Tetralogy of Fallot: what have we actually learned?

‘We have learned nothing after fifteen thousand years’.

Pablo Picasso (after viewing Lascaux Caves paintings, Dordogne, France)

Tertalogy of Fallot (TOF) is our prototype, with, 10 000 citations currently available in PubMed; yet, we continue to discuss it incessantly. Our primary strategies have to some extent been redefined by information regarding late outcomes, such as that presented in the current excellent and comprehensive report from Denmark [1]. Although the major findings have also been noted by other surgical teams, the detailed analysis is useful and seems to have been facilitated by the socially advanced nature of the Danish healthcare system.

The best operative strategy for TOF is still debateable. Most paediatric cardiac surgeons can claim expertise in TOF repair and will strongly defend their own technique so long as the operative morbidity and mortality remain low. This is understandable, as without a consistently good early outcome, long-term issues do assume secondary importance. However, the ECHSA database for the last 20 years shows a 2% and 9.6% hospital mortality, respectively, for infant and neonatal TOF repair (with transannular patch). This suggests that case selection may be imperfect and that early postoperative problems have not actually been eliminated.

Beyond that, many (but certainly not all) of the late issues with TOF relate to a poorly guarded pulmonary orifice, which may be the result of a simple transannular patch reconstruction of confluent right ventricular and pulmonary arterial incisions. Some of the damage may occur early in the postoperative period, followed by a levelling of the curve, and a later accelerated phase. This information has been available for decades; yet, worldwide, the basic Lillehei technique with transannular patch remains the prevalent repair strategy for TOF. We have thus created a new disease entity with its own prevalence, physiology and ‘unnatural’ history, as documented in the Danish study and elsewhere.

Most surgeons agree that the limitation of PI would be desirable, but at what cost? Intentionally leaving some degree of RVOTO to prevent PI is at best unpredictable and often not well accepted by cardiologists and parents, especially if early- or medium-term reoperation is a possibility.

There are a number of ‘valve-sparing’ procedures now available for TOF, but the results seem somewhat disappointing and difficult to reproduce (as in this study). It would be fair to say that there are many patients who are not good candidates for complete native valve preservation, usually due to annular size limitations. Understanding the role of ‘valve-sparing’ procedures is further clouded by the extreme variations in anatomy, preferred age at elective operation, coexisting cardiac and non-cardiac abnormalities and other factors.

Timing of elective operation is also controversial, especially for neonates. Most TOF patients do not actually require neonatal surgery, and in any case, ductal dependency can now be effectively dealt with using various stenting techniques. The contemporary (unresolved) argument is not, therefore, ‘primary repair versus shunt’ but rather ‘neonatal versus non-neonatal elective primary repair’. Most large and experienced centres have settled on elective primary repair around 3 months of age, but as suggested in the present study, there may be consequences in terms of the need for reoperations. There are probably more exceptions than rules. For example, in some parts of the world, patients typically do not even present to a surgical team until well beyond infancy.

Our own experience suggests that for patients of any age, valve reconstruction strategies (‘competence preserving’, but not valve preserving in the strict anatomic sense) are useful when complete valve preservation is not possible or advisable (a large proportion of our cases). The technique involves our standard transatrial-transpulmonary approach, with enlargement (pericardial or PTFE) of the most anterior pulmonary valve leaflet (Sung repair) [2]. The transannular patch is then effectively supra-valvular. This typically results in a competent pulmonary valve with good relief of RVOTO, which may be helpful in the short and longer term. Because a proportion of such cases will still develop PI at some point, we cannot say that this improved technique addresses all of the problems associated with TOF in the longer term. However, centres in Asia, Australia and India (and to a lesser extent in the USA) have embraced the Sung technique with enthusiasm [3–6]. We think that this option, which is reproducible and easy to learn and teach, is worth exploring for suitable patients to improve early- and mid-term outcomes.

There is of course much more to learn and say, but comparative prospective studies or RCTs regarding TOF surgical strategies are unavailable and typically would be extremely difficult to organize. For this reason, it seems likely that we will continue to rely primarily on retrospective analysis, including single-centre and regional/national reports. The present thoughtful Danish study sets a standard for what that should look like.

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