The ECG Blog with Reid

One of the earliest and most recognized ECG manifestations of hyperkalemia is the peaked T wave—a tall, narrow, and symmetric repolarization wave that often raises clinical alarm. But why does excess extracellular potassium cause this specific change?

To truly understand the peaked T wave, we must ...

While cardiac action potentials are often reduced to textbook waveforms and phases, their ultimate purpose is mechanical: to produce calcium influx that activates myocardial contraction. Every depolarization on an ECG—every P wave, QRS complex, and T wave—represents a deeper cellular orchestration o...

Wenckebach phenomenon, or Mobitz Type I second-degree AV block, is traditionally taught as a benign and often physiologic conduction delay within the atrioventricular (AV) node. However, one variant that frequently evades recognition in clinical practice is the rate-related Wenckebach phenomenon, pa...

Digoxin, a cardiac glycoside derived from the foxglove plant (Digitalis lanata), has been a staple in cardiology for centuries. Despite the emergence of newer therapies, it remains relevant in managing atrial fibrillation and heart failure. What makes digoxin unique is its dual mechanism of action—i...

Atrial fibrillation (AF) is classically characterized by an irregularly irregular ventricular rhythm due to chaotic atrial depolarization and random conduction through the atrioventricular (AV) node. However, in rare instances, AF can produce a regular ventricular rhythm—a phenomenon that occurs whe...

Respiratory sinus arrhythmia (RSA) is a common and normal ECG finding that reflects the intricate interplay between the respiratory cycle and heart rate. It is most pronounced in young, healthy individuals and is considered a marker of cardiac vagal tone and autonomic nervous system flexibility. Thi...

Atrial flutter is a macro-reentrant atrial tachycardia defined by organized atrial activity and rapid atrial rates, typically between 250 and 350 beats per minute. While atrial flutter is often grouped into a single category, it is essential to distinguish between its typical and atypical forms. The...

Ashman phenomenon is a fascinating electrocardiographic finding characterized by an aberrantly conducted supraventricular beat. Often seen in atrial fibrillation (AF) or with premature atrial contractions (PACs), it is caused by the rate-dependent refractory properties of the bundle branches. Unders...

The presence of atrioventricular (AV) dissociation is a critical clue in diagnosing ventricular tachycardia (VT). Understanding the anatomy and physiology behind this finding not only strengthens your diagnostic accuracy but also deepens your appreciation of the intricate mechanisms of cardiac condu...

This ECG was initially read as Sinus Bradycardia. What are your thoughts?

Before we begin, I highly recommend reading An Anatomical Approach to ECG.

At first glance the rhythm appears to be a regular bradycardia at a rate of 41 beats per minute, with a QRS morphology consistent with a Right Bund...

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 mysel...