Assoc Prof Harry Mond
December 2, 2024
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In young people, overnight Wenckebach AV block is a common finding. This is usually in the presence of sinus bradycardia/sinus slowing and thus following the dropped beat, there may be a junctional escape beat, terminating the sequence.
This combination of Wenckebach AV block and sinus slowing is an interplay between the vagal innervation of the sinus node (right) and AV node (left). The timing of the PR interval and the junctional escape beat can lead to bizarre tracings.
In this example, there is Wenckebach AV block without an apparent pause. The first complex of the sequence is conducted with a PR interval of 400 ms. Then follows an apparent AV block and junctional escape beat. However, this could be conducted and the concealed P wave (stippled red vertical arrow) is the blocked beat. Or are both dropped?
Here is another example of a dropped beat followed by a junctional escape. In this example, the concealed sinus beat is in the T wave and conducts to the ventricle with first degree AV block. The first PR interval after a pause is always the shortest but not here. One of the many examples of atypical Wenckebach AV block. Remember it is all in the timing!
Dr Harry Mond
October 28, 2026
As its name implies, AVNRT is a reentrant junctional or supraventricular tachyarrhythmia which involves the fast and slow pathways within the AV node creating a self-perpetuating circus movement. It can be divided into typical (slow-fast) or atypical (fast-slow) as well as several rarer forms related to more than one slow or fast pathway with similar electrophysiological properties. On the ECG, they can be identified and differentiated by the positioning of the P wave in relation to the QRS complex, which in turn is related to the direction of the re-entrant AV nodal circuit. However, in about 60% of cases, the P wave is buried in the QRS/T and cannot be identified on the surface ECG.
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.
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