British Registry: Prehospital ECG Associated with Reduced Mortality in ACS Patients

Download this article's Factoid (PDF & PPT for Gold Subscribers)


Patients with acute coronary syndromes (ACS) who receive an electrocardiogram (ECG) prior to arriving at the hospital have lower 30-day mortality compared with those who do not, according to a registry study published online April 14, 2014, ahead of print in Heart. The survival benefit was similar for patients with and without ST-segment elevation myocardial infarction (STEMI).

For the study, Tom Quinn, MPhil, RN, of the University of Surrey (Guildford, United Kingdom), and colleagues looked at processes of care and outcomes for 288,990 ACS patients admitted to 228 hospitals via emergency medical services (EMS) between January 2005 and December 2009 with documentation of whether a prehospital ECG was (n = 145,247) or was not (n = 91,827) performed (ECG use was unknown for 51,916). All data came from the Myocardial Ischaemia National Audit Project (MINAP), which includes all hospitals in England and Wales.

Over the study period, the percentage of patients receiving a prehospital ECG increased from 51% to 64% in the overall population and from 64% to 79% in STEMI patients.

Patients with higher baseline mortality risk, as assessed by the mini-GRACE score, were less likely to receive prehospital ECG. When the study began in 2005, patients with a prehospital ECG were younger, were less frequently female, and had fewer comorbidities. Patients without an ECG were more frequently hypertensive and more likely to have a history of stroke, CHF, chronic renal failure, angina, diabetes, or COPD. However, use of prehospital ECG increased over the study period for women, older people, and patients with CHF or comorbidities.

Mortality Advantage for Prehospital ECG

For all ACS patients, having a prehospital ECG added 6 minutes from EMS call to hospital arrival compared with not having one (52 min vs 46 min). The pattern was similar when STEMI patients were analyzed separately.

After adjustment, use of any reperfusion strategy (PCI or fibrinolysis) was more common in STEMI patients who had prehospital ECG compared with those who did not (85.3% vs 74.4%; P < 0.001), and prehospital ECG was an independent predictor of reperfusion therapy in the STEMI cohort (adjusted OR 1.70; 95% CI 1.63 to 1.78). Additionally, among STEMI patients, the likelihood of undergoing primary PCI within 90 minutes of calling EMS was increased by receiving prehospital ECG (adjusted OR 1.38; 95% CI 1.24-1.54).

Patients who received a prehospital ECG had lower rates of in-hospital and 30-day mortality. The difference was largely driven by STEMI patients who underwent reperfusion. Non-STEMI patients also benefitted from prehospital ECG (table 1).

Table 1. Thirty-Day Mortality

 

Prehospital ECG
(n = 102,831)

No Prehospital ECG
(n = 51,715)

Adjusted OR
(95% CI)

All Patients

7.4%

8.2%

0.94 (0.91-0.96)

STEMI Patients

8.6%

11.4%

0.94 (0.90-0.98)

Reperfused STEMI Patients

7.3%

9.4%

0.94 (0.89-1.00)

Non-STEMI Patients

5.9%

6.5%

0.84 (0.81-0.88)


“This study strengthens the evidence base for guidelines which recommend [prehospital ECG],” the authors write. Current ACC/AHA guidelines advise that each community develop a STEMI system of care that involves a process for prehospital diagnosis and treatment activation.

“The precise mechanism whereby the recording of a [prehospital ECG] was associated with lower mortality in our series remains unexplained and requires further evaluation,” they observe.

Meanwhile, factors that prevent or hinder the implementation of prehospital ECG still require exploration, they add, pointing out that although its use did increase over the study period, it remained suboptimal at 64% of ACS patients (79% of STEMI patients).

Among the possible—and unusual—reasons the authors cite for this suboptimal use are sex differences. Predominantly male EMS staff, for example, may be reluctant to undertake prehospital ECG in female patients because of the need for intimate exposure, they hypothesize. Another possible reason, they add, may relate to patient preference with women possibly being less likely than men to consent to the test.

A Surrogate for Better Care?

In an email with TCTMD, Eric R. Bates, MD, of the University of Michigan Medical Center (Ann Arbor, MI), said prehospital ECG may be a surrogate marker for a better prehospital system of care and greater application of evidence-based interventions known to decrease mortality.

“That would explain the mortality advantage in NSTEMI, where small time-to-treatment delays would be less likely to impact mortality rates,” he noted, adding, “The same could potentially be said for door-to-balloon time, which is also a process-of-care measure rather than a treatment intervention. Nevertheless, the report supports better outcomes with an improved prehospital system of care and it supports current guideline recommendations.”

Dr. Bates noted, though, that as with all observational registry reports, selection bias and confounding cannot be completely controlled. For example, he explained, patients had to access EMS to be a candidate for prehospital ECG, and lower-risk patients received it more frequently.

 


Source:
Quinn T, Johnsen S, Gale CP, et al. Effects of prehospital 12-lead ECG on processes of care and mortality in acute coronary syndrome: a linked cohort study from the Myocardial Ischaemia National Audit Project. Heart. 2014;Epub ahead of print.

 

Related Stories:

Disclosures
  • The study was sponsored by a grant from the British Heart Foundation.
  • Mr. Quinn reports having received funding from Boehringer Ingelheim, the National Institute for Health Research, and The Medicines Company.
  • Dr. Bates reports no relevant conflicts of interest.

We Recommend

Comments