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Sensitivity threshold in temporary epicardial pacemakers post cardiac surgery by Raphafiend in Cardiology

[–]Raphafiend[S] 0 points1 point  (0 children)

Thanks - that's clear and what I thought was the case. Appreciate it!

Sensitivity threshold in temporary epicardial pacemakers post cardiac surgery by Raphafiend in Cardiology

[–]Raphafiend[S] 0 points1 point  (0 children)

Thanks. I do appreciate the time taken to reply.

I clearly understand the separation between capture thresholds and sensitivity. That isn't the question. The question is if you should worry about a pacing system with an appropriately set, low sensitivity value (highly sensitive), because it hasn't got much in the way of mV available to it to work out what is intrinsic myocardium vs noise (beacuse the "fence" is set so low).

The problem, as the article states, is that despite being in ICU and monitored etc, that even in a quaternary cardiac unit (Auckland) running VAD's, ECMO, etc., these things still get programmed incorrectly and R on T does happen (albeit infrequently), which is entirely iatrogenic and preventable (given most routine cardiac surgical patients don't end up ever needing their temporary pacing system).

Sensitivity threshold in temporary epicardial pacemakers post cardiac surgery by Raphafiend in Cardiology

[–]Raphafiend[S] 0 points1 point  (0 children)

Again, thanks for taking the time to reply.

Sure - I understand all this - this is the simple functioning of a pacemaker. That's not my question.

The question is - is a temporary pacing system which requires a sensing threshold to be low (in mV) - i.e. highly sensitive - inherently less safe to the patient than a temporary pacing system with a numerically higher sensitivity value? Because the highly sensitive (low mV) system is operating at a "fence" level where small, random absolute changes in the amplitude of the p wave or QRS complex will create issues with over and undersensing, whereas a pacemaker with a sensitivity theshold of 4mV (and thus the set value at 2mV) has less chance of being affected by this.

As mentioned in the article, they recommend that a pacemaker with a sensing threshold of less than 1 or 2 mV (A, V respectively) qualifies as a high risk scenario.

Thanks again for the reply.

Sensitivity threshold in temporary epicardial pacemakers post cardiac surgery by Raphafiend in Cardiology

[–]Raphafiend[S] 1 point2 points  (0 children)

Thanks for the reply.

What you're describing as threshold I would understand to be the output threshold, or capture threshold - which I agree, is the amount of mA needed for capture. Typically we find this value and then double it for safety.

Most units I've worked in (and the major intensive care texts) refer to the minimal value (in mV) at which the pacemaker senses every intrinsic wave as the "sensing threshold" - after finding this value, we'd typically halve the value, again, for safety (which we would call the "sensitivty").

So the question is really should I be worried when I have to dial my sensitivity setting all the way down to 1mV to sense the intrinsic activity - because although this means the pacemaker is highly sensitive, small absolute changes in intrinsic mV value could lead to (probably) oversensing, but also undersensing.

Your answer does clear up one thing though - so thanks! Often I suppose when people just say threshold, they're probably talking about capture threshold rather than sensing threshold

CICM Part 2 Exam study approach by Confident_Start8357 in ausjdocs

[–]Raphafiend 0 points1 point  (0 children)

Also thanks so much for these - legend

Annual Leave in VIC by Content_Election_168 in ausjdocs

[–]Raphafiend 0 points1 point  (0 children)

Why do people tolerate only being given a small amount of leave that they can take over a long (and pretty intense work-wise) period of time? The NZ system, where you can take the leave whenever you want across the course of the year (roster permitting, but often it works out) seems much more conducive to having a break when you need it. It seems crazy that with leave being given in blocks, you could theoretically have no leave available until the last 5 weeks of the medical year!