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Ann Thorac Surg 1997;64:502
© 1997 The Society of Thoracic Surgeons
DR PEDRO J. DEL NIDO (Boston, MA): Doctor Karl, this is a very nice presentation of a very difficult problem.
Wouldn't it make more sense to try to close the VSD through the aortic root? You have the two great vessels divided, you have taken the coronary arteries off, and you are looking straight down at the morphologic right ventricle. Do you think this approach is easier and perhaps has a lower incidence of AV block?
The other question I had for you is, you are referring to a relatively small subpopulation of children with L-TGA. Many of these children have LVOTO; that is, subpulmonary obstruction. What is your approach to these children, and do you advocate the anatomic repair, which is to divert the LV flow through the VSD to the aorta?
DR KARL: Thank you. I think that the suggestion about the approach to the VSD is a good one, and the experience with the Ilbawi operation supports the concept. I believe that the incidence of heart block is much lower when the VSD is closed from the anatomic right side of the septum, which one could do in this type of repair. We will certainly explore this approach in future cases.
Regarding the anatomic correction for patients with LVOTO, I believe that if the patient is anatomically suitable, it is definitely the way to go. However, there is a large load of prosthetic material, and there may be problems with a conduit that is very close to the midline and at risk in subsequent revisional operations. Failing suitability for anatomic correction, we would still prefer a Fontan operation in this group over classic septation strategies that leave the right ventricle, and especially the structurally abnormal tricuspid valve, in the systemic circuit.
DR DEL NIDO: But you are dealing in most of those patients with subpulmonary obstruction. Your conduit is on the morphologic right ventricle.
DR KARL: That is correct.
DR DEL NIDO: It is actually way over on the left side, so it is unlikely to cause you problems. There are other anatomic considerations such as getting the conduit back posteriorly to the pulmonary artery. However isn't this a better option than doing a Fontan procedure where you are leaving the patient essentially with one ventricle and you still have the AV valve insufficiency problem?
DR KARL: Yes. I was referring only to the location of the ventricular septal defect in directing patients to a Fontan versus an Ilbawi operation strategy.
And regarding your comments about the position of the conduit, this will vary according to the position of the apex and the atrial situs.
DR CONSTANTINE MAVROUDIS (Chicago, IL): I am curious about some patients with corrected transposition on whom one might consider a Fontan operation. We have had particular experience with 2 patients with corrected transposition, VSD, and pulmonary stenosis. We closed the VSD, opened the pulmonary valve as much as possible, and constructed an in-series bidirectional Glenn. The bidirectional Glenn unloaded the volume that was presented to the left ventricle (pulmonic ventricle) in an effort to lower the left ventricular pressure. So far both of these patients are doing well. What do you think of this idea?
DR KARL: I do not have any personal experience with this approach, but I think that it has some merit. One problem is that you still run a significant risk of heart block, but, of course, we face that problem in the double switch as well. The main weakness is that this approach does not deal with the problem of a discordant ventriculoarterial connection, and some of the long-term difficulties that you would run into with classic septation will still apply in this situation. You have only addressed the problem of how to have less blood flowing through a stenotic pulmonary artery. I do not think that it will be as good a solution as an anatomic repair strategy. Perhaps it is a better solution than a Fontan operation; I do not know.
DR BABULAL SETHIA (Birmingham, England): Doctor Karl, I congratulate you on your experience. We have had a very similar experience in 13 patients so far. I would like to ask you two questions.
You alluded in your presentation to the importance of the coronary artery anatomy. Have you actually found any coronary artery anatomy that you thought could not be switched and, therefore, excluded patients from this protocol?
Second, what do you think is the optimal age at which this strategy should be followed, in particular, the relation to a very young age at the time of presentation? We certainly have tended to defer a double-switch procedure until, let's say, a year to 18 months of age as opposed to doing it in the very, very young age group.
DR KARL: Thanks for your comments. Regarding the question about coronary anatomy, 2 patients in our series had a single coronary artery from a nonfacing sinus. One of these patients actually required an interposition graft to achieve coronary translocation without tension. This patient required reoperation to revise the graft 5 years after the original operation. We have also noticed this variety of coronary anatomy in patients undergoing other types of operations for discordant TGA, and I have a feeling that it is more common than is generally appreciated.
Regarding timing of operation, I think it is quite reasonable to defer this procedure to about a year of age, when it is technically much easier to perform the Senning operation. The problem is that one is often faced with a sick newborn who has no banding option due to the severity of the right ventricular dysfunction and tricuspid insufficiency. We have performed the double switch in 2 newborns. One died shortly after operation. I do not think it is a fantastic procedure for newborns, unlike arterial switch for concordant TGA.
Related Article
Ann. Thorac. Surg. 1997 64: 495-502.
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