My medtronic cardiac pacemaker, which is to be replaced soon,  was
implanted for dual-chamber pacing to combat IHSS with left ventricular
outflow obstruction. It has an atrial electrode with faulty
insulation. Since sleeving it did not repair it to the extent where
less than 6 volts could cause the atrium to capture - we decided to
virtually shut it off by lowering the pacemaker heart rate to 40
beats/minute so that the natural rate (50-60) would cause the P-wave
to occur before the atrial electrode would fire.

This did not work too well at first, and I felt often dizzy. My
explanation (not shared by the cardiologist) was that the leakage
through the insulation was so severe that too much charge from the
P-vawe was dissipated before reaching the pacemaker (set at 700
microvolt sensitivity). As a result, the inadeqate charge left, was
not enough to make the pacemaker realize that the P-vawe had already
occurred. As a result, the pacemaker started the a-v interval later,
at the time when the pacemaker heart rate was supposed to trigger the
atrial electrode. The a-v interval having started late, ended late,
and caused the ventricular electrode to fire at the wrong time thus
interfering with the heart synchrony and making me feel often dizzy.

After much persuation my cardiologist reluctantly lowered the
sensitivity from 700 to 500 microvolts, and I felt much better after
that for a year or two.

Recently I felt worse again and this may be due either to a Lupron
(antitestosterone) injection given for prostate cancer, or further
deterioration of the electrode insulation, or to plain aging.

Being age 77 I would like to get a working atrial electrode at the
time the pacemaker is replaced, since not having it at this age might
be more dangerous than the danger involved at pulling it out. The
surgeon, Dr. Mark G. Midei, claims less than 1% mortality in his
experience pulling electrodes out. But the literature (for instance: Z
Kardiol  2001 Aug;90(8):550-6) reports, among others, one death in 24.
Alternatively, instead of pulling out, the faulty electrode could be
capped and left in place.

I am told that 3 and more electrodes have room in the subclavian vein;
but is this also true for an electrode who is sleeved?

I would appreciate if one of your researchers could state an opinion
as to wheter capping or pulling out the faulty electrode would be
preferrable. Iwould also like if you could answer the following
questions

1. Will electricity from the P-vawe be leaked from the faulty capped
electode in sufficient amount to deprive the new atrial electrode of
the charge needed to inform the pacemaker that the P-vawe has
occurred? (The type of malfunction described in the second paragraph)

2 What is the inside diameter of the subclavian vein?

3. What is the outer diameter of a sleeved electrode?

4. Do you have more recent literature sources concerning the mortality
rate of pulling out electrodes?

5. What are the sensitivities of the sensing voltage of the pacemaker
you anticipae will replace my current one the battery of which is
almost depleted?

6. Which electrode is least prone to insulation problems?

7. Any other information that you think might be helpful

The information on my recent and old pacemaker cards (probably but not
certainly accurate) is:

model     serial      date implanted
7962IB    PDD103283H  23 APR 1998
5524M53   LAV006273V  04 NOV 1993
6962      Unknown     17 DEC 1980