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Emergency medical technicians usually make the right call when assessing patients for suspected ST-elevation myocardial infarction (STEMI), according to data from a statewide STEMI network.

Armed with portable ECG results, the EMTs correctly identified STEMI -- and called ahead for cath lab activation -- in 85% of nearly 4,000 patients included in an analysis by J. Lee Garvey, MD, of the Carolinas Medical Center in Charlotte, N.C., and colleagues.

Only 6% of all cath lab activations were canceled because the ECG interpreted by emergency personnel was reinterpreted by hospital personnel, researchers wrote in the Jan. 17 issue of Circulation: Journal of the American Heart Association.

Guidelines from the American Heart Association and the American College of Cardiology recommend a door-to-balloon time for out-of-hospital STEMI patients of less than 90 minutes. One of the strategies employed by some regions is to have either paramedics or emergency physicians interpret the ECG and activate the cath lab, without need for a cardiology consultation.

Several studies attest to the benefit of coordinated STEMI networks in term of reaching guideline-recommended door-to-balloon time. An analysis in 2009 of STEMI networks across the U.S. found that 86% of them reached the target of less than 90 minutes from ambulance to cath lab.

The researchers of that study emphasized the ability of pre-hospital ECG interpretation as one of the more important features of improved door-to-balloon time.

An April 2011 study found that pre-hospital ECGs shortened door-to-balloon time by two-thirds (10 minutes versus 28 minutes for those without a pre-hospital ECG).

One of the potential problems with pre-hospital ECG, according to Garvey and colleagues, is "overtriage ... which refers to activating the cath lab for patients who do not ultimately require emergent catheterization."

To determine the level of false positives in the Reperfusion of Acute Myocardial Infarction in North Carolina Emergency Departments (RACE) initiative, the investigators examined data from December 2008 to December 2009. Ultimately, they included 3,973 individuals whose average age was 60 and of whom two-thirds were male.

The study included 14 percutaneous coronary intervention- (PCI) capable hospitals, as well as 85 non-PCI centers from which patients were transferred.

Most of the patients (85%) for whom the cath lab was activated received PCI (76% of appropriate activations, 65% of all activations). Ten percent of patients transferred to the cath lab did not have occlusive disease.

Of the 15% of activations that were inappropriate, about 5% were deemed inappropriate because of age greater than 90, refusal of treatment, active bleeding, known terminal illness, severe comorbid conditions, and/or a do not resuscitate order, Garvey and colleagues wrote.

The origin of activations were about equal from EMS, non-PCI, and PCI facilities.

Overall, 24.7% of activations by EMS and 7.9% of the cath lab activations ordered by physicians were inappropriate.

Garvey and colleagues cautioned that their results might not be generalizable because their STEMI system has been built over several years, "with specific attention placed on the uniformity of evaluation and treatment strategies."

Also, ECGs were not archived, so those that led to discrepancies could not be verified.

From the American Heart Association:

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