title: Changes in myocardial contraction pattern during initial reperfusion.
abstract: The characteristics of hypercontraction during initial reperfusion were studied in 10 pentobarbitone-anesthetized cats. The left anterior descending coronary artery was occluded for 10 min followed by 1 h of reperfusion, and regional function was assessed by two cross-oriented pairs of sonomicrometers placed in the left ventricular anterior wall. At 1 min of reperfusion (hyperfunctional phase) there was an uniform contraction pattern with 90% recovery of ejection shortening in both circumferential and longitudinal segments. During initial hypercontraction, end-diastolic segment lengths remained unchanged, whereas end-systolic segment lengths decreased transiently. Inotropic stimulation during reperfusion in four additional animals also affected end-systolic lengths more than end-diastolic lengths. This suggests that the initial hyperfunctional phase is due to an inotropic stimulation of the stunned myocardium, most probably caused by intracellular Ca2+ overload. At 5 min of reperfusion a nonuniform contraction pattern had developed with 68% recovery of shortening in circumferential segments vs. 25% in longitudinal segments. The decreased performance in longitudinal segments was paralleled by a delayed start of contraction as well as a decreased velocity of contraction. Because longitudinal segment shortening is a sensitive parameter of subendocardial performance, our results indicate a brief transmural hypercontraction followed by increasing dysfunction (stunning) in the subendocardial layer.
authors.affiliation: Department of Surgery, University of Bergen, Haukeland Hospital, Norway.
authors.forename: S E
authors.initials: SE
authors.lastname: Rynning
authors.forename: S
authors.initials: S
authors.lastname: Birkeland
authors.forename: E
authors.initials: E
authors.lastname: Hexeberg
authors.forename: K
authors.initials: K
authors.lastname: Grong
mesh_terms: D000818:Animals; D002415:Cats; D003326:Coronary Circulation; D006439:Hemodynamics; D008297:Male; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000503:physiopathology; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology