Debate: Direct Cath Lab Activation by Paramedics

WHY PARAMEDICS SHOULD PERFORM AND TRANSMIT 12-LEADS

By Corey M. Slovis, MD, FACP, FACEP, FAAEM

A prehospital ECG accompanied by a prearrival hospital STEMI alert takes only 1--2 minutes to perform, yet can save 15--30 minutes or more in a patient's D2B time, and up to 36 minutes in door-to-needle time for thrombolytics. This is considered a best practice in reducing D2B times, and is endorsed by the AHA and American College of Cardiology.

A study by Swor and colleagues compared (1) no ECGs in the field to (2) ECGs but no prearrival alerts to (3) EMS 12-leads with prearrival hospital alerts in 164 STEMIs transported by EMS. They found if a prealert was used, almost 90% of STEMIs had D2Bs of under 90 minutes. If an ECG was done but the hospital not notified, only half of patients had D2Bs of 90 minutes or less. If no EMS 12-lead was done, the rate dropped to 38%. Similar results were seen in San Diego, where fewer than 25% of patients had D2Bs of less than 90 minutes when no prehospital alert occurred, vs. 80% when the hospital was prealerted.

The question, to me, is which is better: a paramedic and a machine reading a 12-lead, vs. a paramedic, a machine and an MD. There have been three key studies that support the benefits of MD overread of ECGs transmitted from the field. The first, from Boston, showed paramedics were as accurate as emergency physicians and cardiologists in reading for STEMIs. When paramedics identified AMIs, they were 94% accurate--within 1% of the MD groups. Unfortunately, medics did not diagnose 5 of 25 STEMIs.

Another study from San Diego had similar results. Investigators compared MDs to paramedics using the gold standards of true STEMI by ECG, whether the patient went to PCI, and, if they did, if a lesion was found. They found paramedics were correct 78% of the time when diagnosing STEMIs by ECG (vs. 96% for MDs), that only 70% of patients who had prealerts by EMS went to PCI (vs. 89% for MDs), and that at PCI, only 69% of patients had evidence of acute lesions (vs. 89% for MDs). Thus, there was a false activation rate of around 22%--30% when only paramedics and machines were relied upon to diagnose AMIs. In the final study, 5 of 25 "STEMIs" identified by EMS prealerts turned out to be AMI mimics like left bundle branch blocks or LVH.

Reading ECGs takes a lot of practice and experience. I believe paramedics, automated computerized ECG readings and ED-based physicians can work together to provide the optimal approach to minimizing STEMI misinterpretations. Maybe it's just simple math: 1+1+1 is better than 1+1; machine + EMT-P + MD is better than just machine + EMT-P.

Corey M. Slovis, MD, FACP, FACEP, FAAEM, is medical director for Nashville EMS, Nashville (TN) Fire Department.

WHY PARAMEDICS SHOULD ACTIVATE CATH LABS FOR STEMIS

By Raymond L. Fowler, MD, FACEP

Paramedics performing diagnostic-quality 12-lead ECGs early in the course of myocardial infarctions remains a mainstay in the identification of appropriate candidates for percutaneous coronary intervention. Successful paramedic assessment of ECGs for STEMI has been well described. Otto and Aufderheide demonstrated that paramedics could be trained in ECG interpretation targeted to identifying STEMIs. They noted that the addition of assessment for reciprocal ECG changes improved this positive predictive value (PPV) to >90%. In a U.K. study, an analysis of the STEMI-diagnostic abilities of paramedics vs. emergency physicians found 95% accuracy, 91% specificity, 97% sensitivity, a negative predictive value (NPV) of 77%, and PPV of 99%--results that were not significantly different from the emergency physicians' in the study. LeMay et al found paramedic interpretation of ECGs for STEMI to have a sensitivity of 95%, specificity of 96%, PPV of 82%, and NPV of 99%.

Trauma systems have long activated trauma center treatment teams based on paramedic interpretations of patient statuses. Overtriage of trauma patients resulting in trauma team activation is a recognized consequence of the combination of worrisome mechanisms of injury mixed with the breadth of presenting signs and symptoms. Mounting evidence indicates paramedics have begun to be accepted as vital members of the PCI activation team for STEMI patients as well. Hokanson et al studied direct PCI lab activation by paramedics, who achieved D2B times of 49.6 minutes, with 26 of 27 STEMI patients being accurately diagnosed. They concluded that PCI activation can be initiated accurately by paramedics.

Many municipalities currently activate PCI teams based upon paramedic ECG interpretations. Careful paramedic training and intensive coordination with area hospital chest pain committees can allow paramedics to achieve a high sensitivity and specificity for identification of STEMI patients and PCI lab activation. Both hospital and cardiologist commitment to the process is essential, and feedback both to the transporting paramedic team and EMS medical direction provides important loop closure.

Both scientific literature and clinical experience indicate that paramedics can successfully interpret ECGs for the changes associated with STEMIs. The emphasis of EMS systems today, through initial and continuing education and with careful oversight, should be in preparing paramedics to continue taking their rightful position as members of the critical care team.

Raymond L. Fowler, MD, FACEP, is deputy medical director for operations, the Dallas (TX) Metropolitan BioTel (EMS) System.