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Eur J Cardiothorac Surg 2007;32:685-686. doi:10.1016/j.ejcts.2007.07.002
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved
Letters to the Editor |
a Department of Cardiothoracic Surgery, University Hospital of Rion, Patra, Greece
b Faculty of Life Sciences, Imperial College London, United Kingdom
Received 27 April 2007; accepted 2 July 2007.
* Corresponding author. Address: 2A Butler Road, West Harrow, Middlesex, London HA1 4DR, United Kingdom. Tel.: +44 7864958573; Mob.: 306977762897. (Email: stratisapostolakis{at}yahoo.gr; k.akinosoglou07{at}imperial.ac.uk; karolakinosoglou{at}yahoo.gr).
Key Words: Collateral coronary circulation • Coronary artery disease • Model of collateral coronary circulation • Coronary collateral autoregulation
We went through the perfectly constructed reported article by Verhove et al., with great interest [1]. The authors studied the changes of left internal thoracic artery (LITA) and right internal thoracic artery (RITA) flow which were implanted onto left anterior descending (LAD) and circumflex artery (CX), respectively. This was in relation to clamping and declamping of vein graft, implanted onto completely chronically occluded right coronary artery (RCA). They assumed, that the observed reduced flow of RITA after declamping of vein graft, indicates that only the CX artery offers collaterals to chronically occluded RCA. This explanation, in our opinion, could be considered as arbitrary for the following reasons. Firstly, usually during preoperative study of coronary arteriography, we have noticed the periphery of chronically occluded RCA depicted by collaterals from the LAD. Secondly, according to the literature to date, the visible collateral channels arise either from the contralateral coronary artery or from the ipsilateral one [2,3]. Thirdly, in our opinion, we can consider the coronary circulation as a model of three different ‘zones of demands’ of LAD, of CX and that of RCA. These three ‘zones’ communicate with each other after collateral development depending on their demands of blood, and an ‘interior autoregulation’. Consequently, in their model of patients with three-vessel disease, the ‘LAD zone’ with the highest demands develops collaterals with both ‘CX zone’ of quite less demands, as well as with ‘RCA zone’ of even less demands. In a similar way and in the same model, RCA ‘demands zone’ develops collaterals with the two other ‘zones’, that of LAD and CX. After implantation of LITA and RITA onto the ‘zones’ of LAD and CX, respectively, and before declamping of vein graft, it could be argued that these three ‘zones’ share the sum amount of blood offered by both ITAs blood, according to their demands, and giving priority in our opinion, to the higher demands of the ‘LAD zone’. This hypothesis may be supported by the impressive observation that, in contrary to our expectations, the flow of LITA is low and similar with that of RITA, in 75% of the cases (see Table 2). After declamping of the vein graft, the relative small requirements of ‘zone of RCA’ are reached, whereas both communicating ‘zones’, mainly that of CX and less that of LAD, become free of RCA blood diversion, in different percentage each. Indeed, flow in both arterial grafts is reduced after this manoeuvre: mainly that of RITA (significant reduction), and less that of LITA (in about 50% of cases, but to a non-significant degree), as it is depicted in Table 2. They could have examined this hypothesis, if they had temporarily occluded both LITA and RITA and had measured the respective flow of vein graft for every case. Finally, a possible limitation of the study, concerning the interpretation of changes of flow in LITA and RITA, could be the possible (not referred) use of vasodilators (e.g. nitrates) during measurements, which abolishes the autoregulation of collateral circulation [4].
Footnotes
\#9734; The authors of the original paper [1] were invited to reply to this Letter to the Editor but they did not respond.
References
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