Dr Charles B. Huddleston (St Louis, Mo). We have 2 ways to do the same thing: lateral tunnel versus the extracardiac conduit Fontan. They are both relatively simple operations, but 1 does not require any obligatory time of myocardial ischemia, the other does, but again, they both accomplish the same thing. It's a great topic for discussion in both articles and national meetings. In fact, it's so great a topic that it has already been discussed and presented at a number of meetings by several single centers, and it has also been the topic of a couple of meta-analyses of all those single center studies to look at this topic. I would summarize those previous studies as showing really very minimal difference between the 2 techniques despite the purported advantages of the extracardiac Fontan technique.
Your study that shows perhaps a survival advantage of the lateral tunnel is different. One would then ponder why that is. You didn't get into it in your presentation, but having the advantage of looking at the manuscript, it all hinges on 5 deaths in 183 patients who underwent the extracardiac conduit Fontan, and I suggest that those 5 deaths be looked at very carefully to see what led to those deaths. In the manuscript, it describes that 4 of the 5 were due to thromboembolic problems. That, in my experience, has been an unusual cause of death after Fontan operation, and I wonder if you could elaborate on what those thromboembolic complications were.
If anything, I would be a bit more concerned about thromboembolic problems in the lateral tunnel technique, because in that particular type of operation there is all this foreign material that is not only associated with a baffle, but also has an obligatory association with the pulmonary venous atrium and therefore could lead to systemic emboli. At any rate, do you have any comment about that?
Dr Viktoria H. M. Weixler (Boston, MA). Thank you very much for those interesting insights and comments on this clearly very controversial topic. Concerning your first question regarding the differences of our results compared with the results of big meta-analyses; for example, we think that there are many different factors playing into this. First of all, we believe that the comfort level of each surgeon plays a huge role. At our institution we have performed the lateral tunnel for many years with excellent survival rates, so our comfort level toward the lateral tunnel is very high. Also, we think that in most of the meta-analyses, you can see that the variability for the lateral tunnel is rather high compared with the extracardiac conduit. We see that the extracardiac conduit is not done with that much variability versus the lateral tunnel.
As to your question concerning the thromboembolism, we looked at those 5 early deaths, of course, but it's very difficult to actually find 1 cause of death. We found several associations/factors that may have resulted in death in these patients that I describe in the manuscript. So we found that actually there was a high rate of thromboembolism in the early deaths of the extracardiac conduit group. They were described as mainly tunnel thrombosis. We also found a higher proportion of early fenestration closures in the extracardiac conduit group, which can also be related to those early deaths. To define 1 leading cause of death in all these 5 early deceased patients is very difficult in the end.
Dr Huddleston. Along those lines, again focusing on this thromboembolic problem, what is the anticoagulation strategy after the Fontan operation at Boston Children's Hospital?
Dr Weixler. There was aspirin used for pretty much all patients in the lateral tunnel group and also the majority of the extracardiac conduit patients. A small group of extracardiac conduit patients were taking warfarin as far as I can recall but. maybe Dr Emani can give more insight on that.
Dr Sitaram M. Emani (Boston, MA). For the most part, we use aspirin in all patients. A few surgeons in this series used warfarin, but it is actually uncommon; I think 1 strategy used was a prescription anticoagulant for a couple of months and then transition to aspirin. Most patients in both groups were just taking aspirin.
Dr Huddleston. This fenestration issue, a lot of people have looked at the effect of fenestrations on survival after the Fontan, and again, it's a little controversial as to whether fenestrations are helpful in mortality, not only that, but also chest tube drainage time and all that sort of thing. In general, the sense is that it does help with that, but I have certainly been at meetings where that was a topic of debate.
The other thing that is of course different about the groups is the era, the majority of the lateral tunnel Fontan procedures done in the early part of this century and the extracardiac Fontan procedures done basically during the past decade. The other thing that has changed in the practice of the management of congenital heart disease during that same period is a shift, at least at some centers, away from the Blalock-Taussig shunt as the initial source of pulmonary blood flow with the Norwood procedure to the Sano shunt. I have had concerns about pulmonary arterial growth and development with that type of shunt in these neonates relative to the Blalock-Taussig shunt, which I think is better in that regard.
Do you have any notion about how that might have influenced some of these results?
Dr Weixler. What we did was we took the era effect into account, we adjusted for that in the multivariate Cox regression analysis, and there were no differences found. The surgical technique still demonstrated to be an independent risk factor for mortality. It did not change the results. We have to look into differences between previously performed Blalock-Taussig shunt versus Sano-Shunt. As for now, I can't give you an appropriate answer to this.
Dr Huddleston. The deadline for the submission of the abstracts for this meeting was sometime back in the early fall, late summer. So the surgeons at Boston Children's Hospital have had the advantage of seeing the results of this before this meeting. I presume that over the past 9 months no extracardiac conduit Fontans have been performed by the esteemed surgeons listed in this work and that only lateral tunnel Fontan procedures have been performed.
Dr Weixler. It really depends on the patient population. If you take a closer look at our results, I think that we had a slightly younger patient population compared with what is described in literature, and we still showed excellent results for young patients who needed a fenestration undergoing a lateral tunnel technique procedure. I believe I would recommend a young patient who requires a Fontan procedure with a fenestration to undergo a lateral tunnel technique and for older patients who don't necessarily need a fenestration to maybe continue using the extracardiac conduit technique.
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Published online: January 13, 2020
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