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J Thorac Cardiovasc Surg 2008;135:715-716
© 2008 The American Association for Thoracic Surgery
Letter to the Editor |
a Department of Cardiac Surgery, University of Heidelberg, Heidelberg, Germany
b Department of Thoracic and Cardiovascular Surgery, Hannover Medical School, Hannover, Germany
We are grateful for the opportunity to respond to the letter by Kazui and associates. We appreciate the comments on our recent article reporting moderate hypothermic lower body circulatory arrest with selective cerebral perfusion.1
Their comments can be summarized as follows: (1) concern with the safety of moderate hypothermic lower body circulatory arrest with selective cerebral perfusion in regard to protection of other organs, especially the spinal cord; (2) concern about the possibility of left vertebrobasilar ischemia in patients with 2-vessel selective cerebral perfusion; (3) concern that the circulatory arrest time might actually be shorter with the separated graft technique of arch vessel reconstruction compared with the island technique; (4) need for a bail-out technique when the arrest time becomes unexpectedly long; (5) concern about the reason for the high rate of re-exploration for bleeding in our series; and (6) concern that our strategy might be dangerous in complicated cases, such as acute aortic dissection type A, where hypothermic circulatory arrest duration is expected to be longer than 60 minutes.
First, this study was specially designed to answer several of these questions. No differences in complication rates and biologic parameters regarding specific organ protection were observed in the entire and matched study cohort in our study. The issue of paraplegia was also raised during the review process for this article. There was no difference of occurrence of paraplegia in the entire and matched study cohort or in the subanalysis in patients with acute aortic dissection type A. Indeed, the paraplegia rate was 18.2% in the moderate hypothermic arrest group and 0% in the deep hypothermic arrest group, and the P value was .07 in the subanalysis of patients with hypothermic circulatory arrest of longer than 60 minutes. This value of 18.2% appear to be very high, but actually only 2 occurrences of this complication were counted in this subanalysis (0/16 in deep and 2/11 in moderate hypothermic arrest), and we hesitate to conclude anything based on this small number of occurrences.
Second, in our series 23 (6.1%) patients had strokes, but a specific left vertebrobasilar ischemia was detected in no patients. We have no experience with 3-vessel perfusion, including the left subclavian artery, and we have not performed preoperative cerebral angiography/magnetic resonance angiography on a routine basis to examine intracranial arterial communication. However, we consider from our own experience and reports from other institutions2,3 that 2-vessel perfusion represents a safe method.
Third, many diverse methods for arch reconstruction have been devised,4,5 but most surgeons stitch according to their own favorite technique, and usually they use only one method. Therefore it is difficult to say which method is faster. However, the question is beyond the focus of our study. As a conclusion of our article, our method should not be used for patients who require complex total arch replacement expected to require more than 60 minutes of circulatory arrest because our findings did not support that this method has no time limit. If circulatory arrest time would be less than 60 minutes with the separated graft technique in your institute, it appears that this higher-temperature strategy might not be a bad alternative for total arch repair.
Fourth, in our series 85% of patients with circulatory arrest for longer than 60 minutes received total arch replacement. We perform total arch replacement only in selected patients (23% in our study), but if needed, en bloc anastomosis is preferred. Therefore it is difficult to bail out in an unexpected situation requiring prolonged circulatory arrest. However, proper planning helps to avoid this situation.
Fifth, the reason for our relatively high re-exploration rate might be the high number of patients who received aortic root replacement (composite graft according to Bentall or aortic valve reconstruction according to David). Although there have been no data about it, we believe from our daily clinical observation that the combination of those complex aortic root procedures and hypothermic circulatory arrest results in a greater tendency toward bleeding as a result of a coagulation disorder plus long suture lines. In addition, the re-exploration rate for bleeding of less than 2% in arch surgery is surprisingly good, and we would like to congratulate you on your excellent results.
Sixth, as we described in our article, our data did not support that moderate hypothermic lower body arrest has no time limit, and it remains unclear whether it is safe beyond 60 minutes. However, our findings and a similar report recently published6 suggest that deep (<25°C) hypothermic circulatory arrest is not required in all patients.
References
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