Although I have been a certified PA for almost 15 years, I remember those dreaded feelings of anxiety towards ECGs like it was yesterday. Sure, I understood the science, and even read a much-recommended resource on the topic by Dr. Dale Dubin, but putting that knowledge into practice was something else altogether. How did one read and interpret an ECG? I didn’t know how to tackle the problem. It seemed like an insurmountable mountain.
Unfortunately, it was a mountain I had to climb. In multiple clinical medicine courses like Cardiology and Emergency Medicine, the ECG was a major part of the coursework. And yet the more I worked at it, the more it seemed to elude me. This was a problem, because I needed to know the ECG to not only get through PA school, but also do well on my End of Rotation Exams and prepare for the PANCE!
Sound a little (or maybe a lot) like your own struggles? Take heart—there was a solution to be found! One of my mentors helped me TREMENDOUSLY by teaching me the five steps to reading and interpreting ECGs. And yes, I would be happy to pay the information forward to you as a virtual mentor!
The ABCs of ECGs
Let’s start by considering what an ECG is. Essentially, an ECG is a mechanical analysis of the dynamic physiology of the heart.
A bit of a history lesson for you: in 1887, Augustus Waller used a mercury capillary electrometer and observed deflections of the mercury that indicated electrical activity in the heart. Using Waller’s discovery, Willem Einthoven built a modified version of the mercury capillary electrometer and recorded the activity of the heart in an improved way. He developed a string galvanometer, which can be seen in this article from NCBI.
Of course, since Einthoven, there have been many changes to his design that have dramatically improved cardiac care. However, we still thank you, Einthoven!
Why Should PA Students Learn to Interpret ECGs?
As a PA student and future certified PA, your ability to successfully read and interpret ECGs is tantamount to effective practice as a clinician, especially if you work as a cardiology PA, emergency medicine PA, or even as a surgical PA (as they are obtained for preoperative consultations).
If you apply the following 5 Steps, it greatly improves your interpretation, but it really ensures you don’t miss anything on the ECG, as there are multiple “look-alikes” and otherwise hidden nuggets of valuable data that can be easily missed. However, if you follow the steps, you will be less likely to miss those important nuggets!
Alright, now that we’ve set things up, let’s move on to the how and why of the five steps to reading and interpreting ECGs like a cardiologist!
The 5 Steps to Reading and Interpreting EKGs
1. Is the rhythm regular or irregular?
Most ECGs indicate a regular heart rhythm. Observe the QRS complex; moreover, focus on the upward positive deflection, this is the “R” portion of the QRS. These are usually the easiest to identify on an ECG.
I’ll bet you didn’t know that well before I became a PA, I was a DJ! When examining an ECG, be like a DJ: look for the discernable “marching” of beats. If you can appreciate a regular beat—it is regular!
Pro tip: when starting out, consider using calipers to observe the distance between the “R” portion of the QRS. If you don’t have calipers, place a piece of paper just below the Rs and make a mark under subsequent ones. If they appear the same distance, you are regular!
For irregularities, you will not be able to march out Rs!
2. What’s the rate?
The normal rate is between 60 and 100 bpm. Always remember this!
With a regular rhythm, there are two methods to determine the heart rate using a given ECG (whether a 12-lead full ECG or a rhythm strip).
The first is the counting of large boxes. Starting with an R wave that best lines up with a solid (dark) red line, count the lines between until you reach the next R wave. The rates start at 300 bpm with line 1, then 150 bpm with line 2, 100 bpm with line 3, and so on. Here is a very helpful graphic to help you learn the rates:
I would commit them to memory. Do a couple of practice tracings to get this down pat!
For regular (or irregular) rhythms, there is another method. If you consider a typical 12-lead ECG or rhythm strip, the amount of time across the entire thing is usually 10 seconds. You can count the number of QRS complexes that you see in the strip, and multiply by 6. This will give you a 60-second timeframe of beats. For example: if you count 12 QRS complexes on the ECG, you have a rate of 72 bpm (12 x 6)!
3. What do the P waves and the PR intervals look like?
After determining the rhythm and rate, look at the appearance of the P wave. This is referred to as the morphology (i.e., what does it look like). The P wave represents atrial depolarization (and contraction). It should appear like a small round mound. Here are some examples of abnormal appearing ones and their interpretations.
Additionally, are the PR intervals normal? The PR interval is measured leading from the beginning of the P wave to the first part of the QRS complex. It is normal if it’s between 0.12 and 0.20 seconds. This is equal to three to five smaller boxes.
If it is abnormal or there are specific changes, this may indicate a heart block or even a condition called WPW (if it appears short).
4. What do the QRS complexes, ST segment, and T waves Look Like?
The QRS complex represents the depolarization of the ventricles. It should be less than 0.12 seconds (3 small boxes or less).
Is it “tight,” which means the rhythm is being generated by the sinoatrial (SA) node? Or, does it appear wide, which is known as aberrancy? Aberrancy on an ECG is an abnormal conduction of a supraventricular impulse through the ventricles, causing a widened QRS complex that deviates from the normal heartbeat pattern. The ST segment is a subject for an entire blog post on its own!
Bottom line: a normal ST segment should be flat. If it is elevated, there may be myocardial infarction (heart attack) or if it is depressed there may be ischemia (a lack of normal blood flow).
As for the T wave, it represents the repolarization of the ventricles. It should have a gradual hump appearance, not a flipped one. If it is, this may be another sign of ischemia. If it is peaked, the patient may have hyperkalemia (too much potassium in the blood).
5. Interpretation
Here is where all of the data you’ve obtained leads to your diagnosis. Pro tip: if everything is normal, you are looking at a normal sinus rhythm!
Final Thoughts
If you’re interested in learning ECG interpretation based on both single-concept and case-based questions from an online Qbank, take a look at Blueprint PA’s Clinical ECG Qbanks!
Please do not hesitate to reach out to the fabulous, experienced PA tutors at Blueprint Prep for all of the mentoring you need to become an expert on ECGs!
To your success,
Frank Ritz, PA-C, DScPAS, MPAS
Blueprint Test Prep Tutor
Originally published April 2023 / Updated November 2025
