Influence of sotalol on the time constant of isovolumic left ventricular relaxation in anesthetized dogs.
OBJECTIVE
To determine the effects of various doses of sotalol on myocardial relaxation in healthy dogs.


METHODS
12 healthy adult mixed-breed dogs anesthetized with thiopental and alpha-chloralose.


METHODS
Left ventricular pressure (LVP), aortic pressure, and aortic flow velocity were measured. The time constant of isovolumic relaxation (tau) was determined by means of linear regression of the natural logarithm of LVP and by means of direct measurement from the LVP-versus-time curve. Sotalol was administered IV at cumulative doses of 1, 2, 4, and 8 mg/kg to 6 dogs; the other 6 were used as controls. Mean systolic aortic pressure was used to assess afterload, and maximal rate of increase in LVP versus time (dP/dt) was used as an index of contractility.


RESULTS
After administration of the first dose of sotalol, tau was increased significantly, and maximum dP/dt was decreased significantly, compared with baseline values. Administration of additional doses of sotalol did not result in any additional change in tau, but maximum dP/dt increased, and maximum dP/dt after administration of the final dose of sotalol was significantly higher than maximum dP/dt after administration of the first dose. There were no significant changes in mean systolic aortic pressure.


CONCLUSIONS
In healthy dogs, sotalol did not have any negative effect on myocardial relaxation beyond those attributable to its beta-blocking properties, despite an increase in intracellular ionized calcium concentration, as suggested by an increase in maximum dP/dt after an initial decrease.
Seidler
R W
RW
Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210, USA.
Mueller
K
K
Nakayama
T
T
Hamlin
R L
RL
D000768:Anesthesia, General; D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology; D012044:Regression Analysis; D013015:Sotalol / Q000494:pharmacology*; D013599:Systole / Q000187:drug effects; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology*
D013015:Sotalol