Ann Thorac Surg 2008;86:726-734. doi:10.1016/j.athoracsur.2008.04.100
© 2008 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
The Impact of Surgical Ventricular Restoration on Mitral Valve Regurgitation
Roni B. Prucz, BSE,
Eric S. Weiss, MD,
Nishant D. Patel, BA,
Lois U. Nwakanma, MD,
Ashish S. Shah, MD,
John V. Conte, MD*
Division of Cardiac Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland
Accepted for publication April 23, 2008.
* Address correspondence to Dr Conte, Division of Cardiac Surgery, Heart & Lung Transplantation, The Johns Hopkins Hospital, 600 North Wolfe Street, Blalock 618, Baltimore, MD 21287-4618 (Email: jconte{at}csurg.jhmi.jhu.edu).
Presented at the Fifty-fourth Annual Meeting of the Southern Thoracic Surgical Association, Bonita Springs, FL, Nov 7–10, 2007.
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Abstract
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Background: Surgical management of functional mitral regurgitation (MR) in ischemic cardiomyopathy is controversial. Surgical ventricular restoration (SVR) decreases left ventricular volume and may improve MR severity. We assessed the impact of SVR on the degree of MR.
Methods: We retrospectively reviewed patients with ejection fractions (EF) < 0.35 who underwent SVR with coronary artery bypass grafting (SVR+CABG) over a 3-year period. Patients with concomitant mitral valve procedures were excluded. Patients with EF < 0.35 who had CABG alone during the same time period served as control. Mitral regurgitation was graded 0 to 4+ by echocardiogram and ventriculogram. Outcomes included survival, MR grade, and cardiac function.
Results: Thirty-nine patients received SVR+CABG: 3% (1 of 39) had 4+, 10% (4 of 39) had 3+, 51% (20 of 39) had 2+, and 36% (14 of 39) had 0 to 1+ MR. Thirty-five patients with a similar MR distribution underwent CABG alone. Operative mortality was 2.6% for SVR+CABG and 5.7% for CABG patients (p = 0.62). At follow-up, MR grade decreased by 57% (2.24 ± 0.5 to 1.24 ± 0.9, p < 0.001) for the SVR+CABG group compared to 12% (2.25 ± 0.5 to 2.00 ± 0.9, p = 0.27) for the CABG alone group. SVR+CABG patients had significantly less MR than CABG patients at follow-up (1.24 ± 0.9 vs 2.00 ± 0.9, p = 0.007), with 15 patients improving to 0 to 1+ MR postoperatively versus 6 patients in the CABG cohort (p = 0.02). Improvement in postoperative EF was significantly greater after SVR+CABG (0.13% vs 7%, p = 0.04). Three-year survival was 85% for SVR+CABG and 72% for CABG patients (p = 0.39).
Conclusions: SVR+CABG demonstrated greater reduction in MR severity at follow-up than CABG alone. Decreased left ventricular volumes and improved papillary muscle orientation likely contribute to decreased MR after SVR.
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Introduction
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In patients with ischemic cardiomyopathy, alterations in geometry and ventricular size can lead to functional consequences. One such consequence is mitral regurgitation (MR), which has been shown to increase mortality independent of underlying left ventricular dysfunction [1–3]. Ischemic MR is a disease of the left ventricle (LV). Postinfarction remodeling leads to morphologic changes at the annular, subannular, and ventricular levels resulting in MR due to poor leaflet coaptation [2–7]. Decreased survival has been observed for all degrees of mitral regurgitation in patients with postinfarction ischemic cardiomyopathy, even after revascularization and repair or replacement of the incompetent valve [8, 9]. Regurgitant flow through the mitral valve propagates a vicious cycle of LV enlargement leading to worsened ventricular function, reduced exercise capacity, and increased functional decline [1, 10, 11].
Surgical ventricular restoration (SVR) is an established therapy for improving LV function in patients with ischemic cardiomyopathy [12–15]. The procedure helps to reduce the size and restore the elliptic shape of the heart through LV reconstruction. Based on this anatomic restoration, SVR may decrease the severity of MR. Restoration of blood flow to ischemic areas surrounding the muscular mitral apparatus, reduction of short axis dimensions, and lowering of end systolic volumes have all been postulated as mechanisms that may improve MR after SVR [16, 17].
Several studies have compared the efficacy of SVR with mitral valve repair to SVR without mitral valve repair. These studies found that aggressive surgical management combining SVR, coronary revascularization, and mitral valve repair leads to superior clinical outcomes and LV function than SVR alone [16, 18, 19]. However, no study has directly compared the potential benefits of SVR on MR independent of a concomitant mitral valve procedure.
Our group has previously shown that SVR can benefit high-risk patients including the elderly, those with recent myocardial infarction, pulmonary hypertension, multiterritory myocardial infarction, and a severely depressed ejection fraction (<0.20) [20–23]. In this study, we review our institutional experience with SVR patients to determine the effects of SVR on MR independent of mitral valve procedures. We aimed to accomplish this objective by comparing patients with MR who underwent SVR combined with coronary artery bypass grafting (CABG) to a matched cohort of patients who were SVR candidates but received CABG alone. We hypothesize that SVR patients will show improvement in MR after reconstruction.
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Material and Methods
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Study Design
We retrospectively reviewed 303 adult (>17 years) patients with ejection fraction (EF) of less than or equal to 0.35 who underwent CABG with or without SVR for ischemic cardiomyopathy at our institution between June 2002 and December 2005. Our Institutional Review Board approved all aspects of the study and individual consents were obtained. Within this cohort, 62 patients received SVR and CABG (SVR+CABG). We then independently reviewed the series of 241 patients who underwent CABG alone and classified 58 patients as potential candidates for the SVR procedure to serve as our control group (Fig 1). A single surgeon (JVC) independently identified the SVR candidates by reviewing available ventriculograms and echocardiograms to determine their potential candidacy for SVR. Indications for SVR included anteroseptal infarct, enlarged left ventricle, akinesia or dyskinesia in the anterior wall, acceptable basal and lateral wall function, and good right ventricular function [24]. Echocardiograms were the only preoperative images available for 5.6% of patients while ventriculograms were the only preoperative images available for 21.6% of patients. Both ventriculograms and echocardiograms were available for 72.8% of our study group. Patients who had any prior cardiac surgery procedures, concomitant mitral valve repair or replacement, or patients who did not have postoperative imaging were excluded. Postoperative echocardiography was obtained by transthoracic echo (TTE) prior to discharge (28.9%) or at the most recent follow-up (71.1%). The average time for MR grade follow-up was 9.1 ± 12.7 months.
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Fig 1. Flow diagram illustrating the study design and patient categorization. (CABG = coronary artery bypass grafting; EF = ejection fraction; SVR = surgical ventricular restoration.)
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For each patient, the presence of both preoperative and postoperative MR was graded on a scale of 0 to 4+. This grading system is in accordance with accepted standard MR grading with values corresponding to none (0), trace (1+), mild (2+), moderate (3+), and severe (4+) MR. All patients underwent preoperative TTE. The MR grades used in our analysis were obtained primarily from TTE except in cases where transesophageal echo (TEE) data was available, in which case the TEE value for MR grade was used. No intraoperative TEE data was used in the analysis.
Patient Variables
Data collection included demographic characteristics, preoperative risk factors, hemodynamic and operative data, and postoperative complications. Preoperative and postoperative EF and left ventricular volumes (as evaluated using magnetic resonance imaging (MRI), echocardiography, or cardiac catheterization) and New York Heart Association (NYHA) functional class were also assessed. Mortality data was obtained from autopsy reports, physician's records, and the Social Security Death Index. For patients not regularly seen at our institution, follow-up data was collected by telephone interview. Follow-up was 100% with a mean time of 21.8 ± 15.7 months.
Outcome Variables
The primary endpoint was improvement in MR grade. Secondary endpoints included mortality, postoperative EF, improvement in NYHA functional class, length of stay, and other markers of clinical morbidity including development of renal failure, stroke, need for intraaortic balloon counterpulsation, and systemic infection.
Operative Technique
Our operative technique has been described previously [22, 23]. We prefer to perform SVR on the arrested heart whenever possible depending on the basis of cross-clamp time, concomitant procedures, and cardiac function. For patients requiring revascularization, bypass grafting was performed first, followed by SVR. An intraventricular sizing device (Chase Medical, Richardson, TX; Bioventrix, Danville, California) was routinely used with the ventricle sized to 50 to 60 cc/m2 body surface area. A Dacron patch was used to close the ventriculotomy if the defect was greater than 2 to 3 cm long, otherwise a linear closure was used.
Statistical Analysis
Descriptive statistics are presented as mean ± standard deviation (SD) unless otherwise specified. The 
2 and the paired/unpaired Student t test were used to compare categoric and continuous variables, respectively. The Wilcoxon signed rank test was used to compare nonparametric values. The Kaplan-Meier method was used to model survival, which was compared between the two groups by the Mantel-Cox log rank test. SPSS version 13 (SPSS Inc, Chicago, IL) was used for statistical analyses.
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Results
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Baseline Characteristics
After excluding all patients who underwent CABG alone and were not candidates for SVR (n = 183), all patients who received any concomitant surgical procedure (n = 19), and all patients for whom postoperative imaging was not available (n = 27), a total of 74 patients were included in the study (Fig 1). Of these 74 patients, 39 comprised the SVR+CABG cohort while 35 patients within the CABG alone group qualified for inclusion as SVR candidates. Within the SVR+CABG group, 64% (25 of 39) had MR 1+ or greater compared with 69% (24 of 35) within the CABG alone group (p = 0.81). Mean age was 61 ± 10 years for SVR+CABG patients and 63 ± 11 years for the CABG group (p = 0.43). Preoperatively, the SVR+CABG patients were similar to the CABG patients with the exception that more males underwent SVR+CABG (Table 1). All patients had previous myocardial infarction. Within the SVR+CABG group, 3% (1 of 39) had 4+, 10% (4 of 39) had 3+, and 51% (20 of 39) had 2+ MR. Similarly, within the CABG group, 3% (1 of 35) had 4+, 11% (4 of 35) had 3+, and 54% (19 of 35) had 2+ MR (Fig 2). Both groups had a preoperative median MR grade of 2. There were no statistically significant differences in cardiac function, NYHA class, LV size, or presence of angina symptoms (Table 1).
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Fig 2. Preoperative mitral regurgitation distribution of coronary artery bypass grafting (CABG) versus surgical ventricular restoration (SVR)+CABG patients. (MR = mitral regurgitation; grey column = coronary artery bypass grafting [n = 35]; lined column = surgical ventricular restoration [n = 39]).
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Operative Data
SVR+CABG patients had a significantly longer cardiopulmonary bypass time (Table 2). There were no intraoperative deaths in either group. Thirty-day mortality was 2.6% (1 of 39) for SVR+CABG and 5.7% (2 of 35) for CABG patients (p = 0.60). In-hospital mortality, defined as death occurring after 30 days but prior to hospital discharge, was 7.7% (3 of 39) for the SVR+CABG group compared with 11.4% (4 of 35) for the CABG group (p = 1.00).
Mitral Regurgitation
In order to evaluate the effects of the SVR+CABG and CABG procedures on mitral regurgitation, all patients with preoperative MR less than 1+ were removed from this portion of the analysis. Twenty-five patients within the SVR+CABG group and 24 patients within the CABG cohort were thus included. The two groups had similar preoperative and operative characteristics. Importantly, three-vessel coronary artery disease and a history of angina were similar for SVR+CABG and CABG patients. Preoperatively, both groups had a similar degree of MR with each group having a median MR grade of 2 and a mean MR grade of 2.24 ± 0.05 and 2.25 ± 0.05 for the SVR+CABG and CABG groups, respectively. Postoperatively, only the SVR+CABG group had significant improvement in MR grade, with the median MR score improving to 1 (p = 0.008). Mean MR grade decreased by 57% for the SVR+CABG group compared with 12% for the patients undergoing CABG alone (2.24 ± 0.05 to 1.24 ± 0.9, p < 0.001 vs 2.25 ± 0.05 to 2.00 ± 0.9, p = 0.27) (Fig 3). At follow-up the SVR+CABG group had significantly less MR (1.24 ± 0.9 vs 2.00 ± 0.9, p = 0.007), with 60% (15 of 25) of patients improving to 0 to 1+ MR postoperatively versus 25% (6 of 24) in the CABG cohort (p = 0.02) (Fig 4). Overall, 68% (17 of 25) of patients within the SVR+CABG group had improved MR compared with 29% (7 of 24) within the CABG population (p = 0.03). The postoperative change in MR for each patient with a preoperative MR grade 2+ or greater is illustrated in Figure 5. In those patients with an MR grade less than 1+ preoperatively, at follow-up 50% (7of 14) progressed to 2+ MR and 21% (3 of 14) progressed to 3+ MR within the SVR+CABG group. Comparatively, within the CABG group, 36% (4 of 11) progressed to 2+ MR and 27% (3 of 11) progressed to 3+ MR (p = 0.17).
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Fig 3. Preoperative versus postoperative mitral regurgitation grade in patients with preoperative mitral regurgitation 1+ or greater. (** = p < 0.001; grey column = preoperative; lined column = postoperative.)
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Fig 4. Postoperative comparison of MR grade improvement in CABG versus SVR+CABG patients with preoperative MR 1+ or greater. (** = p < 0.05; MR = mitral regurgitation; CABG = coronary artery bypass grafting; SVR = surgical ventricular restoration; grey column = 0 to 1 MR grade postoperatively; lined column = MR grade improvement.)
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Fig 5. Line graph comparing individual postoperative mitral regurgitation change in CABG versus SVR+CABG patients. (CABG = coronary artery bypass grafting; SVR = surgical ventricular restoration.)
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Other Outcome Variables
For the remaining study outcomes, all patients were evaluated regardless of preoperative MR. After surgery, SVR+CABG patients were significantly less likely to be rehospitalized for congestive heart failure (CHF), more likely to have an improved NYHA functional class, and more likely to have improved EF (Table 3). Additionally, SVR+CABG patients had a greater increase in EF when compared with CABG patients (13.1% vs 7.4%, p = 0.04). Follow-up NYHA functional class improved from 3.36 ± 0.5 to 1.87 ± 1.0 (p < 0.001) in the SVR+CABG group versus 3.14 ± 0.8 to 2.00 ± 0.7 (p < 0.001) in the CABG cohort.
Three-year survival was 85% and 72% for SVR+CABG and CABG patients, respectively (p = 0.33), with five late deaths in the SVR+CABG group versus seven in the CABG population (Fig 6). There was no correlation between the degree of preoperative MR and death. Of the seven patients who died in the SVR+CABG group, 17% (1 of 6) had 4+, 50% (3 of 6) had 2+, and 33% (2 of 6) had 0+ MR preoperatively. Of the nine patients who died in the CABG cohort, 22% (2 of 9) had 3+, 44% (4 of 9) had 2+, and 33% (3 of 9) had 0+ MR preoperatively.
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Fig 6. Kaplan-Meier survival curve of CABG and SVR+CABG patients. (CABG = coronary artery bypass grafting; SVR = surgical ventricular restoration; · · · = CABG; — = SVR + CABG.)
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Comment
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Mitral valve regurgitation is a common finding in individuals with an ischemic cardiomyopathy. The longitudinal and transverse elongation of the left ventricle causes lateral displacement of the papillary muscles with a concomitant increase in the interpapillary muscle distance. The resultant leaflet tethering results in MR [2–7]. Revascularization with concomitant SVR and mitral valve repair has been shown to improve left ventricular and mitral valve function [16–18]. However, the question of whether SVR decreases mitral valve regurgitation independent of mitral valve procedures remains to be determined. Although it is well accepted that severe MR be repaired at the time of bypass surgery and SVR, the treatment of patients with lesser degrees of MR remains controversial.
Any comparison between SVR+CABG and CABG groups can be difficult. Previous studies have achieved such comparisons by classifying CABG patients with an increased left ventricular internal diastolic dimension (
6.0 cm) as SVR candidates [25]. However, not all bypass patients with a dilated heart due to ischemic cardiomyopathy are eligible for the SVR procedure. We attempted to mitigate this problem by creating our comparison group through a blinded independent review of preoperative imaging. This resulted in a candidate group that matched our SVR+CABG group in every category with respect to cardiac function. These were patients who in retrospect qualified for the SVR procedure at the time of their bypass operation but did not receive it. Reasons that these particular patients did not undergo SVR include the operating physician not recognizing the patient's candidacy for SVR or the operating physician not being aware of the benefits of SVR in this particular patient population. We recognize this potential source of bias when comparing our two patient groups, but feel that we adequately corrected for this potential error by having the most senior SVR surgeon at our institution review all available imaging in both cohorts to determine candidacy, and by demonstrating that the two groups were nearly identical with regard to preoperative demographics, morbidity, and cardiac function. In our analysis, we noted no significant difference in preoperative MR grade between the two groups. However, postoperatively, patients undergoing SVR with CABG were more likely to have an improvement in MR grade with a significant number of patients improving to 0 to 1+ MR. Our results for the SVR+CABG group mirror those reported by others. Kaza and colleagues [17] showed that in their cohort of 34 patients undergoing SVR+CABG, 60% had improvement in MR and 82% had improvement in EF, with EF increasing from 0.268 to 0.354 [17]. Lee and colleagues [18] reported that in their cohort of patients with an average MR of 1.36 who underwent SVR+CABG without mitral valve repair, MR improved by 53% [18], similar to the 57% improvement that we report here.
Previously published studies have reported MR grades using means and standard deviations to provide a method for evaluating incremental improvement in MR grade. Although statistically less accurate, this information is useful when comparing different treatment modalities, especially if used in conjunction with data that evaluate the absolute number of patients with improved MR. Therefore, for these reasons, and in order to compare our outcomes with previously published studies, we have reported both mean and median MR grades. Menicanti and colleagues [16] showed that in patients with a preoperative MR grade of 2.9 ± 1.2 who underwent SVR+CABG with mitral repair, MR improved to 1.5 ± 1.2 late after surgery. These patients also had significant improvement in EF (0.30 to 0.34) and NYHA functional class. Additionally, this group showed that 87% of patients with 3+ to 4+ MR preoperatively who underwent only SVR+CABG had 1+ to 2+ MR postoperatively [16]. Based on their studies, the group concluded that 2+ MR was detrimental and recommended that even mild MR be corrected [16]. In our SVR+CABG cohort, the average MR grade improved from 2.24 ± 0.5 to 1.24 ± 0.9, with 60% of patients improving to 0 to 1+ MR. At follow-up, left ventricular function, NYHA functional class, and incidence for rehospitalization for CHF were all significantly improved in the SVR+CABG group. It therefore appears that in some patients with 2+ to 3+ MR, SVR+CABG without mitral valve repair may have results comparable with SVR+CABG with mitral valve repair [16, 18]. We suggest that TEE be performed in all patients undergoing SVR+CABG. If the degree of remaining MR after coming off cardiopulmonary bypass is greater than 2+, we advise returning to bypass to repair the valve. Five patients within the SVR+CABG cohort and 7 patients within the CABG cohort had a preoperative MR grade 3+ or greater, but in both study groups, four patients had improved to mild to moderate MR intraoperatively by TEE and therefore no valve procedures were performed. Of note, of these patients at follow-up, only one in the SVR+CABG group had MR 3+ or greater compared with the CABG group, where there were two deaths and two patients with MR 3+ or greater.
The SVR procedure most likely improves MR by reducing chordal tethering and improving left ventricular geometry. Yu and colleagues [26] showed that an increase in left ventricular end-systolic volume is associated with an increase in the interpapillary distance and distance from the anterior mitral annulus to the medial papillary muscle root. During the SVR procedure, the longitudinal axis is shortened by bringing the stretched papillary muscles toward the annulus to reduce the sphericity of the left ventricle thereby reducing ventricular volumes. In a series by Menicanti and colleagues [16] ventricular size and shape improved in patients undergoing SVR, along with reductions in chordal tethering and interpapillary muscle distance. Other studies documenting improved MR after SVR have proposed similar theories [17, 27]. One must be careful, however, to remember that improper placement of the purse-string or "Fontan" stitch too close to the papillary muscles can have detrimental effects and increase tethering of the subvalvular apparatus. Maintaining recognition of this issue in placing the purse string, the use of sizing devices, and the use of patches to reconstruct the ventricle can all reduce the incidence of this problem. Additionally, it is important to note that the SVR procedure does not address the annular dilation component of MR; therefore, for these patients, annular reduction may be needed.
Revascularization alone may play a significant role in the degree of MR reduction in some patients. While we knew that 77% of patients in both study groups had a history of angina, we did not perform standardized testing for ischemia to accurately consider the role of revascularization on reduction in the degree of MR. However, because the percentage of patients with three-vessel coronary artery disease was equal in both groups and MR did not improve equally in the CABG cohort, it is reasonable to consider that SVR itself played a significant role in MR improvement.
The multicenter Reconstructive Endoventricular Surgery returning Torsion Original Radius Elliptical (RESTORE) study evaluated the outcomes of SVR in 1,198 CHF patients, and found an excellent 5-year survival of 69% in patients with ischemic cardiomyopathy after an anterior myocardial infarction [28]. Di Donato and colleagues [15] have retrospectively reviewed 245 SVR patients and found a 5-year survival of 85%. In our series of patients, SVR+CABG patients had a three-year survival of 85% despite preoperative MR. Comparatively, patients undergoing only CABG had a three-year survival of 72%. Although inferior to SVR+CABG, CABG patients did have improved EF, NYHA class, and MR grade at follow-up, with 25% of patients improving to 0 to 1+ MR postoperatively. These results parallel the findings of Wong and colleagues [29], who reported that MR grade decreased from 2.6 to 2.0 after the CABG procedure with a five-year survival of 67.5%. Similarly, Duarte and colleagues [30] reported a 5-year survival estimate of 77% in a similar patient population.
Our clinical observational study has limitations consistent with a retrospective analysis, specifically a strong reliance on patient history and the potential for selection bias. Classifications were based on the review of preoperative imaging and were thus inherently subjective. However, we attempted to mitigate the subjectivity of these classifications by having a single cardiac surgeon review all available echocardiograms and ventriculograms to determine a patient's candidacy for SVR. The surgeon was blinded to all preoperative characteristics and postoperative variables; therefore, inclusion in the study was based solely on cardiac function, ventricular enlargement, and wall motion abnormalities.
We have shown that the addition of SVR to eligible CABG patients leads to improved MR grade, EF, and NYHA functional class. Furthermore, patients who were eligible for the SVR procedure, but did not receive it, were significantly less likely to achieve similar improvements. Therefore, in eligible candidates the SVR procedure should be strongly considered to improve cardiac performance and decrease functional MR. While it is true that longer follow-up will enable us to make long-term conclusions about the benefits of SVR, our initial results indicate the importance of its application to potential candidates.
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Discussion
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DR CARMELO A. MILANO (Durham, NC): I would like to thank the Society for the opportunity to discuss this paper. I think this is a very interesting and novel paper. There are very few papers that look at the impact of ventricular procedures on ischemic mitral insufficiency. Furthermore, with some of the limitations of annuloplasty repair for mitral insufficiency, I think it is important that we look at the impact of other potential options such as ventricular procedures, on ischemic MR. It also is intuitive that these ventricular procedures would have a positive impact on ischemic MR, understanding that some of the etiology relates to the ventricular change, not just annular dilatation. So, again, I commend the Hopkins group and Dr Conte for pioneering in this avenue of research.
The paper, however, is limited. A big limitation is the sample size, of course; there are only about 30 patients in each group. And I had three specific questions. I also want to thank the authors for giving me the paper to read and look at carefully before.
The first question relates to the method of MR assessment. You are comparing preoperative and postoperative MR; is the modality of MR assessment equivalent pre and postop? Are these all TEEs or ventriculograms? Are we comparing the same modalities of assessment of MR before and after and are the time points of assessment on a protocol or were they just conducted at time points when the patients re-presented?
The second question relates to the way you excluded patients who had no or trace MR from the final analysis. I think a broader question is how does the SVR impact on MR in general, and I think the patients who began with minimal MR should be examined as well to know whether the procedure helps prevent these patients from progressing with MR. There were about 10 patients, or a third of each study group, who had 0 or 1+. They were excluded, and I think that we should examine the analysis including those and looking at how those patients changed with or without SVR.
And then lastly, I think it is important to acknowledge the importance of nonsurgical therapies in reducing ischemic MR, namely, afterload reduction, diuretic therapy, even BiV pacing. Were the applications of these nonsurgical therapies equivalent in the two groups, the group that got the SVR and then the group that did not receive that? Again, thank you, and it was a very interesting, novel paper.
MR PRUCZ: Thank you, Dr Milano. In response to your first question, which was regarding how we assessed pre and postoperative MR in these patients, I would like to begin by emphasizing that our aim was to determine the short-term effect of these procedures on mitral valve regurgitation. For all patients, pre and postoperative TTE's were the imaging modality of choice, and our goal was to obtain as recent of a follow-up as possible. However, for 30% of our patient population, the only postoperative TTEs available were those obtained prior to discharge. In contrast, for the remaining 70% of our population, TTEs were obtained at the most recent follow-up, which corresponded to an average time of nine months.
In response to your second question as to why we excluded individuals who had no MR in the broader analysis, we wanted to determine the effect of surgical ventricular restoration on patients who had preoperative mitral valve regurgitation to determine the impact that the addition of SVR to CABG had on their clinical outcomes. Therefore, initially we only focused on those patients with preoperative MR, but we of course did examine those patients that did not have any preoperative mitral regurgitation for completeness. We found that 27% of the patients in the CABG group had 3+ MR at follow-up compared to 21% in the SVR-CABG cohort. Please note that this finding was not statistically significant. Additionally, 37% of the patients who had no preoperative MR in the CABG group remained with no MR at follow-up compared to 29% of patients in the SVR-CABG group, although, once again, this was not statistically significant.
And the third question you asked regarded how we evaluated nonsurgical therapies. Unfortunately, the limitations imposed upon us by our study design (retrospective) make it difficult to address this issue fully since the patients in the two cohorts generally received postoperative treatments from different teams. Specifically, the SVR-CABG patients primarily continued their care at Hopkins while the majority of CABG patients resumed care with their outside referring physician. We do know, however, that all patients in both cohorts were discharged on an aspirin, a beta blocker, an ACE inhibitor, and a statin.
DR IRVING KRON (Charlottesville, VA): This was a very well presented paper and I want to congratulate your group on analyzing this very important subject. As you know, Menicanti has demonstrated that restoration may increase your MR. We agree with your conclusions, but I have two specific questions for you. When should severe MR be fixed at the time of the original procedure? I would have been scared to death to leave 4+ MR at the time and just do a restoration.
You have a final conclusion that is controversial. You say the patients with CABG that have MR probably should have a restoration. Why not just fix their mitral valve? Thank you.
MR PRUCZ: Thank you, Dr Kron. We reviewed the Menicanti paper as well, and we believe that the observed difference is due to modifications of the technique itself. Specifically, we believe that the placement of the Fontan stitch too close to the papillary muscles can actually increase the tethering on the subvalvular apparatus, which is a complication we have observed. Therefore, it is very important that when performing the SVR procedure the purse string be correctly placed, which is why we recommend the use of an intraventricular sizing device to help avoid the potential complication of increased papillary tethering.
With regards to when MR should be repaired, our group considers not repairing the valve only when mild to moderate mitral regurgitation is present. We advocate that in these patients, the CABG procedure and then the SVR procedure be performed. We then remove these patients from bypass, and if we see that these patients continue to have 2+ or greater MR at that time, we return to bypass and do repair or replace the valve. All patients who have moderate to severe MR receive a mitral valve repair. It is also important to remember that we don't believe all patients who undergo CABG with MR should undergo SVR, but only those patients who qualify for SVR based on the etiology of their heart dysfunction.
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Acknowledgments
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Mr Prucz has received research support from the Johns Hopkins School of Medicine Dean's Office and the American Federation for Aging Research. Dr Weiss is an Irene Piccinini Investigator in Cardiac Surgery. Mr Patel is the 2005 Chase Medical Scholar for Surgical Ventricular Restoration. Dr Nwakanma is a Hugh R. Sharp Cardiac Surgery Research Fellow. Dr Conte has received research support from Chase Medical Corporation.
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R. Prucz, E. S. Weiss, and J. V. Conte
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Ann. Thorac. Surg.,
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Abstract
Introduction
