Interact CardioVasc Thorac Surg 2007;6:538-546. doi:10.1510/icvts.2007.157891
© 2007 European Association of Cardio-Thoracic Surgery
Best evidence topic - Cardiac general |
Should patients undergoing coronary artery bypass grafting with mild to moderate ischaemic mitral regurgitation also undergo mitral valve repair or replacement?
Aseem Ranjan Srivastavaa,
Amit Banerjeea,
Samuel Jacobb and
Joel Dunningc,*
a Department of Cardiothoracic and Vascular Surgery, G B Pant Hospital, New Delhi, India
b Department of Cardiothoracic Surgery, Aberdeen Royal Infirmary, Aberdeen, UK
c Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK
Received 16 April 2007;
received in revised form 23 April 2007;
accepted 26 April 2007
*Corresponding author. Tel./fax: +44-780-1548122.
E-mail address: joeldunning{at}doctors.org.uk (J. Dunning).
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Abstract
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A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether mitral valve repair at the time of coronary artery bypass grafting (CABG) in patients with coronary artery disease and mild to moderate mitral insufficiency improves short and long-term outcome. Altogether 465 papers were found using the reported search, of which 16 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that there is good evidence to suggest that moderate mitral regurgitation in patients undergoing isolated CABG adversely affects survival and mitral regurgitation does not reliably improve after CABG alone. Unfortunately, the evidence to support mitral valve repair at the time of CABG to improve long-term survival is still weak. On balance, patients with moderate ischaemic mitral regurgitation having CABG should have mitral repair at the same time, although the evidence to support this is weaker than one might like.
Key Words: Mitral valve insufficiency; Myocardial revascularization; Mitral repair; Coronary artery bypass graft
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1. Introduction
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A best evidence topic was constructed according to a structured protocol. This protocol is fully described in the ICTVS [1].
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2. Clinical scenario
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You are planning coronary artery bypass grafting on a 55-year-old patient with two myocardial infarctions in the past and severe triple vessel disease on angiography. His ejection fraction is 40%. He also has moderate ischaemic mitral insufficiency on echocardiography. It is your usual practice to just perform the bypass grafting, assuming that the myocardial function will improve and the mitral insufficiency will resolve. However, a cardiologist tells you that, in his experience, they always do better if the mitral valve is repaired and the mitral regurgitation often does not improve if this is not done. You resolve to look up this topic in the literature.
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3. Three-part question
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In (patients undergoing coronary artery bypass grafting) does (repair of mild to moderate ischemic mitral insufficiency) improve (survival or functional status).
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4. Search strategy
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Medline 1950–April 2007 using the OVID interface.
[exp mitral valve insufficiency/OR mitral regurgitation OR mitral valve regurgitation.mp OR mitral incompetence.mp OR mitral valve incompetence.mp OR mitral valve insufficiency.mp OR mitral insufficiency.mp] AND [exp Myocardial revascularization/OR revascularization.mp OR exp coronary artery bypass/OR CABG.mp OR Coronary art$ bypass.mp] AND [outcome.mp or exp Treatment outcome/OR exp survival/OR survival.mp OR Ventricular Dysfunction, Left/OR ejection fraction.mp OR Ventricular failure.mp]
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5. Search outcome
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Four hundred and sixty-five papers were found in Medline. From these 16 were deemed to be relevant and were reviewed in full. These are summarized in Table 1.
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6. Results
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Mild and moderate mitral regurgitation (MR) is a common coexisting problem in patients undergoing CABG with reported incidence of 28.2% [8] to 50.7% [2] for mild MR, and 4.0% [8] to 11.8% [2] for moderate MR. However, optimal management of these patients remains controversial. Recent data [5, 9, 12] contest the previous notion that most ischaemic MR will resolve after CABG alone, with a significant number of patients showing progression (12–25% [5], 30.6% [13]) and many more with an unchanged MR grade (28% [5], 52% [9], 35% [12]). Although a significant number of patients will have some reduction in the MR grade (33% [5], 63% [12]), complete resolution appears to be uncommon (14% [5], 8% [9]).
Even with reports that suggest otherwise [10, 12], evidence is now mounting that residual MR in these patients will adversely effect survival [2, 8, 14, 17]; event-free survival [8, 13, 17] and late functional status [13, 17]. While it is known that any degree of MR after myocardial infarction negatively influences survival [18] and that the presence of MR in patients undergoing percutaneous intervention (PCI) portends a lower 3-year survival [19], it appears unlikely that patients undergoing surgical revascularisation will have a different outcome. Results from 16 studies dealing with the subject (Table 1) though conflicting, support similar conclusions.
While the negative impact of residual MR is now documented, the benefits of an additional mitral valve procedure are less convincingly established, with a few studies suggesting a survival benefit [6, 7] while others do not [3, 16]. Higher operative mortality, non-standardised mitral valve procedures, selection bias, small sample size and lack of long-term follow-up are critical drawbacks of these small number of studies. In addition, since all these studies are retrospective, they have a questionable validity in the present era (when mortality for combined CABG and mitral valve repair is decreasing and results of restrictive ring annuloplasty are improving).
A common drawback for all studies is the lack of data on the postoperative medical management of MR, and it still needs to be shown whether a surgical approach will yield better results over an optimised and aggressive medical management of MR in patients post-CABG.
As already stated, many patients with coronary disease and MR will not show remission after CABG alone [5, 9, 12, 13], however, it is equally important to realise that a significant number will, and a blanket procedure on the mitral valve for all patients may be considered unacceptable for many surgeons. There is evidence to suggest that higher preoperative MR grade, LV dysfunction, lower incidence of significant PDA stenosis grafted, LBBB and lack of beta blocker use are risk factors for postoperative MR progression [5]. However, identification of preoperative variables that reliably predict the need to address the mitral valve at the time of CABG is imperative and needs to be directly addressed in future studies and may have a more crucial impact on the issue.
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7. Clinical bottom line
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We conclude that there is good evidence to suggest that moderate mitral regurgitation in patients undergoing isolated CABG adversely affects survival and mitral regurgitation does not reliably improve after CABG alone. Unfortunately, the evidence to support mitral valve repair at the time of CABG to improve long-term survival is still weak. On balance, patients with moderate ischaemic mitral regurgitation having CABG should have mitral repair at the same time, although the evidence to support this is weaker than one might like.
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Abstract
1. Introduction