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Assoc Prof Harry Mond
February 23, 2026
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I was shown this Holter ECG recording and asked if it was ventricular tachycardia.
The rate is 240 bpm and the rhythm irregular with broad QRS complexes and short pauses or breaks. I wanted more information, so I was shown the next ECG.
The rate has now halved to 120 bpm and the rhythm is regular and the QRS complexes remain broad. There may be P waves present? I wanted more tracings!
Although it doesn’t look like it, the rhythm is regular. The red vertical arrows are P waves and map out at about 240 bpm. There are also runs of alternating narrow complexes (yellow highlight).The rhythm is supraventricular tachycardia 240 bpm, with 1:1 and 2:1 conduction and alternating aberration. An alternative is atrial flutter, where antiarrhythmic therapy such as flecainide has slowed the atrial rate allowing 1:1 conduction. In this situation, digoxin blocks the AV node and slows the ventricular rate.If there is 1:1 and 2:1 AV block, then maybe the irregularity seen earlier is Wenckebach AV block?
The first part of the tracing shows the AV block and you can map out the P waves. The irregular broad complex rhythm follows and if we add in the concealed P waves (red stippled vertical arrows), then there is 5:4 Wenckebach AV block with the blue stippled vertical arrows being the dropped beats.The appearance of atrial flutter or supraventricular tachycardia with block and alternating aberration, frequently gives the appearance of a bidirectional tachycardia of which there are many other causes. The next four tracings are typical examples of bidirectional tachycardia due to atrial tachyarrhythmias.
Dr 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.Â
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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