title: Effects of tachycardia on regional wall motion in acute ischemic canine heart.
abstract: Tachycardia accompanies the preload reduction. Our aim is to assess the effect of the heart rate change on wall motion in ischemic heart. In 8 dogs with occlusion of left anterior descending artery, we changed the heart rate (heart rate 90, 120, and 150 beats/minute) after using UL-FS49, a selective bradycardic agent, with atrial pacing. Preload was changed by inferior vena caval occlusion at a heart rate of 90 beats/minute. With either an increase in heart rate or an inferior vena caval occlusion, the end-diastolic length was decreased, but the end-diastolic length relationships between the non-ischemic and the ischemic region made different lines from those of the heart rate change and inferior vena caval occlusion. When increasing the heart rate, isovolumetric shortening was unchanged in the non-ischemic region with more expansion in the ischemic region. While inferior vena caval occlusion at a heart rate of 90 beats/minute, isovolumetric shortening was increased in the non-ischemic region, with more expansion in the ischemic region. Both in tachycardia and by the inferior vena caval occlusion, ejectional shortenings decreased in the non-ischemic and ischemic regions. Our results suggest that, in ischemic heart, tachycardia changes both in the end-diastolic length relationship between the non-ischemic and the ischemic region and at the isovolumetric contraction phase. The changes seem to be not only due to the inferior vena caval occlusion, but also due to tachycardia itself.
authors.affiliation: Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Masahito
authors.initials: M
authors.lastname: Sakuma
authors.forename: Hidenari
authors.initials: H
authors.lastname: Hozawa
authors.forename: Kohtaroh
authors.initials: K
authors.lastname: Komaki
authors.forename: Tohru
authors.initials: T
authors.lastname: Takahashi
authors.forename: Norihisa
authors.initials: N
authors.lastname: Kumasaka
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kagaya
authors.forename: Jun
authors.initials: J
authors.lastname: Watanabe
authors.forename: Kunio
authors.initials: K
authors.lastname: Shirato
mesh_terms: D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D003971:Diastole; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D017202:Myocardial Ischemia; D009206:Myocardium / Q000473:pathology; D011312:Pressure; D013610:Tachycardia / Q000473:pathology*; D013997:Time Factors
chemical_list: D001552:Benzazepines; D002316:Cardiotonic Agents; C043636:zatebradine