Dual Chamber Device

Could someone please explain just what is a dual chamber device and why it would be an "upgrade"?. I have a single lead to the ventricle and an av node ablation that now is 3rd degree heart block and am and always will be in A-Fib. Very happy with what I have, but curious...thank you for an answer.. aldeer

8 Comments

What I was told

by janetinak - 2009-09-24 03:09:15

I have basically the same thing you have & with my last switch out of the battery Doc said he was checking with an echo to see how my (L) ventricle was doing. If it need a boost I'd get another lead there. Turns out I keot the single lead with implantation in the septum (middle between ventricles).I imagine it may be in my future to get a dual lead. This is how I undersrand it. Bet you will get better description from others here.

Good luck,

Janet

It's considered an upgrade.....

by Angelie - 2009-09-24 04:09:04

When you're getting more than you had before.

I had a single chamber (meaning it could only accommodate one lead) pacemaker, and a lead in my right atrium. Unlike the standard lead configurement as you and most people have (usually a single lead is placed in the ventricle) mine was placed in the top chamber- atrium.

My arrhythmias have persisted despite being atrial paced, so in order to get a more "complete" picture as to exactly what my heart is doing- they inserted a second lead into my bottom chamber. Because of the additional lead, I had to get a new pacemaker as well. A dual chamber pacemaker, or one that accepts two leads.

Think of a lead as a camera. Wherever the lead is placed it sends pacing to help your heart beat normally, but it also "sees" what's going on and sends that information up to the pacemaker.

Complex situations require that both chambers be paced, or monitored, therefore giving the proper treatment to keep the top and bottom chambers in sync.

An upgrade is just adding more where as a downgrade would be subtracting. In the pacer world I've never heard of downgrading, though. As in my case and with my young age, doctors try to do the least amount possible to avoid a bunch of "un-natural" wires and such in your heart. Better to try the less first and see how that goes. If it doesn't work you can always add more help as your heart requires it.

Hope this helps some,
Angelie

Pacemakers

by SMITTY - 2009-09-24 07:09:50

Hello Aldeer,

I'll offer my answer to your question about pacemaker upgrades, but I'll not guarantee I'm correct on this. I think there are five categories of pacemakers.

! - A single lead device (so far as I know these are seldom implanted anymore), which can send impulses to only one heart chamber.

2 - A dual lead device that can send impulses to two heart chambers and would be an upgrade over the single lead.

3 - A bivent device which has three leads and can send impulses to the atrial, and both ventricle Chambers. I understand these are used to improve blood pumping capability for people with a low ejection fraction. This would be an upgrade to both the single lead and dual lead devices.

4 - There is also a pacemaker/defibrillator which I thin has three leads (somebody help me on this one) and is capable of sending impulses to two heart chambers and is also capable of sending a shock to the ventricle in the event someone is in V-Fib. While I think this one would be in a class by itself, I guess it could be considered an upgrade over the single lead and dual lead devices.

5 - There is a defibrillator which has a single lead and is used for sending a shock to stop V-Fib. This one would also, in my mind, be in a class by itself.

There could very well be others, but these are the only ones I have heard about

Dual chamber pacemakers

by parmeterr - 2009-09-24 10:09:10

My best answer. Just from experience and much reading on my own. I want to know what is happening in my heart.

I have had a dual chamber pacemaker for the past 12 years plus. Received a replacement earlier this spring. Both made by Medtronic. I have the same condition as you, third degree AV heartblock. The dual chamber works very simply. One lead is implanted into the atria and the other in the ventricle. As the heart produces a beat at the sinus node the atria lead senses the beat and records it in the pacemaker’s computer. Then the ventricular lead senses when it beats. If it is within an offset such as 200 milliseconds, then the pacemaker lets the heart’s ventricles beat on their own. If the ventricles do not beat within this offset, then the pacemaker fires and beats them. This happens every second or every hour of every day. This has been going on in my heart for the past 12 years. I am a 90% pacer which means that 90% of the time, the pacemaker fires and beats the ventricles. Further, I have a minimum heart rate of 50 that the pacemaker keeps. If the heart rate produced by the sinus node falls below 50, the pacemaker takes over and fires thus producing a beat in the atria. Then it still senses the ventricles for their corresponding beat. I call this beating on all four cylinders. I have a low natural heart rate and 50 is not the unusual for me. Usually this is all night.

I have also had two ablations. One in 1993 for AV nodal reentry tachycardia (AVNRT). I was left with second degree AV heart block, which eventually progressed to third degree AV heart block and then my first pacemaker (1997). Just recently I developed atrial flutter, which is similar to atrial fibrillation. My electrophysiologist performed the ablation and I am now beating on sinus rhythm again. I feel much much better. I ran a 9:13 mile last night on the treadmill without much difficulty. Not bad for someone who is about to turn 56.

I don’t know much about single lead pacemakers. With third degree AV heart block, the ventricles still beat but at a slow pace. The heart is producing a “life saving” beat. You can live without atria beating but not the ventricles. I would assume that with a lead only in the ventricles, that it senses and produces a beat as necessary to maintain a reasonable heart rate. Talk with your doctor. He or she should explain the single lead in better detail.

Hope this information helps.

Minor addition

by ElectricFrank - 2009-09-24 10:09:41

Smitty did a good job of describing the types of pacers. I would only add one thing. The modern pacemakers have the option of using any of the leads for sensing as well as pacing.

As an example the dual lead device can sense whether an atrial event happens without pacing and if not supply an impulse. In the case of AV block the atrial senses as above and uses the sensed event to time an impulse to the ventricles. The ventricular lead can also sense whether this chamber beats on its own or needs an impulse in the case of a partial block. This lead can also sense a PVC and initiate a sequence to get things back into correct timing.

You can see how complex this gets and why a manufacturer rep with electronic background can usually do a better job of programming. I shudder to think about all the possibilities of the 3 lead bi-ventricular device. Kind of like playing tennis and volley ball at the same time.

frank

Upgrade

by golden_snitch - 2009-09-25 02:09:19

Hi there!

I had a single-lead pacer pacing my right atrium for about nine years. My sinus node was completely ablated in 1999, and so the pacer was taking over what the sinus node normally does. Last year I developed new arrhythmia, needed (and still need) anti-arrhythmic meds which caused heart blocks, and so I had an upgrade to a dual-lead pacemaker that manages the heart block. But I have to say that not everyone who needs anti-arrhythmic meds develops heart blocks. In my case it seems that the slow pathway modulation in my av-node which I had in 2000 has contributed to my going into heart block more easily.

Single-lead atrial pacemakers are not implanted very often but not for the reason that they don't work well. It's rather that a lot cardios think that their patient might somehow need the second lead (ventricular), and so they go ahead and put in a dual-lead just in case. Also has something to do with personal preferences of the cardio. One can argue about that... In Scandinavian countries there are much more single-lead pacer implants, basically in everyone who has sinus node dysfunction but whose av-node is functioning well.

Personally, I think that a single-lead atrial pacer is just perfect as long as you have sinus node dysfunction only. Let the heart do as much work as possible on its own, and don't put leads in veins that are not really needed because they can always cause blockages. Now ,some might say that they have sinus node dysfunction but are nevertheless paced in the ventricle somehow: True, but one can't say for sure - unless the pacer records the heart blocks on a ECG - that this really is because of heart blocks. Some pacers switch to dual-chamber pacing too quickly, and when not really needed. It's because of certain settings and algoritms.

An add to Smitty's point 4.:
There are Cardiac Resynchronisation Therapy (CRT) devices with and without ICD. Both have three leads but one can give a shock in case of VT/VF, the other can't. Most CRT devices have a build in ICD, but there are a few that don't (one is by Medtronic).

Best wishes
Inga

Another add

by golden_snitch - 2009-09-25 03:09:35

Sorry, I have to add something else:
A single-lead pacer pacing the ventricle seems to be good idea when you are in permanent Afib. The Afib would inhibit the atrial lead anyways. During Afib the impulses in the atriums are just too fast for the atrial lead to keep up with. However, it has been reported that people with a ventricular lead only are more likely to get pacemaker syndrom. But I don't know if this is true when you are in Afib. The patients I have read about had heart block and no Afib.

Best wishes!

Another comment

by pete - 2009-09-25 03:09:55

You should be a lot better off if you have an AV node ablation and are about to get a biventricular cardiac resynchronisation pacemaker.

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