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Assoc Prof Harry Mond
February 23, 2026
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When I saw the accompanying ECGs this week, I almost started crying! Vivid memories of digitalis toxicity flooded back to me when we used foxglove leaf as a cardiac glycoside (digitalis pupurea) packed into a brown tablet - remember Michael, Brian, Leon). Withering first discovered its use in 1775 as treatment for dropsy (rheumatic right heart failure). There was no specified dose of digoxin as the leaf concentrations varied so much. Consequently digitalis toxicity (blurred yellow vision, nausea and diarrhea) was extremely common and associated with arrhythmias on the ECG, particularly with thiazide-induced hypokalaemia. In particular, these were atrial fibrillation with complete heart block, multifocal ventricular ectopics and bidirectional ventricular tachycardia.I remember in the mid to late 1970’s using digitoxin (active ingredient in the body) which as its name implied was toxic and we clearly used the incorrect dose. In the late 1970’s, a purer less toxic form of digoxin (lanoxin) was introduced and almost overnight the toxic arrhythmias disappeared.This tachyarrhythmia was from a 36-year old and I have no history. It is bidirectional ventricular tachycardia characterized by an alternating beat-to-beat QRS axis (QRS vector alternans) thought to be due to Ping-Pong in the His-purkinje system. This suggests that there are alternating ectopic foci originating in the distal His purkinje system from both the left and right ventricles.It was seen with severe digitalis toxicity, but also with the rare autosomal dominant inherited syndrome Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) induced by adrenergic stress (exercise or emotion). I saw a case about 10 years ago. Not surprisingly, it may result in sudden death and cases up to 40 years of age have been reported.Treatment, which is obvious involves reducing the triggers, high doses of beta blockade, maybe flecainide, left cervical sympathectomy and ICDs.
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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