{'fraction_non_alphanumeric': 0.01834862385321101, 'fraction_numerical': 0.0018981335020563112, 'mean_word_length': 5.022857142857143, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
On “Replacement of Mitral Valve Posterior Chordae Tendineae with Expanded Polytetrafluoroethylene Suture: A Finite Element Study” by Karyn Kunzelman, et al.

The article by Kunzelman et al. in this issue of the Journal provides valuable insight into the physical consequences to the cusps and chordae of the rupture of posterior chordae and their replacement by ePTFE sutures. Most of the work on mitral valve repair has been done in ignorance of this kind of information. The reasons for this are simple enough: (1) accurate measurement of localized stresses in individual chordae and parts of cusps involves miniaturized instrumentation that is difficult to apply; (2) the act of accurately placing the measuring equipment involves interference with the valve structures that may cause doubt about the validity of the model; and (3) the cost of such large animal research today commonly exceeds the availability of funds. Fortunately, the model of the mitral valve that Kunzelman et al. have developed and the finite element analysis that they use to examine the functional and physical effects of alterations in valve anatomy provide a welcome alternative method. The model is based upon the real physical properties of the mitral valve and the real physical loads resulting from ventricular pressure and annular contraction, and while the exact precision of the quantitative measurements will, ultimately, need to be confirmed, they are certainly within the general range of what is known and likely to be proportionally accurate. This study addresses the consequences of the commonest form of chordal rupture (i.e., rupture of posterior chordae). Rupture of four marginal and basal chordae is simulated. Subsequently, the consequence of replacing two of these chordae with C-2 ePTFE is examined. The results are what might intuitively have been expected. Rupture increases the load on the cusp and on the adjacent unruptured natural chordae. Replacement with two ePTFE chordae reduces the cuspal stress, but does not completely relieve the stress on the adjacent natural chordae. The obvious conclusion has already been addressed by all the surgeons who are inserting new chordae: the authors’ model has a point attachment of each new chorda to the cusp edge, and this is observed to cause a focal increase of stress. In fact, all surgeons use either a form of figureeight stitch or a pericardial pledget to anchor the suture, and this will appropriately spread the stress. Chordal replacement with ePTFE chordae has come of age: a meeting to mark the tenth anniversary of the first clinical use of ePTFE sutures in mitral valve repair was held on April 27th in San Diego. Surgeons from Japan, Italy, Germany, Canada, and the United States presented data on replacement of natural chordae and reestablishment of annular-papillary connection with ePTFE sutures. The results reported were impressive, yet it was clear that many of the decisions that surgeons make are intuitive and would be usefully backed by hard data. This article provides this kind of data and we anticipate more useful information for surgeons from future applications of these methods.