What Do You Think 35

Rhythm strips: I, II, V2, V6

What do you think?

In order to interpret the ECG, let us start by reviewing the ventricular ectopic.

In summary:

A ventricular ectopic has a

• A premature wide QRS (red highlight) with no preceding P wave.
• The QRS and T wave are discordant (T wave polarity opposite to the QRS).
• Unless there is retrograde conduction to the atria, the sinus cycle is not interrupted (red vertical lines), but there is a concealed P wave embedded in the ectopic T wave (blue stippled line)
• There is a compensatory pause (red horizontal arrow), because the concealed P wave does not conduct to the ventricle.
• The relationship of the ventricular ectopic to the preceding sinus QRS is referred to as the coupling interval (blue horizontal arrow) and with more than one similar ventricular ectopic (unifocal) in the tracing, this interval usually remains constant.

Now, let us return to our ECG.

Sinus rhythm with ventricular ectopics every sixth beat (red highlight).

Ventricular hexageminy. Rarely reported in the literature, not necessarily because it is rare but rather long strips are required to make the diagnosis.                      

What bugs me is that some examples in the literature only have two ventricular ectopics (yellow highlight) with 5 sinus beats between (red highlight) and therefore we do not know if it is really a single sequence or a true run.

Therefore, In order to diagnose ventricular hexageminy, we require at least two sequences or three ectopics.

Let us review the various ventricular “geminy” groupings.

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Ventricular bigeminy: Ventricular ectopic every second beat (red highlight).

Ventricular trigeminy: Ventricular ectopic every third beat (red highlight).

Ventricular quadrigeminy: Ventricular ectopic every fourth beat (red highlight}.

Ventricular pentageminy: Ventricular ectopic every fifth beat (red highlight).

Ventricular hexageminy: Ventricular ectopic every sixth beat (red highlight).

This ECG was reported as ventricular trigeminy with fusion.

What do you think?

There are two very late ventricular ectopics (red highlight) occurring after the P wave in the PR interval and are referred to as end diastolic. The next ventricular ectopic is later again (yellow highlight) and is fusion between the ventricular ectopic and the next sinus generated QRS. The coupling intervals differ and the ventricular ectopics have a fixed coupling interval between them. This is called ventricular parasystole and is easily confused with “geminy”grouping.

Ventricular parasystole:

• Rare ECG finding
• An independent ventricular ectopic focus
• Sinus impulses cannot enter and reset
• Sinus impulses, can however, create refractoriness in the surrounding myocardium causing an exit block.

ECG features:

• Unifocal ventricular ectopics‍
• Variable coupling‍
• Fixed, usually very slow inter-ectopic intervals
• No ventricular ectopics during the refractory periods
• Fusion beats are common depending on the timing.

Our tracing has all these criteria but to be absolutely sure, we need longer strips.

Here is another example which shows how difficult it is to confirm the diagnosis of ventricular parasystole.

• Atrial fibrillation
• The ventricular ectopics are unifocal (red highlight)
• The coupling intervals differ, becoming shorter
• The inter-ectopic intervals are fixed
• The yellow highlight shows that the next ectopic falls in the refractory period of the intrinsic beat.

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Harry Mond