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Assoc Prof Harry Mond
February 23, 2026
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This ECG was reported as dual chamber pacing.
What do you think?There is obvious atrial pacing, but is there ventricular pacing?Let us look closer at the tracing:
There is an atrial stimulus artefact (Ap) followed by a P wave and a prolonged AV delay.There is also a prolonged QT interval which must be mentioned.Because of the prolonged AV delay and QT interval, the atrial stimulus artefact at rest is close to the preceding T wave. If rate adaptive pacing is programmed ON, then with exercise, the atrial pacing rate increases with physiological demand, and the stimulus artefact may become embedded in the T wave. In this situation, atrial systole may occur with closed AV valves and the patient may describe this as walking into a brick wall.There is also a ventricular ectopic present.Because of its close association to a stimulus artefact, some may confuse this for ventricular pacing. However, the timing as shown below makes this an atrial stimulus artefact occurring immediately before the ectopic.
Remember that with atrial pacing, a ventricular ectopic may not be sensed as shown below.
Between the atria and ventricles, there is an electrical barrier at the AV node. Therefore, a ventricular ectopic must be conducted retrograde and depolarize the atria order to inhibit the atrial output and this usually does not happen and results in an atrial stimulus artefact in the ectopic QRS. This is not pacemaker malfunction!
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.
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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