In this first of his Fun With ECG series, our MD Assoc Prof Harry Mond looks at this bizarre atrioventricular (AV) delay. Look closely at the ECG. The AV delay timings don’t make sense. The AV delay for atrial sensing/ventricular pacing (As Vp) is always longer than with ventricular sensing (Vs). In this example the AV delay is longer with As Vs. Read the full clinical case study to discover what's behind this unusual trace.

With a pause about twice the cycle length of the R to R intervals and no P, QRS or T waves, this case tackles one of the most difficult explanations in ECG interpretation and demands a revisit to the fundamentals or “footprints” of Wenckebach AV conduction to unravel what's going on.

In this rare case, we see two very unusual and critical factors that together lead to atrial oversensing and “apparent” violation of the lower rate limit; a very narrow zone of open atrial sensing and far-field R wave sensing. While the first time MD Assoc Prof Harry Mond has seen this as atrial pacing, he explains how the issue can be very easily solved, reminding us, that normally there's no R wave sensing with AAI(R) pacing.

First thoughts on this Holter tracing was artefact, but the native rhythm showed a regular pattern of irregularity! Taking a close look at overnight tracings when the rhythm would be slow and the “artefact” less likely, revealed what was really going on. In this case MD Assoc Prof Harry Mond looks at non-physiologic atrial pacing together with major objections to single lead rate adaptive atrial pacing and why this case is CANNOT be AAI pacing with a ventricular minimisation pacing algorithm.

The Holter monitor tracings of a 44-year old male caused a lot of excitement at CardioScan this week. With 12 bradycardia episodes overnight, it was initially considered Wenckebach AV block. While clinically, rather than visually, correct, it nevertheless, did not fulfil the footprints of Wenckebach and closer examination revealed asymptomatic episodes of sinus bradycardia and second-degree AV block as a result of vagal hypertonia.

Seen for the first time, the pattern in this 24hr histogram gives instantly recognisable clues about what is happening, even without looking at the tracings. Normally, we see a diurnal pattern of rate changes during the day with lower rates at night, but rarely a straight line, unless there is complete heart block (slow) or a regular continual rapid tachyarrhythmia (fast). This, however, is both fast and slow, so what is the diagnosis? We take a closer look to uncover the result.

Handed this ECG, our Medical Director Assoc Prof Harry Mond was asked if it was an example of a rate adaptive pacing, which uses changes in transthoracic impedance to increase the pacemaker rate in response to physiologic demand. It was not a paced rhythm, however, these pacing algorithms create regular artefact on the ECG tracing, whether they are pacing or not in the ventricle. Using examples, we look at the technology and the defining characteristics that identify the correct results for each.

Sinus arrhythmia is unusual in a 63-yr-old but we were asked to amend a ‘normal’ result to reflect this diagnosis. With classical examples of the pattern in under 30s and showing how NOT to confuse it with atrial ectopy, Assoc Prod Harry Mond shows how to uncover the correct result.

The presentation of pseudo Wolff-Parkinson-White Syndrome recently had an international customer return a report with a note pointing out that we had missed the diagnosis of intermittent pre-excitation - the Wolff-Parkinson-White Syndrome. But as Assoc Prof Harry Mond explains in this latest cardiac case study, it is not what it seems. He reveals where the confusion lies, and how to come to the correct diagnosis.