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Letters to the Editor |
a Cardiac Morphology Unit, Imperial College London, National Heart & Lung Institute, London, UK
b Department of Cardio-Thoracic Surgery, Royal Brompton and Harefield NHS Trust, London, UK
c Department of Cardiovascular Surgery, National Cardiovascular Center, Osaka, Japan
Received 17 January 2008; accepted 21 January 2008.
* Corresponding author. Address: Cardiovascular Surgery Department, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. Tel.: +81 6 6833 5012; fax: +81 6 6872 7486. (Email: yagihara{at}hsp.ncvc.go.jp).
Key Words: Fontan operation • Pulmonary arterial size • Nakata index • Lower lobe index
We greatly appreciate the comments by Ovroutski and Alexi-Meskishvili [1] concerning our article [2]. It should be worth noting that the lower lobe index (LLI) of the pulmonary artery (PA), first introduced by Dr Reddy et al. [3], would be more informative than the PA index in the context of a staged Fontan completion because the lower lobe is beyond the surgeon's reach and hence has fewer confounding factors. This was particularly true in the days before advances in catheter intervention that nowadays allow deployment even beyond that level. Anyway, our article is not about which index is more superior to another. Regardless of the type of evaluation methods, the vital issue is how reasonably any given method represents functional efficacy of the whole PA vasculature and how pertinently it predicts the Fontan circulation. Any single morphologic index for PA arborization would not be perfectly representative. That is why clinicians need to consider not only PA size but also other parameters such as PA pressure and pulmonary resistance. In addition, the conventional indices namely the PA index (Nakata index) or the McGoon ratio still seem to remain widely accepted in view of their clinical relevance, utility, and accumulated knowledge in the literature. No alternative indicators for pulmonary vasculature including LLI or pulmonary vein index [4] have replaced the conventional ones. Data values obtained by the conventional methods cannot be translated into the newer formats and, strictly, cannot be compared.
Apart from differences in methodology, the main message in our article [2] is that the small size at a given portion of PA tree itself should not be an absolute contraindication of the Fontan procedure. When a patient possesses favorable conditions for achieving the Fontan circulation (apart from a small PA index), we would not preclude the patient from completion of the Fontan procedure. Furthermore, we have observed a tendency towards a decrease in PA size after the establishment of the Fontan circulation expressed in the format of PA index. We are interested in this tendency as it contrasts with the natural increase in the anticipated normal PA index according to body surface area. We predict that a similar tendency would be the case if alternative indices are applied, as they would reflect the decreased amount of passing blood flow (low cardiac output) and/or non-pulsatile (pumping-chamber-less) PA stream following the Fontan procedure.
References
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