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Address for reprints: David Barron, MD, FRCS(CT), Division of Cardiovascular Surgery, The Labatt Family Heart Centre, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario M5G 1X8 Canada.
Despite the extracardiac conduit (ECC) having become the most widely practiced technique, the lateral tunnel (LT) is still commonly used. We are now faced with a growing list of large, single-institution studies and registry reports that seem to provide contradictory evidence regarding which is preferable. A recent study from Boston Children's Hospital has fueled the debate, suggesting that the LT may offer better outcomes despite the global trend toward the ECC.
is a welcome attempt to appraise the available literature to try and give us a final answer. The wealth of data look ripe for a detailed meta-analysis, but we acknowledge that it is not that simple. Indeed, it is nearly impossible to adjust for the myriad variables and missing data that confound so many of the published studies. Even more importantly, the exact pre-Fontan hemodynamic parameters vary from study to study. Data are frequently incomplete and an intrinsic confounding era effect is often present, considering the earlier development of an LT. All of these make the construction of a meaningful meta-analysis difficult, as previous authors have found.
Knowing the problems of the failing Fontan, it makes good sense to completely exclude the atria from the Fontan circuit, thus avoiding the atrial distension that can be a prequel to atrial arrhythmia and thrombosis. Daley and d'Udekem's analysis
does indeed suggest that ECC may reduce these risks, but that an appropriately sized conduit must be chosen (influenced by age at Fontan). Conversely, incorporation of the right atrium into the Fontan pathway does allow some distensibility and venous capacitance, which may explain why the LT is associated with less and shorter duration of pleural drainage.
The truth seems to be that both provide extremely effective Fontan circulations with nearly entirely equivalent outcomes. In a Fontan physiology, good ventricular function and low pulmonary vascular resistance pretty much trump anything and are likely to be far more important in dictating outcomes than the exact type of the Fontan we choose.
The roles of fenestrations and anticoagulation regimens may also have much more relevance than LT versus ECC.
We can be reassured that both LT and ECC have excellent outcomes and, to some extent, we are free to choose what we are most comfortable with. The authors suggest a randomized clinical trial (always the ideal solution) but the reality is that there may be little appetite for this given that outcomes with both are so good. It may be that new large registries, such as the Australia and New Zealand Fontan Registry, may give us the answer.
Given the efficacy of both techniques, future interest is likely to be more focused on providing augmentation for the existing Fontan circulations, whether as mechanical or bioassisted, temporary or permanent systems. Which is better, LT or ECC? Final answer: We don't know yet (Figure 1).
Disclosures: The authors reported no conflicts of interest.
The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest.
The most widely adopted variations of the Fontan procedure are the extracardiac conduit (ECC) and the lateral tunnel (LT). Over the last decade, there seemed to have been a shift in our practice, with the majority of the Fontan operations being the ECC, on the premise of the simplicity of this procedure and the expectation that it can better prevent the late occurrence of arrhythmias. A recent article in the Journal by a team from Boston demonstrated that in their hands, the ECC was associated with worse early outcomes compared with the LT.