EKG

Lilly’s Pathophysiology of Heart Disease: A Collaborative Project of Medical Students and Faculty, 6th ed., 2015, Chapter 4: The Electrocardiogram

There is a reason I constantly reference this outstanding resource to our students. It is written by medical students for medical students, and strikes just the right balance between concise and deep, and providing the medical student with what they need to know. This chapter exemplifies that balance, providing an excellent overview of ECG in just 38 pages. If you feel weak in your ECG skills, consider reviewing this chapter in detail prior to beginning the course.

Rapid Interpretation of EKGs, by Dale Dubin

Unfortunately, this book is not available as an e-book in our library, but is a very concise and excellent resource for the beginner, if you have the means to purchase a paper copy. It was what we used in our first year of medical school to get beyond the mystery, and get into actually understanding how to interpret an EKG. It could easily be digested over a weekend if you are a quick reader. Your course directors also have one copy of this book, which may be checked out for one week on a first-come, first-served basis.

This book provides a generally excellent introduction to most introductory 12-lead ECG interpretation concepts, but students should not rely on it as a sole resource as others listed provide a deeper explanation of complex topics.

The Only EKG Book You’ll Ever Need, 9th ed., 2019

This more detailed resource is a reference textbook that fulfills its claim in the title, and includes 2 or 3 cases at the end of each chapter to illustrate learning points, with an additional 22 cases in the last chapter of this 400 page book.

ABC of Clinical Electrocardiography, 2ed, 2008

While significantly shorter than 12-Lead EKG Confidence, this resource is more condensed, and may take more time to digest page by page. There is excellent detail with regards to the ECG diagnosis of arrhythmias and other disease processes, and again the resources is loaded with great examples.

Osmosis has a large number of brief, generally well-narrated and visually interesting videos under the Physiology/Electrocardiography heading on their Cardiovascular System page. All total, these videos add up to just over 70 minutes of viewing when viewed completely and at normal recording speed. I have provided ratings for most of them based on my assessment of their quality (on a 5-star scale). Errata for the videos reviewed are listed below.

Physiology/Electrocardiography

• Electrical Conduction in the Heart (6:55)
• Cardiac Conduction Velocity (3:26)
• ECG Basics (8:36)
  • At 1:22, they have the words Resting and Depolarized backwards on the diagram—everything else in that figure is correct. Don’t let that confuse you!
  • The wave of atrial repolarization proceeds in the same direction as the depolarization wave, so the repolarization wave would be in the opposite direction as the depolarization wave. Since the atrial tissue is low in mass, the repolarization wave isn’t really seen well. Not so with the ventricles—the repolarization of the ventricles proceeds in the opposite direction, so the T wave, which represents repolarization of the much larger ventricular mass should go positive in the same direction as the ventricular depolarization (the QRS complex). In other words, the QRS complex and T waves should generally be on the side of the baseline for each lead.
  • Chest leads are also called precordial leads.
  • The first 50 seconds of this video are repeated in all the other ECG videos, so you can skip ahead 50 seconds in all the other videos.

ECG Rate and Rhythm (8:20)

• Atrial flutter is NOT an ectopic focus, it is a disorder of reentry around a central zone of nonconduction.
• Atrial fibrillation is NOT multiple ectopic atrial foci, it is caused by spirals of chaotic “wavelets” of depolarization in atrial muscle, similar to reentry.
• Bundle branch blocks are not an irregular rhythm—they are caused by conduction block in a bundle branch, and are independent of the rhythm for the most part.

ECG Intervals (7:07)

• Ectopic ventricular beats do cause a prolonged QRS complex as stated in the video. In addition to being wider, the QRS will look different than the QRS as conducted down the AV node/His bundle (the video doesn’t show a ventricular ectopic beat).

ECG QRS Transition (3:47)

• The key contextual piece for this brief video is that infarction can shift the R wave transition in the precordial (chest) leads.
• Again, as stated, RVH can cause a transition shift in R wave progression, but LVH does not—it simply increases the voltages in the left-sided direction (so bigger S waves in V1 and V2, and bigger R waves in V5 and V6).

ECG Axis (9:19)

• Watch this video before ECG QRS Transition.
• You can also determine the axis of the P wave and T wave, which is not mentioned in the video. When the P wave axis is abnormal, the atrium is not depolarizing from the sinus node. When the T wave axis is off, there may be strain, a conduction abnormality, or ischemia in the ventricles.
• RVH can cause a transition shift in R wave progression, but LVH does not—it simply increases the voltages in the left-sided direction (so bigger S waves in V1 and V2, and bigger R waves in V5 and V6).

ECG Normal Sinus Rhythm (6:24)

• Watch this video after ECG Basics.
• Don’t worry about Bachmann’s bundle. There is debate about whether this conduction pathway even exists! Just think about atrial depolarization proceeding downward and leftward through the 2 atria.
• The 6 ECG criteria for normal sinus rhythm are not discretely listed in this video. They are:
  • Normal heart rate
  • Regular RR intervals
  • Normal PR interval
  • P wave associated with every QRS complex
  • QRS complex associated with every P wave
  • Normal P wave axis

ECG Cardiac Infarction and Ischemia (10:23)

• Subendocardial ischemia (a pathophysiological state which can be diagnosed on ECG) often causes the symptom of “stable angina”, but the terms are not synonymous.
• Upward sloping ST depression up to 1 mm is within normal limits in an exercising patient. Flat-sloping and downwardly sloping ST depression are more concerning for subendocardial ischemia.
• The narrator doesn’t make it very clear until the very end that the ECG can evolve through phases of myocardial infarction. In STEMI, the ST elevation occurs acutely (pointing towards the injured myocardium), then as the heart muscle pathology progresses from necrosis to fibrosis, the Q wave starts to appear (pointing away from the infarcted/scarred area).

ECG Cardiac Hypertrophy and Enlargement (6:19)

• Tricuspid stenosis certainly does cause right atrial enlargement, but is quite rare.
• The P wave in lead V1 may be normally biphasic. Left atrial enlargement increases the depth and/or length of the negative component.
• Right ventricular hypertrophy (RVH) may also cause a rsR’ appearance to the QRS in V1. In contrast to RBBB, which can also cause rsR’ appearance, the R’ wave in RVH is not very wide.

There are several additional videos under the Pathology heading that include important ECG content, including the Cardiac arrhythmias section on the Cardiovascular System page. These videos have not been reviewed by our faculty for accuracy.

• Viewing ECG Academy basic and advanced videos.
• Completing weekly quizzes (ECG Quiz 50 question quizzes).
• Self-assessing ECG skills using the Life in the Fast Lane top 100 EKGs.