lead into av node instead of left ventricle?

had a visit with device specialist for 3 month check up after Mobitz 2 heart block and implantation of metronic  CRT-P.  she explained that my first lead goes to the R ventricle and the second goes either just above or into av node (where problem was producing heart failure) rather than into left ventricle which was the norm before 3 years ago.  it is not, then, a biventricular pacemaker as the web describes it.  there is a third lead for back up.  

the battery is being used quickly.  right now the info says i have maybe a total of 4.3 years left on it.  i was told 5 to 7 is normal for this pacemaker's battery.  Does anyone else know about the lead to the center of the heart instead of the left ventricle?  does it generally take more battery juice?  What are the issues others are having with this lead placement if any?

2 Comments

Battery usage is a function of lead impedance and usage, not placement

by crustyg - 2020-07-21 08:32:41

The current drain from your PM's battery is really controlled by two main factors: the voltage that the PM has to generate into each lead and the pulse-width required for capture (voltage * pulse-width = energy).  AFAIK, in general the lead impedance and pacing pulse width is a function of how well each lead is embedded and how little fibrosis there is between the lead *tip* and your heart muscle.  Old leads with partly fractured cores can be a problem too.  Lead characteristics aren't a function of where the lead is placed, although it might have some impact on the energy that has to be delivered for effective pacing.  Yes, the amount of paces delivered per hour also affects battery usage but not by as much as energy delivered (except at the extremes: huge energy required 1% of the time is still =>v little drain, *but* a modest energy delivered 100% of the time still isn't that much of a drain).

An ideal lead probably captures at about 0.6V and with a pulse-width of 0.4ms, which is a tiny amount of energy.  Yours are probably needing to be driven a lot harder than that.

I'm only a little over a year in, so PM replacement seems a long way off for me.  *Most* contributors here say that a PM box change is no big deal. 

There's a lot of interest in trying to pace the ventricles as high up towards the AV-node as possible to avoid the well known problems (for some) of extensive, long-term RV-apical pacing, assuming that His-bundle isn't possible.  Traditional CRT third leads go into the coronary sinus and snake down a little to stimulate the top of the LV - quite unlike the traditional RV-apical lead.  It sounds as though you have a traditional RV-apical lead.

I may have misunderstood your description, and if so I apologise.  I *suspect* that it's the RV-apical lead that's been producing the LV-remodelling and hence HF, and your near-AV-node lead hasn't achieved much (hence the HF).  Getting a third lead into the coronary sinus can be very difficult in some folk - the curves just aren't quite right to enter without causing damage.

I know that if my EP doc said to me 'pops (he's a lot younger than I am), you're going to need a PM change every 4-5 years to stay healthy and active', my reply would be 'where do I sign up for that?'  Compared to dear friends falling by the wayside with horrible cancers, I feel lucky.

But I do understand that you may not feel so blessed.

CRT?

by AgentX86 - 2020-07-21 22:45:50

I'm confused by your post.  When you say the first lead goes into the RV and the second into the AV node.  Does it go into the AV node from the atrium?  "Above the AV node" is the right atrium.  It sounds like you have a lead in the bundle of His, which is just below the AV node and above the right and left bundle branches.

Certainly you must have a, RA lead?  This part is confusing. 

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