Assoc Prof Harry Mond
February 23, 2026
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92-year old, one-eyed cardiothoracic surgeon with labyrinthine degeneration and bilateral foot drop. Plans to cut back his surgical sessions.
Holter monitor shows two nocturnal episodes of bradycardia (yellow highlight):
Both are called 2:1 second degree AV block(red highlight).
What do you think?
My first thoughts were the 06:53:12 tracing was non-conducted atrial bigeminy.
To summarize: Non-conducted atrial ectopic:
Let us relook at the timing of our tracings.
The P-P intervals (red arrows) are near identical in timing with lost P waves in the lower tracing(red-yellow arrow) and the pause about twice the P-P intervals.
I suggest that the lower tracing is 2:1 AV block with 3:2 sino-atrial block. Both tracings have 2:1 AV (Wenckebach) block and one also sino-atrial Wenckebach sequences. This is called a pan-conduction defect, because of block in both nodes.
The footprints of typical sino-atrial Wenckebach block.
Here is a case of sino-atrial Wenckebach block:
As the incremental increase of sino-atrial conduction becomes shorter(red highlight), so do the P-P intervals with the shortest before the sinus pause (yellow highlight).
Another example of a pan-conduction defect with bundle branch blocks.
This illustration is the “full hand” of conduction system disease. There is sinus rhythm and the QRS shows both left bradycardia dependent (red highlight) and right (yellow highlight)bundle branch block. The Wenckebach AV block sequences, range from long to 2:1, whereas the sino-atrial dropped beats (red shadow arrows) occur irregularly(blue highlight). The feature of the Wenckebach sino-atrial block is that the shortest P-P interval is before the sinus pause (green highlight).
The techs were correct. Both tracings show 2:1 AV block.
It isn’t always what you think it is!!!
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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