title: Echocardiographic characteristics and causal mechanism of physiologic mitral regurgitation in young normal subjects.
abstract: BACKGROUND
  It has become evident that mitral regurgitation (MR) is not uncommon in healthy subjects, and Doppler color flow mapping is a technique that imparts important information relevant to its detection.
  
  
  OBJECTIVE
  Using transthoracic echocardiography, this study evaluated the mechanism of physiologic MR in young normal subjects using transthoracic echocardiography.
  
  
  METHODS
  The study population consisted of 48 young normal subjects (mean 21 +/- 5 years) with MR (physiologic MR group), 40 age-matched young normal subjects (mean 20 +/- 5 years) without MR (control group), 45 patients (mean 41 +/- 15 years) with mitral valve prolapse with MR (MVP group), and 27 patients (mean 59 +/- 13 years) with ruptured chordae tendineae (rupture group).
  
  
  RESULTS
  Men were predominant in the rupture group, whereas there were no significant gender differences in the other three groups. Left ventricular end-diastolic dimension and left atrial systolic dimension were slightly smaller in the physiologic MR group than in the control group, but were significantly smaller than those in the MVP and rupture groups. The ratio of the maximum anteroposterior diameter to the maximum transverse diameter on chest radiography and the ratio of the short- to long-axis diameter of the left ventricular cavity at end diastole, determined from two-dimensional short-axis echocardiogram, were significantly lower in the physiologic MR group than in the other three groups. Mitral regurgitation occurred more frequently at the posteromedial commissural site in the physiologic MR and MVP groups, whereas there was no preference for location in the rupture group. Early systolic MR was often observed in the physiologic MR group, whereas pansystolic MR was common in the MVP and rupture groups.
  
  
  CONCLUSIONS
  As a causal mechanism for physiologic MR detected in young normal subjects, "flattening" of the thorax during growth may cause morphologic abnormalities of the left atrial and ventricular cavities, resulting in spatial imbalance of the mitral complex and resulting in malcoaptation of the valve.
authors.affiliation: Department of Internal Medicine, National Sanatorium Higashitokushima Hospital, Tokushima, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Mishiro
authors.forename: T
authors.initials: T
authors.lastname: Oki
authors.forename: A
authors.initials: A
authors.lastname: Iuchi
authors.forename: T
authors.initials: T
authors.lastname: Tabata
authors.forename: H
authors.initials: H
authors.lastname: Yamada
authors.forename: K
authors.initials: K
authors.lastname: Manabe
authors.forename: K
authors.initials: K
authors.lastname: Fukuda
authors.forename: M
authors.initials: M
authors.lastname: Abe
authors.forename: Y
authors.initials: Y
authors.lastname: Onose
authors.forename: T
authors.initials: T
authors.lastname: Ishimoto
authors.forename: S
authors.initials: S
authors.lastname: Ito
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D018618:Echocardiography, Doppler, Color; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging / Q000502:physiology*; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012016:Reference Values