This article appears in the June-July 2019 edition of Canadian Paramedic Association: https://canadianparamedicine.ca/featured-edition, pp.38-40
Paramedic ECG Interpretation
Paramedics practice medicine in unpredictable environments thus necessitating the need to utilize a number of different skills and technologies to improve patient assessment and treatment. One particular skill that has gained increased importance and relevance as recognized by the 2015 edition of the American Heart Association guidelines is early Electrocardiogram (ECG) acquisition and accurate interpretation. This skill has been shown to improve patient outcomes. (1)
Emergency Health Services Nova Scotia is addressing this need by offering two distinct ECG interpretation courses. A key message delivered by the facilitator at the outset of each course is, “we don’t read ECG’s; we interpret them in combination with the clinical presentation and history of presenting illness of our patients”. In Nova Scotia, we have combined comprehensive cardiovascular and coronary anatomy education with ECG interpretation to advance the skill itself. As an example, Paramedics of all scopes who attend these courses are taught the importance of understanding ‘currents of injury’ and their impact on ST segment morphology changes as an early identifier of impending occlusion myocardial infarction (OMI). Renowned physician, Dr. Stephen Smith, supports this belief by stating “a well-informed subjective interpretation of the ST segment is perhaps as accurate as any measured criteria” (personal communication). This supports the trend of moving away from the use of millimeter criteria as the sole predictor of OMI and instead adding to it by more closely examining the morphology of the ST segment. (2)
ECG 1.0 and 2.0 were created and offered as part of an elective education model launched in Nova Scotia in April 2016. Since the ECG course inception a number of positive patient outcomes have been reported which are thought to be directly related to the Paramedic’s completion of the course. The Paramedics involved in these cases observed that they likely would not have identified the OMI without having attended the ECG 1.0/2.0 course. In this article, cases are presented that outline how this education has led to real-world changes in clinical decision-making and practice.
ECG Interpretation 1.0
ECG 1.0 is targeted towards all scopes of practice including primary, intermediate, advanced and critical care Paramedics. The course reviews the important and growing role of the prehospital ECG in the treatment of acute coronary syndrome (ACS), among other pathologies. This course provides learners with a foundational knowledge essential to interpreting basic and advanced cardiac dysrhythmias by identifying cardiac anatomy and physiology, identifying ECG changes consistent with early STEMI markers and aligning a patient’s presentation, history of presenting illness, and ECG in the course of patient care.
ECG Interpretation 2.0
ECG 2.0 is also targeted to all scopes of practice. Feedback from the initial ECG interpretation course was that Paramedics wanted more information on this topic and with all scopes being asked to obtain and interpret 12 leads; further education is of high importance for all Paramedics. ECG 2.0 builds upon concepts introduced in t ECG 1.0 by focusing more on ACS physiology, ST segment morphology and signs of impending MI. STEMI mimics such as pericarditis and hyperkalemia, and corresponding assessment strategies to help determine a working diagnosis are discussed in depth.
Three cases are presented. All cases originated as either an initial Primary Care Paramedics (PCP) crew or mixed ACP/PCP crew. In each case, the Paramedics identified abnormal morphology associated with an ongoing MI (often mistaken as ischemia) or an impending MI with ECG changes that informed Paramedic prediction of MI. The Paramedics identified that the ECG education 1.0 & 2.0 resulted in their improved ability to accurately identify and interpret the ECG. They reflected that they likely would not have identified these cases as OMI without the training.
Case 1. Posterior MI
In case 1, PCP identified early markers of OMI and expedited not only treatment but timely transport to definitive care.
A PCP crew responded code 1 for a 62 year old male with a sudden onset of bilateral arm numbness and diaphoresis. Upon arrival the patient was found sitting at the kitchen table with his wife present. The Paramedics noted that the patient appeared anxious. The patient indicated that he felt as though he may ‘pass out’. The patient had a heart rate of 45, blood pressure of 110/66, and oxygen saturation of 98%. Of note, the patient had a history of hypertension, hyperlipidemia, angina, and depression.
The Paramedics obtained a 12 lead and upon immediate ECG interpretation recognized a possible ‘posterior-lateral MI’ (Figure 1). To confirm this, the Paramedics performed a modified 12 lead which clearly showed ST segment elevation of 0.5 mm in leads V8 & V9 (Figure 2). A modified 12 lead, which is taught in ECG 1.0, can be performed by following the steps described in Table 1.
Table 1. Description of modified 12 lead process.Process 1) Locate the patient’s left scapula. 2) Palpate downward until you reach the point at which the bone comes to the inferior angled end (similar to a triangle which has been positioned upside down). 3) Place 2 fingers directly below this now anatomically located inferior boney process. 4) Place an electrode directly below your 2 fingers and in line with the inferior angle. 5) Move the wire from lead V5 to this newly placed electrode (this becomes V8). 6) Rotate the same 2 fingers to the right so that they are now parallel with the spine (paravertebral). 7) Place an electrode to the right of your 2 fingers, directly in line with the one previously placed. 8) Move the wire from lead V6 and connect it this newly placed electrode (this becomes V9). 9) Label these lead changes on the 12 lead print out from your cardiac monitor as you may not remember which one was the modified 12 lead. 10) Don’t forget about the right ventricle and the importance of recognizing right ventricular infarction! Move precordial lead V4 to the right side of the sternum in the same anatomic position as originally placed but on the opposite side of the chest at the 5th intercostal space at the mid-clavicular line. This gives the best view at any suspicious activity occurring in the right ventricle.
During this call, ALS back up was requested and the patient was treated under the Nova Scotia prehospital reperfusion therapy guideline.(3) Tenecteplase (TNK) was administered in the home and the patient was transported to the nearest regional facility with complete resolution of symptoms and ECG upon arrival.
Learning Point:Acute posterolateral MIs usually have no significant R WAVE (a very small one could be present), and they SHOULD have ST depression that is flat or downward-sloping and T waves that are minimal or still inverted. Remember: these are RECIPROCAL changes!
Case 2. Impending Inferior MI
A mixed ACP/PCP crew responded code 2 for a 48 year old male with a complaint of nausea and jaw pain. Upon arrival the patient was found sitting on the steps to the front door of his home stating that he’s “sorry for calling but didn’t know what else to do”. Vital signs and a 12 lead ECG were obtained. The patient had a heart rate of 79, blood pressure of 80/60, and oxygen saturation of 96%. The patient had a history of arthritis, hypertension, and anxiety. Both members of the crew interpret the ECG and agree that the ST segment depression noted in lead aVL with potential hyper-acute T waves in leads II, III and aVF to be a concerning finding for an impending inferior wall MI (Figure 3). The crew decided to consult with the Clinical Support Paramedic who echoed their concerning findings and serial ECGs were performed (Figure 4). The patient was transported to a tertiary facility capable of performing primary percutaneous coronary intervention (PCI) and upon arrival the monitor indicated ***acute MI suspected***. The patient underwent treatment by the cath lab.
Learning Point: aVL and the inferior leads have a unique relationship in that when an inferior MI is present, the reciprocal change of ST depression in lead aVL may appear BEFORE the indicative change of ST elevation in the inferior leads II, III, and aVF.
Case 3. Partial Left Main Occlusion
A PCP crew responded code 1 for a 56 year old male complaining of epigastric discomfort with pain in the neck and teeth. Upon their arrival, the patient was found sitting in the living room. The patient states that he’s had a heart attack in the past but “this feels way worse”. Vital signs and a 12 lead ECG are obtained (Figure 5). The patient had a heart rate of 83, blood pressure of 96/60, and oxygen saturation of 95%. The patient had a history of an MI 5 years previously, Gastroesophageal reflux disease, and hypertension. The Paramedics recognized that the patient had ST segment elevation in lead aVR which was observed to be greater than that noted in lead V1 with concomitant ST segment depression in eight leads. The PCP crew requested ALS back up for a patient with possible left main coronary artery (LMCA) stenosis. The ECG was faxed to the nearest hospital for consultation. Based on the Paramedic’s interpretation of the 12 lead, the Emergency Department (ED) physician requested direct transport to their location at the tertiary care facility and bypass of the local community hospital. Upon arrival, obvious indications of OMI were present. The patient was taken to the cath lab with resolution of symptoms post cath intervention.
Learning Point: These particular ECG changes are consistent with a partial LMCA occlusion and therefore represent diffuse subendocardial ischemia. Although the occlusion may be considered partial is does however represent a lesion in a particularly ominous vessel, resulting in a massive potential area of risk. Lead aVR is reciprocal to the ST depression that is occurring in the other leads because of its location on the right arm. The injury current would be traveling toward the basal septum which is directly in line with the positive pole of aVR & V1.
These cases, and supporting literature, demonstrate the fundamental value of early Paramedic acquisition and interpretation of the ECG (as supported by the latest edition of the American Heart Association Guidelines). The examples demonstrate that all scopes of Paramedic practice are able to accurately identify and recognize the importance of ST segment morphological changes associated with early OMI, given sufficient training.
Nova Scotia, through its elective education program, has supported this finding with the creation of what some would say is ‘cutting edge’ ECG education. The course content focuses on the added value of understanding how cardiovascular anatomy and physiology can improve accurate Paramedic ECG interpretation. Improving paramedic knowledge of critical concepts such as cardiac morphology and injury currents can lead to improved patient time to reperfusion, and most importantly, improved patient outcomes. These courses have also led to increased Paramedic increased confidence and competence in ECG interpretation in Nova Scotia.
Paramedic clinicians in Nova Scotia do not read ECGs, rather they interpret them.
I would like to thank my ECG mentor, Dr. Jerry Jones, who has provided me with expert guidance on the skill of ECG interpretation. I would like to thank Dr. Judah Goldstein for providing editorial support and aiding with revisions as well as EHS Performance & Development for supporting this work. I would also like to thank the late Mr. Rick Goulet for fostering my passion for ECGs. Finally, I would like to thank EHS Paramedics in Nova Scotia for their support of the courses and dedication and commitment to improving their knowledge of ECG interpretation. This has undoubtedly led to improved patient care within our system.
Though these cases are based on actual calls, the case details (e.g. ages & vital signs) and events have been modified to protect patient confidentiality and privacy and to focus on the ECG interpretation rather than the call management in its entirety.
- American Heart Association. Highlights of the American Heart Association Guidelines update for CPR and ECC. 2015. Retrieved on January 2, 2019 from: https://eccguidelines.heart.org/wp-content/uploads/2015/10/2015-AHA-Guidelines-Highlights-English.pdf.
- Gorgels APM. ST elevation and non ST elevation acute coronary syndromes: should the guidelines be changed. Journal of Electrocardiology. 2013; 46: 318-323.
- Emergency Health Services Nova Scotia. Chest Pain 6228.02 available at: https://novascotia.ca/dhw/ehs/documents/CPG/EHS6228.02%20Chest%20Pain.pdf. Retrieved on January 2, 2019.