Assoc Prof Harry Mond
May 19, 2025
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Last week I presented a series of ECGs on dual AV nodal pathway physiology.
In one ECG, I missed another form of dual AV nodal pathway physiology, which allows the creation of echo beats.
Let us revisit the ECG as I presented it.
Junctional ectopic (red highlight).
The junctional focus does not penetrate the fast pathway allowing sinus conduction to recommence though the fast pathway, albeit with first degree AV block.
This is NOT a junctional ectopic but rather an echo beat.
Now let me present it again but this times with less trimming of the ECG.
Look at it carefully and try and find echo beats.
There are two different echo beats present.
Thus there is a complex interplay between the slow and past pathways, which I am going to call “pingpong in the AV node”.
Let us review this interplay.
Follow the progression of slow(s) and fast (F) pathway conduction. There are three areas of interest.
Remember the slow pathway has a short refractory period which may allow two slow pathway conductions (both anterograde and retrograde/retrograde) to occur close to each other or more likely there is more than one slow pathway which has been reported during electrophysiology studies.
Can I hear you screaming to tell me more about echo beats?
Well you need to wait until the next fun with ECGs.
Harry Mond
October 16, 2026
Retrograde conduction is defined as conduction from an ectopic site to the atrium via the AV node or accessory pathway and referred to as VA conduction. II results in a P wave configuration which differs from an anterograde P wave, and in most ECG leads is inverted. The site from where the impulse originates can be the AV node, Bundle of His, distal conducting system or the body of the ventricles including ventricular pacing. On the ECG, the QRS complex usually precedes the inverted retrograde P wave but on occasion may follow it.
October 1, 2026
In 1970, I commenced work as a “novice” cardiologist at The Royal Melbourne Hospital. Training at that time was learning how to recognise the diastolic murmur of mitral stenosis and making sure the ECG and chest x-rays were the correct way up. As this was prior to coronary artery surgery, stenting and echocardiography, the ECG was a highly respected tool for the diagnosis of many conditions. I was fortunate to befriend a number of the gurus of ECG interpretation who taught me to look into the soul of an ECG. Today, even though the ECG is the first investigation performed by a cardiologist, the art of ECG interpretation has been lost because we depend on the new tools for cardiac diagnosis.
September 18, 2026
Dr Thura Thant asked for an opinion on this confusing ECG. By using arrows and highlight, the ECG bared its soul and gave me an answer. See if you can work it out? What do you think?
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