A Foreword to ECG Essentials

For over a century, the electrocardiogram (ECG) has been a cornerstone of modern medicine. The pursuit of visualizing and recording the heart’s electrical activity began in the early 1900s with Willem Einthoven’s string galvanometer, a large machine that weighed 600 pounds and filled two rooms. Today, the technology fits into devices as small as a smartwatch. The ECG is quick to perform, inexpensive, and non-invasive, yet the wealth of information it provides can be life-saving, helping to diagnose a heart attack within minutes or uncover dangerous arrhythmias. But despite the ECG’s importance in clinical medicine, its interpretation can overwhelm and discourage new learners because of how challenging a skill it is to acquire. I know this challenge firsthand.

Early in my training, I relied on memorizing classic ECG patterns from the textbooks, lacking insight into why the tracings appeared as they did. When faced with a new patient’s ECG, I was constantly comparing it to a reference, hoping for a perfect match. Unfortunately, if I didn’t have a reference diagnosis in mind, I was lost and didn’t know how to start interpreting the ECG from the basics. Even when I had a reference, small deviations in the tracings from textbook examples left me unsure of the relevance of the changes. Were they inconsequential, artefactual, or a sign of a different diagnosis altogether? This uncertainty eroded my confidence, and if I couldn’t be trust my ECG interpretation, how could I use it to guide patient care? 

My perspective began to change after watching cardiologists interpret ECGs. They could draw out incredible details about the heart’s structure and function from subtle variations I barely noticed, and I found it incredibly impressive. I wanted to do the same, to use the ECG not just to match patterns, but as a tool to gain genuine insight into a patient’s heart. I dedicated myself to understanding the mechanisms, evidence, and history behind various ECG findings. As I did, I started to feel more comfortable with ECGs, and even excited by challenging tracings. I found I could make more accurate diagnoses and truly impact patient care.  

After years of working with junior learners, I know these challenges weren’t unique to me, but rather reflected the daunting and steep nature of the learning curve for ECGs. I learned to recognize the specific conceptual “brick walls” my learners would hit during interpretation, and discovered a passion in helping them chip away at those barriers, one principle at a time. This ultimately inspired me to share my approach on a wider scale.

My goal with this website is to reframe how we learn the skill of ECG interpretation. Instead of promoting rote memorization, this resource is dedicated to understanding the “why.” We’ll focus on the underlying physiology that creates the tracing, giving you a mental framework to logically deduce what’s happening in the heart. The aim is to build your clinical reasoning so you can confidently tackle any ECG, not just the ones that look familiar.

You’ll find this site is structured as a comprehensive curriculum, with topics arranged through bite-sized lessons, often featuring clinical cases. Each lesson introduces only a couple of new concepts, gradually building upon the previous lessons, so the complexity increases naturally. For that reason, the best way to learn is to start at the beginning and work your way through in order. Of course, for those who want to brush up on a particular area, an index is available to jump to a specific topic. 

Crucially, we’ll emphasize how ECGs are never interpreted in a vacuum. You’ll learn how the clinical context shapes your diagnosis, how to troubleshoot your approach as the context changes, and how to reason your way through your differential diagnoses when faced with ambiguity. Key electrophysiology concepts will be woven into every section, with deeper dives available for those wanting to go further. To avoid long walls of text, graphics used liberally to clarify concepts along the way.

This entire resource is completely free to use. The aim is not instant expertise, but steady growth in your confidence and skill. By no means am I the definitive expert, as I’m learning too. Nonetheless, I hope that the knowledge I’ve gathered so far will help allow you to approach ECGs with more curiosity and build confidence with your interpretations.

Let’s get started.