Strip 79

VF


First Glance:

From across the room it looks like a chaotic non-perfusing rhythm.

Discussion:

We are looking at the ‘pads’ lead at a gain of 150%.

This could be ventricular fibrillation, or artifact, or maybe a bit of torsades. If you had more strip you would have known it was definitively VF. If it was torsades we would have treated the same- ie: shock.

Everybody clear?!!..


Here we see conversion to a wide complex rhythm after defibrillation, and that rhythm is interesting too. It’s initially irregular without obvious P waves. Then we start seeing divots in the ST segment. Note them here (purple triangles) in this excerpt:

 

Those negative divots in the ST segment look a lot like a retrograde P in lead II. Maybe the AVN was conked out after the shock, but a few beats later it is now conducting retrograde P waves with every ventricular beat. This would be an expected retrograde P morphology, because the ‘pads’ lead is like lead I or II, which normally has an upright P. Retrograde P waves would likely appear negative.

So this would suggest conversion to accelerated idioventricular rhythm or aberrant junctional tachycardia. But what of those positive deflections? (orange circles above). These look like normal P waves, and it looks like there might be one buried in the QRS complex between the first and third one (meaning they were probably going at a regular rate). But.. they don’t seem to correlate to the QRS rhythm. Is this AV dissociation? That would also suggest ventricular vs aberrant junctional, but what doesn’t make sense is how there would be two competing atrial rhythms (the regular retrograde P waves, and the normal presumably sinus dissociated rhythm).

Well, if you break out the calipers it turns out the orange P waves are not actually regular- they might be incidental non-conducted PACs from an excitable epinephrine-stimulated heart. No sense dwelling on it- the differential is the same for either of these possibilities.

Final Impression?

Course VF defibrillated to accelerated idioventricular rhythm vs aberrant junctional tachycardia @ ~100 bpm.

Management implications:

Shock first, ask questions later. And just because you see a conversion doesn’t mean you shouldn’t be doing compressions.

 The Take-home Point:

The shockable ventricular rhythms are all related, in that they are hyperactivity of the ventricle in one way or another.

Monomorphic VT (or just ‘VT’ for short) is a ventricular rhythm that is usually caused by a single reentry pathway. VF is a chaotic rhythm where we see the superimposed electrical activity of many tiny ventricular reentry circuits raging away, with no concerted contraction, and therefore no concerted cardiac output.

Polymorphic VT is where there are multiple reentry circuits. This results in a faster less organized rhythm. It seems to me that monomorphic VT and VF are the two extremes of ventricular tachycardias, and in between are an entire spectrum of similar rhythms, with polymorphic VT smack in the middle. The difference between VF and polymorphic VT has always seemed like something of a grey area to me.

Good thing we don’t have to think too hard about this in the resus room. If unstable with pulse: sync shock. If unstable with no pulse: defibrillate. VF and VT and polymorphic VT (including torsades) all get the same therapy in a pulseless code, so the bedside differention doesn’t carry a lot of weight when you are in a rush.

VF is always pulseless. Polymorphic VT is generally going to become pulseless if sustained. Monomorphic VT can sustain cardiac output for a long time (or perhaps indefinitely), depending on the patient.

 

 

1purple_starOne star strip. Students should identify presence of a shockable rhythm immediately.

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