title: Baroreflex sensitivity and heart rate variability in conscious rats with myocardial infarction.
abstract: The baroreflex sensitivity (BRS) and the heart rate variability (HRV) were studied in conscious rats after myocardial infarction (MI; induced by coronary artery ligation) and after sham operation (SH). BRS was determined by linear regression of R-R interval vs. arterial pressure changes induced by nitroprusside or methoxamine (intravenous bolus). HRV was calculated from 3-min electrocardiogram recordings. Left ventricular end-diastolic pressure and plasma atrial natriuretic peptide were increased after MI; plasma norepinephrine and basal heart rate (HR) remained unchanged. At 3 and 28 days after MI, BRS was reduced as indicated by decreased reflex bradycardia (RB) (MI, 0.66 +/- 0.13 and 0.78 +/- 0.07 ms/mmHg; SH, 1.27 +/- 0.16 and 1.48 +/- 0.14 ms/mmHg, respectively; P < 0.05 MI vs. SH). At 56 days after MI, BRS was normalized. RB was unaffected by atropine 3 and 28 days after MI but reduced in all other groups. The increase of basal HR by atropine 3 and 28 days after MI was less than in all other groups. HRV (SD of mean N-N interval, coefficient of variance, low- and high-frequency power; studied at 28 and 56 days) was similar in all groups. It is concluded that BRS is transiently depressed in rats with left ventricular dysfunction after MI probably due to a reduced reflex vagal activity. Even though basal HR and HRV are unchanged after MI, a temporary attenuation of tonic vagal activity is unmasked after autonomic blockade.
authors.affiliation: Department of Cardiology, University of Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Krüger
authors.forename: A
authors.initials: A
authors.lastname: Kalenka
authors.forename: A
authors.initials: A
authors.lastname: Haunstetter
authors.forename: M
authors.initials: M
authors.lastname: Schweizer
authors.forename: C
authors.initials: C
authors.lastname: Maier
authors.forename: U
authors.initials: U
authors.lastname: Rühle
authors.forename: H
authors.initials: H
authors.lastname: Ehmke
authors.forename: W
authors.initials: W
authors.lastname: Kübler
authors.forename: M
authors.initials: M
authors.lastname: Haass
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D003331:Coronary Vessels; D006339:Heart Rate / Q000502:physiology*; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009203:Myocardial Infarction / Q000503:physiopathology*; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012044:Regression Analysis; D013997:Time Factors; D016277:Ventricular Function, Left / Q000502:physiology
chemical_list: D009599:Nitroprusside; D008729:Methoxamine; D009638:Norepinephrine