Authors: Patrick Mescher, OSU MS4 // Michael Barrie, MD OSUEM
Standing in the physician’s office of a local Emergency Department I heard the familiar clunk of a chart being dropped into the metal bin. I walked over and picked up the chart and read “Chief Complaint: Chest Pain,” thinking to myself how this was the fifth “chest pain” I’ve seen this shift. After diagnosing GERD, costrocondritis, and pneumonia with previous patients, I felt comfortable evaluating this chief complaint so I went calmly to the patient’s room. But as I walked to the bedside I found a visibly uncomfortable patient, profusely perspiring. He told me he was having crushing chest pain. I was immediately concerned this may be the real deal STEMI.
I was then perplexed when the initial ECG returned without clear ischemia or STEMI. My attending insisted that a repeat ECG be done shortly there after. This time even computer got it right, reading **STEMI** across the top. The patient was given aspirin and rushed to the cath lab. When reflecting on this case, I wondered why give the medications that we do to patients with an acute STEMI?”
There is a pneumonic to help remember STEMI medications –
- M – morphine
- O – oxygen
- N – nitroglycerin
- A – Aspirin, Antiplatelet
But, evidence has show that the only intervention with benefit is Aspirin, and the other agents in MONA can potentially cause harm.
Aspirin 324mg should be given to the patient as soon as possible. Aspirin is given as soon as possible as it is the only intervention outside of surgical intervention that is shown to reduce mortality in an acute MI, anywhere from 20-50% depending on the study. Of note, the original study was done with 162mg of Aspirin (2 ‘baby’ aspirin) chewed in mouth for best oral bioavailability. The number needed to treat is 42 to save 1 life in STEMI.
STEMI patients should also be considered for antiplatelet therapy in route to the cath lab. At many centers clopidogrel 600mg is the agent of choice, but many institutions are now using the preferred agents of ticagelor 180mg or prasugrel 60mg so long as patients are without contraindications (Absolute contraindications to prasugrel include a history of stroke or transient ischemic attack (T.I.A.) or active pathological bleeding. Weight <60 kg and age ≥75 years are relative contraindications). The antiplatelet is given prior to percutaneous coronary intervention (PCI) in anticipation of a stent being placed to help prevent early re-infarction or stent collapse. Heparin can be given prior to PCI to prevent and thrombosis during or immediately after the procedure because of the significant endothelial damage from the catheterization and stent placement, however this is unlikely to be used in STEMI patients and is reserved for NSTEMI patients that do not need emergent revascularization.
It is reasonable to treat the patient’s pain, because it can in theory decrease strain on the heart. However, this has not been shown to be of benefit in acute STEMI beyond just treating pain.
Oxygen only if needed to maintain SATS above 90%. Oxygen should not be routinely used, as hyperoxia can worsen reperfusion injury. However, in patients with clinical signs of cardiogenic shock, pulmonary edema, and hypoxia supplemental oxygen (or bipap) is appropriate.
Nitroglycerin can be used in patients without concurrent use of Viagra or suspected right sided infarct. This is because nitroglycerin reduces preload, and thus heart strain, and oxygen demand. However, if there is a right sided lesion the heart’s ability to perfuse the body is preload dependent. Giving nitroglycerine to a patient with an inferior STEMI could lead to catastrophic loss of blood pressure and end organ perfusion.
Treat every patient as if it’s your first patient of the day and never rely on one piece of information. Simply because the first EKG returned normal does not rule out an evolving STEMI or other serious pathologies. History, physical exam, and clinical gestalt are vital to providing appropriate patient care.
- Protective Effects of Aspirin against Acute Myocardial Infarction and Death in Men with Unstable Angina — Results of a Veterans Administration Cooperative Study . http://www.nejm.org/doi/full/10.1056/NEJM198308183090703
- A randomized controlled trial of oxygen therapy in acute myocardial infarction Air Verses Oxygen In myocarDial infarction study (AVOID Study). http://www.sciencedirect.com/science/article/pii/S0002870311008271
- Effects of pretreatment with clopidogrel and aspirin followed by long-term therapy in patients undergoing percutaneous coronary intervention: the PCI-CURE study. http://www.sciencedirect.com/science/article/pii/S0140673601057014
- The NNT – http://www.thennt.com/nnt/aspirin-for-major-heart-attack/
- Up to Date Overview of the acute management of ST-elevation myocardial infarction, and Antiplatelet agents in acute ST elevation myocardial infarction.