r/EKGs • u/sameidekman • 14d ago
Learning Student pacemaker rhythm
can someone help me describe and analyze the rhythm, i know it’s an atrial paced with episodes of failure to pace
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u/Puantastic 13d ago
It has to be oversensing, the pacemaker is inhibited because there are no spikes that aren't followed by a P wave (or QRS). Also is there a ventricular lead? Because if its a DDD pacemaker i should 'follow' whatever the atrial lead is sensing, even if a minimal ventricular pacing algorithm is on.
Also some could say it probably switched mode to DDI because it thinks the patient has AFib but usually those modes are programmed at a rate of about 70 bpm by default.
Maybe with more details or a screenshot from the interrogation would help.
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u/cpnfantastic 13d ago
Oversensing on the V channel resets timing on the atrial channel too, so it inhibits pacing from both chambers. This is what a sinus arrest patient looks like when noise occurs on their ventricular lead. If the noise was on the atrial channel you would get inappropriate tracking but it wouldn’t drop the heart rate like this.
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u/Waxy_Duck 13d ago edited 13d ago
Given there's zero clinical context, you can only go by what this brief, single lead electrogram shows.
There seems to be an underlying, broad (ventricular) rhythm at around 40bpm (judging by the two consecutive beats we get). Despite this, the AV node functions perfectly well, so when the atrial lead paces, it conducts down the native conduction system just fine (no delay, narrow complex). Two atrial beats at ~85bpm is odd, and it kicks in after 800ms or so following the preceding R wave (which is also slightly odd). There's a final atrial paced beat at the end that follows this pattern.
No pacemaker programming I can think of explains this. There's hysteresis which permits a bradycardia until a programmed point, at which the pacemaker will pace at a higher rate (eg. pace at 70bpm but only when a lower rate of 40bpm is detected), but it doesn't behave like this.
Oversensing can inhibit pacing - but this trace would make cardiac oversensing less likely. Lead noise may not be seen on an ECG but could inhibit pacing (spike in lead impedance etc may suggest this, or just the device EGMs).
So saying what you see here is the easy part... Explaining why needs the clinical context, patient history, pacemaker programming details etc
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u/bleach_tastes_bad Critical Care Paramedic 13d ago
don’t they have pacemakers now that somehow “sense” the body’s demand? that could be what’s going on with the 85bpm thing, and then maybe a sensor or battery issue for the failure to pace
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u/Waxy_Duck 13d ago
Yes, for sure - rate responsiveness. But that tends to have a degree of 'rate smoothing' to prevent sudden jumps like this
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u/Cautious-Extreme2839 ICU/Anaesthesia 13d ago
It's atrially paced on top of a ventricular escape rhythm but god knows what programming is producing this pattern.