Atypical MI Symptoms & Acute Coronary Syndrome: A Review
Personal anecdote:
I remember my first time coming upon an atypical MI presentation. We were dispatched to a geriatric woman’s home, priority 3, for reports of a fall. The caller specified they didn’t wish to transport the woman - she had fallen getting out of a car and just needed some assistance standing up and getting inside the home. It is a call that occurs thousands of times in EMS systems, and each one is handled routinely without incident in the vast majority of cases.
I arrive on scene, the bright eyed Paramedic student I was, and begin to assess the patient. It was true - she had just fallen getting out of the car, and was a bit weak upon arrival. She was able to answer questions and respond to us. However, her family noted her mental status was slightly off from baseline. Her daughter stated that the nursing home had provided a dose of pain medication and “messed up all her meds” prior to her discharge from the SNF earlier that day.
The call was ultimately BLS at first, but we wanted to proceed to transport regardless because of the slight difference in mental status. The BLS crew member and I helped the patient up and situated her on the stretcher as my Paramedic preceptor went inside the home to get her SNF chart and find a DNR. The family stated that the patient had a DNR, but was unable to produce it when asked. My partner and I loaded the patient without incident and began our pre-transport assessment in the back of the unit.
The patient denied chest pain, shortness of breath, or any complaints besides nausea and weakness. She was able to answer questions, but was a poor historian. Knowing that geriatric women, especially diabetics, have abnormal signs for cardiac issues, I decided to put a 12Lead on the patient just for good measure as my preceptor boarded the unit. The LifePak printed a strip itself - an ominous sign. There it was, in bold text up at the top of the page - ANTEROLATERAL STEMI DETECTED.
After manually reviewing it with my preceptor, we confirmed it. We had just taken our routine BLS call and upgraded it to a priority 1 STEMI alert. Without any DNR paperwork to change the outcome of the call, we started a line, provided Aspirin, ran through the rest of her vitals, and started transport to our closest cardiac intervention center. We transmitted our findings enroute, and after a bit of confusion between the ER doc and the cardiology attending, had the cath lab preactivated for our arrival.
A Review of MIs
AMIs - otherwise known as myocardial infarctions and commonly known as a “heart attack” - is the clinical manifestation of a large blockage within one of the 3 coronary arteries of the heart. Patients with coagulopathies of all sorts are at risk for thrombus development, especially as they grow older. It is especially common in patients with atherosclerosis, as the fatty plaque deposits within the arteries eventually accumulates to cause a total occlusion. In the United States, heart disease is the leading cause of death for older adults. With a high index of suspicion and proper recognition of the MI signs & symptoms, we can better treat our patients and seek proper definitive care.
There are two types of MIs - STEMI and NSTEMI. STEMI MIs are cases of occlusion within the artery as a result of both platelet aggregation and fibrin formation leading to a thrombus within the artery. These types of MIs produce ST elevation on EKGs and thus more easily recognizable than NSTEMIs. With each section of a 12lead EKG corresponding to a geographic area of the heart, we are able to localize these in the field and give the cath lab a heads up prior to our arrival. These are confirmed with labwork for troponin - a biomarker for cardiac tissue death.
The definitive care for this type of MI is ultimately cath lab intervention. By placing stents within the coronary arteries, interventional cardiologists are open to reopen occluded arteries and restore blood flow immediately to affected myocardial tissue.
The other type of MI -an NSTEMI -is not detectable on EKGs. NSTEMIs are an accumulation of platelets rather than denser fibrin, leading to an impartial occlusion. While impartial, NSTEMIs are still large enough to cause myocardial ischemia and can actually be more threatening as they more easily missed than STEMIs in the case of atypical symptoms. The definitive treatment for an NSTEMI is fibrinolytic medication administration. Some state EMS protocols allow for any emergency room to perform this, but it comes with significant risk. These medications are best administered within 3 hours of symptom onset, but can be delivered at varying times.
The signs and symptoms between STEMI and NSTEMI do not differ significantly beyond the absence of ST elevation with an NSTEMI. General field treatment includes oral administration of aspirin as an antiplatelet, nitroglycerin for its vasodilatory effects and reducing cardiac preload, establishing vascular access, repeat EKG assessments, early activation of hospital systems, pain management, and treating other concurrent symptoms.
Classic Signs & Symptoms:
The classic signs and symptoms for an AMI include the following:
Chest “pressure” or pain
Can often radiate, especially to the left side of the body
Classic radiation symptoms include the left jaw and left arm during episodes of chest pain
Pain may increase or decrease with severity or activity as myocardial oxygen demand increases while perfusion remains poor
Nausea
Shortness of breath, dyspnea
An oxygen starved heart is failing to provide adequate perfusion - leading to an eventual state of hypoperfusion & shock. Oxygen saturation may be low in MI patients, especially as it progresses
Generalized weakness
An MI compromises the heart’s ability to effectively circulate blood - dropping perfusion. Weakness can be an easily missed sign of an MI
Unexplained, sudden onset weakness should raise your index of suspicion significantly
Atypical Signs & Symptoms + Atypical Populations
Atypical MI symptoms are hard to do justice - after all, they are atypical. One of the best ways to analyze a patient’s propensity for developing atypical symptoms in the case of an AMI is to review their population demographics and risk factors.
The major demographics for those who commonly show atypical AMI symptoms include the elderly, diabetics, those with significant comorbidities, and women. As someone meets more of these criteria, they become more and more likely to present with atypical symptoms - and thus increasing your index of suspicion during assessment. While a 68 year old man with hypertension having chest pain with radiation to the left jaw and arm sounds like a classic MI, the 78 year old female with a history of diabetes and sudden onset generalized weakness post-syncopal episode should receive just as rigorous of an assessment. It is the cases where the symptoms are easily missed that our assessment skills in the field are able to make the most impact.
As people age, our sensory abilities decrease. The elderly, on average, sense less pain, feel less heat, and develop atypical findings for all sorts of things. This degradation of the senses applies to the coronary arteries and internal tissues, too. With diabetic neuropathy, we see an even further decrease in the normal sensations of pain in elderly diabetic patients. Elderly patients with polypharmacy of any kind should also raise your index of suspicion, as even the most extensive research in the world still fails to adequately review the interactions of certain commonly prescribed drugs and their effects on the human body’s normal pain sensations in the case of AMI.
Atypical MI patients often have different reported painful locations beyond the usual chest pain symptoms. Common anginal equivalents include pain in the epigastric area, pain in the upper back or classically between the shoulder blades, pain in the right arm, or even up into the neck on either side. Atypical patients also often report pain with different qualifiers - rather than stating it is pain outright, they will describe it as a “pressure,” a “stretching” sensation, or merely a feeling of indigestion. Patients may also underreport their pain levels, describing it as “achy” or “dull.” All of these findings should increase your index of suspicion, especially if the patient meets an at-risk category for atypical symptoms as described above.
To summarize some common atypical symptoms and findings, please see below:
Epigastric, back, shoulder blade, neck, or other arm pain
Any sort of unexplained pain should receive a full history work up and assessment for the underlying cause
The index of suspicion should increase with atypical patient populations. An 87 year old diabetic female whose only report is abdominal pain may be having a STEMI, and could still require an ALS cardiology assessment
Even if the patient reports relief with antacid medications, it does not rule out cardiac cause
Unexplained or sudden-onset nausea or weakness
It is common for sudden onset nausea or weakness to be found in conjunction with an unexplained syncopal episode, especially with geriatric populations
With ventricular tachycardia and other dysthymias being a number one cause for syncopal episodes, it is important that syncope patients receive a cardiology assessment
Unexplained emesis
Any sort of reported chest “pressure” or “heaviness” feeling
While a 12Lead EKG is an excellent tool for investigating cardiac issues in the field, it is also not our only one. Using a good physical assessment, understanding the pathophysiology behind conditions, and having an understanding for diagnostic tools that are currently outside the realm of EMS can help make us better providers, provide better care to our patients, and coordinate better with definitive care centers.
For additional reading on the subject of STEMIs, NSTEMIs, and cardiac emergencies in general, please see below:
ReliasMedia - Acute Myocardial Infarction Diagnosis: Atypical Presentations
BMJ - The Pathophysiology behind Syncopal Episodes
