title: Anatomic properties of myocardial bridge predisposing to myocardial infarction.
abstract: BACKGROUND
  A myocardial bridge (MB) that partially covers the course of the left anterior descending coronary artery (LAD) sometimes causes myocardial ischemia, primarily because of hemodynamic deterioration, but without atherosclerosis. However, the mechanism of occurrence of myocardial infarction (MI) as a result of an MB in patients with spontaneously developing atherosclerosis is unclear.
  
  
  RESULTS
  One hundred consecutive autopsied MI hearts either with MBs [MI(+)MB(+) group; n=46] or without MBs (n=54) were obtained, as were 200 normal hearts, 100 with MBs [MI(-)MB(+) group] and 100 without MBs. By microscopy on LADs that were consecutively cross-sectioned at 5-mm intervals, the extent and distribution of LAD atherosclerosis were investigated histomorphometrically in conjunction with the anatomic properties of the MB, such as its thickness, length, and location and the MB muscle index (MB thickness multiplied by MB length), according to MI and MB status. In the MI(+)MB(+) group, the MB showed a significantly greater thickness and greater MB muscle index (P<0.05) than in the MI(-)MB(+) group. The intima-media ratio (intimal area/medial area) within 1.0 cm of the left coronary ostium was also greater (P<0.05) in the MI(+)MB(+) group than in the other groups. In addition, in the MI(+)MB(+) group, the location of the segment that exhibited the greatest intima-media ratio in the LAD proximal to the MB correlated significantly (P<0.001) with the location of the MB entrance, and furthermore, atherosclerosis progression in the LAD proximal to the MB was largest at 2.0 cm from the MB entrance.
  
  
  CONCLUSIONS
  In the proximal LAD with an MB, MB muscle index is associated with a shift of coronary disease more proximally, an effect that may increase the risk of MI.
authors.affiliation: Department of Pathology, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan. yukio@med.toho-u.ac.jp
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Yoshikiyo
authors.initials: Y
authors.lastname: Akasaka
authors.forename: Koyu
authors.initials: K
authors.lastname: Suzuki
authors.forename: Mieko
authors.initials: M
authors.lastname: Fujiwara
authors.forename: Takafumi
authors.initials: T
authors.lastname: Ogawa
authors.forename: Kazuto
authors.initials: K
authors.lastname: Yamazaki
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Niino
authors.forename: Michio
authors.initials: M
authors.lastname: Tanaka
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ogata
authors.forename: Shojiroh
authors.initials: S
authors.lastname: Morinaga
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Ebihara
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kawahara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sugiura
authors.forename: Toshiro
authors.initials: T
authors.lastname: Takimoto
authors.forename: Akio
authors.initials: A
authors.lastname: Komatsu
authors.forename: Toshihito
authors.initials: T
authors.lastname: Shinagawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Taki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Satoh
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yamada
authors.forename: Maki
authors.initials: M
authors.lastname: Yanagida-Iida
authors.forename: Reiko
authors.initials: R
authors.lastname: Shimokawa
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Shimada
authors.forename: Chiaki
authors.initials: C
authors.lastname: Nishimura
authors.forename: Kinji
authors.initials: K
authors.lastname: Ito
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Ishii
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001344:Autopsy; D003324:Coronary Artery Disease / Q000453:epidemiology / Q000473:pathology*; D003331:Coronary Vessels / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D054084:Myocardial Bridging / Q000453:epidemiology / Q000473:pathology*; D009203:Myocardial Infarction / Q000453:epidemiology / Q000473:pathology*; D012307:Risk Factors; D017539:Tunica Intima / Q000473:pathology; D017540:Tunica Media / Q000473:pathology