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Ann Thorac Surg 1996;62:179-183
© 1996 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Results of Represervation of the Chordae Tendineae During Redo Mitral Valve Replacement

Division of Cardiovascular Surgery, The Toronto Hospital, University of Toronto, Toronto, Ontario, Canada

Accepted for publication March 9, 1996.

	Abstract

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Background. Previous studies have shown that preservation of the chordae tendineae improves early and late postoperative left ventricular function after mitral valve replacement. This report describes the results of represervation of the chordae tendineae during redo mitral valve replacement in patients who had their chordae tendineae preserved during their initial operation.

Methods. Fifty-four patients undergoing reoperative mitral valve replacement with preservation of their chordal annular attachments (chordae group) were compared with 187 patients who had redo mitral valve replacement without preservation of the chordae (nonchordae group). The interval between the initial operation and the reoperation was 8.7 ± 4.4 years in the chordae group and 8.6 ± 4.9 years in the nonchordae group (p= 0.315). Seventy-three patients underwent aortic valve replacement during their redo mitral valve replacement compared with 168 patients who had mitral valve replacement alone. There were 15 patients who had their chordal attachments represerved during redo double-valve replacement.

Results. In the chordae group, intraoperative assessment revealed excellent chordal connections between the preserved papillary muscles and the mitral annulus in all patients. One patient had adhesions between the preserved chordae and the stent of the tissue valve. The chordal attachments were preserved during insertion of the second valve in all patients. The incidence of low output syndrome and operative mortality in the chordae group was 16.7% and 7.4%, respectively. In the nonchordae group, the incidence of low output syndrome was 27.3% (p= 0.112 compared with the chordae group) and the operative mortality was 13.4% (p = 0.236 compared with the chordae group). In patients with double-valve replacement, represervation of the chordae was associated with a reduction in low output syndrome (0% versus 24%; p = 0.034) and mortality (6.7% versus 15.5%; p = 0.374).

Conclusions. Preservation of the chordal attachments between the papillary muscles and the mitral annulus can be accomplished during reoperative mitral valve replacement. Represervation of the chordae tendineae may reduce postoperative low output syndrome, especially in high-risk patients undergoing redo double-valve replacement.

	Introduction

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Numerous laboratory [1–8] and clinical [9–17] studies have shown that preservation of the chordae tendineae improves early postoperative ventricular function after mitral valve replacement. We recently reported that ventricular function remains improved 56 months postoperatively [18]. However, there is little information on the long-term status of the preserved chordae tendineae and the papillary muscles, or on the feasibility of preserving the chordae tendineae during mitral reoperation. This study reviews 54 patients who had preservation of their chordae tendineae during their redo mitral valve replacement and compares them with 187 patients who underwent reoperation without having their subvalvular apparatus preserved.

	Patients and Methods

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
The clinical records were reviewed of 241 consecutive patients who underwent redo mitral valve replacement at our institution between January 1988 and December 1994. Fifty-four patients underwent mitral valve replacement having their chordal attachments preserved during their redo operation (chordae group), whereas 187 patients underwent conventional operation without preservation of any subvalvular apparatus (nonchordae group). All patients who had preservation of their chordae at the previous operation had their chordal attachments preserved during their second operation.

The preoperative characteristics are presented in Table 1. There were 88 men (37%) and 153 women (64%) with a mean age of 58.6 ± 12.6 years (range, 17 to 82 years). One hundred eighty-one patients (75%) had one previous mitral valve replacement and sixty (25%) had multiple previous open heart procedures including at least one previous mitral valve replacement. The interval between the initial operation and the repeat procedure was 8.6 ± 4.8 years (range, 0 to 26.2 years) and was similar between groups.

The indications for the repeat operation [19] were prosthetic valve endocarditis (n = 22), nonstructural failure (paravalvular leak or prosthetic dehiscence, n = 23), prophylactic replacement of Björk-Shiley convexoconcave valve (n = 5), and structural prosthetic mitral valve failure (n = 191). Twenty-seven percent of the patients in the nonchordae group had multiple previous cardiac procedures compared with 19% in the chordae group (p < 0.01). All other preoperative characteristics were similar between the two groups.

Operative Technique
Cardiopulmonary bypass was established and maintained with mild to moderate systemic hypothermia (28° to 32°C), and blood cardioplegia in a 4:1 mixture was employed for myocardial protection. Myocardial revascularization was performed for any significant coronary artery lesion with a reasonable distal vessel. Between 1982 and 1987, there has been a gradual evolution to chordal preservation by all surgeons. Patients who were operated on before 1984 were likely to have had their chordal apparatus removed during their initial operation. Other possible reasons for prior excision of the chordal attachments include severe rheumatic mitral stenosis where fibrosis of the chordae precluded preservation, or excision of the papillary muscle tips before insertion of a mechanical valve to avoid leaflet impingement. At our institution, the posterior leaflet of the mitral valve and all chordal attachments are now preserved even during insertion of a mechanical valve. When fibrosis necessitates excision of the chordae tendineae, Gore-Tex (W. L. Gore & Assoc, Flagstaff, AZ) sutures are employed to resuspend the papillary muscles.

During redo mitral valve operations, the prosthetic annulus is carefully dissected free from the native subvalvular apparatus. Before implantation of the new prosthesis, the chordal attachments to the mitral annulus are inspected to ensure proper tension and repaired if necessary.

Statistical Analysis
Statistical analysis was performed with the SAS program (SAS Institute, Cary, NC). Univariate data were analyzed using a ² or Fisher's exact test where appropriate, and continuous data were evaluated by Student's t tests. Continuous variables are reported as mean ± standard deviation. Statistical significance was assumed at p less than 0.05.

	Results

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Operative Findings and Procedures
All patients who presented with preserved chordae were found to have intact papillary muscles with chordal attachments to the mitral annulus. None of the papillary muscles were atrophic. In 1 patient, some of the preserved posterior chordae were adherent to the stent of the bioprosthesis and required careful dissection to separate the chordal attachments and implant them into the new mitral sewing ring. The procedure was successful, and most of the chordae were preserved and the continuity between the papillary muscles and the mitral annulus was maintained. Eleven patients required four sets of 4-0 Gore-Tex sutures to replace the native chordae by techniques previously described [20]. Eight patients had both anterior and posterior chordae preserved at their initial mitral valve replacement. Seven of these patients had both chordae preserved during the reoperation. Forty-six patients had preservation of the posterior chordae only. Thus, all patients who presented with previously preserved chordae had some chordae preserved at repeat operation.

The base of the papillary muscle was still present for as long as 22 years after the initial operation in 7 patients who had undergone mitral valve replacement before 1974, at which time the chordae tendineae and papillary muscle tips were excised. The remnant papillary muscle allowed for the placement of Gore-Tex sutures. These 7 patients were included in the chordae group. The remaining 187 patients who had undergone conventional mitral valve replacement at their initial operation underwent conventional repeat operation.

Pathologic findings of the previous prosthetic valve revealed the following: cusp tear (n = 132), paravalvular leakage or prosthetic dehiscence (n = 23), heavy calcification (n = 29), thrombosis (n = 19), abscess (n = 13), normal Björk-Shiley valve (n = 5), vegetation (n = 3), and not described (n = 28).

Operative Results
The operative results are summarized in Table 2. There were no differences in the size of the implanted valve between groups (chordae 28 ± 3 mm versus 28 ± 2 mm; p = 0.374). Eight patients (15%) in the chordae group required coronary artery bypass grafts compared with 13 patients (7%) in the nonchordae group (p = 0.506). Forty patients (17%) received a bioprosthesis at their redo operation, whereas 201 patients (83%) received a mechanical valve. The incidence of aortic (n = 73, 30%) or tricuspid valve (n = 62, 26%) procedures was similar between groups. The aortic cross-clamp time and the cardiopulmonary bypass time were similar in the two groups. Five patients (9%) in the chordae group required postoperative intraaortic balloon pump support compared with 24 patients (13%) in the nonchordae group (p = 0.361). The requirement for postoperative inotropes was similar between groups (chordae 54% versus nonchordae 59%; p = 0.488). The incidence of postoperative low output syndrome (the requirement of intraaortic balloon pump or inotropic support for greater than 30 minutes to maintain a systolic blood pressure greater than 90 mm Hg and a cardiac index greater than 2.1 L•min^-1•m^-2) was lower in the chordae group (17% versus 27%), but the difference was not statistically significant (p = 0.112). The incidence of postoperative stroke (chordae 7% versus nonchordae 5%; p = 0.457) and renal failure (chordae 9% versus nonchordae 11%; p = 0.573) was similar between groups. There were four operative deaths in the chordae group (7%) compared with 25 deaths (13%) in the nonchordae group (p = 0.236).

View larger version (26K): [in this window] [in a new window]   Fig 1. . Effects of chordal preservation on postoperative low output syndrome (LOS) and operative mortality (OM). (AVR = aortic valve replacement; MVR = mitral valve replacement.)

The independent predictors for postoperative low output syndrome were preoperative angina (odds ratio = 2.23; 95% confidence interval = 0.869 to 5.710) and male sex (odds ratio = 1.77; 95% confidence interval = 0.95 to 3.27). The Hosmer-Lemeshow goodness of fit p value for this model was 0.101, with an area under the receiver operating characteristic curve of 59%.

Preservation of the chordal apparatus failed to emerge as an independent predictor of either postoperative low output syndrome or operative mortality.

	Comment

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
More than a decade has passed since the revival of the chordae-sparing mitral valve replacement [1, 10]. Preservation of the subvalvular apparatus during operation has become the preferred technique when feasible. We recently presented the late results of a randomized trial comparing preservation of the chordae tendineae with no preservation [18]. Our results indicate that even 7 years postoperatively, those patients with preserved chordae and papillary muscles had better left ventricular function when compared with patients who underwent resection of the subvalvular apparatus. This finding corresponds to other reports of improved left ventricular function after papillary muscle preservation [16, 17]. Olinger [21] published a case report of preservation of the chordae tendineae during repeat mitral valve replacement in 1992. The present article reports the morphologic appearance of the preserved chordae and papillary muscles found at reoperation in a series of patients up to 22 years (range, 1 to 22 years) after the initial chordae-sparing operation.

In our experience, the preserved chordae tendineae and papillary muscles were in excellent condition after the initial chordae-sparing procedure. The presence of intact and nonatrophic papillary muscles suggested that they were still functioning. In patients who had undergone operation before 1974 and had their chordae and papillary muscles excised, we were able to resuspend the remnant papillary muscle base to the mitral annulus with the aid of artificial Gore-Tex sutures. We encountered little difficulty in preserving the chordae during repeat operation. In most patients, the sewing ring of the prosthetic valve was carefully excised from the mitral annulus and a new valve inserted without dissection of the chordae. When a mechanical valve was inserted, we were careful to ensure that the mechanical poppet did not entrap any portion of the native subvalvular structures. In patients who received a monoleaflet valve, the major orifice was oriented upward to avoid interference from the posterior chordae. Implanting the St. Jude Medical bileaflet valve was easier than the Sorin valve when the chordae tendineae were being preserved.

The operative mortality was similar in the two groups. We found no difference in preoperative predictors of postoperative mortality. Patients in the nonchordae group had a greater number of previous cardiac procedures. However, multiple previous operations did not predict either mortality or the development of low output syndrome.

The incidence of postoperative low output syndrome was less in patients undergoing chordae-sparing procedures; however, this too failed to reach statistical significance. In a high-risk subset of patients undergoing simultaneous aortic and mitral valve replacement during their reoperation, the incidence of low output syndrome was reduced by preservation of the chordae tendineae (chordae 0% versus nonchordae 24%; p = 0.034).

The power of the present study in detecting a difference in operative mortality or low output syndrome was 24% and 68%, respectively. If we had more patients in our study, we may have found a significant improvement with chordal preservation. For the observed difference in operative mortality (7% versus 13%) and low output syndrome (17% versus 27%), we would have required 391 and 268 patients per group, respectively, to achieve statistical significance at = 0.05.

Preservation of the chordae tendineae and papillary muscles is now a standard procedure during mitral valve replacement [22]. We believe that preservation of the chordae tendineae is technically feasible and may improve outcomes after reoperative mitral valve replacement.

	Acknowledgments

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Supported by the Heart and Stroke Foundation of Canada. Doctor Rao is a Pharmaceutical Roundtable Research Fellow of the Heart and Stroke Foundation of Canada, Dr Weisel is a career investigator of the Heart and Stroke Foundation of Ontario, and Dr Ikonomidis is a Research Fellow of the Heart and Stroke Foundation of Ontario.

	Footnotes

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Presented in part at the Sixty-eighth Scientific Sessions of the American Heart Association, Anaheim, CA, Nov 13–16, 1995.

Address reprint requests to Dr Weisel, The Toronto Hospital, EN14-215, 200 Elizabeth St, Toronto, Ontario, M5G 2C4, Canada.

	References

Top Footnotes Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Vivek Rao Masashi Komeda Richard D. Weisel John S. Ikonomidis Tirone E. David Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rao, V. Articles by David, T. E. Search for Related Content PubMed PubMed Citation Articles by Rao, V. Articles by David, T. E.