P veins contain muscle fibers connected to the left atrium. These muscle fibers may be electrically active and serve the source of atrial tachyarrhythmia. Compatible with this hypothesis, a more recent study demonstrated that all 4 pulmonary veins might serve as the source of focal atrial fibrillation (AF). The direction of mitral regurgitation (MR) flow in patients with mitral valve prolapse (MVP) is unusual. However, the mechanisms causing AF in patients with MVP have not been fully investigated. In this study, we investigated whether the direction of MR flow in the left atrium of patients with MVP plays an important role in the prevalence of AF and tested the hypothesis that the site of MVP predicts AF. • • • From January 1992 to December 1999, 118 adult Japanese patients (69 men, 49 women, mean age 50 18 years) with echocardiographic documentation of MVP, who were either admitted to our hospital or were outpatients, were enrolled in this study. Eightysix of 118 patients had floppy valves. Criteria for exclusion from the study were congenital heart disease, Marfan’s syndrome, rheumatic heart disease, coronary artery disease, significant aortic stenosis, aortic regurgitation, cardiomyopathy, lone AF, and paroxysmal AF. No patient was taking any drugs (i.e., diuretic or antiarrhythmic drugs). We performed electrocardiography and echocardiography before medical and surgical treatment, and evaluated the clinical characteristics. Chronic AF was defined as AF documented by electrocardiography on 2 occasions on at least 2 visits to the outpatient clinic or the hospital 6 weeks apart. This study was approved by our institutional human investigations committee, and written informed consent was obtained from all patients before participation. M-mode, 2-dimensional, and color Doppler transthoracic echocardiography were performed in all patients with a Toshiba 160A system (Toshiba Medical Systems Co. Ltd, Tokyo, Japan) or a Hewlett-Packard SONOS 2500 system (Hewlett Packard, Palo Alto, California) with a 2.5MHz transducer. The left atrial diameter, left ventricular end-diastolic dimension, and left ventricular end-systolic dimension were determined by M-mode echocardiography. Fractional shortening of the left ventricle was determined with the M-mode echocardiogram in the standard manner. Echocardiographic morphologic characteristics of the mitral leaflets were estimated from images obtained from the parasternal longand short-axis views, and apical 4-chamber and long-axis views. Two-dimensional echocardiographic evidence of prolapsed leaflets was defined as a superior protrusion of the mitral leaflets into the left atrium, crossing the plane of the mitral annulus, with the coaptation point of the leaflets remaining at or superior to the mitral annular plane during systole. The site of MVP was assessed by 2-dimensional and color Doppler echocardiography. MVP was located at 6 sites: 3 anterior mitral leaflet sites (anterior commissural site, middle site, posterior commissural site) and 3 posterior mitral leaflet sites (medial scallop, middle scallop, lateral scallop). The involved site of scallop was determined by 2 different, independent observers and by the same observer on repeated assessment. The severity of MR was estimated by color Doppler echocardiography with a 2.5-MHz transducer. The degree of MR was assessed in terms of the distance in the left atrium reached by regurgitant flow from the mitral valve orifice, the maximum regurgitant jet area expressed as a percentage of the left atrium area, and the proximal isovelocity surface area visible in any view. MR was classified as trivial, mild, moderate, or severe. In this echocardiographic study, some patients were withdrawn because of suboptimal technical quality. Patients with MVP in 2 sites were excluded from the study, because leaks often include several scallops of the posterior leaflets. The clinical variables were age, sex, history of hypertension, current cigarette smoking, diabetes mellitus, and hypercholesterolemia. Hypertension was defined as a systolic blood pressure of at least 140 mm Hg or a diastolic blood pressure of at least 90 mm Hg From the Department of Cardiology and Community and Family Medicine, Jichi Medical School, Minamikawachi-Machi, Tochigi, Japan. This study was supported in part by a Research Grant 12670686 from the Ministry of Education, Science and Sports, Tokyo, Japan. Dr. Yamamoto’s address is: Department of Cardiology, Jichi Medical School, Minamikawachi-Machi, Tochigi, Japan 329-0498. E-mail: kyamamoto@jichi.ac.jp. Manuscript received February 25, 2001; revised manuscript received and accepted May 18, 2001. TABLE 1 Patient Characteristics
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Jul 1, 2002
Aree Kantachuvessiri 
Open Access
