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Eur J Cardiothorac Surg 2005;27:932-933
© 2005 Elsevier Science NL
Letter to the Editor |
Cardiac Unit, Great Ormond Street Hospital, Great Ormond Street, London WC1N 3JH, UK
Received 3 December 2004; accepted 24 January 2005.
* Corresponding author. Tel.: +44 207 813 8853; fax: +44 207 813 2395. (E-mail: m.kanani{at}ich.ucl.ac.uk).
Key Words: Congenital heart disease • Valve disease • Atrioventricular septal defect • Cardiac morphology
We read with interest the article published by Al-Hay and colleagues [1]. They report commendable results for the repair of partial AVSD with separate orifices over 21 years. The conclusion that the hypothesis that the ‘cleft’ or zone of apposition (ZoA) in the left atrioventricular (AV) valve should always be closed, is not proven. We think they go far too far in making their conclusion. Further, we must challenge some of the observations made in the light of our own observations and other's experiences of the management of the left AV valve in partial AVSD.
The design of their study cannot allow them to ‘test a hypothesis’. The study is retrospective and observational, with no randomisation or predefined primary measures of outcome. The study groups they report are unequal and not contemporaneous. One could, just as reasonably, argue that any difference could have occurred by chance.
One may also reasonably conclude that those in whom the ZoA was left open were also those in whom the surgeon, at the time, felt had the least dysplastic and more morphologically robust valve. This is an intangible judgement that cannot be measured retrospectively, but may confound any subsequent conclusions drawn about the outcome.
Time and experience are showing that the ZoA between the bridging leaflets is not, and cannot, be managed as a simple commisure, and that the left AV valve falls morphologically short of the ‘gold-standards’ set by its mitral counterpart. We have observed, in morphological specimens in the archives of specimens held at Great Ormond Street, Pittsburgh and Boston museums (report in preparation [2]), that the left AV valve in atrioventricular septal defects is deficient in terms of coaptation of the leaflets and sub-valvar cordal support, with the morphology of the left AV valve in the variants with separate orifices, the very subject of the report by Al-Hay and colleagues [1], lying at the most extreme and adverse end of this sub-valvar deficiency.
The authors describe the ‘cleft’ in the LAVV as a septal commissure. It is not [3]. Morphologically, the ends of the zone of apposition between the two leaflets of the mitral valve, the so-called "commissures", have an unmistakably characteristic arrangement of support from a single fan-shaped cord that arises from the apex of the supporting papillary muscle. The ZoA in AVSD always lacks this fundamental arrangement. As seen most often in the defect with separate orifices, it is completely unsupported at its septal extent. Why manage this zone as commisure by leaving it unclosed if it does not meet the basic morphologic standards of the end of the zone of apposition between the two leaflets of the mistral valve? Other teams have done so, only to find that long-term competence of the valve is compromised, even if initially it proves to be competent.
Furthermore, the authors justify their practise by comparing it to the tri-leaflet repair proposed by Carpentier, in which the ZoA was not closed. It needs to be understood that Carpentier did not simply leave the zone open, but executed a whole system of integrated repairs requiring extensive additional surgery to the leaflets, annular attachments, cords and papillary muscles [4].
Evidence in medicine is rarely absolute, requiring testimony from different sources over a lengthy period. We believe that the balance of probabilities, given the results of others' and our own observations, suggests that the zone should be closed, even in valves which seem to be potentially competent. The data presented in the study from Al-Hay and colleagues [1], at best adds only subsidiary evidence. We agree that there remains controversy, and the paper from Al-Hay and colleagues [1] supports that contention. Formally to test the hypothesis that the ZoA should always be closed, however, requires a prospective randomised study with fixed criteria for inclusion and outcomes.
References
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