LETTERS TO THE EDITOR
Reply
Maurice Enriquez-Sarano, MD, FACCa
a Cardiovascular Diseases and Internal Medicine, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
We appreciate the interest of Drs. Harris and Maron regarding our recent article in JACC (1). In their comments, Drs. Harris and Maron raised the question of an "increased" or "enhanced" risk of sudden death in mitral regurgitation due to a flail leaflet. We did not use such terms, because there is no available method to compare the rates of sudden death between patients and the general population. Therefore, it is impossible to determine whether rates of sudden death are statistically in excess of those observed in the population. This is an important limitation of all studies on sudden death. Age-stratified rates of sudden death were reported in the Framingham Study (2). An informal comparison of those rates suggests that at similar ages, rates of sudden death in mitral regurgitation due to a flail leaflet (without risk factors for sudden death) are approximately twice those observed in the general population (0.8% vs. 0.37%). Hence, the terms "relatively common" or "notable" seem more appropriate to describe the rates of sudden death observed in mitral regurgitation due to a flail leaflet.
The issue raised regarding coronary artery disease (CAD) is an important one. The age of patients with a flail leaflet is also an age at which there is a relatively high prevalence of CAD. However, as in our study, practicing cardiologists usually assess the risk of sudden death without the information provided by coronary angiography, a test usually performed only preoperatively. If we examine, as suggested by Drs. Harris and Maron, patients without a history of possible CAD, the 10-year rate of sudden death is 17.2 ± 4.7%. In patients in functional class I or II, with an ejection fraction  60%, no atrial fibrillation and no history of possible CAD, the linearized sudden death rate is 0.86% per year. Therefore, accounting for a history of clinically overt coronary disease would not have modified the conclusion of our study. Both the notable rate of sudden death in patients with mitral regurgitation due to a flail leaflet and the decreased rate of sudden death observed after mitral regurgitation surgery suggest a link between mitral regurgitation and this dreadful event.
The other question raised by Drs. Harris and Maron is about the concept of mitral valve prolapse and flail leaflets. Contrary to the statement of Drs. Harris and Maron, the criteria for a diagnosis of a flail leaflet (page 2079, Methods) and the cause of a flail leaflet (page 2079, Results) are explicitly mentioned. We are not aware of criteria supporting the description of mild, moderate or severe degrees of flail leaflets mentioned by Drs. Harris and Maron. In contrast, the degree of mitral regurgitation can be assessed and is mentioned in the Results section. Among the 317 patients in whom the degree of mitral regurgitation was graded, 82% had grade III or IV mitral regurgitation. Nevertheless, the comments of Drs. Harris and Maron raise an important question that will need to be addressed in future studies. The respective risks of sudden death attached to the degree of mitral regurgitation, left ventricular volume overload or left atrial volume overload, and to the morphologic characteristics of the mitral valve (i.e., simple mitral valve prolapse vs. flail leaflet or the presence of severe myxomatous infiltration), cannot yet be analyzed. Recently, it has been suggested that mitral valve prolapse is uniformly a good prognosis (3). It is unclear how these various components of the clinical presentation of patients with mitral valve diseases contribute to the outcome, in particular to the risk of sudden death. We agree that further studies are needed on the outcome of various types of mitral valve disease. Such studies will require analysis of large population-based groups of patients with mitral valve disease. At this point, our study allows us to define the notable risk of sudden death incurred under conservative management by patients with flail leaflets, who represent a large group of candidates for surgical correction of mitral regurgitation.
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References
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1. Grigioni F, Enriquez-Sarano M, Ling L, et al. Sudden death in mitral regurgitation due to flail leaflet. J Am Coll Cardiol. 1999;34:2078–2085[Abstract/Free Full Text]
2. Kannel WB, Doyle JT, McNamara PM, Quickenton P, Gordon T. Precursors of sudden coronary death: factors related to the incidence of sudden death. Circulation. 1975;51:606–613[Abstract/Free Full Text]
3. Freed LA, Levy D, Levine RA, et al. Prevalence and clinical outcome of mitral-valve prolapse. N Engl J Med. 1999;341:1–7[CrossRef][Medline]
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