Dr. Glenn Barnhart discusses the evolution of the Cox Maze procedure with respect to their respective lesions sets and theory.
For the hearing impaired members of the AFibSurgeons.org community, we have provided a written transcript below:
Glenn Barnhart: I’m going to target a couple of specific areas that I think are important to understand, for all of us to understand, as surgeons, in trying to avoid some of the pitfalls of AF surgery. The first thing I want to talk about is the atrial septum.
I have a good understanding of the atrial septum because this really relates a lot to some of the misinformation, honestly, that’s been put out there regarding heart block and the need for a pacemaker. If we look at the Triangle of Koch, which is this area here, it is an area that’s bordered by the tricuspid valve and the tendon of Todaro. Of course, the AC node lives inside that, along with the His bundle right in here. The triangle is completed by the line that runs from this point down to here, and the coronary sinus ostium lives inside there.
AV node is there, His bundle, as we have talked about is right there. It’s important to realize, of course, that that’s in the atrial septum and that’s the tendon of Todaro. In the evolution of the Maze procedure, this is a diagram of the Maze I procedure, and specifically, this is looking at the atrial septum lesion that was placed there by Jimmy Cox during the Maze I procedure. You can see that the septal lesion was well outside of the region of the AV node, if placed in the proper location. It really was impossible to cause heart block, if performed properly.
The Maze II procedure, that line was moved a bit more posteriorly, as you can see, and the upper end of the septal lesion terminated at the SVC. The Maze III procedure took that line even further back here, and it was really posterior to the orifice before. Remember, the Maze II was up here and Maze III took it back here. With the Maze IV procedure, it was taken out completely. It really is impossible for the Maze IV procedure to have any heart block, as you can see. Heart block occurs, of course because of damage to the AV node or the His bundle, and you’re nowhere near the AV node or His bundle on a Maze IV procedure.
If we look at the Maze procedure, and all these circles here and lines that you see here are the macro re-entrant circuits that are associated with the Maze IV procedure, and obviously they are numerous. That’s why there are so many lesion sets to address all of those issues. When you do the Maze procedure, and a Cox IV Maze procedure specifically, this is what you end up with, so that all of those lesions are – all those macro entrant circuits are gone. You can see here the AV node or SA node that lives up in here, can still conduct to the mass of atrial tissue, but this area here is no longer activated. Of course, what we’re trying to do is eliminate the pulmonary vein sites, which we know about 85-90% of all activity of atrial fibrillation comes from the pulmonary veins. This is what we’re keeping intact.
The other thing I’d like to say at this point is when you start doing a lot of a-fib surgery, you have to start thinking about the atrial mass as one chamber, electrophysiologically. It’s not really two chambers, it’s one chamber. Actually, Leonardo DaVinci taught us that 500 years ago. He talked about the atrial chambers contracting together and seeming to be one, knowing that they were two. It is important that you think about it that way because you will begin to appreciate more and more the importance of having the right-sided lesions along with the left-side lesions.
There are many patterns to the Maze procedure, as I’ve talked about, but only one principle. The Maze procedure really should not be used as a generic label for anything done in the atrium. Unfortunately, today that still goes on. Somebody does something in the atrium, they call it a Maze procedure, it is not the case. This is an example, so-called Wolf “Mini Maze”. This is not a Maze procedure. Basically, it’s a pulmonary vein isolation with a clip on the left atrial appendage. “Left-Sided Maze”, this is not a Maze procedure. People call it a Maze procedure, and I tend to do that myself sometimes, but technically, it really is not a Maze procedure because you’re not completing the “Maze” that I’ve shown you in a few slides earlier, to interrupt all macro re-entrant circuits. That is not a Maze procedure.
The “Dallas Lesion Set” – Left Side Only. This was a way of trying to prevent post-operative mitral flutter that we’re going to talk about in a few minutes, but it really has nothing to do with the Maze concept.