ECG Basics


10 Steps to Learn ECG Interpretation

Learning the art of ECG interpretation requires intellect, commitment, effort and — perhaps most importantly — an organized approach.

I have spent thousands of hours (yes, thousands) looking at 12-lead ECG tracings, studying ECGs for the cardiology boards, interpreting ECGs for direct patient care, and developing ECG tutorials and quizzes for Learn the Heart.

Assuming that most of you reading this blog do not have that much time, allow me to share what I have discovered in my years teaching ECGs to make the process simpler — and maybe even enjoyable.

ECGs Made Easy?

Learning all of ECG interpretation is going to take time and it is not quite so easy. To be proficient, it will take effort. Some memorization and pattern recognition will be required. The more you see, the more you will remember. Having a pair of calipers is helpful.

Step 1. Learn the Basics of a 12-lead ECG Tracing

Knowing the basic parts of an ECG tracing will lay a good foundation for everything else that is to come. The different waves, complexes and intervals need to be ingrained in your brain. How many seconds is a full ECG tracing? How much time does each big box and each little box represent?

This is not the time to learn about the different P-wave morphologies that occur with atrial enlargements and ectopic atrial rhythms — but rather, it is the time to learn what the normal P wave looks like and what it represents. It’s a similar concept for the other parts of the ECG.

The Learn the Heart ECG Basics module contains detailed articles on various waves, segments, intervals and more.

Step 2. Determine Heart Rate on the ECG

To determine whether bradycardia, a normal heart rate or tachycardia is present requires the knowledge to calculate the heart rate on the ECG. Remember to apply these techniques to both the atrial rate, which is measured by the rate of the P wave, and the ventricular rate, which is measured by the rate of the QRS complex.

Read Determining Rate.

Step 3. Determine Axis on the ECG

The axis on the ECG can give a clue to many different pathologic states. Unless you are going into electrophysiology as a career, the only axis that you need to measure is that of the QRS complex.

Know the causes of left axis deviation, right axis deviation and when the axis is indeterminate (northwestern). Also, know the quick shortcuts to determine the axis.

Read Determining Axis.

Step 4. Learn Abnormal Heart Rhythms

Learning a normal sinus rhythm was taken care of in Step 1. Now, it is time to learn the below rhythms. Review multiple examples of each in the individual ECG Reviews sections below.

Step 5. Learn Chamber Hypertrophies and Bundle Blocks

Learning chamber hypertrophies and bundle blocks can be difficult. Atrial enlargements are not too difficult, but the criteria for left ventricular hypertrophy can be overwhelming. In my opinion, there is no need to memorize them all, but rather just the main two or three.

With left and right bundle branchs, the “bunny ears” are easy to spot in right bundle branch blocks, although not always present. Don’t forget to learn what a non-specific interventricular conduction delay looks like, as well.

Step 6. Learn Acute MI and Ischemic ECG Findings

This is the fun part of ECG interpretation. Some of the acute MI ECG findings, such as anterior ST segment elevations and inferior ST segment elevation MIs, are obvious. The tough part is identifying the more subtle ECG changes.

Know when ST segment elevation is due to ischemia and when it is due to other causes, including left ventricular aneurysm or left ventricular hypertrophy. Likewise, know when ST segment depression is due to digoxin ECG changes.

Step 7. Learn the Everything Else Including Atypical ECG Findings

Some repetition and memorization is required. The list of things that go into this category is long. Review the list below.

Step 8. Quiz, Quiz, Quiz and Review, Review, Review

Take the Learn the Heart ECG Quizzes and Cases, then review once again, or as many times as you’d like, when you identify a gap in your knowledge. You can never look at too many 12-lead ECG tracings. In real life, you see full 12-lead ECG tracings — so that is how you need to test yourself.

Step 9. Review ECGs in Real Patient Case Scenarios

Whether you are a medical student in clinical rotations, an EMT or an internist in practice, or another health care professional, looking at the ECGs that you will encounter in everyday practice is important. See how the ECG fits the clinical scenario. Sometimes the best way to remember an ECG finding is to associate it with an interesting case that you experienced personally.

Alternatively, you can practice with ECG Cases, like the examples in the Learn the Heart ECG Library — online or in a textbook — in which a patient scenario is presented and the ECG that goes along with it is revealed.

Step 10. Teach Others How to Read an ECG

I have learned the most about ECG interpretation by developing content for Learn the Heart and teaching ECG courses in person. If you can put yourself in a position to teach students or your colleagues about ECGs, you will solidify your skills tremendously.

The Practice of Medicine – Never Stop Learning

Keep reviewing. One day, you will stop and think, “Wow, I think I get it.” Follow Learn the Heart and read the articles regularly. This will keep things fresh in your mind and will even introduce you to rare ECG tracings. – by Steven Lome, DO, RVT