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Ann Thorac Surg 2002;73:1690
© 2002 The Society of Thoracic Surgeons

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Correspondence

Second order anterior mitral leaflets play a role in preventing systolic anterior motion: reply

^a Department of Cardiovascular and Thoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine, Stanford, CA 94305-5407, USA

e-mail: dcm{at}stanford.edu

To the Editor

I welcome the opportunity to respond to the thoughtful letter by Professors Obadia and Janier from Lyon which addressed our article [1] because we share their concern that dividing the anterior leaflet second-order (or "strut") chordae tendineae might well have adverse consequences on left ventricular (LV) systolic pump function, as shown earlier in Obadia’s ex vivo isolated porcine heart experiment [2]. Further, the recent recommendation from Levine’s group [3] that purposeful division of second-order chordae be used therapeutically to treat ischemic mitral regurgitation (IMR) is most worrisome since that maneuver could exacerbate further the impaired LV systolic function that patients with IMR already have.

To set the record straight, we by no means meant to imply that severing the strut chordae did not have possible adverse effects of LV systolic function. The goal of our experiment, as the title of our article indicates, was simply to examine what happened to anterior leaflet shape and valvular competency in vivo after dividing two (of several) second-order chordae in sheep hearts after a prolonged time on cardiopulmonary bypass. While we observed no statistically significant deterioration of LV global hemodynamics (see Table 1, page 538), this does not necessarily mean that no adverse effect of second-order chordal cutting occurred because: 1) We did not examine more meaningful load-independent indexes of regional or global LV systolic pump performance; and 2) with only 8 sheep, a Beta or type II statistical error could exist since LV dP/dt and LV peak systolic pressure fell by 13% and 12%, respectively, after chordal division. Moreover, subsequent analysis of our data has confirmed that regional LV systolic function assessed as r-PRSW (regional preload recruitable stroke work relationship [regional end-diastolic area—regional stroke work]) did indeed fall in the LV regions subtending the insertion of the papillary muscles. This observation would corroborate the earlier conclusions of Obadia and colleagues [2] where all second-order chordae were divided in ex vivo pig hearts. Obadia’s previous experiment had important limitations, eg, LV systolic function was measured using only a single pair of ultrasonic drystals in the anterolateral LV wall, which is a load-dependent index; a paragraph on pages 538–9 of our article [1] summarizes other differences between the experimental preparations. Finally, sheep may not be the best experimental model to assess the differential effects of the primary and secondary chordae on LV systolic function, because sheep have relatively few second-order chordae inserting on the anterior leaflet and none of them are considerably larger (or more "stout" appearing) than the others or the primary (marginal) chordae, as is seen in man or pigs.

Obadia and Janier’s other notion that the anterior leaflet second-order chordae also possess an "anti-SAM function" is intriguing, especially in small ventricles where the aortic-mitral angle is acute, but we have no clinical experience nor experimental data to confirm or refute this hypothesis.

References

1. Timek T.A., Nielsen S.L., Green G.R., et al. Influence of anterior mitral leaflet second-order chordae on leaflet dynamics and valve competence. Ann Thorac Surg 2001;72:535-541.[Abstract/Free Full Text]
2. Obadia J.F., Casali C., Chassignolle J.F., et al. Mitral subvalvular apparatus: different functions of primary and secondary chordae. Circulation 1997;96:3124-3128.[Abstract/Free Full Text]
3. Messas E., Guerrero J.L., Handschumacher M.D., et al. Chordal cutting—a new therapeutic approach for ischemic mitral regurgitation. Circulation 2001;104:1958-1963.[Abstract/Free Full Text]

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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): D. Craig Miller Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Miller, D. C. Search for Related Content PubMed Articles by Miller, D. C. Related Collections Valve disease Related Article