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Ann Thorac Surg 2006;81:411-412
© 2006 The Society of Thoracic Surgeons
Cardiac Unit, Institute of Child Health, London, United Kingdom
* Address correspondence to Dr Anderson, Cardiac Unit, Institute of Child Health, 30 Guilford St, London, WC1N 1EH United Kingdom (Email: r.anderson{at}ich.ucl.ac.uk).
As Horia Muresian [1] states in the opening sentence of the abstract to the work describing the structure and vascular supply of the arterial roots, "precise knowledge of anatomical details is of utmost importance in complex procedures such as the Ross operation." This study shows the relevant anatomy with exquisite clarity, and should be compulsory reading for all surgeons undertaking this operative maneuver [1]. It is more gratifying for me to study the beautiful preparations and interpretations, since as is stated in the opening section of the Results section, "a true annulus doesn't actually exist." As is also emphasized, my colleagues and I have been promulgating this concept for several years [2–4], yet whenever I attend surgical meetings, or joint cardiac conferences, I continue to hear descriptions of the "annuluses" of the aortic and pulmonary valves, yet I can never be sure of the structures being described. In reality, as Muresian [1] demonstrates so clearly by the meticulous dissections, which as emphasized are "planned and performed in order to expose the hidden details and intricate relations of the cardiac structures, particularly those of surgical and echographical significance," both the aortic and pulmonary roots extend between the basal ring and the sinutubular junction. The leaflets of the arterial valves are suspended within these roots in semilunar fashion (Fig 1), with the hinge lines crossing the anatomic ventriculo-arterial junction. This junction between the ventricle and the arterial root, a true anatomic ring, is best seen in the pulmonary root, where the valvar leaflets are uniformly supported at the ventricular base by the musculature of the free-standing subpulmonary infundibulum. Although Muresian [1] does not stress the point, the basal ring is no more than an abstract geometric plane, because there is no anatomic structure that joins together the nadirs of attachment of the leaflets of the arterial valves in either the right or the left ventricle. It is this basal ring, nonetheless, which is usually described as the "annulus" by the echocardiographer when sizing the arterial roots, albeit that the experienced investigator recognizes that the roots expand at the mid-sinusal layer before constricting again at the level of the sinutubular junction. Measurements of the diameter at all three levels, therefore, are necessary if a full picture is to be provided of the dimensions of the two arterial roots. Muresian [1] emphasizes the need to maintain different dimensions for the sinutubular junction as opposed to the basal ring when transferring the pulmonary autograft to the aortic position during the Ross procedure.
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In addition to stressing the interdigitations of arterial sinuses and supporting ventricular structures that constitute the arterial roots [2], Muresian [1] also shows in superb detail the nature of the arteries that irrigate them. In the series of hearts available for investigation, it was the second artery originating left of the infundibulum that constituted the major septal artery, although in other hearts it was the first artery, and in some the third artery. Muresian [1] also states that it did not prove possible to identify any external landmark that marked the likely site of the major perforating artery, although in our own study, we had believed that a vertical line taken through the medial papillary muscle with the heart positioned in attitudinally appropriate orientation would serve this purpose [5]. As I look at the illustrations provided by Muresian [1], it seem to me as though the major septal perforating artery does track along the course that we were trying to describe in our own article [5]. Suffice it to say, in the light of our potential disagreement, that it is the area of the subpulmonary infundibulum related to the antero-cephalad limb of the septomarginal trabeculation, or septal band, that constitutes the region of greatest potential danger for damaging the major perforating artery. Attention to the excellent dissections of Muresian [1] shows the precise relationships.
Finally, Muresian [1] also sheds additional light on a topic that has been producing considerable controversy in Europe [6], which has also received significant publicity in the American literature [7]. This is the claim that the ventricular myocardium is arranged in the form of a "unique myocardial band" [6, 7]. As far as I am aware, other than in the dissections of Torrent-Guasp and colleagues [8], there has been no independent anatomic verification of this hypothesis, which flies in the face of 400 years of anatomical investigation [9]. In the most recent exchange in this ongoing polemic, Buckberg [10] claims that confirmation of the existence of the band is provided by corrosion casts and evidence of strain formation. However, neither of these techniques provides any evidence relating to the myocardial architecture of the ventricular walls. Despite this lack of supporting evidence, von Segesser, in a recent editorial comment [11], raised the possibility that the cleavage plane between the subpulmonary infundibulum and the aortic root existed because of the nature of folding the purported unique myocardial band. As Muresian [1] rightly points out, the muscular cleft to be found at the base of the ventricular septum is no more than the point of entry of the septal perforating arteries. In reality, as shown by so many anatomists over several centuries, the myocardium is arranged as a functional mesh, and has no resemblance to the skeletal musculature as seen in the trunks or limbs [9]. In this era of evidence-based medicine, it is incumbent on those such as Buckberg [10], who place so much emphasis on the unique myocardial band as the solution to so many problems of ventricular architecture [7], to perform independent morphologic studies. Only in this way, as shown by the beautiful investigation of Muresian [1], will the inquisitive investigator establish the true anatomic facts.
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