Posted by steve giddings on April 03, 2002 at 18:08:50:
In Reply to: Re: Lone AF, Steady State Exercise, and the Maze Procedure posted by Anders Kingstedt on April 03, 2002 at 13:25:21:
I agree with Paul that the apparent incidence/ prevalence of AF appears to be higher in chronic aerobic exercisers than in the sedentary population, and likely other types of athletes. It is difficult to prove a causal relationship. Folks who like to exercise because they are good at, find it rewarding, etc, may also have a propensity for af. It may be because a larger baseline heart size, greater capacity to enlarge with training, etc but the correlation is there.
The best studies using transesophageal echo to assess atrial function show that >90% have left atrial contraction 6 months post op. Cox last published number was 93%. Left atrial transport is compromised by the incisions encircling the pulmonary veins, which blocks electrical signalling to that portion of the la, about 25% of total left atrial volume. This probably doesn't make a whole lot of difference because the right atrium works normally and so the same amount of blood per stroke is delivered to the left side, and the left side pumps everything delivered to it. Most blood delivery from atrium to ventricle is passive anyway, atrial contraction responsible for about 15-20% of total in young adults. This fraction increases with age, as the heart stiffens, making atrial function more important as we all grow older.
Concerning formal performance studies pre and post op. I don't know of any either. I can tell you my own experience.
I train regularly on a rowing ergometer during the winter. The "erg" measures work output in watts and then converts that value to an etsimated meter/sec or 500 meter split time. Rowers measure their fitness periodically by doing 2000 and 5000 or 6000 meter tests on these things. There are even indoor competitions.
My last 2k erg time at age 51, in 1998 was 6:59.9. I went into AF during the last part of the test, but held my splits to the end. This year, four years later, my best time was 6:49.4. The test correlates reasonably well with VO2 max, maximum aerobic capacity. VO2max is in turn directly dependent on cardiac output. That 10 second difference translates to an 7% increase in absolute power output. The per year handicap generally assigned in the 50-60 year age group is 3 seconds per year, so functionally, I'm in better shape now than prior. My training regimen is pretty much the same.
Summary. The MAZE works, as you all know.