Circulation. 2006;114:I-573-I-576
doi: 10.1161/CIRCULATIONAHA.105.001230
(Circulation. 2006;114:I-573 – I-576.)
© 2006 American Heart Association, Inc.
Surgery for Valvular Heart Disease |
Impact of Moderate Functional Mitral Insufficiency in Patients Undergoing Surgical Revascularization
Eugene A. Grossi, MD;
Gregory A. Crooke, MD;
Paul L. DiGiorgi, MD;
Charles F. Schwartz, MD;
Ulrich Jorde, MD;
Robert M. Applebaum, MD;
Greg H. Ribakove, MD;
Aubrey C. Galloway, MD;
Juan B. Grau, MD;
Stephen B. Colvin, MD
From the Departments of Cardiothoracic Surgery (E.A.G., G.A.C., P.L.D., C.F.S., U.J., R.M.A., G.H.R., A.C.G., J.B.G., S.B.C.) and Cardiology (U.J., RMA.), New York University School of Medicine, New York, NY.
Correspondence to Eugene A. Grossi, MD, New York University Medical Center, Suite 9-V, 530 First Ave, New York, NY 10028. E-mail grossi{at}cv.med.nyu.edu
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Abstract
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Background— Mild and moderate functional ischemic mitral
insufficiency present at the time of surgical revascularization
present clinical uncertainty. It is unclear whether the relatively
poor outcomes in this cohort are dependent on valvular function
or related to left ventricular dysfunction. The purpose of this
study was to examine the early and late outcomes in patients
with less-than-severe functional ischemic mitral insufficiency
at the time of isolated coronary artery bypass grafting (CABG).
Methods and Results— From 1996 through 2004, 2242 consecutive patients undergoing isolated CABG were identified as having none to moderate mitral regurgitation (MR) and no valve leaflet pathology. All of the patients at this single institution routinely had an intraoperative transesophageal echocardiography, prospectively quantified MR, and ejection fraction (EF). The New York State Cardiac Surgery Reporting System infrastructure was used to prospectively collect in-hospital patient variables and outcomes. Social Security Death Benefit Index was used to determine long-term survival. Odds ratio and significance (P value) are presented for each determined risk factor. There were 841 patients (37.5%) with no MR, 1137 (50.7%) with mild MR, and 264 (11.8%) with moderate MR. The patients with moderate MR were more likely to be older, female, and have more renal disease, previous MI, congestive heart failure, previous cardiac surgery, and lower EFs. Hospital mortality was independently and significantly associated with renal disease, decreasing EF, increasing age, previous cardiac operation, and cerebral vascular disease. Multivariable analysis revealed decreased survival with increasing age, previous operation, congestive heart failure, diabetes, nonelective operation, decreasing EF, and the presence of moderate MR (expß = 1.49; P=0.007) and mild MR (expß = 1.34; P=0.033).
Conclusions— Independent of ventricular function, mild and moderate functional mitral insufficiency are associated with significantly decreased survival in patients undergoing CABG. Whether correction of moderate functional MR at the time of CABG improves outcome still needs to be determined.
Key Words: mitral valve • regurgitation • ischemia
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Introduction
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Functional mitral regurgitation (MR) secondary to coronary artery
disease, also known as ischemic MR (IMR), is not rare in patients
with coronary artery disease.
1 MR, even if mild, is an independent
predictor of post-myocardial infarction (MI) mortality.
2 Similarly,
the presence of MR in patients undergoing percutaneous coronary
intervention decreased survival over 3 years.
3 MR has also negatively
influenced long-term outcomes after surgical revascularization.
4 Although it is well accepted to correct severe MR at the time
of coronary artery bypass grafting (CABG), there is less consensus
about the indications for intervention with either 2+ or 3+
MR.
5–8 In addition, it is uncertain whether the poorer
outcomes in this group are dependent on the valvular dysfunction
or whether it is merely a surrogate marker of extensive comorbidities,
particularly the amount of ventricular dysfunction. Short of
randomization, the determination of the appropriateness of such
valvular intervention will depend on the analysis of the risks
and expected benefits. We reviewed our patients to explore the
impact of less-than-severe MR at the time of isolated CABG.
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Methods
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All of the patients undergoing isolated CABG from 1996 through
2004 were identified in the cardiac surgery institutional database
of New York University Medical Center, Tisch Hospital. All of
the patients undergoing cardiac surgery at New York University
were intraoperatively studied with transesophageal echocardiography
(TEE), which analyzed leaflet pathology and graded MR and left
ventricular (LV) ejection fraction (EF). We identified 2242
patients without any structural leaflet pathology and less-than-severe
MR, and these are the subjects of this report. Definitions of
preoperative risk factors are those used in the New York State
Cardiac Surgery Reporting System. This is a state-mandated,
audited cardiac risk factor and outcome data collection instrument
where the data are prospectively collected by trained nurse
clinicians. Follow-up survival information was obtained by querying
the Social Security Death Benefit Index.
All of the transesophageal echocardiography examinations were performed after induction of anesthesia and before the start of each case. Examinations were done by an attending cardiologist or appropriately credentialed anesthesiologists and recorded for later interpretation by an attending cardiologist. Examination of the maximal length and width of the regurgitant jet in the 4- and 2-chamber views were used in the determination of the severity of MR.9 Moderate-to-severe and severe MR were excluded from this study; none and trace were analyzed as no MR.
Statistical analysis was performed with SPSS statistical software (SPSS Inc). Continuous variables were analyzed by Student’s t test and categorical variables by the 
2 test. Multivariate analyses of hospital mortality were performed with backwards stepwise logistic regression; survival analysis was performed using the Cox methodology.
We had full access to the data and take full responsibility for its integrity. We have all read and agree to the article as written.
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Results
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We identified 2242 patients undergoing isolated surgical revascularization
without any structural mitral valve abnormalities. Of this group,
841 patients (37.5%) had no MR, 1137 (50.7%) had mild MR, and
264 (11.8%) had moderate MR. The patients with moderate MR were
more likely to be older, female, and have more renal disease,
previous MI, congestive heart failure (CHF), previous cardiac
surgery, and lower EFs (
Table 1.) The comorbidities of diabetes,
cerebral vascular disease, peripheral vascular disease, chronic
obstructive pulmonary disease, and the presence of multivessel
disease did not significantly differ among the groups.
Overall hospital mortality was 1.9%. The incidence of mortality associated with the presence of each risk factor, as well the subanalysis by MR category, is presented in Table 2. Almost universally, increased MR was associated with an increased risk ratio for any given individual risk factor. Multivariable analysis revealed that hospital mortality was independently and significantly associated with renal disease, decreasing EF, increasing age, previous cardiac operation, and cerebral vascular disease (Table 3). Nonemergent operation, CHF, and worse MR category were weakly associated with increased mortality.
Five-year all-cause mortality survival was 84±1.0% for all of the patients. Survival was 86±1.0% for patients with no MR, 84±1.0% for patients with mild MR, and 70±1.0% for patients with moderate MR (P<0.001; Figure 1). Multivariable analysis for all survival revealed that age, previous operation, CHF, diabetes, nonelective operation, and decreasing EF were all associated with decreased overall survival (Table 4). Likewise, both the presence of moderate MR (expß = 1.49; P=0.007) and mild MR (expß = 1.34; P=0.033) were independently associated with decreased overall survival.
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Kaplan-Meier survival graph of moderate MR vs mild MR vs no MR. Freedom from all-cause death, stratified by the preoperative presence of moderate, mild, or no MR.
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Discussion
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This study demonstrates that, independent of ventricular dysfunction,
both mild and moderate MR are associated with decreased survival.
This contravenes the previous assumption that the poor outcomes
associated with coronary disease and functional MR were a direct
result of the ventricular injury and associated comorbidities,
that is, functional MR is not a surrogate variable for LV dysfunction
and coronary disease burden. This is similar to the recent findings
of Schroder et al
10 at Duke University who saw worse outcomes
associated with both mild and moderate MR. Unlike their study,
which included MR of all types, not just functional, we limited
our analysis to those patients with functional MR only. In addition
to the etiologic differences of the mitral dysfunction, the
Duke group routinely used provocative testing with afterload
challenge and volume loading in the operating room to "offset"
the potential effects of general anesthesia in assessing the
MR; this is not our protocol. The negative long-term survival
impact of mild MR parallels the findings in the post-MI
2 and
the postpercutaneous coronary intervention
3 patient populations.
This is despite the fact that neither of these often quoted
series had a very in-depth analysis of patient comorbidities
as in our current series.
The recent case-controlled CABG alone study by Lam et al11demonstrated a significant increase in relative risk of hospital death in the presence of moderate MR (mild MR was not analyzed). Using propensity-matched cohorts, they found the presence of moderate IMR as an independent risk factor for mortality and that this risk persisted for 5 years as compared with controls without MR. They concluded that there was no reliable improvement in MR after CABG, and there was an increased mortality, similar to series, which persisted into the late period. The importance of moderate MR as an independent risk factor for hospital mortality only reached borderline significance in our series. Of note, moderate MR in their series was composed of both 2+ and 3+ MR.
The potential surgical impact of repairing MR was evaluated by the recent Cleveland Clinic analysis,12 which compared survival outcomes of degenerative and functional ischemic MR patients who underwent revascularization and repair. Via propensity analysis, they found that the "large survival discrepancies between patients with ischemic and degenerative MR is attributable to the differences in patient profiles, particularly the extent of ischemic disease and LV dysfunction." Although their patient population was skewed toward severe MR, 15% of ischemic patients had 2+ MR. and 51% had 3+ MR. By correcting the MR, long-term survival became dependent on the preexisting comorbidities.
Limitations
Despite the prospective collection of our data, this study is retrospective. The strength of the study is that it represents a very large cohort of consecutive patients from an institution very experienced with IMR. Although it is acknowledged that there is a significant incidence of intraoperative MR underestimation by TEE,13 this methodology was applied equally to our entire cohort, and this is exactly the information that is presented to the surgeon in the operating room. Using this type of data will help establish an understanding of the incremental risk imposed on the patient as viewed intraoperatively by the surgeon. In addition, the presence of advanced degrees of MR can lead to an overestimation of ventricular performance based on EF. However, this value is still the most widely reliable and applicable clinical indicator of LV performance available.
Conclusions
In all patients undergoing isolated CABG without severe MR, the presence of moderate MR, and even mild MR, is associated with decreased survival. This association is independent of the severity of LV dysfunction and the numerous comorbidities seen in this patient cohort. Furthermore, no association was found between the amount of coronary artery disease and the outcomes in these patients. However, it remains unknown whether MV repair at the time of CABG will improve the survival of patients with mild or moderate MR or alter the unfavorable natural history of this disease.
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Acknowledgments
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Disclosures
None.
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Footnotes
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Presented at the American Heart Association Scientific Sessions,
Dallas, Tex, November 13–16, 2005.
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Abstract
Introduction