Time is Myocardium
The following article was published in the summer 2007 issue of UW Health's Level One newsletter for emergency medicine health professionals:
You are called to the home of a 50-year-old woman who is complaining of severe chest pain for 30 minutes. She is diaphoretic, ill-appearing and holding her chest. Her blood pressure is 100/40, heart rate is 120 and her oxygen saturation is 88%.
You spend 15 minutes on scene taking a thorough history and physical exam. You have a 15-minute transport time to the emergency department and administer aspirin, nitroglycerin and supplemental oxygen with no change in her condition.
On arrival to the emergency department, a 12 lead ECG is ordered. Ten minutes later, the 12 lead ECG is completed and set at the patient's bedside. Five minutes later, the emergency physician picks up the 12 lead ECG and immediately recognizes ST-elevation (a marker for an acute heart attack).
The interventional cardiology team is activated, which takes 35 minutes to prepare cath lab. Once ready, the patient is transported to the cath lab (5 minutes), and 30 minutes later a balloon is inflated in the left coronary artery, restoring blood flow to a large section of the starving myocardium.
Her ED arrival to balloon inflation time is 85 minutes. She becomes very hypotensive in the lab and requires a balloon pump. Ultimately, she suffers massive left ventricular damage and spends 3 weeks in the ICU before succumbing to multisystem organ failure. This patient died from an STSegment Elevation Myocardial Infarction (STEMI).
The same scenario is presented. This time, a 12 lead ECG is performed in the field by the treating EMTs at the patient's bedside. ST segment elevation is immediately identified and radio report is initiated two minutes into transport.
"We are transporting a STEMI to you with a 10-minute ETA."
Immediately, the cardiac catheterization lab team is activated. Ten minutes later, the patient arrives in the ED and is transferred emergently to the cardiac cath lab. The patient receives similar treatment, but ultimately has a door-to-balloon time of 60 minutes.
Echo reveals minimal left ventricular dysfunction and she is discharged on hospital day number three.
It's Only a Few Minutes
Minimizing reperfusion time is critical to improving survival and quality of life of heart attack patients. Minutes count! As demonstrated in the case above, minimizing scene time is critical, and scene time of less than 10 minutes should be standard.
Perform essential tasks during drive time and call to report to the ED as early as possible.
All paramedic EMS units should be trained to perform AND interpret field 12 lead ECGs. This requires interpretation skills to rapidly identify STEMI and the ability to differentiate this from other 12 lead ECG abnormalities (bundle branch blocks, early repolarization).
Currently, all three Madison hospitals are activating their cardiology teams based upon paramedic interpretation of STEMI.
EMT-I and EMT-B providers can be trained to perform a 12 lead ECG, but are not trained to interpret a 12 lead ECG. Thus, they require the ability to transmit the 12 lead ECG to the treating hospital for interpretation.
All of the major monitor manufacturers have cell phone based telemetry systems. However, these systems are highly variable, transmit to manufacturer-specific receiving sites and have a high transmission failure rate. Most of these failures are related to cell phone signal interruption, or cell tower inability to transmit data (switch technology).
There are several systems that are being developed in hopes of a more consistent transmission system, but currently, transmission success rates in urban areas is <70% and much lower in rural areas.
- Time is myocardium:Minutes can mean the difference between life or death
- Minimize scene time:Less than 10 minutes
- Paramedic services: A 12 lead ECG at patient's bedside with immediate hospital notification once STEMI is identified
- EMT-B/EMT-I:Find out if a 12 lead ECG transmission is supported in your area. Before purchasing 12 lead capable monitors, ask vendor to test and prove transmission capability in your area
- EMT-B/EMT-I:Stay tuned - transmission alternatives are being developed/tested
- Rural EMS:Establish protocols to reduce interfacility transport delays between hospitals
- Know the capabilities of your local hospitals: It may be better to bypass community hospitals and directly transport to a hospital capable of performing cardiac catheterization