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Ann Thorac Surg 2005;79:1926-1933
© 2005 The Society of Thoracic Surgeons
a Department of Cardiothoracic and Vascular Surgery, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
b Department of Cardiology, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
c Department of Biostatistics, Cardiothoracic Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
Accepted for publication October 4, 2004.
* Address reprint requests to Dr Chowdhury, Department of Cardiothoracic and Vascular Surgery, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India (E-mail: ujjwalchow{at}rediffmail.com).
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Abstract |
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METHODS: Various techniques of chordal preservation during mitral valve replacement for rheumatic heart disease in 451 patients between 1996 and 1999 are described. The mean age was 35.6 ± 19.0 years (range, 15 to 55 years). Seventy patients had complete excision of the subvalvular apparatus (group I), 124 had preservation of the posterior chordopapillary apparatus (group II), and 257 had total chordal preservation (group III). Echocardiography was performed preoperatively, at discharge, at 1 year, and at 4 years.
RESULTS: Chordal preservation groups (II and III) demonstrated significant improvement (p < 0.05) in left ventricular function immediately and late postoperatively. Reduction of left ventricular end-systolic and end-diastolic volume was significant in the chordal preservation groups (II and III) as compared to the nonchordal group (group I; p < 0.005). The total chordal group demonstrated greater fractional change of left ventricular end-systolic volume as compared to the posterior chordal and nonchordal group. The left ventricular ejection fraction and fractional shortening continued to decline over time in the nonchordal cohort (p = 0.05 and p = 0.001, respectively) and did not improve by 4 years. Statistically significant change in ejection fraction occurred in the chordal preservation groups as compared to the nonchordal group.
CONCLUSIONS: We conclude that total chordal preservation is possible in the large majority of rheumatic patients and confers significant long-term advantage by preserving left ventricular function. The surgical technique should be individualized.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentAcknowledgmentsReferences |
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The following criteria were taken into consideration for MVR with or without chordal preservation.
Patient Characteristics
Institutional review board approval for this study protocol was available and informed consent was obtained from all patients. Four hundred and fifty-one consecutive patients undergoing MVR for rheumatic heart disease from January 1996 through December 1999 at All India Institute of Medical Sciences, New Delhi, India, were included in this prospective study (Fig 1). Their demographic and clinical profiles are depicted in Table 1. Dyspnea on exertion was the predominant symptom, and 447 patients (99.1%) were in New York Heart Association (NYHA) functional class III or IV. Congestive cardiac failure was present in 167 (37.0%) patients. Two per cent (9 of 451) of patients had associated atrial septal defect, and 7.5% (34 of 451) had left atrial thrombus. Atrial fibrillation was present in 307 (68%) patients. Fifty-five patients (12.1%) had prior closed mitral valvotomy, 62 patients (13.7%) had previous balloon mitral valvuloplasty, and 25 patients (5.5%) had undergone prior mitral valve repair. During this period, 315 patients with mitral regurgitation underwent mitral valve reconstruction by the techniques described by us earlier [6].
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There was no statistically significant difference in the patient population among the three groups (Table 1). The severity of symptoms and type and number of medications given preoperatively were comparable.
Valve Pathology
Two hundred and eighty-eight patients (63.8%) had combined mitral stenosis and regurgitation, and 163 (36.1%) had predominant mitral stenosis. All patients of the nonchordal and posterior chordal group had either a mixed type of lesion or predominant mitral stenosis. Total chordal preservation was possible in 60% of patients with mixed mitral valve disease and in 51.5% of patients with mitral stenosis. Overall, 43.0% (194 of 451 patients) had mitral valvular calcification.
Surgical Techniques
A median sternotomy (n = 416) or a right anterolateral thoracotomy (n = 35) was used. Moderately hypothermic (28–32°C) cardiopulmonary bypass was established by ascending aortic and bicaval cannulation. Antegrade cold blood cardioplegia and topical hypothermia were used for myocardial preservation. The mitral valve was approached through a left atrial incision behind the interatrial groove in 442 patients. Transseptal approach was employed in patients with associated atrial septal defect (n = 9).
Prosthetic valves were inserted using 2–0 Ethibond sutures (Ethicon, Cincinatti, OH) over polytetrafluoroethylene pledgets. The St Jude (St Jude Medical, Inc, St Paul, MN) mechanical prostheses (SJM 33 mm, 104 patients; 31 mm, 173; 29 mm, 114; 27 mm, 33; 25 mm, 27) (Table 1) was used in all patients. Disc movement was checked for interference by the preserved chordae tendinae. Fifteen patients (3.3%) underwent concomitant tricuspid annuloplasty. The mean aortic cross-clamp time was 36.0 ± 11.2 minutes (range, 24 to 70 minutes), and the cardiopulmonary bypass time was 44.6 ± 12.8 minutes (range, 38 to 88 minutes).
Techniques of Chordal Preservation
Total chordal preservation
The valve was analyzed intraoperatively in a systematic manner to allow the optimal techniques to be chosen (Fig 2A–D). The subvalvular apparatus was preserved using the technique described by Miki and colleagues [7]. After incising the anterior mitral leaflet in the center from edge to base, it was separated 3 to 4 mm from the annulus and a central ellipse-shaped portion was excised, leaving a 5 to 10 mm rim of leaflet free edge attached to the primary first order or marginal chordae tendinae. The anterior and posterior mitral commissures were incised and the papillary muscles were split.
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While securing the prosthetic valve on the annulus, the posterior valve sutures were tied first. Excessive tissue within these chordal "buttons" that cannot be safely excised was pulled out of the subvalvar area using a nerve hook. The "chordopapillary buttons" were held on the atrial side (outside the sewing ring) when the valve was seated and the sutures were tied, thus preventing outflow tract obstruction or mechanical obstruction. If the posterior leaflet was excessively redundant or the chordae tendinae were elongated, the leaflet was imbricated into the mitral annulus using pledgeted sutures.
Posterior chordal preservation
In this technique, the anterior mitral leaflet with its attached chordae tendinae was completely excised. The posterior leaflet with the chordopapillary support mechanism was retained. The posterior mitral leaflet was incised at two or three points in between scallops from edge to base, when necessary.
Annulus Decalcification and Reconstruction
In most instances, the calcification process involved the commissures and was limited to the annulus with variable extension to the posterior myocardial wall, basal and intermediary chords, and head of one or several papillary muscles. Calcification was dealt with by excision of the calcified segment, shaving off the calcified leaflet margin, squeezing or milking out the calcific debris from the mitral annulus, and partial excision of the posterior mitral leaflet with the involved chordae tendinae.
Decalcification was done by using a knife to incise the atrial endothelium at the margin of the calcified bar. Then the base of the mural leaflet was incised at the edge of the calcium bloc and retracted. Keeping the edge of the dissecting knife against the calcium, the fibrous capsule overlying the calcium was incised. A thick hemostat and a peanut swab were used to milk out the calcific debris from within the capsule. No patient required "en-bloc" resection of the calcium deposit or "sliding atrioplasty" of the left atrium.
Nonchordal Group
The mitral valve was completely excised, including the leaflets and the subvalvular apparatus in cases of severe subvalvular fusion or calcified mitral leaflets with annular extension. One or two chordal buttons-pillars of the posterior mitral leaflet were retained in some cases.
Extensive scarring, shortening, and thickening of the chordopapillary apparatus precluded the use of artificial Gore-Tex sutures (WL Gore and Associates, Flagstaff, AZ) to resuspend the remnant papillary muscle base to the mitral annulus. The technique of valve insertion was the same in all groups. An everting mattress suture (ie, pledgets on the atrial side) was used in all cases. The left atrial appendage was routinely ligated. No surgical procedure was performed for atrial fibrillation.
Postoperative Studies
These included six-month clinical examinations, electrocardiograms, chest radiographs, cinefluoroscopy, and echocardiography. The functional class at follow-up was noted. Results were reported according to prescribed criteria [8].
All patients received warfarin and aspirin (100 mg/d) for anticoagulation to maintain an international normalized ratio (INR) between 3.0 and 3.5. A minimum of 48 months follow-up was mandatory for this study.
Echocardiographic Studies and Measurements
Transthoracic two-dimensional (2D), color flow and Doppler echocardiography was performed using a Hewlett-Packard-Sonos-5500 with 2.7 or 3.5 MHz transducer. Prosthetic valve function was assessed on 2D apical four-chamber view, and M-mode parasternal long-axis view. Left ventricular outflow tract obstruction was assessed on an apical five-chamber view, and by Doppler study. A Doppler velocity of greater than 2 m/s was considered significant for LVOTO.
Preoperative studies were performed within 7 days before surgery. Postoperatively, all survivors were followed echocardiographically at the time of discharge from hospital, at 1 year, and at 4 year follow-up. All late echoes have been grouped into one time period (48 months) with a range no greater than 6 months. Echocardiographic data were measured according to American Society of Echocardiography criteria [9].
Statistical Analysis
Data were analyzed with Biomedical Data Processing Statistical Software (University of California Press, Berkeley, CA) and SPSS 7.0 statistical package (SPSS Inc, Chicago, IL). Descriptive statistics were calculated for continuous and categorical variables. Student’s t test was used to identify significant differences between two groups of continuous variables. Repeated measures two-way analysis of variance (ANOVA) with the Bonfferoni posthoc test was used to assess the influence of time (preoperatively vs postoperatively vs 4 years) for type of operative procedure on all echocardiographically derived variables.
Percentage change between the preoperative and postoperative values were calculated and compared by one-way ANOVA with posthoc (LSD) analysis for the three groups. The 
2 test was used to identify association among the groups for categorical variables. A p value less than 0.05 was considered significant.
Mortality rates were calculated depending on the total number of years of follow-up for each patient. Actuarial estimates were calculated using the Kaplan-Meier technique and the log-rank test was performed to analyze statistically the difference of survival among the three groups [10]. Valve-related events were reported as per the standard published criteria [8].
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Results |
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All patients were administered oral angiotensin converting enzyme (ACE) inhibitors after extubation (0.5 to 1.0 mg/kg; every 8 hours) before weaning from inotropic agents. Digoxin, diuretics, and ACE inhibitors were weaned at varying time intervals. Amiodarone was used for intractable atrial fibrillation.
Late Outcomes
There were 14 late deaths (3.1%: group I, n = 6; group II, n = 5; group III, n = 3) due to ventricular arrhythmias (n = 2), anticoagulant hemorrhage (n = 2), congestive heart failure (n = 2), and viral hepatitis (n = 1). Five patients had valve thrombosis. Two of these developed major cerebrovascular accidents after streptokinase administration and subsequently died. Three patients had successful thrombolysis.
Thromboembolic Complications
Fifteen patients had thromboembolic complications. Three of them died, 6 recovered with residual weakness, and 4 recovered completely. In 2 patients, the deficit was transient. No single factor was found to be associated with incidence of thromboembolism.
Prosthetic Valve Endocarditis
Five patients developed prosthetic valve endocarditis. They were treated conservatively and two of these died.
Four hundred and twenty-six survivors (94.46%) achieved the mandatory 48-month postoperative follow-up. Their preoperative and postoperative records were reviewed. Follow-up was 100% complete (range, 1 to 96 months) and yielded 3327.06 patient-years of data with a mean follow-up time of 93.72 months (standard error [SE ± 0.86]; 95% confidence interval [CI] = 92.02 to 95.41 months). The actuarial survival at 96 months was 84.29 ± 0.04% in group I, 94.17 ± 0.02% in group II, and 96.01 ± 0.01% in group III (Fig 3). By log-rank test, the difference of survival was statistically significant among the three groups (p = 0.0002). All survivors of group II and III (n = 361) were in NYHA functional class I or II at their last follow-up. A 92.3% (60 of 65) of survivors of group I are in NYHA functional class I and II. A 63.5% (195 of 307) of patients who had preoperative atrial fibrillation continue to remain in atrial fibrillation. Chordopapillary preservation techniques did not affect the outcome of postoperative atrial fibrillation (p = 0.61). There were no structural deteriorations or reoperations.
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Comment |
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To overcome the limitations of bileaflet preservation, a variety of techniques have been introduced [7, 12–14]. These differ primarily in the location where the anterior leaflet chordae are inserted in the mitral annulus. The tension of the preserved main anterior leaflet chordae may act on the posterior annulus (Feike’s technique), the trigonal area (Miki’s technique), on the anterior annulus (Khonsari’s I and II technique), or on a point half-way between these locations (Hetzer’s technique) [7, 12–14]. Magnetic resonance studies of annulus motion have indicated interesting phenomena characteristic of the respective techniques, such as parallel prosthetic movement with Khonsari’s technique and tilting of the prosthesis in Feike’s technique [14].
There are differences in the tension on chordae during the cardiac cycle in various techniques but there is no established method for predefining chordal length at the time of prosthetic implantation, nor for determining the required length according to the various types of mitral disease, left ventricular dimensions, or location of chordal reattachment. The use of artificial Gore-Tex chordae during MVR has been popularized by some; we have not used the same [15, 16]. There is a possibility of thickening and hardening of the preserved chordae tendinae because of restricted physiologic movement by the prosthetic valve [13, 14]. We believe that a divided, shifted, and reaffixed anterior leaflet with chordae tendinae may not interfere with the left ventricular outflow tract (LVOT) [16]. No chordal structure obstructed the LVOT with this technique. Doppler echocardiographic examination did not show any evidence of LVOTO in any patient with preserved anterior mitral leaflet. Technically, total chordal preservation was feasible in 60% of our patients with mixed mitral valve disease and in 51.5% of patients with predominant mitral stenosis.
An argument against preservation of the anterior leaflet was that only undersized valve prosthesis could be implanted [[1–4]. However, we have implanted a 29 to 33 mm prosthesis in 85.6% of patients with total chordal preservation, suggesting that preservation of the anterior mitral leaflet does not preclude implantation of a large prosthesis.
Complete Versus Partial Chordal-Sparing MVR: Effects on Left Ventricular Volume and Function
Preserving the subvalvular mitral apparatus has been recognized as necessary for improvement of left ventricular systolic function, exercise capacity, and better survival after MVR [1–4, 11, 16, 17]. It has been shown to preserve regional left ventricular mechanics and three-dimensional contraction synergy, and may prevent myocardial rupture [1–4, 11, 16, 17].
Reports addressing the issue of left ventricular mechanics with bileaflet or posterior leaflet MVR are limited [2–4, 11, 17]. Although Hannein and colleagues [3] and Rozich and colleagues [17] demonstrated the superiority of chordal-sparing MVR over conventional MVR, no significant differences were noted between patients receiving either posterior or bileaflet chordal preservation.
Our study demonstrates that MVR with bileaflet or posterior chordal preservation is associated with a lesser incidence of postoperative low output syndrome (p = 0.000) and better long-term survival than conventional MVR (p = 0.0002; Fig 3). Also, patients undergoing bileaflet-preserving MVR derived greater functional benefit than patients undergoing MVR without chordal preservation.
Echocardiographically, the total chordal-preservation group demonstrated statistically significant improvement of left ventricular diastolic and systolic dimensions over posterior and nonchordal groups (Tables 2 and 3). Similar results were reported by others [2–4, 11, 16, 17]. This supports the observation that chordopapillary preservation is an important determinant of postoperative left ventricular function, and the increased afterload produced by a competent valve is of less consequence.
Limitations of This Study
This study was not randomized. Given the mounting evidence favoring conservative mitral valve surgery, a prospective, randomized controlled trial may no longer be considered ethical.
Our methods of measuring left ventricular function may be criticized for inaccuracy, because these are operator dependent. However, all echo measurements were performed by experienced cardiologists. We have not assessed global and regional systolic stress, which is increased after chordal transection.
Conclusions
We conclude that total chordal preservation is possible in the majority of patients undergoing MVR for rheumatic heart disease. An appropriate sized prosthesis can be implanted despite bileaflet preservation. This technique provides superior results compared to non and partial chordal preservation. We hope these technical modifications will be useful to surgeons attempting to emulate this approach on an individual basis.
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Acknowledgments |
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This article has been cited by other articles:
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  R. Garcia-Fuster, V. Estevez, O. Gil, S. Canovas, and J. Martinez-Leon Mitral valve replacement in rheumatic patients: effects of chordal preservation. Ann. Thorac. Surg., August 1, 2008; 86(2): 472 - 481. [Abstract] [Full Text] [PDF]
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 T. Athanasiou, A. Chow, C. Rao, O. Aziz, F. Siannis, A. Ali, A. Darzi, and F. Wells Preservation of the mitral valve apparatus: evidence synthesis and critical reappraisal of surgical techniques Eur. J. Cardiothorac. Surg., March 1, 2008; 33(3): 391 - 401. [Abstract] [Full Text] [PDF]
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 J. I. Fann, N. B. Ingels Jr., and D. C. Miller Pathophysiology of Mitral Valve Disease Card. Surg. Adult, January 1, 2008; 3(2008): 973 - 1012. [Full Text]
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 S. H. Rahimtoola The Year in Valvular Heart Disease J. Am. Coll. Cardiol., January 17, 2006; 47(2): 427 - 439. [Full Text] [PDF]
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