Pacemaker Mediated Tachycardia

Pacemaker Mediated Tachycardia (PMT)

by Gemita - 2024-03-25 18:03:32

Ukegirl, I recently researched this for our FAQs.  Yes, the pacemaker can be responsible for a number of abnormal rhythms and yes you should make an appointment to go back to the pacemaker clinic and they should be able to stop episodes of PMT by making some settings adjustments.  Termination can also be achieved by applying a magnet to the pacemaker pocket or by taking AV nodal blockers (beta-blockers which I see you are already on, or a calcium channel blocker), which can prevent the tachycardia by slowing/blocking the VA conduction if PMT becomes more persistent.

As background, PMT is a complication that can occur in dual-chamber pacemakers in patients with ventriculo-atrial (VA) conduction (also known as retrograde VA conduction) through the atrioventricular (AV) node or an accessory pathway.  This is the backwards conduction phenomena in the heart, where the conduction comes from the ventricles or from the AV node and travels “upwards” into the atria (opposite direction to normal).   Loss of synchrony between the atria and ventricles can lead to abnormal heart rhythms which can decrease cardiac functioning and output. This typically happens when there is a premature ventricular beat that disrupts the normal cycle and separates the P wave from the QRS complex, thus serving as a triggering event for the tachycardia. I see you are getting PVCs and are very symptomatic with them and also during PMT episodes.

If PMT is confirmed, management involves reprogramming the pacemaker to increase the post ventricular atrial refractory period (PVARP). This is an atrial resting period after the ventricle has contracted.  By increasing the duration of PVARP, there is less likelihood that retrograde conduction will be sensed, and PMT will be triggered. Another option would be changing the sensitivity of the atrial lead, so that sinus P waves are sensed, but not retrograde P waves.

Modern pacemakers have certain manufacturer-specific algorithms that allow detection and early termination of PMT, including the use of adaptive PVARP in pacemakers with rate response, automatically prolonging the PVARP after an earlier than normal ventricular activation (PVC) is sensed, or dropping a ventricular paced beat after the pacemaker has been pacing at the maximum tracking rate for a specific period of time.

Definitive diagnosis of PMT is achieved by performing device interrogation and examining the telemetered intracardiac electrograms. This will show retrograde conduction with atrial sensed beats following ventricular paced beats, whereas in normal situations, the atrial sensed beats should precede ventricular pacing.  

I know this is technical and I am only beginning to understand some of it myself, but I hope this helps.  Good luck

AT, PMT & CLS

by Penguin - 2024-03-26 05:42:00

Hi, 

Yes, go back to your techs.  If PMT and PVCs are showing on your report you already have confirmation of possible cause (PVCs - x 4 p/hr) and effect (PMT).  Not all PMs evidence PACs. 

Pacemakers which are programmed to DDD can cause PMT. Sometimes we are aware of it and sometimes not, but prolonged, incessant PMT can be harmful. 

You may also have something called Rate Response turned on in which is referred to as CLS on Biotronik pacemakers. Rate Response and Atrial Tachycardia may cause the spikes in heart rate that you've mentioned and these can trigger PMT too.  Rate Response can also trigger Atrial Tachycardia episodes....so it's a bit of a roundabout! 

Evening out the spikes in heart rate and any sudden changes in h/rate might be helpful to you. I don't have a biotronik device and don't know enough about the settings to comment, but your techs should be able to help.  Sometimes it's possible to alter rate response so that it increases /decreases your heart rate during / after exercise more slowly to avoid sudden jumps in heart rate.  These sudden changes of heart rate can provoke AT. 

You probably already have an Atrial Tachycardia Detection Rate programmed. Again, I'm no expert on Biotronik devices but it should be possible for your pacemaker to detect AT from 130 bpm upwards.  Once detected your device should deal with your AT episode by switching to a pacing mode that doesn't track your AT.  This should improve your symptoms.  Check that this is programmed when you see your techs perhaps?

Most pacemakers these days have PMT termination settings e.g. when they sense PMT they put measures in place to stop it. These measures may include lengthening something called 'PVARP' which Gemita mentions above.  Again, check that PMT termination is programmed, which I suspect it will be. 

I hope this helps a bit and I haven't confused you. Let us know how you get on.  Check the information I've provided with your techs because they will know more about your Biotronik settings than I do! 

Thank you for your comments!

by UkeGirl - 2024-03-26 20:47:22

I so appreciate your input and I have scheduled an appointment with the EP Clinic.

Deleted Comment

by Penguin - 2024-03-27 07:15:27

Just to say, I just posted about the VP suppression mode used by Biotronik. My thoughts were that it may help as I thought it might operate in AAI and mode switch to DDD (AAI->DDD pacing modes don't usually cause PMT).  However, I've just read that VP suppression may actually cause PMT.  Therefore I've deleted it as an unhelpful comment. 

If you look at this link (bit complicated) and scroll down to the section titled, 'Switch from DDD to ADI' and keep scrolling, you will find an indented section which explains this.  

https://www.cardiocases.com/en/pacingdefibrillation/specificities/pm-pacing-modes/biotronik/pacing-modes-specific-biotronik

Discuss this with your techs to see if it is the cause perhaps.  Usually VP suppression gets programmed in sinus node disease to stop unnecessary v.pacing.  

Less helpfully, I see that Biotronik devices do not record an EGM when the device switches to DDI.  This means that the reason for your mode switch will not be evidenced e.g. if it mode switches to avoid v.pacing during an AT episode.  Other stats are recorded, but you might like to enquire about your AT episodes and how they will be evidenced?  

(Edited)