What Do You Think 27

ECG report stated: “Atrial and ventricular bigeminy”.

What do you think?

On superficial inspection, there is sequential atrial bigeminy (red highlight) and broad QRS ectopic bigeminy (yellow highlight).

Are the wide QRS complexes ventricular? Maybe not!

The ectopic coupling intervals are not constant, but gradually shorten (red arrows).

The wide QRS ectopics have a very short coupling interval and are conducted to the ventricle in the refractory period resulting in progressive left bundle branch block aberration.Before total AV block occurs, the coupling interval once again lengthens and the next ectopic conducts normally.

Therefore, all the ectopics are atrial.

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Normally “unifocal” atrial bigeminy will have fixed coupling intervals. Why then do the atrial ectopic coupling intervals, progressively shorten?

Indeed, is this atrial ectopy?

Let us review the cycling period of the ectopics.

The cycling period of the“ectopics” or inter-ectopic intervals are fixed (blue arrows) and in the presence of varying coupling intervals, consider atrial parasystole.  

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Atrial parasystole:

• Very rare ECG finding (maybe, we don’t look or consider).
• Independent, slow atrial ectopic focus with fixed inter-ectopic intervals.
• Sinus impulses cannot enter and reset. In contrast, the sinus pacemaker can be reset by the parasystolic focus (green arrows).
• Sinus impulses, however, can create refractoriness within the surrounding myocardium, causing an exit block.
• Depending on the timing, parasystolic complexes may result in apparent AV block, aberrant ventricular conduction and even atrial fusion.
• I was always taught that atrial parasystole occurred with digitalis toxicity, which is very rare today.

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Remember the hallmarks of atrial parasystole:

• Varying atrial coupling intervals
• Fixed atrial inter-ectopic intervals

In contrast atrial bigeminy:

• Unifocal atrial ectopics
• Fixed coupling intervals

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We have previously discussed ventricular parasystole. With both, the diagnosis is always difficult, controversial and this even applies to cases in the literature.

To be absolutely sure, we need long strips.

Finally, our ECG original report said: “Atrial and ventricular bigeminy”.

Can they occur sequentially?

Sequential atrial bigeminy (red highlight) and ventricular bigeminy (yellow highlight).