title: Analysis of postsystolic myocardial thickening work in selective myocardial layers during progressive myocardial ischemia.
abstract: BACKGROUND
  Myocardial function is transmurally heterogeneous. Postsystolic work may functionally reflect ischemic but viable myocardium. We calculated systolic and postsystolic regional myocardial work index (RMWi) in subendocardial and subepicardial layers of myocardium supplied by a slowly occluding coronary artery.
  
  
  METHODS
  Progressive stenosis of the left anterior descending coronary artery lasting 11 +/- 5 days (end point) was induced in 10 dogs, and pressure-strain loops were obtained from subendocardial and subepicardial layers of apical and middle anterior segments by intracardiac ultrasound.
  
  
  RESULTS
  At baseline, the RMWi was significantly higher (P < .05) in the subendocardial layer. At the end point, there was no significant change in the RMWi in ischemic myocardium; however, the postsystolic RMWi was higher (P < .05) in the subendocardial layer and accompanied a decrease in subendocardial myocardial blood flow, although viability was largely maintained.
  
  
  CONCLUSIONS
  A significant subendocardial postsystolic RMWi at rest suggests an impending ischemic injury in coronary artery disease when segmental function is still preserved.
authors.affiliation: Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
authors.forename: Jianwen
authors.initials: J
authors.lastname: Wang
authors.forename: Stig
authors.initials: S
authors.lastname: Urheim
authors.forename: Josef
authors.initials: J
authors.lastname: Korinek
authors.forename: Theodore P
authors.initials: TP
authors.lastname: Abraham
authors.forename: Eileen M
authors.initials: EM
authors.lastname: McMahon
authors.forename: Marek
authors.initials: M
authors.lastname: Belohlavek
mesh_terms: D000818:Animals; D023921:Coronary Stenosis / Q000150:complications / Q000000981:diagnostic imaging*; D018450:Disease Progression; D004285:Dogs; D004452:Echocardiography / Q000379:methods*; D005260:Female; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology; D013599:Systole; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology