Prehospital ECG Cuts Mortality in STEMI and NSTEMI: UK Study

April 17, 2014

GUILDFORD, UK — Obtaining an ECG in the prehospital setting makes it more likely patients with ST-elevation MI (STEMI) will get reperfusion therapy and, in both STEMI and non-ST-elevation MI (NSTEMI) patients, can significantly improve 30-day survival, suggests a cohort study based on registry data covering England and Wales[1].

It may be the first large prehospital-ECG study to go beyond gains in processes of care to show a clinical benefit in ACS and a substantial benefit in NSTEMI; it's probably the largest to make the link between the prehospital ECG and institution of fibrinolytic therapy and/or primary PCI, according to the authors. The study was published April 14, 2014 in Heart.

The findings "strengthen the guideline recommendations to record an ECG in the ambulance and [could help promote] widespread implementation of ECGs in ambulance systems of care," lead author Prof Tom Quinn (University of Surrey, Guildford, UK) told heartwire in an email. "The ambulance ECG represents an opportunity to identify patients who will benefit from expert cardiac care; not recording an ECG represents a missed opportunity to improve process of care and outcomes for ACS patients, including those with atypical presentations."

With respect to the novel finding of a clinical benefit in NSTEMI, Quinn said it shows that a 12-lead ECG should be performed in all patients in whom a cardiac cause for symptoms is suspected. "We need to inculcate a culture of 'low threshold for ECG recording' in the ambulance."

The study looked at 288 990 patients admitted to hospitals for ACS from 2005 to 2009 after emergency medical service (EMS) transport who entered the Myocardial Ischaemia National Audit Project (MINAP) MI registry. The 50.3% of the cohort from whom prehospital ECGs were obtained tended to be younger, had more comorbidities, and were less likely to be female than those without prehospital ECGs.

"Having an ECG recorded added around six minutes, on average, to the delay in patients reaching the hospital, something that the public and some clinicians may be concerned about given the time-critical nature of STEMI in particular," Quinn noted, adding, however, that it appears to be "time well spent" because obtaining the ECG improved clinical outcomes.

Adjusted Mortality Odds Ratio (95% CI), Prehospital vs No Prehospital ECG, by ACS and Revascularization Status

Mortality end point Total (n=154 546) STEMI (n=72 638) STEMI with primary PCI (n=14 063) NSTEMI (n=81 908)
Hospital 0.85 (0.82–0.88) 0.88 (0.84–0.93) 0.89 (0.72–1.12) 0.76 (0.72–0.80)
30 d 0.94 (0.91–0.96) 0.94 (0.90–0.98) 0.91 (0.77–1.07) 0.84 (0.81–0.88)

In the study:

  • Mortality was significantly reduced for both STEMI and NSTEMI patients who had a prehospital ECG, compared with those without prehospital ECGs.

  • In STEMI, patients with prehospital ECGs showed higher rates of primary PCI within a "call-to-balloon time" of 90 minutes and fibrinolytic therapy within a door-to-needle time of 30 minutes.

  • In STEMI, any reperfusion strategy was 70% more likely in the prehospital-ECG group (p<0.0001).

  • Reperfusion therapy was significantly less likely in patients older than 75, women, and those with diabetes.

"It is possible that, in a predominately male EMS workforce, staff were reluctant to undertake ECG in women because of the need for intimate exposure or that some female patients declined to have an ECG for similar reasons or because of cultural/religious norms," Quinn speculated. "There may also have been patients (particularly the elderly and those with diabetes) in whom the presentation was atypical and ambulance staff didn't consider doing an ECG because they didn't suspect ACS."

He pointed out that in England and Wales, "EMS paramedic staff are trained to perform and interpret 12-lead ECGs on scene or transmit for expert review" if ECG transmission is available. "I suspect our findings are generalizable to other systems, including those with physician- or nurse-staffed ambulances . . . and certainly to North America, which has similar capabilities to here."

The study was funded by the British Heart Foundation. Quinn discloses receiving funding from Boehringer Ingelheim, The Medicines Company, and the National Institute for Health Research. The coauthors had no disclosures.

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