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J Thorac Cardiovasc Surg 2007;133:1483-1492
© 2007 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
Division of Cardiovascular Surgery and Department of Anesthesia, Toronto General Hospital, University Health Network, and University of Toronto, Toronto, Ontario, Canada.
Read at the Eighty-sixth Annual Meeting of The American Association for Thoracic Surgery, Philadelphia, Pa, April 29-May 3, 2006.
Received for publication May 14, 2006; revisions received January 7, 2007; accepted for publication January 29, 2007. * Address for reprints: Michael A. Borger, MD, Division of Cardiovascular Surgery, Toronto General Hospital, 4N-451, 200 Elizabeth St, Toronto, Ontario, Canada M5G 2C4. (Email: michael.borger{at}med.uni-leipzig.de).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Methods: We compared echocardiographic and clinical data in patients who underwent chordal-cutting mitral valve repair (n = 43) and those undergoing conventional mitral valve repair (control, n = 49) for ischemic mitral regurgitation.
Results: Patients who underwent chordal cutting had a higher prevalence of recent myocardial infarction, left main disease, diabetes, and peripheral vascular disease (all P < .05). Left ventricular ejection fraction was lower in the chordal-cutting group (33 ± 2% vs 44 ± 2%) (mean ± SE) and preoperative tent height was greater (11.7 ± 0.5 vs 9.7 ± 0.6 mm; both P < .01). In-hospital mortality was 10% in control patients and 9% in the chordal-cutting group (P = .9). Other complication rates were similar for the two groups. The reduction in tent height before-to-after repair was similar in the two groups of patients, but those undergoing chordal cutting had a greater reductions in tent area (53 ± 3% vs 41 ± 3%; P = .01). The chordal-cutting group also had greater mobility of the anterior leaflet, as measured by a reduction in the distance between the free edge of the anterior mitral valve leaflet and the posterior left ventricular wall (24 ± 3% vs 11 ± 4%; P = .01). Control patients had more recurrent mitral regurgitation during 2 years of follow-up by univariate (37% vs 15%; P = .03) and multivariate analysis (P = .03). Chordal cutting did not adversely affect postoperative left ventricular ejection fraction (10% ± 5% relative increase in left ventricular ejection fraction vs 11% ± 6% in the control group; P = .9).
Conclusion: Chordal cutting improves mitral valve leaflet mobility and reduces mitral regurgitation recurrence in patients with ischemic mitral regurgitation, without any obvious deleterious effects on left ventricular function.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Chronic IMR is defined as mitral regurgitation (MR) occurring greater than 1 week after MI with (1) one or more left ventricular (LV) segmental wall motion abnormalities, (2) significant coronary disease in the territory supplying the wall motion abnormality, and (3) structurally normal mitral valve (MV) leaflets and chordae tendineae.1
IMR is an important cause of congestive heart failure and is associated with worse long-term survival after MI.2-4 The prevalence of chronic IMR may be increasing with time, as a higher proportion of patients survive acute MI. It has been estimated that 1.2 to 2.8 million Americans currently have IMR.1,5
The most common operation performed for chronic IMR is undersized mitral annuloplasty, as popularized by Bolling and colleagues.6,7 Although undersized mitral annuloplasty can be performed with acceptable rates of morbidity and mortality, several investigators have questioned its durability. McGee and colleagues8 demonstrated that recurrent MR (moderate-to-severe or severe) develops in 30% of patients 1 year after undersized annuloplasty, a finding that has been confirmed by others.9-11 In addition, undersized annuloplasty does not improve long-term survival in patients with chronic IMR.12 Such findings have led investigators to examine alternative methods of surgical treatment for IMR.
Recent advancements in the understanding of chronic IMR pathophysiology have led to new approaches in therapy.1,13 It is now widely accepted that the predominant cause of chronic IMR is apical displacement and tethering of the MV leaflets, preventing central coaptation during systole. Infarcted myocardium (predominantly in the posteroinferior territory) displaces the MV leaflets apically and outwardly and decreases ventricular force required to close the leaflets.14 The mitral annulus may dilate and therefore contribute to the regurgitation, but IMR can occur with a normal-sized annulus.
Such insights recently led to a novel surgical approach for chronic IMR. Messas, Levine, and colleagues15,16 demonstrated that division of MV secondary chords (the "chordal-cutting" procedure) results in decreased leaflet tethering and decreased mitral insufficiency in a sheep model of IMR. Secondary chords attach to the belly of the MV leaflets and cause kinking of the anterior leaflet in patients with IMR, resulting in the "seagull sign" on echocardiography.1 The chordal-cutting procedure may relieve leaflet tethering, an important cause of recurrent mitral insufficiency after MV repair.11 The operation has been described in case reports,17,18 but clinical experience is very limited to date. We herein describe our early results in a group of patients undergoing the chordal-cutting operation and compare the clinical and echocardiographic outcomes with those of patients undergoing conventional MV repair for IMR.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Follow-up was obtained by telephone and mail questionnaire of patients or family members, or both, between January 1 and February 28, 2006. The first chordal-cutting operation was performed at our institution in May 2003. Some surgeons adopted this technique over the following 2 years whereas others continued to perform undersized mitral annuloplasty during the entire study period. Because the length of follow-up was longer in the control group, we truncated follow-up in all patients to 2 years postoperatively.
Surgical Technique
Indications for MV repair were symptoms of heart failure (New York Heart Association class II or greater) and moderate or more (ie, 2+ or more) MR on preoperative echocardiography, although some patients with 1+ MR also underwent MV repair. Intraoperative transesophageal echocardiography (TEE) was used to confirm the pathologic condition (ie, leaflet tethering) but not to determine whether or not MV repair was indicated.
A left atriotomy was performed posterior to the interatrial groove and the MV was thoroughly inspected to rule out nonischemic pathologic abnormalities. Interrupted 2-0 braided sutures without pledgets were placed along the posterior annulus from the medial to lateral fibrous trigones. A flexible incomplete annuloplasty band (Cosgrove–Edwards annuloplasty system; Edwards LifeSciences, Irvine, Calif) was inserted in both groups of patients. The annuloplasty band was moderately undersized in all patients and ranged from size 26 to 32, depending on the patient’s body surface area.
In the chordal-cutting group, we divided secondary chords to the anterior leaflet, posterior leaflet, and the commissure that arose from the papillary muscle or muscles affected by the infarcted myocardium. Secondary chords arising from normal papillary muscles were not divided. The affected papillary muscle was identified by preoperative echocardiography or ventriculography or both. Secondary chordal cutting was performed before insertion of the annuloplasty band to optimize exposure. Secondary chords were carefully separated out from primary chords with a nerve hook, confirming their attachment to the belly of the leaflets rather than to the free edge. All secondary chords from the affected papillary muscle(s) that could be identified were divided.
Echocardiography
Transthoracic echocardiography was performed preoperatively, before discharge, and during the most recent follow-up in patients. MR grade was quantified as none or trivial (0), mild (1+), moderate (2+), moderate-to-severe (3+), or severe (4+) on the basis of color jet area and shape, pulsed wave Doppler of pulmonary veins, and proximal isovelocity surface area.19 LV ejection fraction was calculated by the modified Simpson and Quinones method.20
Intraoperative TEE was used to measure several variables before and after MV repair in a subset of patients. Measurements were performed by a single echocardiographer (P.M.), who was blinded to patient group assignment. All measurements were obtained via the mid-esophageal 120° view, with the exception of tent height and area, which were obtained in the apical 4-chamber view. The measured variables were (1) mitral annulus diameter, (2) tent height (distance from the leaflet coaptation point to the mitral annulus), (3) tent area (area formed by the triangle between annular plane and the apex of the leaflet coaptation point into the ventricle during systole), and (4) anterior MV leaflet–posterior left ventricle (distance between the free edge of the anterior MV leaflet and the posterior LV wall as a measure of anterior leaflet mobility). Measurements were obtained during two different cardiac cycles and the average value was recorded. None of the patients had atrial fibrillation during measurement acquisition.
Statistical Analysis
Categorical variables are expressed as percentages and continuous variables are expressed as mean ± standard deviation throughout the manuscript, with the exception of echocardiographic data, which are expressed as mean ± standard error. All statistical analyses were performed with the SAS system (SAS version 8.1; SAS Institute, Inc, Cary, NC). Categorical variables were compared with 
2 or Fisher exact tests, and continuous variables were compared with unpaired t or Wilcoxon tests. Stepwise multivariable logistic regression analysis was used to determine the independent predictors of recurrent MR. Survival and event-free survival were analyzed with the methods of Kaplan and Meier univariately and Cox regression multivariately.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Detailed measurements were obtained from intraoperative TEE in 82% of patients (n = 75). The intraoperative TEE digital tape was irretrievable in 12 patients or had inadequate images in 3 patients, whereas 2 patients had a contraindication to TEE examination. As can be seen in Table 4, the tent height (distance between the coaptation point of the MV leaflets and the mitral annulus) was significantly greater in the chordal-cutting group before MV repair. Chordal cutting resulted in a significantly increased reduction in the tent area after MV repair (the area between the mitral annulus and the coaptation point of the leaflets), as well as increased reduction in the distance between the free edge of the anterior MV leaflet and the posterior LV wall.
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As noted earlier, LV function was significantly worse in the chordal-cutting group preoperatively. The change in LV ejection fraction from the preoperative to the follow-up period was similar in the two groups of patients: 10% ± 28% relative (not absolute) increase in the chordal-cutting group versus 11% ± 39% in the control group (P = .9).
Clinical Outcomes During Follow-up
Survival 2 years postoperatively was 82% ± 6% in the control group and 79% ± 9% in the chordal-cutting group (P = .8, Figure E1). The causes of death during follow-up in the chordal-cutting group were complications of perioperative stroke in 1 patient and hemolysis and end-stage renal failure in 1 patient. In the control group, the causes of death during follow-up were congestive heart failure, renal failure, and thoracic aneurysm surgery (1 patient each). Cox regression failed to reveal any independent predictors of long-term survival.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Mitral annular dilation may also occur and can lead to increased insufficiency, but annular dilation is not essential for the development of IMR.
MV repair results in better survival than MV replacement in patients with IMR, except in high-risk patients, in whom survival is similar for the two techniques.21,22 The most commonly performed surgical procedure for IMR is isolated undersized annuloplasty. Isolated annuloplasty is reproducible and can be performed with acceptable rates of morbidity and mortality, even in high-risk patients.6,7 However, undersized annuloplasty does not significantly improve long-term survival when compared with medical management.12 Several investigators have described a high rate of MR recurrence, approximately 30%, after undersized isolated annuloplasty for IMR.8-11 Such findings have led investigators to examine a host of other surgical options, including the edge-to-edge (Alfieri) repair, infarct plication, papillary muscle imbrication, papillary muscle "sling," surgical relocation of the posteromedial papillary muscle, and posterior MV restoration.1 The amount of clinical experience with each of these techniques is very limited.
Messas, Levine, and associates15,16 proposed division of the secondary chords as a method of improving leaflet mobility and decreasing leaflet tethering for chronic IMR. Secondary chords result in kinking of the anterior MV leaflet in chronic IMR but are not required to prevent leaflet prolapse. Messas and colleagues demonstrated that dividing secondary chords in a sheep model of acute15 and chronic16 IMR resulted in improved leaflet coaptation and reduced MR, without leaflet prolapse or decline in LV ejection fraction. The chordal-cutting operation is intended to prevent persistent leaflet tethering after MV repair, an important cause of recurrent IMR.11 It has been described in a few case reports in humans,17,18 but clinical experience is very limited.
We started performing the chordal-cutting operation in 2003 and have been performing this procedure in an increasing number of patients over time. The current article describes our early results with this group of patients and compares them with a group that underwent isolated undersized annuloplasty. The chordal-cutting group had an increased prevalence of several preoperative risk factors, including worse LV function, than the control group. This finding probably reflects our increased comfort level with the chordal-cutting procedure and our willingness to perform this operation in higher-risk patients.
We used a flexible, incomplete annuloplasty band for all patients in the current study. Several articles in the literature have discussed the optimal annuloplasty device for patients with chronic IMR, with conflicting results. Although many surgeons prefer a complete ring,23 we use an incomplete band because we do not believe dilation of the intertrigonal distance plays a major role in the pathogenesis of IMR.24 In the current study, the mitral annulus measured 3.4 ± 0.1 mm in all patients (Table 4), which is within the range of normal values.25 Although it can be argued that our results may have improved with the use of a complete, rigid ring, it is important to stress that both groups of patients received the same annuloplasty device and therefore a comparison of the two groups should yield a valid estimate of the effect of chordal cutting.
The predominant concern for the chordal-cutting operation has been possible deleterious effects on LV function. Rodriguez and colleagues26 used an acute IMR sheep model to demonstrate that division of the anterior leaflet secondary chords results in decreased LV function. These investigators demonstrated decreases in end-systolic elastance and preload recruitable stroke work, as well as increased transmural strain and altered LV geometry, after anterior leaflet chordal cutting in acutely ischemic sheep. These same investigators also demonstrated that chordal cutting had no beneficial effect on mitral insufficiency in an acute sheep model of IMR.27 These findings are in contrast to the studies by Messas and associates,16 which demonstrated reduced MR and no decrease in LV ejection fraction at a mean period of 33 weeks after chordal cutting in a chronic ischemia model. A recent publication by the same investigators demonstrated preservation of LV volumes, ejection fraction, systolic ventricular elastance, preload-recruitable stroke work, and LV rate of pressure rise after secondary chordal cutting.28 One explanation for these discrepant findings is that acute ischemia models are more likely to show decreases in LV function because the papillary muscles and surrounding myocardium are normal. In contrast, models of chronic ischemia are more representative of the clinical situation in which papillary muscles and surrounding myocardium are infarcted and scarred. Cutting secondary chords that arise only from infarcted myocardium, as done in the current study, may not be as deleterious as cutting chords from normal, healthy myocardium.
We failed to demonstrate any significant echocardiographic decrease in LV function after chordal cutting in the current study, a finding that can be supported by several lines of evidence. First, there was no significant increase in inotrope usage or low cardiac output syndrome in the chordal-cutting group, despite the fact that this group had worse LV function than control patients. Second, operative mortality was similar for the two groups, despite a higher prevalence of several risk factors in the chordal-cutting group. Our perioperative mortality rate for the chordal-cutting group (9%) was similar to that achieved in large series of MV repair for IMR (approximately 10%).21,29 Third, division of secondary chords has been performed for more than 20 years during MV repair for myxomatous disease (during sliding annuloplasty and chordal transfer procedures) with excellent long-term results and no obvious deleterious effects on patient survival or symptoms.30 We therefore believe that chordal cutting does not adversely affect LV function in patients with chronic IMR.
In the current study, recurrent moderate or more MR was observed in 37% of the isolated annuloplasty group. Other investigators have achieved better results after MV repair for IMR, particularly Braun and associates.31 These investigators had an 8% rate of MR recurrence 18 months postoperatively. One possible explanation for their better results is that these investigators used a complete, rigid ring with more aggressive undersizing. However, we should once again stress that both groups of patients in our study received the same size and type of annuloplasty device and therefore the incremental effect of chordal cutting should be valid. Although the MR recurrence rate in our control group is relatively high, it is well within the quoted range in the literature.8-11
The mechanism of recurrent MR after isolated annuloplasty is likely related to persistent leaflet tethering.11 Division of secondary chords was associated with a decreased recurrence rate of MR in the current study by univariate and multivariate analysis. The decreased recurrence rate was particularly noteworthy given that patients in the chordal-cutting group had increased MV leaflet tenting preoperatively (Tables 1 and 4), a risk factor for recurrent MR.11,32
Chordal cutting may reduce MR by increasing leaflet mobility and decreasing leaflet tethering.15,16 In the current study, patients subjected to chordal cutting had decreased MV tent height and tent area after MV repair. They also had a decreased distance between leaflet coaptation and the posterior LV wall, suggestive of increased mobility of the anterior leaflet. Other investigators have demonstrated increased anterior leaflet mobility and concave curvature after division of the secondary chords.33,34 Despite our positive findings, recurrent MR still occurred in 15% of the chordal-cutting group. We can infer that chordal cutting represents an incremental improvement over isolated annuloplasty for surgical treatment of IMR, but it is not the final answer for this vexing clinical problem.
Study Limitations
The main limitation of the current study is its retrospective and nonrandomized design. A randomized clinical trial would be the most appropriate method of comparing chordal cutting with undersized annuloplasty for IMR. However, MV repair for IMR is an uncommon surgical procedure, despite the large number of patients with this disorder, and therefore a randomized trial is unlikely to be performed in the near future. Since chordal cutting is currently being performed in several centers around the world, the current study represents the best available data on this new procedure.
Another limitation of the current study is our method of assessing postoperative LV function. We used transthoracic echocardiography, which is load-dependent. Although all clinical tests of LV function are load-dependent to a certain extent, rest and exercise nuclear angiography may be a better measure of LV function and may be preferable for future studies.
Another possible limitation is that patients in the chordal-cutting group had a higher prevalence of recent MI and a higher percentage of left internal thoracic artery usage, which may have led to better reverse remodeling and less MR postoperatively. However, type of operation performed was the only independent predictor of recurrent MR in our multivariable analysis, even after adjusting for preoperative MI and left internal thoracic artery usage.
The final limitation of our study is the relatively short period of follow-up. It is possible that chordal cutting is not as durable as undersized annuloplasty for IMR, but only time will tell. However, the current study included up to 2 years of follow-up, and most cases of MR recur within the first year after MV repair for IMR.8
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Conclusions |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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Acknowledgments |
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References |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionConclusionsReferences |
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