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Eur J Cardiothorac Surg 2005;27:472-474
© 2005 Elsevier Science NL
David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Rm 62-258 CHS, Los Angeles, CA 90095, USA Options of Bio-Engineering, California Institute of Technology, 1200 E. Califoria Blud., Pasadena, CA 91125, USA
* Corresponding author. Tel.: +1 310 206 1027; fax: +1 310 825 5895. (E-mail: gbuckberg{at}mednet.ucla.edu).
The purpose of placing this report of diffusion tensor imaging into a surgical journal is not clear. This is a time-consuming study that is technically well done to permit data accumulation.The acquisitions for a complete DTI data set usually take about 9h, yielding about 200,000 helix angle measurements from each heart. There is extensive background for use of this MRI method in the literature, including histological evaluation by Scollan et al. and Chen et al. [1,2], and the central theme of each paper validates the suggestion of Streeter [3] about the oblique and helical configuration of the fiber orientation. Diffusion tensor imaging papers [4] provide clear eigenvector pixel images of orientation angulation going from epicardium to endocardium of around +60 to –60°, yet the authors do not include this helical pattern in their data base and refer to this blueprint in only one sentence in their discussion.
This paper amplifies the sustained effort from Lunkenheimer and Anderson to show that the ventricular band concept of Torrent-Guasp is wrong. The diffusion tensor method in dead hearts simply supports the suggestions of Streeter about the helical formation of the ventricle. In fact, each prior MRI paper defines the angle of inclination in the dead heart as the helical angle, with clockwise and counterclockwise fibers traversing the ventricular wall, through 0, to define the +60 and –60° inclination angle, as well as transverse dimensions. Similar examples also appear in studies by Hsu, Forder, Geerts (cited in their references), Costa et al [5] using strain, and many others that look at the helical configuration of fibers with diffusion tensor MRI methods.
Unfortunately, this concept of helical inclination is completely missing from their results, with a description focus that is directed toward the circular middle portion. Architecture has a structure function counterpart, and the recognized oblique fiber orientation is consistent with the twisting action of torsion that is very evident by tagged MRI studies [6,7]. The authors focus upon the transverse orientation supports the constriction and dilation described by William Harvey [8], who also viewed the dead heart, and thus could not recognize the twisting elements of function that are so visible in the experimental laboratory and in the operating room in conical hearts with normal excitation contraction coupling. How does transverse architecture explain the twisting function, and should not the recognized but excluded oblique pattern also be cited to promote better understanding of living action?
This is the first study of diffusion tensor imaging in the surgical literature. The authors should accept the responsibility of providing a clear and cohesive picture of what they see, so that surgeons who wish to expand their data base can learn from this introduction of MRI methodology. Their discussion statement about the precision of their own study is self-serving when compared to reports of other investigators that present clear-cut and more complete data, not just the pictures that comprise the Schmid manuscript.
The anisotropic quality of fiber orientation of dead tissue is also matched in functioning tissue, as tagging MRI studies [6], show a clockwise and counter clockwise twisting motion of the live heart show that this motion is more pronounced towards the apex [7]. This structure function correlate defines the importance of the reciprocal obliquity of fibers with the orientation that is well known, prior to this paper. The enclosed images in Figs. 1 and 2 are taken from Chen et al and Geerts et al [2,4] to characterize this fiber orientation and the angulations; similar linear figures are basic to all prior diffusion tensor MRI reports, yet remain absent from this manuscript.
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The helical formation is central to the architectural description of the reciprocal spirals that Torrent-Guasp considers to comprise the architecture of the ventricle, and diffusion tensor imaging supports this, just as the collagen network that weaves around these fibers does in Lunkenheimer's prior work. Prior work by Saber et al [12], using DENSE MRI technology, supports the strain development that may follow this fiber orientation. Consequently, diffusion tensor studies support a helical configuration, by showing that the helices within fibers have inclination angles from +60 to –60°, a finding in concert with development of finite element models of stress and strain [13] and the sequential twisting of that defines the functional activity in live hearts with normal excitation contraction coupling. Of great interest is their Fig. 5 that may indeed show the transverse elements defined by Torrent-Guasp for the basal loop. How do the authors explain this finding? Why do they call the epicardium longitudinal, when it is oblique?
This paper does not provide a clear background about prior work, excludes a central helical theme of fiber orientation, thus deviating from what is suggested by the forefathers of anatomy [14], like Lower, Senec, Krehl, Ludwig, Mall and others who did not have this elegant MRI tool for support. The present study in dead hearts focuses only upon the circumferential mid myocardium rather than the recognized oblique fiber orientation gradation from epicardium to endocardium.
This report seems written to disprove the myocardial band, yet the fiber orientation reported in the literature supports a helix, and exclusion or denial of this central architecture is not an acceptable way to introduce the surgical world into methods that are new in our literature. It seems that investigation, rather than condemnation should be our goal, especially when the target is the education of surgeons who must act upon this information is the objective of using a cardiac surgical journal. This aim differs from submission to an MRI journal where the expert editors focus predominantly upon the merits of diffusion tensor technology.
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This article has been cited by other articles:
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  A. F. Corno, M. J. Kocica, and F. Torrent-Guasp The helical ventricular myocardial band of Torrent-Guasp: potential implications in congenital heart defects Eur. J. Cardiothorac. Surg., April 1, 2006; 29(Suppl_1): S61 - S68. [Abstract] [Full Text] [PDF]
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A. F. Corno Reply to Lunkenheimer et al. Eur. J. Cardiothorac. Surg., November 1, 2005; 28(5): 780 - 780. [Full Text] [PDF]
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R. H. Anderson, S. Y. Ho, K. Redmann, D. Sanchez-Quintana, and P. P. Lunkenheimer The anatomical arrangement of the myocardial cells making up the ventricular mass Eur. J. Cardiothorac. Surg., October 1, 2005; 28(4): 517 - 525. [Abstract] [Full Text] [PDF]
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