Assoc Prof Harry Mond
February 23, 2026
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72 year-old astronaut with acrophobia.
What do you think?
Looks bizarre but is not difficult.
Like I have said many times “break it down to its basic elements”!
Write down an answer before you proceed.
Let us review how, with bradycardia, “concealed” sinus P waves (red stippled arrows) emerge from within ventricular ectopics (red highlight):
The sinus P waves related to the ectopics (red stippled arrows) do not conduct, and because the conducting system is refractory, there are compensatory pauses.
Our tracing has what appears to be a compensatory pause, but this is due to PR interval extension from 200ms to 700 ms and therefore the ectopic is interpolated.
Summary: Ventricular interpolation
Ventricular ectopic (yellow highlight) with a non-concealed sinus P wave (red stippled arrow) lying outside the absolute refractory period and therefore can conduct to the ventricle, albeit with a prolonged PR interval. Although no compensatory pause, the R-R interval with the embedded ectopic is longer (1340 ms) than without (1140 ms)by an amount equal to the lengthening of the PR interval (200 to 400 ms).
Let us return to our ECG.
The appearance is a “reversed” Wenckebach AV block without a dropped beat.
Does it exist?
Yes it exists!
Regular sinus rhythm (red vertical arrows). There are repeated reversed Wenckebach AV block sequences(shortening red horizontal arrows) without a dropped beat. The changes in the R-R intervals exclude complete heart block.
This has been reported without a dropped beat together with a bundle branch block and syncope.
The one above is real, but in our case, it is not and is therefore a pseudo-reversed Wenckebach AV block.
In summary, our ECG showed:
Sinus bradycardia with an interpolated ventricular ectopic resulting in very long PR intervals, a pseudo-compensatory pause and a pseudo-reversed Wenckebach AV sequence.
It’s all in the timing.
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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