Use of right ventricular pressure increase rate to evaluate cardiac contractility in horses.
OBJECTIVE
To establish reference values for right ventricular maximal rate of increase in pressure (dP/dt(max)) in horses and determine the usefulness of this variable to evaluate cardiac contractility.


METHODS
15 crossbred horses, 3 to 20 years old.


METHODS
Cardiac catheterization was performed, using a high-fidelity catheter tip micromanometer, to determine right ventricular dP/dt(max). The following mathematic corrections were made: for preload, (dP/dt(max))/instantaneous total pressure, (dP/dt(max))/instantaneous developed pressure, and (dP/dt(max))/end diastolic pressure; for afterload, (dP/dtCPIP)/common peak isovolumic pressure. Wedge pressure was measured simultaneously, using a Swan-Ganz catheter. A negative inotropic drug, detomidine hydrochloride, was administered to 6 horses to examine the effect of the negative inotropic drug on right ventricular dP/dt(max) and derived variables.


RESULTS
The mean right ventricular dP/dt(max) was 477 (+/- 84.1) mm Hg/s in 15 horses. A 40% decrease in dP/dt(max) was found for 30 minutes after detomidine administration. Variables that correct for preload and afterload were influenced similarly. Detomidine administration also caused a 24% increase in mean wedge pressure, probably indicating reduced left-sided cardiac contractility.


CONCLUSIONS
Right ventricular dP/dt(max) may be a useful clinical variable for determining acute changes in cardiac contractility in horses.
Nollet
H
H
Department of Internal Medicine and Clinical Biology of Large Animals, Faculty of Veterinary Medicine, University of Ghent, Merelbeke, Belgium.
Van Loon
G
G
Deprez
P
P
Sustronck
B
B
Muylle
E
E
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D006328:Cardiac Catheterization / Q000662:veterinary; D003864:Depression, Chemical; D005260:Female; D006736:Horses / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D011312:Pressure; D016276:Ventricular Function
D000700:Analgesics; D007093:Imidazoles; D007527:Isoenzymes; C041255:detomidine; D007770:L-Lactate Dehydrogenase