Will Moderate Ischemic Mitral Regurgitation Improve with CABG?
Will Moderate Ischemic Mitral Regurgitation Improve with CABG?
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco. Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Penicka M, et al. Predictors of improvement of unrepaired moderate ischemic mitral regurgitation in patients undergoing elective isolated coronary artery bypass graft surgery. Circulation. 2009;120:1474-1481.
Ischemic mitral regurgitation (IMR) in patients referred for coronary artery bypass graft surgery (CABG) improves with revascularization in some cases, but in other cases it does not. In patients with severe IMR, mitral annuloplasty is recommended at the time of CABG. However, in patients with moderate IMR, it is not clear if mitral annuloplasty should be performed. Combined CABG plus mitral annuloplasty carries a higher mortality than isolated CABG and, therefore, if annuloplasty could be avoided in selected cases, that would be preferable. To safely avoid mitral annuloplasty, it would be necessary to have predictors of which patients would have an improvement in IMR by revascularization alone. Accordingly, Penicka et al performed a prospective, observational study of patients with ischemic cardiomyopathy and moderate IMR undergoing isolated CABG surgery and followed them for 12 months to determine preoperative predictors of improvement in IMR.
Penicka et al recruited patients referred for CABG who also had moderate IMR on echocardiography. They underwent detailed echocardiographic evaluation, including tissue Doppler imaging (TDI), and met the following criteria: stable left ventricular (LV) dysfunction with LV ejection fraction < 45% for at least three months, vena contracta 0.3 to 0.7cm, ratio of jet to left atrial (LA) area 20%-40%, and the absence of organic mitral leaflet pathology. TDI at the myocardial segment adjacent to the papillary muscles was used to assess synchrony of LV contraction. Patients also underwent dual-isotope, single-photon, emission-computed tomography (SPECT) with F18-fluorodeoxyglucose and technetium-99m tetrofosmin to determine myocardial viability in the 16-segment model. Follow-up at 12 months following CABG included echocardiography for assessment of mitral regurgitation. After excluding patients who had unstable clinical syndromes, overt heart failure or acute coronary syndromes in the prior 30 days, concomitant mitral valve lesions, or significant aortic valve pathology, 135 patients were enrolled. Patient demographics were well matched between groups. The mean age was 65 years, the majority were males, and 30% were diabetic. All patients underwent CABG alone with no other surgical procedure, and the mean number of bypassed vessels was 3.4.
Results: Perioperative mortality occurred in 4.4% and a further 6.2% died before 12-month follow-up, leaving 121 evaluable patients. Improvement in mitral regurgitation occurred in 57 patients, while the other 64 patients failed to improve (30 unchanged, 34 deteriorated). The number of dysfunctional but viable segments and preoperative dyssynchrony between the papillary muscles were the most accurate predictors of improvement of IMR following CABG. Lack of preoperative dyssynchrony (defined as < 60 ms between onset of contraction of the papillary muscles) showed the best ability to predict improvement in IMR, with positive and negative predictive values of 89% and 85%, respectively. The presence of five dysfunctional but viable segments also was predictive of improvement in IMR, although not as strongly predictive as lack of dyssynchrony. In patients who had both features (i.e., lack of significant dyssynchrony and five viable segments), 93% showed improvement in IMR. In contrast, only 34% of patients with dyssynchrony and 18% of patients without viability showed improvement in IMR after CABG. On multiple logistic regression, only five viable segments (odds ratio 1.45) and absence of dyssynchrony (odds ratio 1.49) significantly predicted improvement in IMR. Patients whose IMR improved were less likely to die (3.5% vs. 18.8%; p < 0.05) or be hospitalized for heart failure (5.3% vs. 21.9%; p < 0.01). Penicka et al conclude that reliable improvement in moderate IMR following isolated CABG was only observed in patients who had both viable (but dysfunctional) myocardium and the absence of dyssynchrony between the papillary muscles.
Commentary
Patients with coronary artery disease, ischemic cardiomyopathy, and ischemic mitral regurgitation are a heterogeneous group. Patients present at various stages of LV dysfunction and, eventually, the scarred LV irreversibly fails. Expecting that a single surgical approach, such as CABG alone or CABG plus mitral annuloplasty, would suit all patients is overly simplistic. Prior studies of adding mitral annuloplasty to CABG in these patients have, thus, yielded inconsistent results. This study identifies two features that can predict whether IMR will improve with revascularization alone and, thus, may help select the right operation for the right patient. Echocardiography with TDI and SPECT imaging are widely available imaging modalities that may help clinicians decide the most appropriate surgical option for these patients. Patients who exhibit severe dyssynchrony and/or have few viable myocardial segments have more advanced ischemic LV damage and their IMR is less likely to improve with revascularization alone. They may, therefore, require CABG plus mitral annuloplasty. However, in patients with both large amounts of viable myocardium and the absence of dyssynchrony, revascularization alone is likely to improve IMR and, thus, they may only require CABG without mitral valve surgery. Importantly, reducing mitral regurgitation was associated with lower hospitalization and mortality rates in this study. Tailoring the appropriate operation for each patient based on preoperative predictors like this may yield better outcomes, but this requires validation in prospective, randomized treatment studies.
Ischemic mitral regurgitation (IMR) in patients referred for coronary artery bypass graft surgery (CABG) improves with revascularization in some cases, but in other cases it does not.Subscribe Now for Access
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