Ann Thorac Surg 2006;81:981
© 2006 The Society of Thoracic Surgeons
Original article: Cardiovascular
Invited commentary
Andrew D. Cochrane, FRACS
Department of Cardiac Surgery, Melbourne Royal Children's Hospital, Flemington Rd, Parkville, Melbourne, Victoria, 3052 Australia
(Email: andrew.cochrane{at}rch.org.au).
This report is an interesting and potentially important case series showing that the period of cardioplegic arrest during the Norwood operation can be avoided, and that avoidance of this period may have important beneficial effects on survival [1]. The authors report a series of 26 infants, 13 in each group, with a mortality of 39% in the cardioplegic group and no deaths in the group of infants who received continuous myocardial perfusion.
However, before widespread application of this technique, a number of potential limitations of this report require consideration.
First, the mortality in the group receiving conventional surgery is high (39%), and this is significantly higher than the reported mortality in many large pediatric centers performing reasonable numbers of the Norwood operation still using cardioplegic arrest, in which a mortality of 20% (or even lower) would be regarded as acceptable.
Second, the numbers are small, and although statistical significance is achieved, only small changes in the numbers would be needed for that effect to disappear. With only one death in the continuous perfusion group, statistical significance would be lost. Similarly if the mortality in the cardioplegic group were reduced to 25%, the difference would disappear. This indicates that the results are not particularly robust.
Third, this is a retrospective, observational study, with the technique performed in each case based on surgical preference, and not on a prospective randomized study. Therefore a small retrospective study is open to several potential sources of error and is well documented in the literature (ie, patient selection bias resulting in unequal groups, the effect of different surgeons with different preferences and skills, and the effect of the surgical era if there have been other improvements in surgical, anesthetic, and intensive care experience, and the quality of care over the course of time). Indeed there is a difference in the two groups of infants documented by the researchers, because preoperative inotropes were found to be a risk factor, and the patients with that risk factor belonged to the cardioplegic group with the higher mortality. Many small observational studies that suggest a large benefit from a new therapy have been proven incorrect when an adequately powered and prospective randomized controlled trial has been performed.
Although the authors may be proven correct in time, and this technique does have its theoretical advantages, this interesting report should not result in widespread changes in policy but should act to stimulate proper, well organized, and larger randomized studies of this technique so that pediatric cardiothoracic surgeons can join our colleagues in adult cardiac surgery in the development of a proper evidence base to our speciality.
 |
References
|
|---|
- Photiadis J, Asfour B, Sinzobahamvya N. Improved hemodynamics and outcome after modified Norwood operation on the beating heart Ann Thorac Surg 2006;81:976-981.[Abstract/Free Full Text]
Top
References