title: Delayed onset of subendocardial diastolic thinning at rest identifies hypoperfused myocardium.
abstract: BACKGROUND
  Onset of myocardial relaxation is highly energy dependent. Perfusion and therefore energy substrate delivery are predominantly reduced in the subendocardial myocardium in the early stages of progressive ischemia. We hypothesized that delayed onset of subendocardial diastolic thinning will functionally identify regionally hypoperfused resting myocardium.
  
  
  RESULTS
  Progressive left anterior descending coronary artery stenosis was induced by an ameroid occluder and maintained for 1 or 2 weeks (end point) in 12 dogs. M-mode tissue Doppler images of the anterior apical and middle segments (testing region) and middle inferior segment (control region) were acquired selectively in the subendocardium and subepicardium. The time to the onset of thinning was measured with the use of tissue Doppler velocity (TOTv) and a thickness function (TOTt). At the end point in the testing region, myocardial flow was significantly lower in the subendocardial layer (P<0.05) in all animals, whereas viability staining showed preserved transmural viability in 10 dogs and thin subendocardial necrosis in 2 dogs. Both TOTv and TOTt were significantly (P<0.01) prolonged in the testing region. The mean difference between subendocardial and subepicardial TOTv values versus that in the control region identified the ischemic region, even when only dogs with hypoperfused but transmurally viable myocardium were considered (P<0.05). Systolic and diastolic myocardial velocities did not identify subendocardial hypoperfusion.
  
  
  CONCLUSIONS
  In resting myocardium subtended to progressive coronary stenosis, a delayed onset of subendocardial thinning suggests an early stage of hypoperfusion, before the development of local wall motion abnormalities.
authors.affiliation: Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minn 55905, USA.
authors.forename: Jianwen
authors.initials: J
authors.lastname: Wang
authors.forename: Theodore P
authors.initials: TP
authors.lastname: Abraham
authors.forename: Josef
authors.initials: J
authors.lastname: Korinek
authors.forename: Stig
authors.initials: S
authors.lastname: Urheim
authors.forename: Eileen M
authors.initials: EM
authors.lastname: McMahon
authors.forename: Marek
authors.initials: M
authors.lastname: Belohlavek
mesh_terms: D000818:Animals; D003326:Coronary Circulation; D023921:Coronary Stenosis; D003971:Diastole; D004195:Disease Models, Animal; D004285:Dogs; D015150:Echocardiography, Doppler; D005260:Female; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D009336:Necrosis; D013997:Time Factors