CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Blase A. Carabello, MD*
* Medical Care Line Executive, Houston Veterans Affairs Medical Center, Veterans Affairs Medical Center, Bldg 100, Room 4C211, 2002 Holcombe, Houston, Texas 77030-4211 (Email: blaseanthony.carabello{at}med.va.gov).
I thank Dr. Kapoor for his interest in my review (1) and entirely agree that improvement in symptoms often accompanies surgery for secondary mitral regurgitation (MR). The remaining question is: how does surgery do so? Three potential mechanisms come to mind. First, there is the placebo effect of surgery. Over 5 decades ago implantation of the internal mammary artery directly into the myocardium and/or ligation of the internal mammary arteries reduced the symptoms of myocardial ischemia, whereas more recently sham knee surgery had an equal outcome to arthroscopic lavage and/or debridement (2–4), demonstrating the power of the placebo. It seems highly unlikely that sham mitral surgery will ever be performed to test the placebo hypothesis, but it should be kept in mind. A second mechanism by which mitral valve surgery for secondary MR might be helpful is the one that seems most obvious, by elimination of the MR. The Acorn trial found substantial reverse remodeling in the mitral valve repair arm of the trial supporting this mechanism (5). However, almost all mitral repairs also alter the mitral annulus, and many rings now attempt to alter ventricular geometry, raising this as a third possibility (6). Thus it is unknown whether it is the annuloplasty or correction of the MR or both that is beneficial. It would have been enlightening if the Acorn trial had an Acorn-only arm. Quite possibly it would have been as effective as the annuloplasty.
We have much to learn about the role of secondary MR and its correction in the treatment of heart failure. It seems so simple to say "it's there, it's bad, let's fix it," and that might be the correct approach, but it also might not be. Let's not let the genie out of the bottle until we have better proof.
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1. Carabello BA. The current therapy for mitral regurgitation J Am Coll Cardiol 2008;52:319-326.[Abstract/Free Full Text]2. Vineberg A, Munro DD, Cohen H, Buller W. Four years' clinical experience with internal mammary artery implantation in the treatment of human coronary artery insufficiency including additional experimental studies J Thorac Surg 1995;29:1-32discussion 32–6. 3. Johnson AS, Griffin R. Bilateral internal mammary artery ligation in coronary artery disease: clinical report of thirty cases J Mich State Med Soc 1959;58:84-85.[Medline] 4. Moseley JB, O'Malley K, Petersen NJ, et al. A controlled trial of arthroscopic surgery for osteoarthritis of the knee N Engl J Med 2002;347:81-88.[CrossRef][Web of Science][Medline] 5. Acker MA, Bolling S, Shemin R, et al. Acorn Trial Principal Investigators and Study Coordinators Mitral valve surgery in heart failure: insights from the Acorn Clinical Trial J Thorac Cardiovasc Surg 2006;132:568-577.[Abstract/Free Full Text] 6. Guy IV TS, Moainie SL, Gorman III JH, et al. Prevention of ischemic mitral regurgitation does not influence the outcome of remodeling after posterolateral myocardial infarction J Am Coll Cardiol 2004;43:377-383.[Abstract/Free Full Text]
Related Article
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Role of Mitral Valve Surgery for Secondary Mitral Regurgitation in Heart Failure
- John R. Kapoor
J. Am. Coll. Cardiol. 2009 53: 74.
[Full Text]
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