A colleague of mine asked me “Why would you put a 48 hour holter monitor on a pacemaker patient? Surely the pacemaker is going to record any arrhythmia’s anyway?” (to think I was told there is no such thing as a stupid question…) I am joking of course its a question that brings up something quite pertinent that is always worth remembering.
A pacemaker only does what it is programmed to do. In its crudest form if you told a pacemaker only to record Ventricular Tachycardia’s that were over 200bpm then a lot of VT’s wouldn’t be recorded. The pacemaker cannot figure out in the same way a human can that the regular broad complex at 170bpm is a VT and should be recorded, it simply does at is told like a well trained dog.
So when a patient comes in and is complaining of cardiac symptoms that do not comply with the e-grams and alerts on the device, is there something going on that is overlooked. It is also worth considering if the pacemaker is functioning properly all of the time and not just when the patient is in the clinic and also are any algorithms in play that you haven’t considered.
I once had a patient who’s blood pressure was under investigation and it was found that it was elevated at night. This was mentioned in my clinic. The pacemaker was using an old style method of Rate Drop Response that I was not familiar with in that it was using a large hysteresis (50bpm) with a fast base rate (110 bpm) this seemed to be working well as the patient had no further syncopal episodes. We put a 24 hour holter monitor on to investigate and it was found that their heart rate spent the whole evening at 110 bpm! A long story short is that their sleeping heart rate was triggering the pacemaker to kick in and when it dropped to look for an instrinsic heart beat it was not coming through and so pacing continued. When she woke up in the morning and her heart rate increased above 60 and the paced base rate subsided.
Without the holter monitor we would have never have known! They are also useful in VVI devices to assess atrial activity and AAI devices to assess Ventricular Activity.
Don’t discard the Holter they still have a vital role to play!
A complete explanation of these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.