A normal sinus rhythm will display a rate of 60-99 beats/minute; P waves followed by QRS complexes, and upright P waves in leads I and Il(Meet & Morris, 2002).
STEMI ECGs will display ST-segment elevation at the J-point in more than 2 contiguous leads. ECG displaying NSTEMIs horizontal or downsloping ST-depression and/or T wave changes.
There is not one single proven interpretation method that is most efficient and accurate, and physicians of all levels and specialties displayed deficiencies in interpretation ability.
A standardized ECG education approach and interpretation method may improve accuracy in all healthcare providers
An electrocardiogram (ECG) displays different waveforms that map the electrical impulses moving through different areas of the heart during the cardiac cycle (Prutkin, 2019). The P wave, PR interval, QRS complex, ST segment, T wave, and (sometimes) U make up these ECG waves (Prutkin, 2019). In a standard 12 lead ECG, the leads represent different areas of the heart. Leads II, III, and aVF are associated with the inferior surface; V1 to V4 with the anterior surface; I, aVL, V5, and V6 with the lateral surface, and V1 and aVR with the right atrium and cavity of the left ventricle (Meet & Morris, 2002)
Providers rely heavily on ECG interpretation of these leads for the detection of irregular cardiac rhythms, conduction abnormalities, and myocardial infarction as well as to explore and better understand several other cardiac diseases, like valvular heart disease and pericarditis (Prutkin, 2019).
ECG Interpretation Methods
Despite the weight clinicians give ECG results, there seems to be a surprisingly underwhelming amount of knowledge on the optimal – most accurate and time efficient – ECG interpretation method. UpToDate advises clinicians to follow a systematic approach while other methods, like the CRISP method that was designed for perioperative nurses to rapidly interpret ECGs, promote quick interpretation using only certain leads or waveforms (Prutkin, 2020/Atwood & Wadlund, 2015). Automatic diagnosis from ECG machines present likely interpretations, but may hold too much influence. When the automatic interpretation was incorrect, physician confidence and accuracy suffered, especially non-cardiologists (Bond et al., 2018).
Readings in a “Normal ECG”
To ensure a normal sinus rhythm, where the SA node conducts the electrical impulse from the atrium to the ventricles,lead II is most commonly prolonged for viewing of the P waves (Sauer, 2020). Every P wave should be followed with a QRS complex and will be upright in Leads I and II (Meet & Morris, 2002). The heart rate should be between 60-99 beats/minute (Meet & Morris, 2002). The normal cardiac axis, the mean direction of the ventricular depolarization, is between -30 and 90 degrees (Meet & Morris, 2002). This is interpreted with positive (upright) QRS complexes in Leads I, II (Prutkin, 2019).
A Must Know: Myocardial Ischemia/Infarction ECG changes
A patient experiencing myocardial ischemia/infarct will produce an ECG that displays one of the following: a) findings consistent with ST-elevation myocardial infarction (STEMI) or b) findings consistent with non-ST elevation myocardial infarction or unstable angina (NSTEMI). STEMIs, the classic “heart attack” ECG, display ST-segment elevation at the J-point in more than 2 contiguous leads (Prutkin, 2019). NSTEMIs cause a new horizontal or downsloping ST-depression ≥0.5 mm in two contiguous leads and/or T inversion >1 mm in two contiguous leads with prominent R wave or R/S ratio >1 (Goldberger, & Prutkin, 2021).
ECG Interpretation Deficiencies
A 2020 JAMA systematic review found that physicians’ ECG interpretation ability varied widely, but ultimately revealed major interpretation deficiencies across all training levels and specialties (Cook & Pusic, 2020). Even after educational interventions, physicians still showed deficiencies in accurately interpreting ECGs and only improved to 67% accuracy.
These studies suggest the need for a standardized ECG interpretation and education system, one with proven accuracy and conducive to a clinician’s busy schedule, that can be utilized by and taught to all health care professionals (Cook & Pusic, 2020).
Want to learn more..
To learn more and earn CE credits on ECG-related topics, visit our new Learning Center:
Atwood, D., & Wadlund, D. L. (2015). ECG Interpretation Using the CRISP Method: A Guide for Nurses. AORN journal, 102(4), 396–408. https://doi.org/10.1016/j.aorn.2015.08.004
Bond, R. R., Novotny, T., Andrsova, I., Koc, L., Sisakova, M., Finlay, D., Guldenring, D., McLaughlin, J., Peace, A., McGilligan, V., Leslie, S. J., Wang, H., & Malik, M. (2018). Automation bias in medicine: The influence of automated diagnoses on interpreter accuracy and uncertainty when reading electrocardiograms. Journal of Electrocardiology, 51(6). https://doi.org/10.1016/j.jelectrocard.2018.08.007
Cook DA, Oh S, & Pusic MV. Accuracy of Physicians’ Electrocardiogram Interpretations: A Systematic Review and Meta-analysis. JAMA Intern Med. 2020;180(11):1461–1471. doi:10.1001/jamainternmed.2020.3989
ECG Interpretation
Devin Pinaroc, FNP-C
Takeaways
An electrocardiogram (ECG) displays different waveforms that map the electrical impulses moving through different areas of the heart during the cardiac cycle (Prutkin, 2019). The P wave, PR interval, QRS complex, ST segment, T wave, and (sometimes) U make up these ECG waves (Prutkin, 2019). In a standard 12 lead ECG, the leads represent different areas of the heart. Leads II, III, and aVF are associated with the inferior surface; V1 to V4 with the anterior surface; I, aVL, V5, and V6 with the lateral surface, and V1 and aVR with the right atrium and cavity of the left ventricle (Meet & Morris, 2002)
Providers rely heavily on ECG interpretation of these leads for the detection of irregular cardiac rhythms, conduction abnormalities, and myocardial infarction as well as to explore and better understand several other cardiac diseases, like valvular heart disease and pericarditis (Prutkin, 2019).
ECG Interpretation Methods
Despite the weight clinicians give ECG results, there seems to be a surprisingly underwhelming amount of knowledge on the optimal – most accurate and time efficient – ECG interpretation method. UpToDate advises clinicians to follow a systematic approach while other methods, like the CRISP method that was designed for perioperative nurses to rapidly interpret ECGs, promote quick interpretation using only certain leads or waveforms (Prutkin, 2020/Atwood & Wadlund, 2015). Automatic diagnosis from ECG machines present likely interpretations, but may hold too much influence. When the automatic interpretation was incorrect, physician confidence and accuracy suffered, especially non-cardiologists (Bond et al., 2018).
Readings in a “Normal ECG”
To ensure a normal sinus rhythm, where the SA node conducts the electrical impulse from the atrium to the ventricles, lead II is most commonly prolonged for viewing of the P waves (Sauer, 2020). Every P wave should be followed with a QRS complex and will be upright in Leads I and II (Meet & Morris, 2002). The heart rate should be between 60-99 beats/minute (Meet & Morris, 2002). The normal cardiac axis, the mean direction of the ventricular depolarization, is between -30 and 90 degrees (Meet & Morris, 2002). This is interpreted with positive (upright) QRS complexes in Leads I, II (Prutkin, 2019).
A Must Know: Myocardial Ischemia/Infarction ECG changes
A patient experiencing myocardial ischemia/infarct will produce an ECG that displays one of the following: a) findings consistent with ST-elevation myocardial infarction (STEMI) or b) findings consistent with non-ST elevation myocardial infarction or unstable angina (NSTEMI). STEMIs, the classic “heart attack” ECG, display ST-segment elevation at the J-point in more than 2 contiguous leads (Prutkin, 2019). NSTEMIs cause a new horizontal or downsloping ST-depression ≥0.5 mm in two contiguous leads and/or T inversion >1 mm in two contiguous leads with prominent R wave or R/S ratio >1 (Goldberger, & Prutkin, 2021).
ECG Interpretation Deficiencies
A 2020 JAMA systematic review found that physicians’ ECG interpretation ability varied widely, but ultimately revealed major interpretation deficiencies across all training levels and specialties (Cook & Pusic, 2020). Even after educational interventions, physicians still showed deficiencies in accurately interpreting ECGs and only improved to 67% accuracy.
These studies suggest the need for a standardized ECG interpretation and education system, one with proven accuracy and conducive to a clinician’s busy schedule, that can be utilized by and taught to all health care professionals (Cook & Pusic, 2020).
Want to learn more..
To learn more and earn CE credits on ECG-related topics, visit our new Learning Center:
https://learn.npace.org/products/important-cardiology-considerations-when-performing-sports-physicals
https://learn.npace.org/products/assessment-of-cardiac-murmurs
Other Resources:
ABC of clinical electrocardiography: Introduction. I—Leads, rate, rhythm, and cardiac axis
The Normal Electrocardiogram: Resting 12-Lead and Electrocardiogram Monitoring in the Hospital
Accuracy of Physicians’ Electrocardiogram Interpretations: A Systematic Review and Meta-analysis | Cardiology | JAMA Internal Medicine
The essential skill of ECG interpretation: How do we define and improve competency?
References:
Atwood, D., & Wadlund, D. L. (2015). ECG Interpretation Using the CRISP Method: A Guide for Nurses. AORN journal, 102(4), 396–408. https://doi.org/10.1016/j.aorn.2015.08.004
Bond, R. R., Novotny, T., Andrsova, I., Koc, L., Sisakova, M., Finlay, D., Guldenring, D., McLaughlin, J., Peace, A., McGilligan, V., Leslie, S. J., Wang, H., & Malik, M. (2018). Automation bias in medicine: The influence of automated diagnoses on interpreter accuracy and uncertainty when reading electrocardiograms. Journal of Electrocardiology, 51(6). https://doi.org/10.1016/j.jelectrocard.2018.08.007
Cook DA, Oh S, & Pusic MV. Accuracy of Physicians’ Electrocardiogram Interpretations: A Systematic Review and Meta-analysis. JAMA Intern Med. 2020;180(11):1461–1471. doi:10.1001/jamainternmed.2020.3989
Goldberger, A., & Prutkin, J. (2021, February 14). Electrocardiogram in the diagnosis of myocardial ischemia and infarction. UpToDate. https://www.uptodate.com/contents/electrocardiogram-in-the-diagnosis-of-myocardial-ischemia-and-infarction?search=EKG&source=search_result&selectedTitle=2~150&usage_type=default&display_rank=2#H99426212.
Meek, S., & Morris, F. (2002). ABC of clinical electrocardiography.Introduction. I-Leads, rate, rhythm, and cardiac axis. BMJ (Clinical research ed.), 324(7334), 415–418. https://doi.org/10.1136/bmj.324.7334.415
Prutkin, J. (2019, June 10). ECG tutorial: Basic principles of ECG analysis. UpToDate. https://www.uptodate.com/contents/ecg-tutorial-basic-principles-of-ecg-analysis?search=EKG%20reading%20&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H7491826.
Sauer, W. (2020, October 20). Normal sinus rhythm and sinus arrhythmia. UpToDate. https://www.uptodate.com/contents/normal-sinus-rhythm-and-sinus-arrhythmia?search=normal%20sinus%20rhythm&source=search_result&selectedTitle=1~150&usage_type=default&display_rank=1#H7014381.
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