title: Effects of volume loading, propranolol, and heart rate changes on pump function and systolic time intervals of the left atrium in open-chest dogs.
abstract: Left atrial (LA) pressure-dimension curve was constructed and the area of A-loop (AAL, in mm.mmHg) which reflected LA stroke work was measured in 14 open-chest dogs before and after saline infusion, in 14 dogs before and after propranolol administration under fixed heart rate and in 12 dogs while atrial pacing rate was increased stepwise. The peak +dP/dt of LA systolic pressure (LA +dP/dt, in mm Hg/s) and LA percent fraction shortening (LA %FS) were obtained as indices of LA pump function. The peak -dP/dt of X descent in LA pressure (LA -dP/dt, in mm Hg/s) was measured as an index of LA relaxation. From pulsed Doppler mitral flow velocities, A-wave acceleration (AC, in cm/s2), LA pre-ejection period corrected by P-wave duration (LA PEPc), and LA ejection time (LA ET) were measured. AAL, LA +dP/dt, AC, LA %FS, and LA -dP/dt increased after saline infusion (AAL; 2.2 +/- 1.6 to 5.1 +/- 3.3 (p < 0.05), LA +dP/dt; 34 +/- 16 to 52 +/- 23 (p < 0.05), AC; 320 +/- 90 to 472 +/- 98 (p < 0.05), LA %FS; 9 +/- 4 to 12 +/- 4 (p < 0.05), and LA -dP/dt; 38 +/- 28 to 60 +/- 32 (p < 0.05)) and decreased after propranolol administration (AAL; 2.9 +/- 1.9 to 1.2 +/- 0.7 (p < 0.05), and LA +dP/dt; 42 +/- 19 to 28 +/- 11 (p < 0.05), AC; 332 +/- 92 to 254 +/- 102 (p < 0.05), LA %FS; 14 +/- 5 to 8 +/- 5 (p < 0.05), and LA -dP/dt; 36 +/- 19 to 26 +/- 18 (p < 0.05)), but did not change significantly during heart rate increments. LA PEPc decreased after saline infusion (114 +/- 11 to 104 +/- 14 (p < 0.05)) and increased after propranolol administration (108 +/- 8 to 129 +/- 13 (p < 0.05)). As pacing rate was increased, LA PEPc and LA ET showed no significant changes. Both AAL and LA +dP/dt correlated significantly with LA PEPc (r = -0.76 and -0.66), but not with LA ET (r = -0.08 and -0.04). In conclusions, LA pump function was augmented by volume loading and decreased by propranolol, but unchanged by heart rate increments. These changes in LA pump function were reflected by LA PEPc, but not by LA ET. LA PEPc is a useful index of LA pump function which is not heart rate dependent.
authors.affiliation: Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
authors.forename: Y P
authors.initials: YP
authors.lastname: Wang
authors.forename: K
authors.initials: K
authors.lastname: Takenaka
authors.forename: T
authors.initials: T
authors.lastname: Sakamoto
authors.forename: W
authors.initials: W
authors.lastname: Amano
authors.forename: F
authors.initials: F
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Igarashi
authors.forename: J
authors.initials: J
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Aoki
authors.forename: M
authors.initials: M
authors.lastname: Sonoda
authors.forename: M
authors.initials: M
authors.lastname: Mashita
mesh_terms: D000818:Animals; D016279:Atrial Function, Left / Q000187:drug effects / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation / Q000502:physiology; D004285:Dogs; D004452:Echocardiography; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology*; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D012965:Sodium Chloride; D011433:Propranolol