Single Chamber Pacing

AV node

by Selwyn - 2019-07-17 06:15:42

Normal transmission of electical impulse is from the right atrium SA node ( the so called 'heart's pacemaker'), across the atrium, to the AV node ( at the junction of the upper and lower chambers of the heart), through the conduction bundles ( of His) to the ventricles. 

A normal ECG ( EKG) shows whether the AV node is functional. (the P-R interval on the ECG ). Anything over 200msecs and first degree heart block ie. between the SA node and AV node.

A pacemaker forms a 'spike' on the ECG, so your friend may expect to see a spike/P wave, then a normal QRS-T complex on the ECG. 

When the AV node is knacked, the ventricles tend to beat ( hopefully, they will!) at the intrinsic rate of the heart muscle ie. 30-35 beats per minute. Unfortunately, sometimes the muscle decides to have a rest, and we have a cardiac 'a rest'!

How to find out if the AV node is working well

by Gotrhythm - 2019-07-17 15:21:25

Are you asking, if there is only one (atrial) lead, can the pacemaker sense the activity of the AV node--and by extension, the activity of the ventricles? Will interrogation show the AV node working?

Although I have a dual lead pacemaker, for a couple of years, only the atrial lead was turned on, so in effect I was single lead paced.

For a while everything was fine. But after a year or so, I began having what felt like a different kind of PVC or something. I was told that without turning the ventricle lead on, there was no way for the pacemaker to sense or record activity in the ventricle.

Fast forward a year. I passed out after feeling what felt like the world's worst PVCs, and paramedics were called. While I was being transported in the ambulance, and going in and out of consciousness, the EMT could watch what was happening on the EKG. He told me he saw heart block.

Both my cardiologist and EP pooh-poohed the EMT's findings. At my insistence, a Holter monitor test was done. A Holter monitor is an EKG that you wear for a period of a day or two. It showed lots and lots of PVCs--oh, and a little occasional heart block, the EP mumbled. Other stuff happened and to make a long story short, I fired both of them.

If your friend is wondering if something is wrong with the AV node, he will for sure need an EKG, and likely need a Holter monitor test to find out. 

Inaccuracy creeping in here....

by crustyg - 2019-07-18 06:11:06

Pardon me Selwyn, the SA node is in the right Atrium - slip of the pen when you wrote ventricle.

Your friend needs to be a lot clearer about the question.  There's a clear cultural choice about Atrial pacing versus Atrial+Ventricle pacing for patients with a failing/failed SA node +/- heart failure.  In some countries single lead pacing in the right atrium is the norm, other countries always go for dual lead.  A large study, DANPACE, gathered evidence about what was best for patients, and the results are too long to go into here, but it depends on your starting condition, and to some extent, what you want from your PM.

Single atrial pacing assumes that AV-node conduction is good and will remain so.  Many of us have some degree of coronary artery disease which tends to make AV-node conduction less reliable in later years - EP procedures is another cause!

Smart EPs tend to install atrial and ventricular leads at first implantation, even if only the atrial lead is used for the first few years.  In poorer countries, there's a real cost saving in a single lead and a smaller PM box - this stuff isn't cheap (but it's not mega expensive either).

Having a second lead implanted <x> years after the first lead +PM box is a pain, but it's all doable.