Coronary Revascularization Alone or with Mitral Valve Repair

Abstract

We sought to evaluate retrospectively the outcomes of patients at our hospital who had moderate ischemic mitral regurgitation and who underwent coronary artery bypass grafting (CABG) alone or with concomitant mitral valve repair (CABG+MVr).

A total of 83 patients had a reduced left ventricular ejection fraction and moderate mitral regurgitation: 28 patients underwent CABG+MVr, and 55 underwent CABG alone. Changes in mitral regurgitation, functional class, and left ventricular ejection fraction were compared in both groups.

The mean follow-up was 5.1 ± 3.6 years (range, 0.1–15.1 yr). Reduction of 2 mitral-regurgitation grades was found in 85% of CABG+MVr patients versus 14% of CABG-only patients (P < 0.0001) at 1 year, and in 56% versus 14% at 5 years, respectively (P = 0.1), as well as improvements in left ventricular ejection fraction and functional class. One- and 5-year survival rates were similar in the CABG+MVr and CABG-only groups: 96% ± 3% versus 96% ± 4%, and 87% ± 5% versus 81% ± 8%, respectively (P = NS). Propensity analysis showed similar results. Recurrent (3+ or 4+) mitral regurgitation was found in 22% and 47% at late follow-up, respectively.

In patients with moderate ischemic mitral regurgitation, either surgical approach led to an improvement in functional class. Early and intermediate-term mortality rates were low with either CABG or CABG+MVr. However, an increased rate of late recurrent mitral regurgitation in the CABG+MVr group was observed.

Coronary artery disease (CAD) can lead to ischemic mitral regurgitation (MR) due to myocardial ischemia or infarction in the absence of any intrinsic organic disease of the mitral valve. Uncorrected chronic MR is associated with a poor prognosis in patients after coronary revascularization by means of coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasty.^1–5 Many investigators have evaluated the pathogenesis of ischemic MR and have been able to show the crucial role of changes in the geometry of the left ventricle (LV) and papillary muscle due to the myocardial scarring that results in annular dilation and leaflet tethering.^6–8 Because of higher morbidity and operative mortality rates associated with combined revascularization and mitral valve surgery,3,4,9,10 some surgeons have advocated revascularization alone,^11,12 while others have recommended concomitant mitral valve surgery3,4,9,10,13–15 in order to optimize patients' cardiac function and long-term prognosis.

The clinical usefulness of combined surgery remains unclear due to the prolongation of cardiopulmonary bypass time and the additional technical complexity of such surgery in these patients. Although most surgeons would agree that mild MR can be treated by CABG alone and that severe MR should be corrected at the time of CABG, the optimal approach toward the management of moderate ischemic MR remains controversial. It has been shown that patients with moderate MR have lower survival rates after undergoing CABG alone than do patients who have no MR or mild MR,¹⁶ and that CABG alone leaves many patients with substantial residual MR.¹³ Although many studies have been undertaken in order to define the risk factors for high mortality rates and the appropriate approach, there is no clear consensus regarding the optimal treatment of these high-risk patients.

Most published studies that have focused on differences in outcomes between CABG alone and with concomitant mitral valve repair (MVr) were not limited to a single MR grade, and various mitral valve surgical procedures were used. In this study, we reviewed the outcomes of the most problematic subgroup of patients in terms of surgical approach—patients with moderate MR. We evaluated the effectiveness of CABG alone and CABG with MVr with regard to changes in functional class, postoperative MR, LV function, and survival.

Patients and Methods

Patient Population. We reviewed the medical records of 504 patients with MR who underwent revascularization alone or in combination with MVr at our hospital from March 1991 through September 2004. A total of 83 patients with moderate MR who underwent CABG and met the criteria of ischemic MR were included in this study. The definition of moderate (3+) MR was adopted from Aklog and colleagues,¹³ and we added the requirements of LV dysfunction (LV ejection fraction [LVEF], < 0.50) and a history of myocardial infarction. Patients with rheumatic, myxomatous, infectious, or congenital diseases of the mitral valve were excluded. Patients with MR due to papillary muscle rupture, torn or elongated chordae tendineae, or ballooning or scalloping of the mitral leaflets were also excluded. Twenty-eight of the 83 had undergone combined CABG+MVr surgery. In each instance, the operative approach for concomitant MVr had been chosen by the attending surgeon.

Evaluation of Mitral Regurgitation Preoperatively and during Follow-Up. The severity of preoperative MR was evaluated by use of left ventriculography alone (11%), transthoracic echocardiography alone (19%), or both (70%). Echocardiographic postoperative follow-up was available for 76% of the patients within the 1st year and for 39% of the patients during follow-up (13 mo–5 yr).

Contrast Left Ventriculography. The severity of MR was evaluated by use of preoperative left ventriculography and a previously described grading system.¹⁷

Echocardiography. Real-time 2-dimensional echocardiographic imaging was performed with use of an HP Sonos®, a Philips/ATL 5000 (Philips Medical Systems Co.; Bothell, Wash), or an ACUSON Sequoia™ color Doppler system (Siemens Medical Solutions USA, Inc.; Malvern, Pa). Images were recorded onto videotape or (since 2003) onto a Camtronics digital system. Transthoracic echocardiography was performed preoperatively in all patients within 1 month before surgery in accordance with previously described methods.8,9,13,14 The follow-up MR grade was defined semiquantitatively by visual estimation of the regurgitation jet area in relation to the left atrial area, modified from Nanda's criteria (regurgitant jet area/left atrial area between 20% to 40% for moderate MR¹⁸), or on the basis of the size and geometry of the regurgitant jet.¹⁹ Successful valve repair was defined as the reduction of MR by 2 or more MR grades.^14,15

Cause of Valve Disease. The cause of valve disease was determined from direct visual inspection of the mitral valve leaflets, annulus, chordae tendineae, and papillary muscles. If the valve was not repaired, the cause was determined from echocardiographic findings. An ischemic cause was concluded if the mitral leaflets and chordae appeared normal but there were findings of papillary muscle infarction or thinning, papillary muscle ischemia, or mitral annular dilation associated with LV dilation and healed infarction.^14,15

Surgical Procedure. Ischemic MR was repaired by 1 of several annuloplasty techniques at the discretion of the operating surgeon. No specific criteria were used in selecting a particular annuloplasty technique for an individual patient. Ring annuloplasty was performed by using an undersized ring in all cases, including Carpentier-Edwards Classic (Edwards Lifesciences LLC; Irvine, Calif), Dacron, pericardial, St. Jude Tailor® (St. Jude Medical, Inc.; St. Paul, Minn), and Medtronic (Medtronic Inc.; Minneapolis, Minn). No suture annuloplasty, ancillary leaflet repair, or chordal shortening procedures were performed in these patients. All patients who underwent MVr left the operating room with only mild MR as seen on intraoperative transesophageal echocardiography.

Postoperative Follow-Up. After surgery, follow-up was performed by means of a mailed questionnaire, telephone interview, or examination in our offices. Follow-up was conducted annually.

Statistical Analyses

Summary results for numeric variables were presented as mean ± SD. Summary results for categorical variables were presented as frequency and percentage. Group differences in numeric preoperative and operative variables were evaluated by use of the t test or the Wilcoxon rank sum test, as appropriate. Group differences in categorical preoperative and operative variables were evaluated by use of the Fisher exact test. The amount of missing data increased with increasing time after surgery. In order to preserve sample size, standard repeated-measures analysis of variance was not used to determine change across time (more than 2 time points). Instead, within-group change across 2 time points was determined by use of the paired t test or the Wilcoxon signed rank test, as appropriate. Group differences in change across 2 time points were evaluated by use of the t test or the Wilcoxon rank sum test. Survival was estimated in accordance with the Kaplan-Meier method, and group differences in survival with the log-rank test. Stepwise multivariable Cox proportional hazards regression was used to determine predictors of the risk of death.

Multivariate logistic regression was used to calculate the probability (propensity) of mitral repair (C statistic, 0.82). Model variables included age, baseline LVEF, sex, hypertension, diabetes mellitus, smoking history, family history of CAD, angina pectoris, history of myocardial infarction, baseline New York Heart Association (NYHA) functional class III or IV (vs lower), history of percutaneous transluminal coronary angioplasty, history of surgery, left main disease, presence of 3 or more diseased vessels, and year of surgery. Propensity within 0.05 was then used to match MVr patients with CABG-only patients; this resulted in 23 propensity-matched pairs. A significance level of 0.05 was used throughout. Statistical calculations were performed with use of SAS version 9.1 (SAS Institute, Inc.; Cary, NC).

Results

The mean age of the entire cohort was 68 ± 11 years, and 68% were men. Most patients (83%) presented with 3-vessel disease and a high prevalence of angina pectoris (70%). All patients had impaired LV function (mean LVEF, 0.38 ± 0.11), which may explain the high incidence of patients in NYHA functional class III or IV (77%). Patients also had significant noncardiac comorbidities, such as diabetes mellitus (34%), hypertension (64%), cerebrovascular events (21%), peripheral arterial disease (25%), and chronic obstructive pulmonary disease (14%). The mean duration of follow-up was 5.1 ± 3.6 years (range, 0.1–15.1 yr).

The baseline characteristics of the groups of patients who underwent CABG alone and CABG+MVr are presented in Table I. No significant differences in preoperative characteristics were found between the groups. More CABG+MVr patients had symptoms of heart failure (NYHA class III or IV) (P = 0.1), but fewer had angina pectoris (P = 0.08). The postoperative characteristics are shown in Table II. The CABG+MVr patients experienced significantly longer cross-clamp and on-pump times.

TABLE I. Preoperative Clinical Characteristics of the Groups

TABLE II. Postoperative Characteristics of the Groups

Survival. The 30-day mortality rate was similar in both groups (P >0.9). Intermediate-term survival was similar in both groups (P >0.9) (Fig. 1). One- and 5-year survival estimates in the CABG+MVr and CABG-only groups were 96% ± 3% versus 96% ± 4% and 87% ± 5% versus 81% ± 8%, respectively. Multivariable Cox regression analysis showed that significant predictors of death were diabetes mellitus (hazard ratio, 4.77; 95% confidence interval [CI], 1.45–15.7; P = 0.01), age (hazard ratio, 1.05; 95% CI, 1.02–1.18; P = 0.006), and preoperative LVEF ≥0.35 (hazard ratio, 4.49; 95% CI, 1.44–13.95; P = 0.009). The performance of MVr was not a significant predictor in the Cox model.

Fig. 1 Survival of 83 patients who underwent CABG only or CABG+MVr for moderate ischemic MR.

The summary table provides mean survival estimates (± SE) at 30 days and 1, 5, and 7 years, respectively.

CABG = coronary artery bypass grafting; MVr = mitral valve repair

Change in Mitral Regurgitation Grade. Changes in MR grade among the surviving patients are shown in Figure 2. Significant early (within 12 mo) postoperative improvement in MR grade was found in the CABG+MVr patients, in comparison with the CABG-only patients (P < 0.0001). At follow-up, there was a trend (P = 0.08) toward less MR in patients who had undergone the combined surgery. Among the survivors, 85% of CABG+MVr versus 14% of CABG-only patients (P < 0.0001) experienced a reduction of at least 2 MR grades within 1 year; and 56% versus 14%, respectively, within 1 to 5 years (P = 0.1). At long-term follow-up, unchanged grade 3+ MR was observed in 17% of the CABG group and 11% of the CABG+MVr group (P >0.9). A worsening of MR (to severe MR) was found at 5 years in 30% of the CABG group and 11% of the CABG+MVr group (P = 0.4); however, the difference did not reach statistical significance, likely due to the small number of patients for whom a follow-up echocardiogram was available.

Fig. 2 Changes in IMR grade at follow-up.

P value in figure refers to differences between groups. P < 0.05 was considered statistically significant. Within-group comparisons:

*CABG only, change in MR grade, baseline to 1 year, P = 0.36; **CABG+MVr, change in MR grade, baseline to 1 year, P < 0.004;

†CABG only, change in MR grade, baseline to 1–5 years, P = 0.07;

‡CABG+MVr, change in MR grade, baseline to 1–5 years, P = 0.03.

CABG = coronary artery bypass grafting; MR = mitral regurgitation; MVr = mitral valve repair; Post-op = postoperative period; Pre-op = preoperatively

Change in Left Ventricular Ejection Fraction. Improvement in postoperative LVEF was observed in each group (Fig. 3). Patients who underwent CABG alone showed significant improvement in LVEF at 1 year (P = 0.002) and at 1 to 5 years' follow-up (P < 0.0001). The CABG+MVr patients showed significant improvement at 1 year (P = 0.02) but not at 1 to 5 years (P = 0.4) (Fig. 3). Group differences in LVEF change over these times were not significant (P = 0.7 and P = 0.4 in the CABG and CABG+MVr groups, respectively).

Fig. 3 Changes in LVEF at follow-up.

P value represents differences in LVEF between the groups. P < 0.05 was considered statistically significant. Within-group comparisons:

CABG only versus CABG+MVr, change in LVEF, baseline to 1 year, P = 0.7;CABG only versus CABG+MVr, change in LVEF, baseline to 1–5 years, P = 0.24.

CABG = coronary artery bypass grafting; LVEF = left ventricular ejection fraction; MVr = mitral valve repair; Post-op = postoperative period; Pre-op = preoperatively

Change in Functional Class. The changes in NYHA functional class are presented in Figure 4. Improvement in heart-failure symptoms occurred postoperatively in both groups within 1 year and remained stable at 1- to 5-year follow-up. Postoperative NYHA class I or II status was found in 87% of the CABG group versus 67% of the CABG+MVr group at 1-year follow-up (P = 0.06), and in 82% versus 63% within 1 to 5 years (P = 0.1).

Fig. 4 Changes in NYHA functional class at follow-up.

P value in figure refers to differences between the groups. P < 0.05 was considered statistically significant. Within-group comparisons:

*CABG only, change in NYHA class, baseline to 1 year, P < 0.0001;

**CABG+MVr, change in NYHA class, baseline to 1 year, P < 0.0001;

†CABG only, change in NYHA class, 1–5 years, P < 0.0001;

‡CABG+MVr, change in NYHA class, 1–5 years, P < 0.0001.

CABG = coronary artery bypass grafting; MVr = mitral valve repair; NYHA = New York Heart Association; Post-op = postoperative period; Pre-op = preoperatively

Propensity Analysis. Although both groups were similar with respect to important baseline characteristics, propensity analysis was performed in order to minimize the effects of selection bias on outcomes. We matched 23 patients who underwent CABG with 23 who underwent CABG+MVr (receiver operating characteristic area C statistic, 0.82). Baseline preoperative characteristics were similar in the matched pairs, as was survival (P = 0.14). Significantly more improvement of MR was found in the CABG+MVr group at 1-year follow-up than in the CABG-only group (P = 0.0001) (Table III). No significant changes in LVEF at 1 year and 1 to 5 years were found in either group. There was a trend toward a larger 1st-year increase in LVEF in the CABG+MVr patients. Patients in both groups showed improvement in NYHA class at 1 year and remained unchanged within 1 to 5 years' follow-up.

TABLE III. Changes in Mitral Regurgitation Grade, NYHA Functional Class, and Left Ventricular Ejection Fraction in 23 Propensity-Matched Pairs

Discussion

Chronic ischemic MR, defined as functional MR in the presence of a normal leaflet structure, is due to CAD that affects the LV. In most cases, ischemic MR is a result of myocardial infarction; however, it can also be associated with ischemia.^20,21 Ischemic MR is present in as many as 20% of patients who have CAD, and it is associated with a worse prognosis after myocardial infarction and after revascularization.^3,22,23 The survival of patients with ischemic MR is related to the grade of regurgitation: survival rates are lower in patients with a greater degree of MR.²

The indications for surgery in patients with chronic ischemic MR are not well defined. The surgical approach for patients with severe MR is generally accepted and includes MVr in addition to revascularization; however, even in this population, the combined operation reduced the MR grade but did not improve survival rates.²⁴ Patients with mild or mild-to-moderate MR are usually considered for CABG only; however, several studies have determined a progression of mild MR to moderate or even severe grades in up to 25% of CABG-only patients, over time.^13,25–27 Conflicting findings have been reported regarding the survival of patients with mild-to-moderate MR: several studies have shown that survival in this population is not affected by ischemic MR.11,12,28,29 However, a more recent study showed decreased long-term survival in patients who had moderate MR,²⁵ suggesting that a more aggressive surgical approach should be considered.

Although it would be logical to suggest combined CABG and MVr in patients who have moderate MR, the impact of the MVr procedure on long-term survival, functional class, and LV improvement is still a matter of debate. A recent retrospective study showed no differences in survival among patients with moderate (3+) MR who underwent CABG alone versus patients who underwent CABG+MVr.³⁰

In our previously published analysis of our entire experience with patients who had ischemic MR,³¹ we found that patients with milder MR who underwent combined CABG and MVr experienced higher 30-day mortality rates and lower survival rates at 5 and 8 years in comparison with CABG-only patients. However, in patients with moderate and severe MR, we found a trend toward better survival in the 1st year with CABG+MVr, and no significant differences in 5-year survival rates.³¹

In the present study, we found that combined CABG and MVr in patients with moderate ischemic MR resulted in a greater decrease of early postoperative MR than did CABG alone. Either surgical approach led to improvement in functional status. Patients in both groups had low early and late mortality rates, despite the presence of impaired LVEF and moderate MR. Early death, intermediate-term survival, change in postoperative NYHA functional class, and LVEF were similar in both groups. Our chief results have been supported by a large, very recent report regarding ischemic moderate-to-severe MR,³² which found that additional MVr is insufficient to improve long-term clinical outcomes.

Survival and Its Predictors. The difference in 30-day mortality rates was not statistically significant between the CABG+MVr group and the CABG-only group (3.5% vs 1.8%; P >0.9). Previous investigators found significantly higher rates of early death in the MVr group, suggesting CABG alone as the preferable treatment option in patients with moderate MR who were also at high operative risk.³³ Another study, which also included patients with moderate MR, showed similar operative mortality rates.²⁴

In our study, we found that patients of either surgical option had very low early and intermediate mortality rates, despite the presence of multiple comorbidities, impaired LVEF, and moderate MR. This observation implies a decreasing risk and a growing benefit of surgery in the recent era for this extremely sick patient population.

The 1- and 5-year survival rates in CABG+MVr versus CABG alone were very similar (96% vs 96% and 87% vs 81%, respectively). The 5-year survival rates were higher than those in reports from 2005 and before,^30,34,35 but similar to those in more recent reports.^32,33 This can be partially explained by improvement in surgical techniques,²¹ which has resulted from a better understanding of the mechanism of ischemic MR.⁶ In addition, early surgical intervention can prevent LV remodeling that results from MR.³³ Previous studies have reported results of surgery in patients who had advanced myocardial disease and possibly irreversible damage.^21,35 Another explanation for our report of better survival is that, in our study, we included only patients who underwent MVr, and not patients in whom valve replacement was performed as a result of unsuccessful complex repair.

The predictors of survival with use of the Cox regression model were diabetes mellitus, age, and preoperative LVEF ≥0.35. The MVr procedure did not have a significant effect on survival after these variables were included. We also used propensity analysis to minimize the effect of confounding variables on patient outcome, but we found no differences in survival between the groups. Supporting our results is a case-controlled study that found similar intermediate-term survival in 58 CABG patients with moderate MR and case-matched patients without MR, suggesting that moderate ischemic MR need not be corrected at the time of CABG.¹¹ Several recent articles in which propensity analysis was used to develop control groups in order to compare CABG-only patients with CABG+MVr patients did not report a survival benefit that was attributable to mitral valve surgery.^32,34,35

Functional Improvement. We found a significant improvement in postoperative NYHA functional class in both groups in the 1st year after surgery. Furthermore, the patients remained stable during follow-up to 5 years. However, no significant differences in changes in NYHA class were observed between the groups, and the propensity analysis did not alter our results. Accordingly, revascularization was found to have a positive impact on functional status among patients with moderate MR. Similar to our results, several prior studies showed that revascularization with MVr improved NYHA class in patients with MR.^24,32,35

Change in Degree of Mitral Regurgitation and Left Ventricular Function. In this study, we found that the postoperative reduction of MR by 2 or more grades was significantly more frequent after CABG+MVr in comparison with CABG alone (85% vs 14%, P < 0.0001) within the 1st year, and that reduction in grade was only a trend from 1 to 5 years (56% vs 22%, P = 0.1). The lack of sustained significance may be due to relatively small numbers at longer follow-up. Accordingly, MVr resulted in acute reduction of moderate ischemic MR. This observation has been supported by other studies.^30,32,36

Although we found a trend toward less MR in the CABG+MVr group at late follow-up, 22% of patients in this group and 47% in the CABG-only group still had moderate or severe MR. The percentage of patients with MR on follow-up might be underestimated in our study due to the small number of patients for whom an echocardiogram at 5 years was available. Recurrence of MR can be explained by the fact that MR is more a ventricular than a valvular disease; therefore, mitral annuloplasty does not have a direct effect on later changes in ventricular geometry and function that contribute to the pathogenesis of ischemic MR.7,26–28,32 On the basis of previously published data, up to one third of patients experienced the recurrence of moderate MR or progression to severe MR^7,37; however, a subsequent report found even higher numbers of recurrent moderate MR in 37% of patients and severe MR in as many as 20%.³⁶

These findings suggest the recognition that myocardial factors are a chief cause of ischemic MR, and that there is the consequent necessity to examine modifications of existing repair methods, apply supplementary procedures (such as chordal cutting, infarct plication, and papillary muscle slings), develop new repair techniques, and re-examine the possible benefit of older techniques (such as mitral valve replacement with subvalvular apparatus preservation in selected cases²⁰), in order to confront the problem of late recurrent MR. New repair techniques will likely require long-term follow-up in order for their benefit to be shown.³⁸

Improvement in postoperative LVEF was observed in both groups within the year after surgery. Patients who underwent CABG alone showed significant early and late improvement over preoperative LVEF in comparison with those who underwent combined surgery, but only a small number of follow-up echocardiograms was available for this analysis. In the propensity-matched groups, no significant changes were found in LVEF at 1 year or 1 to 5 years in either group, although there was a trend toward an increase in LVEF in the 1st year in the patients who underwent the combined surgery. On the basis of the report that used comprehensive measures to evaluate LV remodeling in patients with recurrent mild-to-moderate MR, no significant changes in LVEF were found during the follow-up period; however, the worsening of MR over time paralleled an increase in LV volumes and sphericity index.⁷ A lack of significant increase in LVEF (and recurrence of MR) in patients with CAD may be due to recurrent ischemic events that occurred during the longer term and affected the LV.

Study Limitations

The chief limitation of this study is its retrospective nature with various sources of bias. Selection bias and lack of a uniform method of repair (different types of rings) are important limitations. Decisions to perform concomitant MVr were made on the basis of surgical considerations and preferences. The surgeon may have selected repair for those patients who had worse intraoperative MR or heart failure, and thus may have repaired valves in the sicker patients. The similarity of outcomes may imply an actual benefit of MVr in these patients. A randomized prospective design would overcome this limitation. Of note, we performed a separate propensity analysis in order to deal with the potential of selection bias.

Another limitation is the echocardiographic evaluation of MR grade and the lack of complete follow-up. Because of the retrospective nature of the study, we were unable to use newer measures for MR, such as proximal isovelocity surface area and effective regurgitant orifice. However, in most patients, the preoperative MR grade was evaluated by both ventriculography and echocardiography, which partially overcomes any grading problem. In all patients, preoperative evaluation was on the basis of transthoracic studies, and intraoperative MR downgrading thus could not affect the selection of patients. No data were available regarding LV wall motion abnormalities, which are important in the setting of MR; however, the inclusion criteria of this study were an LVEF of less than 0.50 and a history of myocardial infarction. Accordingly, we believe that our patient population was representative of patients who have MR.

Small sample size, especially in the propensity analysis, is another limitation of this study—the consequence of selecting a very homogeneous group with only moderate MR grade, a history of myocardial infarction, impaired LV function, and a single mitral valve surgical approach (mitral valve repair). The propensity analysis involved only 23 pairs, but it reflected an appropriate receiver operating characteristic, and this subanalysis was used chiefly to confirm the findings in the entire group.

Conclusions

In the recent past, patients who have undergone either CABG alone or CABG+MVr surgery have experienced very low early and late mortality rates, despite the presence of multiple comorbidities, impaired LVEF, and moderate MR. Mitral valve repair can be performed safely, concomitantly with CABG, in patients who have moderate ischemic MR. In such patients, the combined procedure resulted in a greater decrease in early postoperative MR than did CABG alone. Either surgical approach resulted in significant improvement of postoperative NYHA functional class. However, there was a high rate of late recurrent MR in the combined-surgery group, which perhaps accounted for the observed lack of survival benefit or improvement in LVEF in this group. Prospective randomized studies are warranted in order to evaluate the potential benefit of concomitant MVr in this patient population.

Acknowledgment

We would like to acknowledge Christopher Capelli, BS, for his support in data collection.