ECG Basics and Interpretation Made Easy

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

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

ECGs Made Easy?

I imagine it is understood that learning all of ECG interpretation is going to take more than 10 minutes of your time and that it is not quite so easy. To be proficient, it will take a bit of 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. But when using LearntheHeart.com to learn ECGs, don’t scratch your computer monitor please. Now that this is understood, let’s get down to it.

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

First things first. 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 the crazy things such as the different P-wave morphologies that occur with atrial enlargements and ectopic atrial rhythms — but rather, just to know what the normal P wave looks like and what it represents. It’s a similar concept for the other parts of the ECG.

Read ECG Basics.

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, measured by the rate of the P wave, and the ventricular rate, 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.

Be sure to 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, learn the below rhythms like the back of your hand. Be sure to review multiple examples of each in the individual ECG Reviews and Criteria sections below.

Step 5. Learn Chamber Hypertrophies and Bundle Blocks

Sometimes this can be the most difficult part. Atrial enlargements are not too bad, but the criteria for left ventricular hypertrophy can drive you crazy. No need to memorize then all, just the main two or three.

Left and right bundle branch are not too bad, either. The “bunny ears” are easy to spot in right bundle branch blocks — though 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

Again, some repetition and memorization is required. The list of things that go into this category is long — so let’s get going.

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

Taking ECG quizzes, then reviewing once again when you identify a gap in your knowledge, is key. You can never look at too many 12-lead ECG tracings. In my opinion, you should not take a quiz that only shows a snippet of an ECG, a QRS complex or just a rhythms strip. 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, looking at the ECGs that you encounter in practice is important. See how the ECG fits the clinical scenario. Sometimes the best way to remember an ECG findings is to associate it with an interesting case that you experienced personally.

Alternatively, you can practice some ECG cases — online or in a textbook — in which a patient scenario is presented to you, then the ECG that goes along with it is revealed.

Step 10. Teach Others How to Read an ECG

There is no question whatsoever in my mind that I personally have learned the most about ECG interpretation by developing content for LearntheHeart.com 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. Teach your spouse or your dog. Whatever works for you.

The Practice of Medicine – Never Stop Learning

Just keep on reviewing. One day, you will stop and think “Wow, I think I get it.” Sure, you can memorize every criteria and detail about the various ECG findings. But with the availability of internet access in the hospital and on your smartphone, why not just bookmark a nice reference page? Eventually, if you look things up enough times, you will commit them to memory.

Follow an ECG blog, and read the articles regularly. This will keep things fresh in your mind and introduce you to crazy and/or rare ECG tracings.

– by Steven Lome, DO, RVT

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