H. Nollet et al., Use of right ventricular pressure increase rate to evaluate cardiac contractility in horses, AM J VET RE, 60(12), 1999, pp. 1508-1512
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.
Animals-15 crossbred horses, 3 to 20 years old.
Procedure-Cardiac catheterization was performed, using a high-fidelity cath
eter tip micromanometer, to determine right ventricular dP/dt(max). The fol
lowing mathematic corrections were made: for preload, (dP/dt(max))/instanta
neous total pressure, (dP/dt(max))/instantaneous developed pressure, and (d
P/dt(max))/end diastolic pressure; for afterload, (dP/dt(CPIP))/common peak
isovolumic pressure. Wedge pressure was measured simultaneously, using a S
wan-Ganz catheter. A negative inotropic drug, detomidine hydrochloride, was
administered to 6 horses to examine the effect of the negative inotropic d
rug 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 det
omidine administration, Variables that correct for preload and afterload we
re influenced similarly. Detomidine administration also caused a 24% increa
se in mean wedge pressure, probably indicating reduced left-sided cardiac c
ontractility.
Conclusions and Clinical Relevance-Right ventricular dP/dt(max) may be a us
eful clinical variable for determining acute changes in cardiac contractili
ty in horses.