This entry is not intended to supersede medical direction, protocols, standing orders or guidelines. Review of this material does not give an individual the right to practice medicine.
There are a few different situations wherein ST elevation does not fit into a specific pattern. As a newer paramedic, seeing bizarre patterns can be overwhelming and can cause undo anxiety for both the crew and the patient. Today, we’re going to be talking about reasons that a patient can experience global ST elevation on a 12-lead. Before delving into the causes of global ST elevation, let’s take a second to review the layout of a 12-lead EKG and the correlating arteries that feed into different sections of the heart.
Review of Coronary Artery Function & Anatomy
In order to fully understand what you’re looking at on a 12-lead, you should understand which arteries feed into which sections in the heart. There are two main coronaries that branch out, supplying blood to the heart: the right coronary artery and the left main coronary. To start, the right coronary artery (RCA) branches off into several branches that typically feed into the right atria, the lateral right ventricle, and the inferior aspect of the heart (Ogobuiro & Tuma, 2018). A key point to identify is that the RCA supplies blood to the SA and the AV node, meaning that RCA occlusion can often result in bradycardia.
The second main artery is the left main coronary artery (LMCA). The LMCA bifurcates into two separate arteries: the left circumflex artery (LCx) and the left anterior descending (LAD). The LCx supplies blood to the lateral wall of the left ventricle and, in roughly 10% of patients, to the inferior portion of the heart (Ogobuiro & Tuma, 2018). This leaves the LAD to supply blood to the anterior ventricular septum and the anterior portion of the heart (Ogobuiro & Tuma, 2018).
Breaking Down the 12-Lead EKG
Shapes of ST Elevation
Five Common Causes of Global ST Elevation
- Benign Early Repolarization
- Takotsubo Cardiomyopathy
- Wraparound LAD
Benign Early Repolarization
The majority of the time, benign early repolarization is found in otherwise healthy people under the age of 50 (Alemzedah-Ansari, 2018). While the name signals that this condition is “benign”, there is evidence that is on the contrary. This condition, while even if nothing is discovered during the time of the event, could be a preceding event for sudden cardiac arrest (Ali, et al, 2015). Specific EKG findings can vary depending on the text that you look at it. One source states that benign early repolarization is characterized by (Alemzedah-Ansari, 2018):
- Concave ST Elevation in V2-V5
- Notching at the J-Point
- Asymmetrical T-Waves
- No reciprocating ST Depression
- No progression of ST Elevation over time
I hate the term “treat the patient, not the monitor”. It’s almost as bad as hearing stretchers referred to as prams. While this common mantra tends to focus on lack of awareness to diagnostic tools, there is a bit of pragmatism regarding this condition. Although there can be a STEMI mimic on a 12-lead, these patients have a very specific presentation.
Pericarditis is caused by inflammation of the pericardium, the membrane that provides the outside layer of the heart. As with the other two conditions in this entry, pericarditis has a set of clearly defined risk factors. Taking a detailed patient history can make coming up with this differential diagnosis drastically easier. Patients that have autoimmune diseases, e.g. lupus or rheumatoid arthritis, experienced viral infections, or have had a recent OMI or heart surgery are at higher risk of developing pericarditis (Cleveland Clinic, 2020).
There are a few distinct clinical findings that providers would look for. Due to the inflammation surrounding the heart, patients noticeably have less tolerance lying supine and will most likely prefer to sit up. Pericarditis often also presents with pleuritic chest discomfort, e.g. sharp or stabbing pain on inspiration or exhalation. In addition to this, it is not uncommon to see periods of dyspnea or aggravation of a cough. One other key indicator of pericarditis is the presence of a pericardial friction rub (Rahman & Liu, 2011). This is characterized by high-pitched, scratchy tones when auscultating heart tones; yes, you should auscultate heart tones… Here is a great example of what pericardial friction rub actually sounds like.
There are a variety of things that can be noted on an EKG pointing prehospital providers in the right direction. Most commonly, there will be widespread ST elevation in Lead I, II, III, aVL, and aVF, as well as the precordial leads, with the exception of V1 (Burns, 2019). Another common finding is ST depression and PR elevation in aVR (Burns, 2019). If you take a look at the 12-lead that is provided below, notice the dramatic J-point notching that is not characteristic of true ST segment elevation.
While pericarditis is typically a viral infection that causes inflammation in the pericardium, myocarditis is caused by inflammation of the main heart muscle itself. There are a few different causes of myocarditis (primarily viral infections, e.g. Epstein-Barr, varicella, etc.), toxicity from alcohol abuse or cocaine use, as well as Lyme disease (Harvard Health, 2020). There are reports of approximately 9% occurrence of myocarditis involved in sudden cardiac arrest (Schultz, et al, 2009). Additionally, males are more likely to acquire myocarditis than females (Schultz, et al, 2009).
It is not uncommon for patients that have myocarditis to be asymptomatic. However, for the patients that do show symptoms, these symptoms can be broad ranging and difficult to pinpoint. Among the symptoms that patients can have are chest discomfort, dyspnea at rest, peripheral edema, and fatigue. Due to the viral infection component, patients with myocarditis can often present signs of viral infections, e.g. malaise, fatigue, fever, sore throats, etc.
When we’re talking about EKG findings, it is important to note that myocarditis does not always result in global ST elevation, but there are instances wherein it can. In the situations where global ST elevation is noted with suspected myocarditis, these widespread elevations can often be contributed to accompanying pericarditis (Burns, 2019). The most common EKG findings are going to be tachycardia, QT Prolongation, and widespread T Wave inversions (Burns, 2019).
Takotsubo cardiomyopathy is certainly a tough condition to diagnose; certainly it is not going to be diagnosed in the field alone. There are a couple of key points that should be discussed about this condition, though. This condition is referred to as “broken heart syndrome” and results in some type of potentially “reversible left ventricular dysfunction” that is not associated with coronary ischemia (Akashi, et al, 2008). Essentially, the left ventricle experiences either hypokineses (partial or complete loss of muscle movement), akinesis (impairment of muscle movement), or dyskinesis (abnormality of movement). There is general consensus that in many cases of Takotsubo Cardiomyopathy there are documented cases of extreme emotional or physical stressors such as:
- Verbal or physical confrontation
- Extreme grief
- Extreme anxiety, e.g. stemmed from abuse, etc.
- Physical exhaustion from overwork.
While this list is certainly not comprehensive, once again, obtaining a detailed patient history of preceding factors is extremely important. A composition of several studies done by Akashi et al shows that there are a few other characteristics that could lead providers to be suspicious of this condition:
- Primarily occurs in women
- The age range fluctuates around roughly 54-84
- Large % of occurrence of preceding stressor, mainly emotional
- The majority of cases present with chest discomfort
A 2016 article published by the AHA gives a few findings that can assist practitioners in spotting EKG differences between Takotsubo Cardiomyopathy and STEMI changes. Prior to discussing these findings, it is crucial to note that Takotsubo, similarly to OMI, does not always present with STE (Frangieh, et al, 2016).
Typically, the LAD feeds into the anterior portion of the heart, as well as the left side of the heart. However, there can be a subset of patients that have an LAD that extends to the inferior portion of the heart and supplies blood to that region. In a true wrap-around LAD situation, the LAD supplies blood to the inferior wall of the heart, as well as the anterior and left side of the heart. Due to the location of the LAD in these cases, there will typically be ST elevation in the inferior ( Lead II, Lead III, aVF), septal (V1 & V2), anterior (V3 & V4), as well as the lateral (V5 & V6) leads. Another, simpler way to remember this is to look for inferior and precordial elevation (Burns, 2019).
As a result of having such a large amount of blood supplied by the LAD, patients with wraparound LAD STEMIs are more likely to have poor outcomes in comparison to patients with LAD involvement in the anterior portion of the heart only (Kobayashi & Maehara, 2019). A 2019 analysis found that patients with wraparound LADs were to be at risk for developing stress induced cardiomyopathy, increasing the likelihood of developing heart failure (Choi, et al, 2019).
One of the main differences that is noted with a wraparound LAD versus other types of global ST elevation presentations is the noticeable ACS symptoms. These patients will, typically, have the same symptoms and vital signs associated with someone experiencing an OMI because… well, they are having an OMI. When conducting a patient assessment, these patients will likely have contributing risk factors that should tip you off to looking for confirmation of ACS.
- Akashi, Y. J., Goldstein, D. S., Barbaro, G., & Ueyama, T. (2008). Takotsubo cardiomyopathy: a new form of acute, reversible heart failure. Circulation, 118(25), 2754-2762.
- Ali, A., Butt, N., & Sheikh, A. S. (2015). Early repolarization syndrome: a cause of sudden cardiac death. World journal of cardiology, 7(8), 466.
- Burns, E. (2019, June 4). Anterior Myocardial Infarction. Retrieved from https://litfl.com/anterior-myocardial-infarction-ecg-library/
- Burns, D. E. (2019, March 16). Myocarditis ECG Changes. Retrieved from https://litfl.com/myocarditis-ecg-library/
- Burns, E. (2019, March 16). Pericarditis. Retrieved from https://litfl.com/pericarditis-ecg-library/
- Choi, B. I. W., Min, J., & Umhoefer, K. (2019). Wrap Around Left Anterior Descending Coronary Artery in Stress Induced Cardiomyopathy: Fiction, or Reality?. Circulation, 140(Suppl_1), A11513-A11513.
- Cleveland Clinic. (2020). Pericarditis . Retrieved from https://my.clevelandclinic.org/health/diseases/17353-pericarditis
- Deshpande, A., & Birnbaum, Y. (2014). ST-segment elevation: distinguishing ST elevation myocardial infarction from ST elevation secondary to nonischemic etiologies. World journal of cardiology, 6(10), 1067.
- Frangieh, A. H., Obeid, S., Ghadri, J. R., Imori, Y., D’Ascenzo, F., Kovac, M., … & InterTAK Collaborators. (2016). ECG criteria to differentiate between Takotsubo (stress) cardiomyopathy and myocardial infarction. Journal of the American Heart Association, 5(6), e003418.
- Harvard Health Publishing. (2020). Myocarditis. Retrieved from https://www.health.harvard.edu/a_to_z/myocarditis-a-to-z
- Kobayashi, N., & Maehara, A. (2019). Left anterior descending artery wrapping around the left ventricular apex predicts additional risk of future events after anterior myocardial infarction. Anatolian journal of cardiology, 21(5), 259-260.
- Ogobuiro, I., & Tuma, F. (2018). Anatomy, Thorax, Heart Coronary Arteries. In StatPearls [Internet]. StatPearls Publishing.
- Rahman, A., & Liu, D. (2011). Pericarditis: clinical features and management. Australian family physician, 40(10), 791.
- Schultz, J. C., Hilliard, A. A., Cooper Jr, L. T., & Rihal, C. S. (2009, November). Diagnosis and treatment of viral myocarditis. In Mayo Clinic Proceedings (Vol. 84, No. 11, pp. 1001-1009). Elsevier.