Cardiac Markers in EMS

Cardiac enzyme tests are a valuable tool for risk stratification of cardiac patients. Some time ago, it became possible to use very simple tests called Point of Care (POC) tests or bedside tests, for determining if the patient has positive cardiac enzymes. At the same time, newer tests like Troponin I (or Troponin T) have improved diagnosis because of their being very specific to cardiac muscle. If a patient has a positive Troponin test 4-6 hours or more after the onset of chest pain, they need specialized treatment soon. Other “older” enzyme tests that are often combined with Troponin are CK-MB and Myoglobin. The value of these tests is that used in combination with Troponin, they can help you identify when the cardiac event occurred.

 

12 Lead ECG’s have nearly become a standard of care in EMS. But how accurate are they by themselves at identifying those at greatest risk? Well, here may come a surprise. Many of the cardiac patients at risk will not have ECG changes. Non-ST segment elevated patients with Acute Coronary Syndrome (Non-STEMI, ACS, or formerly unstable angina for the old dogs) actually have a high risk of death. These patients could have a greatly reduced mortality rate with early and aggressive treatment. The problem is that many ACS patients don’t get this treatment, and consequently die later. Half of these ACS patients will have non-diagnostic ECG’s. That is where a Troponin test comes into play. It can help EMS providers identify Non-STEMI patients early enough to make a real difference.

 

Unfortunately, these tests are not CLIA waived (like Glucose) so you have to go through some bureaucratic hoops to use them. Only a small handful of EMS Systems actually do use them. But they are simple and highly accurate. You just put a few drops of venous blood from a Green Top Tube in a disposable plastic cassette that looks a lot like a pregnancy test. If you get a line on the test strip they are Troponin positive. That means they have had damage to the heart muscle. That should justify a trip to a specialized center of Cardiac Care, ideally a Chest Pain Center with a 24/7 interventional cath lab.

 

In EMS the young drunk with no insurance is flown to a Trauma Center. But the cardiac patients still go to the closest hospital. Is this best for the patient, or because they have good insurance and a job? I often wonder why we have selectively ignored the benefits of taking patients where they can get the best care. We take Pediatrics to Pediatric Hospitals, we take Burns to Burn Centers, but the Bank Vice President with Chest Pain still goes into a little suburban hospital and stuck in a unit bed while his infarct extends. I sometimes think community hospitals don’t mind flying the drunk downtown (he won’t pay anyway), but want to keep the cardiac patient with Blue Shield.

 

Field tests for cardiac enzymes could help us overcome the financial drivers that keep our Cardiac patients from getting the best possible care. We have ignored the AHA guideline that if it is less than 30 minutes more transport time to get to a real cardiac center, we should take them there. If we were to implement Cardiac Markers in the Field combined with a 12 Lead ECG – we could accurately identify over 97% of patients who would benefit from the trip to a specialized Chest Pain Center.

 

One of the latest developments in this field is a new test, called FABP. FABP stands for Heart-type fatty acid-binding protein (h-FABP). The neat thing about this test is that it uses a tiny sample. You literally just use a finger prick sample of whole capillary blood. Just like Troponin I, it will enable early prediction of cardiac risk, in a more convenient test. This test is very new and I don’t think it is available here in the US, but the evidence is quite favorable to date. Maybe if we make these simple tests even simpler, we might someday be able to get a CLIA waived cardiac enzyme test on ambulances. Then we could take all the cardiac patients at risk to the most appropriate destination. It would save thousands of lives, and improve the quality of life for many of our nations most productive citizens.

 

 

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About Dan White

I'm a retired Paramedic and EMS Instructor with 35 years EMS and emergency medical product experience. I love canoes, cars and EMS. I write about EMS Technology on the Paramedic Blog, the Insights on Innovation column for EMS1.com, on AmbulanceWorld.com and Multibriefs.com. I work for Intersurgical, Inc. managing EMS sales and distribution. I can be reached directly at 573-240-0002. Follow me @Paradan on Twitter
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