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Eur J Cardiothorac Surg 2007;31:430-437. doi:10.1016/j.ejcts.2006.11.040
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved

An analysis of the spatial arrangement of the myocardial aggregates making up the wall of the left ventricle

^a Institute of Biomedical Engineering, University and ETH Zürich, Gloriastrasse 35, CH-8092 Zürich, Switzerland
^b Experimental Thoracovascular and Cardiac Surgery, University of Münster, Domagkstrasse 11, 48149 Münster, Germany
^c Institute of Numerical Mathematics, University of Münster, Einsteinstrasse 62, 48149 Münster, Germany
^d Cardiac Unit, Institute of Child Health, University College, London, UK

Received 18 August 2006; received in revised form 16 November 2006; accepted 22 November 2006.

^_* Corresponding author. Tel.: +41 44 632 4587; fax: +41 44 632 1193. (Email: dorri{at}biomed.ee.ethz.ch).

Objective: We used the technique of peeling of myocardial aggregates, usually described as ‘fibres’, to determine the spatial arrangement of the myocytes in the left ventricular wall of a healthy autopsied human heart. Methods: We digitised the left ventricular outer and inner boundaries, as well as the pathways in space, of almost 3000 aggregates harvested from the left ventricular myocardium. During the process of gradual peeling, we sought to identify the myocardial aggregates as uniformly as possible. Despite this, interpolation was necessary to complete the pattern so as to construct a unit vector field that represented the preferred direction of the myocardial aggregates throughout the entirety of the walls of the left ventricle of this individual human heart. Results: Apart from the overall systematic arrangement of the aggregates necessary to achieve physiologic ventricular contraction, we documented substantial local heterogeneities in the orientation of the myocardial aggregates. In particular, a significant proportion of aggregates was found to intrude obliquely with respect to the ventricular boundaries, with markedly heterogeneous distribution. Moreover, the distribution of the helical angle of the aggregates relative to the ventricular base varied notably throughout the left ventricular free walls and the septum. Within the generally quite uniform and continuous structure of the ventricular mass, we were, however, unable to identify any organised tracts or functional subunits such as a ‘helical ventricular band’, nor did we find radial fibrous lamellas coursing across the ventricular wall. Conclusion: We suggest that the impact of local anatomical inhomogeneities, associated with gradients in regional contractile function on global ventricular dynamics, has been systematically underestimated in the past. Our analysis confirms furthermore the continuous nature of the myocardium associated with an overall gross organisation of the fibre direction field; however, there is no evidence of substructures compartmentalising the ventricles.

Key Words: Heart • Left ventricular architecture • Myocardial aggregates fiber orientation