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J Thorac Cardiovasc Surg 2008;135:1402-1404
© 2008 The American Association for Thoracic Surgery
Letter to the Editor |
a Divison of Cardiovascular Surgery, Mayo Clinic, Rochester, MN 55905
b Department of Anatomic Pathology, Mayo Clinic, Rochester, MN 55905
We are delighted that our article stimulated such interest from our colleagues across the Atlantic and, in particular, that it has stimulated a discussion of every surgeon's two favorite topics—history and anatomy! We appreciate the authors' expression of sympathy for us, describing our figure legend as "embarrassing." Not at all! We stand by our comments and encourage the debate. There is too little such good-natured banter among the members of our profession.
The authors of the letter site a rather vague phrase from the article by Nicks, Cartmill, and Bernstein1
referring to carrying the incision "posteriorly...across the aortic ring as far as the origin of the mitral valve." Does "as far as" mean "not into?" Perhaps, but how then does one interpret the very figure, part b, from Nicks' article included in our manuscript? We take exception to the statement by Ne
i
, Kneevi, and Borovi that "it is obvious" that the anterior leaflet of the mitral valve is not entered. And what is "the aortic ring?" Linguistics aside, it is physically impossible to cross the nadir of the attachment of the noncoronary cusp without entering the anterior leaflet of the mitral valve. The latter is simply what lies beyond the former. There is no territory between.
In support of our argument, we marshal three lines of evidence: First, and admittedly weakest, is the senior author's (T.M.S.) own experience as a clinical surgeon. Every time he does an aortic valve replacement, sutures placed at the nadir of the noncoronary cusp and at the nadir of the left cusp enter the base of the mitral valve. This is simply what lies below the "surgical annulus"—if we dare use the term "annulus" at all.2
Second, we refer to Dr Robert Anderson's work monograph3 titled "Clinical Anatomy of the Aortic Root," in which he directly addresses first and foremost the surgeon's persistent irrational reference to "the enigmatic annulus." Anderson then clarifies the relationships between the more anatomically definable "semilunar attachments" of the valve cusps to the aortic wall, the "ventriculo–arterial junctions," and the "basal ring." The last of these connects the nadir of the semilunar attachments and represents the "ring" that Nicks' incision crosses. As Anderson3 writes in reference to the noncoronary sinus, "the base of this sinus is exclusively fibrous in consequence of the continuity between the leaflets of the aortic and mitral valves." This is the intervalvular fibrosa. In contrast, as one moves toward the commissural posts, there is, indeed, a fibrous wall between the semilunar attachments or "surgical annulus" and the anterior leaflet of the mitral valve. This is one of the so-called "forgotten" interleaflet triangles or what we would term the intervalvular trigone.4 Indeed, it is this very structure that permits "annular" enlargement in the manner described by Nuñez and associates5 without entering the roof of the left atrium (LA).
Third, we offer photomicrographs (
Figure 1) through the intervalvular trigone and intervalular fibrosa. Figure 1, A, is a section through the commissure between the noncoronary or posterior cusp (PC) and left coronary cusp. A remnant of the former is apparent. Note that the elastic layers of the media of the aorta end at this "surgical annulus" and that the roof of the LA is loosely adherent to the aorta for a distance extending from well above to well below the semilunar attachment right down to the point where it is quite densely attached to the anterior mitral leaflet (AML). It is this length of aorta below the semilunar attachments and above the attachment of the AML—the interleaflet triangle—that is exploited in the Nuñez enlargement. In Figure 1, B, however, taken through the nadir of the posterior cusp, one can appreciate that the region of dense attachment of the roof of the LA begins immediately below the semilunar attachment and the termination of the medial elastic tissue. It is the thickness of this attachment that permits one to enter the AML for a distance without violating the dome of the LA. One can also appreciate that the apparent "base of the AML" looks quite different depending on one's perspective. From the aortic or ventricular side, the AML clearly begins immediately below the semilunar attachment, whereas from the atrial side, because of the thickness of the LA itself, the base of the AML seems to be well below the attachment of the aortic valve cusp. The muscle of the LA essentially folds down over the base of the AML.
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i, Kneevi, and Borovi for their interest and welcome the debate. What could be more fun than spirited disagreement among colleagues!
References
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