
EMS transport
Despite the benefits of EMS for chest pain patients, many patients misinterpret their symptoms, delay calling EMS, or use personal transportation to go to the hospital. Public education campaigns have not shortened the overall time interval from symptom onset to hospital arrival, but they have increased the proportion of ACS patients who use EMS [62].
Destination protocols
Almost 80% of the adult population of the United States lives within 60 driving minutes of a PCI‐capable center [63]. Of those patients whose closest hospital is not capable of PCI, 74% require additional transport time of less than 30 minutes to reach a PCI‐capable institution. Many states and communities have developed protocols to facilitate EMS transport of STEMI patients directly to hospitals with 24/7 capability to perform PCI. In a study of 19,287 patients, comparing states that allowed EMS to bypass closer non–PCI‐capable institutions and transport directly to a PCI‐capable institution, it was found that in bypass‐approved states, 57% of people exhibiting myocardial infarction received PCI in <90 minutes and 82% underwent PCI within 120 minutes of EMS contact. In states with no bypass policies, only 45% of people received PCI within 90 minutes and 77% within 120 minutes [64]. In Ottawa, a STEMI bypass protocol for EMS was implemented in May 2005 [65]. Paramedics performed a 12‐lead ECG, and if STEMI was identified in a hemodynamically stable patient, the patient was transported directly to the region’s single cardiac center catheterization laboratory with prehospital notification of the impending arrival of the STEMI patient. To do so, EMS often bypassed one of the four other EDs in the city. The median first door‐to‐balloon time was 69 minutes for patients brought to the catheterization laboratory directly by EMS, compared with 123 minutes for those needing interhospital transfer. In the Netherlands, prehospital identification of patients with STEMI and transport to a PCI‐capable center, bypassing other EDs, was associated with improved left ventricular function [66].
Some systems are directing EMS to take STEMI patients directly to the heart catheterization lab, bypassing the ED. The strategy reduces door‐to‐balloon
