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Eur J Cardiothorac Surg 2005;28:366-367
© 2005 Elsevier Science NL
Letter to the Editor |
a Experimental Heart Surgery, University Clinic, Domagkstrasse 11, 48149 Muenster, Germany
b Cardiac Unit, Institute of Child Health, University College, 30 Guilford Street, London WC1N 1EH, UK
Received 21 April 2005; accepted 22 April 2005.
* Corresponding author. Tel.: +49 251 83 56256; fax: +49 251 83 56257. (Email: redmann{at}uni-muenster.de; r.anderson{at}ich.ucl.ac.uk).
Key Words: Myocardial structure • Inhomogeneities • Tertiary structure
It is our pleasure to respond to the letter from Criscione, Rodriguez and Miller [1], since it brings a touch of sanity and reality to the ongoing saga of the ‘ventricular band’ [2–5]. Our purpose in submitting our review [3] to the Journal was to bring the anatomic shortcomings of the concept [2] to the attention of your readers. We considered this important, since the supporters of the concept seemed intent on drawing surgical inferences from these observations [2]. As pointed out by Criscione and his colleagues [1], this is likely to be counter-productive. Criscione and his associates [1] also make pertinent reference to the aphorism coined by Mencken—"For every problem there is one solution that is simple, neat, and wrong". They suggest that ‘incomplete’ would be more appropriate when considering the purported myocardial band. As they show in their own letter, nonetheless, this would be gilding the lily, since the anatomical concept of discrete and reproducible fascicles of myocardium existing within the ventricular mass is unequivocally wrong.
The evidence pointing to the impossibility faced by any who seek to demonstrate such a tertiary pattern within the myocardial mass is shown in Fig. 2 of the latest submission by Torrent-Guasp and his supporters [4]. The top right-hand panel of this illustration shows ‘dissection cleavage planes’. As the figure also shows, these planes are multiple. Indeed, the specific plane chosen would be entirely at the whim of the dissector. More striking, any dissector reproducing Torrent-Guasp's preparation, instantly realises that the procedure violates the thus defined cleavage plane overtly at five prominent sites, and then continuously lacerates it while severing the spatially interwoven syncytium. As is stated by Criscione and his colleagues [1]: "the helical myocardial fibers within the ventricular mass are arranged in syncytial fashion and assemble into transmural branching laminar sheets". This is entirely in keeping with our own understanding of the structure of the ventricular walls.
With regard to the microsonometric data cited by Buckberg [5] it is hardly convincing evidence, since the onset of shortening of the myofibres may be markedly delayed relative to the onset of contraction because it is load-dependent. The inhomogeneous pattern of linkages between myocytes, and hence, between layers is a well recognised feature of the myocardial syncytium particularly. Mutual loading of a population of adjacent myocytes, therefore, would be expected to vary, as indeed we have shown by direct measurements [6]. Criscione and colleagues [1], furthermore, point to significant flaws in Buckberg's interpretation of his own results [5] with respect to timing of the dynamic events. At all events, the histology of the septal component of the ventricular mass, in which delayed contraction is supposed to occur, is marked by a pronounced spatial interweaving. The consequence of this particular alignment of myofibres is that the individual myocytes act upon each other, in much the same fashion as skeletal myofibres in the tongue act upon one another. The result is to provide an intricate pattern of mutual control of shortening of the myofibres with regard to both amount and timing. If investigators rely on microsonometry to identify these activities, they should realise that the resulting signal will depend on the exact position of the crystals. The results obtained, therefore, can vary greatly depending on the particular conditions of coupling between the fibres aligned in different planes in the chosen area of investigation.
As we have sought to show [3], apparently without success as far as the supporters of the ‘myocardial band’ are concerned [4,5], ventricular myocardium is not arranged in the fashion of skeletal muscles, and is not arranged as individual units, each with their own origin and insertion. Instead, as now endorsed by Criscione and colleagues [1] the individual myocardial cells are packed together within a supporting matrix of fibrous tissue to produce the arrangement we chose to describe as a ‘syncytial mesh’. Criscione and colleagues [1] intepret the arrangement as a ‘continuum’. We have no problems with this description. We avoided such a description in our review, since our understanding was that the group from Auckland [7] based their concept on division of the muscular ventricular walls by radial fibrous sheets extending from epicardium to endocardium [7]. We are now pleased to learn that Criscione and colleagues share our own opinion that "the myolaminae are highly discontinuous and thus begin and end many times between the inner wall and the outer wall" [1,8]. This fact in itself is sufficient to disprove in its entirety the concept of the ‘ventricular myocardial band’.
In summary, therefore, we thank Criscione and his colleagues [1] for their excellent contribution to this ongoing debate [9]. We discard the concept of the ‘ventricular myocardial band’ simply because it has no anatomic foundation.
Footnotes
1 Tel.: +49 251 83 52541; fax: +49 251 83 56257. 
2 Tel: +44 207 905 2295; fax: +44 207 905 2324.
References
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