How to Approach Every ECG - 7 Steps

If you are anything like me, mnemonics do you no good. 

My first run in with what I'll call "mnemonic failure" occurred back when I was a student on rounds in the Critical Care Unit. The team comprised of the Attending Physician, 2x Resident Physicians, 1x PA and 2x students (one of which was myself).

We had a uremic patient with altered mental status. The Attending quickly turned his attention to us students:

"What are the indications for urgent hemodialysis?"

I knew the mnemonic. AEIOU. I answered that the "U" was for uremia (obviously, since they had just read off his labs). I then sat there, unable to recall the A, E, I or O of the mnemonic as we stood outside the patient's room. It wasn't that I didn't know them, but the information was not stored in my brain in such a way where I could functionally recall it. Accordingly, it served me no good purpose.

At this point, I knew memorization was not the answer. I needed a system in place. Something that I could practice, or "grease the groove" with.

Back to ECGs

I tell you this story to highlight the need for our brains to "flex." Often times we are taught pattern recognition and memorization for ECG findings, only to feel completely lost and unable to apply them to real world ECGs. 

This is why I approach every ECG from an anatomical perspective. By doing so, we use the ECG tracing to explain the cardiac electrophysiology. 

I'll outline a basic Anatomical Approach to the ECG below. But know this: this is not a "one size fits all" algorithm. Rather, it is a flexible means to navigate the complexities of each rhythm.

Step 1 - General Overview of the Rhythm

• Assess the rate and regularity of the rhythm. Are the QRS complexes wide or narrow?
• Recall that Sinus Rhythms are driven by the SA Node and, thus, will behave in a predictable way. Look for anything that stands out, or that occurs in a non-predictable way. 

Step 2 - Evaluate Atrial Activity

• Is Atrial Depolarization driving the rhythm? (aka are there P waves leading to QRS complexes)
• Evaluate the morphology of the Atrial P waves. Are they originating from the SA Node? Are they Ectopic? Does the morphology remain consistent throughout the rhythm?

Step 3 - Assess AV Nodal Function

• How does the AV Node handle those Atrial P waves? Are each P wave being conducted to a Ventricular QRS complex? If so, what is the PR interval (normal is 120-200ms).
• Check for any pauses/gaps in the rhythm that might suggest a dropped beat.

Step 4 - Ventricular Depolarization

• Is the QRS complex narrow or wide? If wide, can this be explained by a bundle branch block? Or is this of ventricular origin? Use the QRS axis to aid you.
• Take a quick Look for right and left ventricular hypertrophy here, too.

Step 5 - Ventricular Repolarization

• Measure and evaluate the QT interval. When corrected, is it appropriate for the given rate (remember that the QT interval varies with heart rate).
• Evaluate the "T wave axis," Remember that T waves generally have the same axis as the QRS complex. Look for any T wave inversions.

Step 6 - Evaluate for Ischemia & Infarction

• Use your understanding of lead anatomy here. High lateral (I & aVL), Lateral (V5 & V6), Inferior (II, III & aVF), Septal (V1 & V2), and Anterior (V3 & V4).
• Is there a focal vascular event? Remember that the coronary arteries (Left Anterior Descending, Left Circumflex, Right Coronary, Posterior Descending, etc.) feed focal regions of myocardium. Assess for focal ST segment changes in the form of elevation, depression, hyperacuity. Global ischemia from events such as severe anemia, rate related ischemia might cause diffuse ST segment depressions.
• The presence of Pathological Q waves is highly specific for prior myocardial infarction (typically age indeterminate).

Step 7 - Put it all together

• Given your findings, can this be explained physiologically? If not, reevaluate your workflow and rationale. Don't have anchoring bias.

Give this a try the next time you are interpreting an ECG. Just like riding a bike, it takes time to master your workflow. Use this as a launching point for your own personalized approach.

-Reid

ECG Lectures with Reid