Pacemaker and Syncope – Cardiac Pacemakers for Treatment of Vasovagal Syncope (Fainting)
Many people have pacemakers
that do not have Heart Block
. An alternative reason that a Cardiac Pacemaker
may be implanted is to combat the heart rate drop associated with a Cardioinhibitory form of Vasovagal Syncope (Fainting).
This is where a person can suffer a quick and sudden drop in heart rate and contractility (the force) of the heart beat and this causes a loss of consciousness.
To show how this works I am going to use Medtronic’s Rate Drop Response Algorithm that is available on these devices.
Rate Drop Response (RDR) is designed to provide backup pacing and prevent associated symptoms in patients who experience occasional episodes of significant drop in heart rate. Now many of you may be asking why or how this is different from a normal pacemaker program i.e. when a heart is going too slow the pacemaker kicks in and makes the heart beat at at least 60 bpm.
A very good question! To answer this you need to consider the patient. In this type of Syncope (fainting) the patient has not only had a sudden reduction of heart rate but also in the hearts efficiency at pumping blood. SO a heart rate of 60BPM is probably not going to be sufficient to stop them fainting and even if it did, the patient would still feel pretty unwell!
Rate Drop Response works in 2 Stages. Recognising that the patient is having an ‘episode’ and then by increasing the heart rate to around 100BPM for a couple of minutes. The increased heart rate of 100 BPM should be enough to compensate for the initial loss of blood flow (the pacemaker can not pick the drop in heart rate INSTANTLY) and also compensates for the hearts temporary inefficiency to pump blood.
Now the Techie Bit – Lets get our Geek On.
Rate Drop Response provides two methods for detecting significant rate drops: Drop Detection and Low Rate Detection. Both can be programmed on if necessary.
As shown in the example below, with Drop Detection, the device intervenes when the Ventricular rate drops by a specified number of beats per minute to below a specified heart rate within a specified period of time. These conditions are established by programming the Drop Size, Drop Rate, and Detection Window parameters, respectively.
In PLAIN ENGLISH – The pacemaker is always watching the heart rate and if it drops by 25 BPM within a minute and that drop goes below 60 BPM then the pacemaker will kick in at 100BPM.
E.g. A patient s out running and then sits on the sofa, her heart rate drops from 130 BPM to 80 BPM within the first minute – this is fine as her heart rate is still above 60 BPM.
She then gets up to go and have a shower her heart rate drops from 80-45bpm within a minute window. This is not OK because it is a drop of OVER 25 BPM within a Minute and to a heart rate of BELOW 60BPM. The pacemaker will then pace the heart at 100 BPM for 2 Minutes and stop her fainting.
Low Rate Detection
As shown in the example below, with Low Rate Detection, the device intervenes when the atrium is paced at the Lower Rate for the number of consecutive beats specified by the Detection Beats parameter.
This means that no ‘DROP’ is required just a heart rate below 60 BPM for 3 consecutive beats. When this occurs the pacemaker will kick in.
Drop and Low Rate Detection On
When both detection methods are programmed, the device intervenes when either Drop Detection or Low Rate Detection criteria are met.
Intervention and Step Down
When a rate drop is detected, the device paces the heart at the programmed Intervention Rate for the programmed Intervention Duration. In the example I gave this was 100 BPM for 2 Minutes.
After the Intervention Duration is complete, the device reduces the pacing rate by 5 BPM steps every minute. This step-down process continues until the natural heart beat takes over again and the patients ‘episode’ has ended.
Programming considerations and restrictions:
If the device is just using the Low Rate Detection (3 Consecutive beats under 60 BPM) this may trigger inappropriately and frequently when the patients heart rate drops naturally at night. Therefor the sleep feature may be used to decrease the detection rate at night to below 50/45 BPM.
I hope this has cleared how pacemakers can treat Vasovagal Syncope (providing its the right type)
I have seen many examples of this treatment being completely successful!
NB This is for a specific type of Fainting, if you are syncopal/pre syncopal because of pauses or heart block then this programming is not needed.
Further explanation around these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.
Thanks for Reading
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