In essence the Biotronik Closed Loop Stimulation (CLS) Algorithm is a Rate Response function that will adapt the pacing rate of a patients pacemaker based on intracardiac impedance measurements that are effected by an individuals Autonomic Nervous System.
In plain English this means that in patients where Rate Response is required (the Sino Atrial Node isn’t functioning properly) the Biotronik CLS will be able to adapt the heart rate based on the patients metabolic demand…. Pretty cool hey!
How it does this:-
When there is a requirement for increased Cardiac Output the Autonomic Nervous System tells the Sino Atrial Node to increase the heart rate. When the Sino Atrial node is not functioning properly the heart has a plan B. It hasn’t increased its rate but it can increase its stroke volume, the volume of blood expelled with each beat. The force of contraction is known as the myocardium inotropy which affects all myocardial cells in the heart. The pacemaker lead tip recognises these increases in inotropy as small changes in UNIPOLAR RIGHT VENTRICULAR lead impedance and adapts its pacing rate accordingly. See how the pacemaker fits into the autonomic nervous system in image 1.
The pacemaker now knows the rate of the heart and the myocardial inotropy and using this information can calculate a suitable heart rate at that time.
PRO’S – Yaaaaay:- This algorithm is very dynamic and has advantages over rate response algorithms that use a piezo-electric crystal on its own, for one the patients heart rate won’t needlessly increase when they are driving on a bumpy country lane!
Cons – Boooooo: – This article http://www.ncbi.nlm.nih.gov/pubmed/12914629 found the CLS to cause postural pacemaker tachycardias in some patients.
CLS has been shown to be beneficial in preventing vasovagal syncopy too,
Finally, here is a video that demonstrates the differences between CLS and an Accelerometer (Piezo-Electric Crystal) on real patients! for those of you who like to watch… hmmm
A complete explanation of these topics and more is available in the book Pacemakers Made Easy by Carl Robinson.
Time to go Mattress Shopping.
Thanks for reading.
The Cardiac Technician
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