STEMI: Longer Door-to-Balloon Times for ER Self-Referrals

April 2, 2011 (New Orleans, LA) - In a recent study conducted at two hospitals in San Francisco, 44% of patients ultimately referred to the cardiac cath lab for suspected ST-elevation MI (STEMI) had shown up to the emergency department on their own. But the remainder who hitched a ride in an ambulance progressed through the emergency department and into the cath lab significantly faster, despite needing more intensive care in the ED.

The reason? Most of those presenting by ambulance had undergone electrocardiography in the field or in transit, reported Dr James M McCabe (University of California, San Francisco) here today in a presentation for the media at the American College of Cardiology (ACC) 2011 Scientific Sessions . And as reported many times by heartwire , the prehospital ECG is a well-established driver of shortened door-to balloon times.

McCabe is scheduled to present the findings in the general session on April 4. He and his colleagues, he said to heartwire , are sure the reason self-referrals took longer to get to the cath lab wasn't that they were somehow managed less urgently than those taking the ambulance. "People who were brought by ambulance but did not get a [prehospital] ECG had times that were no different from people who showed up on their own. That suggests most of the benefit was driven by the ECGs."

The take-home message for people who believe they may be having a heart attack, McCabe said, "is to take an ambulance. You're doing yourself a disservice if you don't. And when you get into the ambulance, do what you can to get an electrocardiogram, because the benefits of ambulance use don't stop when it stops at the door of the hospital. There's a clear ripple effect of increase in benefit through the initial stages of the hospitalization."

He cautions that at the time of the study and even now, paramedics in San Francisco don't have the capability to transmit prehospital ECGs to emergency-department personnel; in the current analysis, they were viewed only after the patient arrived. "You can imagine the impact of the ECGs will be far greater once people [in the emergency department] can see them before the patient even arrives."

Compared with the 157 self-referrals, the 199 patients who arrived by ambulance showed an adjusted 26% improvement in door-to-balloon time (p=0.004), 62% improvement in door-to-cath-lab-activation time (p<0.001), and 66% improvement in ECG-to-cath-lab-activation time (p<0.001). But there was no difference between the two groups in cath-lab-arrival-to-balloon time, suggesting that the benefit of arrival by ambulance is driven by what goes on in the emergency department.

Self-referrals and ambulance users had not differed significantly with respect to age; race; or risk factors such as diabetes, hypertension, dyslipidemia, or coronary disease history; nor did they differ in MI location by ECG or in distribution of the culprit lesion within the coronaries.

On the other hand, ambulance users were sicker and needed more critical care in the emergency department; despite that, they got to the cath lab sooner, McCabe observed. They had more cardiac arrest (28% vs 5% for self-referrals, p<0.01) and need for intubation (23% vs 3%, p<0.01) and pressors (13% vs 3%, p=0.01); they had lower systolic blood pressures and heart rate (p=0.01 for both).

Strikingly, according to McCabe, a prehospital ECG wasn't obtained from a full 43% of the patients presenting by ambulance, pointing to an opportunity to improve patient by "broadening the indications for a prehospital ECG."

McCabe had no disclosures.

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