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Case Study #1
It's a sunny fall morning outside Wilmington, DE, when a BLS ambulance from the Elsmere Fire Company and paramedics from New Castle County (NCC) EMS are dispatched to a call for chest pain. The medics arrive to find a 54-year-old man on oxygen being loaded into the fire company's ambulance. The BLS crew reports that the patient is complaining of chest pain, rated 8 out of 10, with shortness of breath and nausea since earlier in the day. He has no medical problems and takes no medications, but says it's been several years since he's seen a doctor. His vital signs are: pulse rate 62, in a normal sinus rhythm with a first-degree AV block; respiratory rate 24, with clear breath sounds; blood pressure140/80; and pulse ox 98%. He would like to go to the VA Medical Center right down the street.
The paramedics continue to assess the patient and perform a 12-lead ECG that shows ST elevation in leads V1-V3, with reciprocal ST depression in leads II, III and aVF (Figure 1). This ECG is diagnostic of an acute MI, and a second is then performed to rule out right-side involvement. Paramedics tell the patient he's having a heart attack and recommend he be transported to a facility with emergent cardiac catheterization capability, which the VA does not have. He then requests to be taken to Christiana Hospital in Newark, a self-designated "heart center" about 10 minutes away.
During transport, one paramedic gives the patient 162 mg of aspirin to chew and starts an IV. His partner then calls the base physician at Christiana to request a "heart alert." The patient is given sublingual nitroglycerin, one inch of nitroglycerin paste and 5 mg of morphine sulfate under Delaware's AMI protocol. The physician on the radio agrees with the prehospital assessment and directs the crew to bypass triage and go directly to a resuscitation bay in the ED upon arrival.
The patient reports feeling much better after receiving the medications; he rates his pain at 4 out of 10, and repeat ECGs show that the ST elevation has resolved (Figure 2). The crew is met in the ED by a heart alert team with a cardiologist, who elects to send the patient to the cath lab after viewing the initial prehospital 12-lead ECG.
Case Study #2
It's early in the evening when a BLS ambulance from the Claymont Fire Company and New Castle County paramedics are dispatched to an unconscious diabetic at a suburban home. Paramedics arrive to find a 60-year-old male on oxygen being extricated from the residence in a stair chair by the BLS crew. They report that the patient had a syncopal episode after standing up and was unresponsive for a few minutes. The patient is pale and diaphoretic and complains of feeling weak. He reports a history of non-insulin-dependent diabetes but no other medical problems. He denies any chest or abdominal pain.
The patient's vital signs are: pulse 114, in sinus tachycardia with no ectopy on the monitor; respiratory rate 20, with clear breath sounds; blood pressure 102/60; pulse ox 96%; and blood sugar 458 mg/dL. A 12-lead ECG shows a right bundle branch block, ST elevation greater than 5 mm in leads V2-V4 and reciprocal ST depression in leads III and aVF (Figure 3). The paramedics recommend he be transported to St. Francis Hospital in Wilmington, which is the nearest heart center.
During transport paramedics administer aspirin, start two large-bore IVs and apply one inch of nitroglycerin paste. The base physician at St. Francis is contacted, and the hospital's heart alert team is activated. The patient continues to deny chest pain and maintains his vital signs. He is transferred to the cath lab shortly after arriving in the ED.
Background
In both of the above cases, the prehospital 12-lead ECG had a dramatic impact on field treatment, choice of transport destination and the patient's ED course. New Castle County EMS has been performing and interpreting 12-lead ECGs for the past six years. This allows paramedics to triage patients with suspected acute coronary syndromes and has been shown to reduce "door to reperfusion" times in hospitals. Once these patients are identified, crews can elect to transport them to a specialized heart center in a manner similar to referring trauma patients to a trauma center.
Determining Destinations
Emergent balloon angioplasty has become the preferred treatment option for patients with suspected MIs. The best results come when the procedure is performed at a high-volume facility with surgical backup, and when the procedure can begin within 90 minutes of the patient's arrival at the hospital.1 In New Castle County, any patient whose ECG shows ST segment elevation in the setting of an MI (STEMI) is transported to a heart center with these capabilities. Hospitals and EMS have worked to develop a "heart alert" notification system that takes advantage of the early information a prehospital 12-lead ECG provides.
A 12-lead ECG is performed on any patient complaining of chest pain or an anginal equivalent, such as difficulty breathing, weakness or nausea. If the ECG shows ST elevation greater than 1 mm in two continuous limb leads (leads I, II, III, aVF, aVL) or 2 mm in continuous precordial leads (leads V1-V6), the patient is transported to a heart center even if a closer hospital must be bypassed. Air medical transportation has also been used to transport heart alert patients in outlying areas of the county.
Minimizing Delays
NCC paramedics are encouraged to call the hospital early in the care of an identified STEMI patient to request a heart alert. This activates a specialized team at the hospital. If time permits, information about the patient's cardiologist and physician is relayed in the radio report so that their medical records and information about any previous ECGs can be obtained before they arrive.
During a heart alert activation, a cardiologist is summoned to the ED and a catheterization lab is prepared, even in off hours and before there is a commitment to take the patient to the cath lab. The patient is quickly stabilized in the ED and transferred to the cath lab for definitive treatment.
Supported By Research
Three studies performed in New Castle County demonstrate that prehospital 12-lead ECGs and early activation of a heart alert team significantly reduce the time from arrival at the hospital to definitive treatment.
One study compared the time from arrival at the ED to receiving reperfusion therapy (either with thrombolytics or emergent catheterization) between patients who had prehospital 12-lead ECGs performed and those whose initial ECGs were done in the hospital. This time was significantly less in the group that had field ECGs performed.2 Studies performed in other metropolitan areas have produced similar results.3
Another trial compared door-to-reperfusion times between patients who arrived at the hospital by private vehicles and those who arrived by EMS. This study showed that patients who arrived by private vehicles experienced treatment delays, some of which made them ineligible for emergent balloon angioplasty.4
These findings are not meant to fault the ED staff. At any given time in an overcrowded ED, there are many patients complaining of chest pain, and they all must have ECGs performed with a limited number of machines and personnel. When the patient calls 9-1-1, they will have at least two EMS providers caring only for them, and an ECG and vital signs can be obtained immediately. With practice, 12-lead ECGs can be performed very quickly in the field and do not significantly delay scene times.
A third study performed in New Castle showed that prehospital treatment of chest pain will resolve ECG changes indicative of an MI in a significant number of patients.5 While this is good in the short term, the lack of a pretreatment ECG could cause a delay in definitive treatment in the hospital. Patients with abnormal prehospital 12-lead ECGs present a convincing argument to be taken to the cath lab early for definitive therapy that will possibly prevent an acute deterioration of their condition.
Impact On Treatment
In addition to the triage function of the field 12-lead ECG, proper interpretation allows paramedics to localize the area of infarction and adjust their treatment. Delaware's ALS treatment guidelines have an acute MI protocol for patients with positive ECG findings, which includes a standing order for up to 5 mg of morphine to be administered as soon as IV access is obtained if the systolic BP is over 100. If an ECG shows right-side ST elevation and the patient has clear breath sounds, a 500cc fluid bolus may be administered before nitroglycerin to help prevent hypotension.
Even in patients who do not meet the heart alert criteria, 12-lead ECGs help detect acute coronary syndromes in atypical presentations, determine the origin of tachycardias and raise the index of suspicion for a pulmonary embolism or electrolyte imbalance.
False Alarms
New Castle County paramedics are very accurate at 12-lead ECG interpretation and requesting heart alerts appropriately. More than 800 12-lead ECGs are performed each month among NCC's eight paramedic units. Activation of the heart alert team takes people away from other duties in the hospital (and from their homes during off hours), so it's important to minimize false alarms. Paramedics work with online medical control to confirm ST elevation with reciprocal changes in the setting of an MI, and not normal variations of the ST segment with benign or subtle problems such as hypertrophy, bundle branch blocks or early repolarization. Interpretation is also routinely discussed at case reviews and in continuing education.
Conclusion
Prehospital 12-lead ECGs are emerging as a standard of care for all ALS systems. New Castle County paramedics have found them to be an invaluable tool to assess patients with acute coronary syndromes, transport them to appropriate facilities, specify treatments for them and get them definitive care more quickly.
References
Bob Sullivan, NREMT-P, is a paramedic and assistant public information officer with New Castle County (DE) EMS.
Robert A. Rosenbaum, MD, FACEP, is the EMS Medical Director for New Castle County EMS and Clinical Assistant Professor of Emergency Medicine for the Christiana Care Health System in Newark, DE.
