Objective—To determine the influence of age, body
weight (BW), heart rate (HR), sex, and left ventricular
shortening fraction (LVSF) on transmitral and pulmonary
venous flow in clinically normal dogs.
Animals—92 client-owned dogs 3 months to 19
Procedure—Transthoracic Doppler echocardiography
recordings of transmitral flow and pulmonary venous
flow were obtained in conscious unsedated dogs.
Influence of age, BW, HR, sex, and LVSF on diastolic
variables was assessed, using statistical methods
such as ANOVA on ranks and univariate and multivariate
forward stepwise linear regression analyses.
Results—Age significantly influenced isovolumic
relaxation time (IVRT; r = 0.56), ratio between peak
velocity of the early diastolic mitral flow wave-to-peak
velocity of late diastolic mitral flow wave (E:A;
r = –0.44), deceleration time of early diastolic mitral
flow (DTE; r = 0.26), and peak velocity of atrial reversal
pulmonary venous flow wave (AR-wave; r= 0.37).
Significant changes of mitral inflow and pulmonary
venous flow variables were evident only in dogs > 6
and > 10 years old, respectively. Body weight significantly
influenced DTE ( r = 0.63), late diastolic flow
duration ( r= 0.60), and AR duration ( r= 0.47), whereas
HR significantly affected DTE ( r = –0.34), IVRT
( r= –0.33), and peak velocity of AR ( r= 0.24). Sex or
LVSF (range 22 to 48%) did not influence any echocardiographic
Conclusions and Clinical Relevance—Age, BW, and
HR are important factors that affect filling of the left
atrium and left ventricle in clinically normal dogs. (Am
J Vet Res 2001;62:1447–1454)
Objective—To compare flow-mediated vasodilation (FMD) measurements in brachial and femoral arteries of healthy dogs habituated to the assessment method, evaluate repeatability of these measurements, and investigate effects of blood pressure cuff inflation time on femoral artery FMD measurements.
Animals—11 healthy adult Miniature Schnauzers.
Procedures—Arterial luminal diameter and blood flow velocity integral (FVI) were measured before and after cuff inflation of 5 minutes' (brachial and femoral arteries) or 3 minutes' duration (femoral artery) in separate experiments. A blood pressure cuff was inflated to > 200 mm Hg distal to each imaging site to increase local blood flow to induce reactive hyperemia. Changes in FVI after cuff deflation, FMD, and between-dog and within-dog coefficients of variation (CVs) were determined.
Results—After cuff inflation of 5 minutes' duration, greater changes were detected in median change in FVI and FMD of brachial arteries (174.0% and 8.0%, respectively), compared with values determined for femoral arteries (32.0% and 2.1%, respectively). Between-dog CV for brachial artery FMD was 34.0%, compared with 89.6% for femoral arteries, and within-dog CV was 32.5% for brachial arteries versus 51.6% for femoral arteries after cuff inflation of 5 minutes' duration.
Conclusions and Clinical Relevance—In healthy Miniature Schnauzers, FMD was greater and more repeatable in brachial arteries than in femoral arteries. Reactive hyperemia was inconsistently induced in femoral arteries following 3- or 5-minute cuff inflation times. Brachial, but not femoral, artery FMD measurement is a potentially useful research technique for measurement of endothelial function in dogs.
Objective—To determine between-pony and within-pony variations and interobserver and intraobserver agreements of a technique for measurement of flow-mediated vasodilation (FMD) in healthy ponies.
Animals—6 healthy pony mares (weight range, 236 to 406 kg; body condition score range, 3/9 to 7/9; age range, 14 to 25 years).
Procedures—In each pony, the left median artery was occluded with a blood pressure cuff (inflated to > 300 mm Hg for 5 minutes). Two-dimensional ultrasonographic images of the artery were recorded for 30 seconds before cuff inflation and for 2 minutes after cuff deflation. Maximum luminal diameters of arteries were compared with their baseline diameters to calculate FMD (relative percentage increase in luminal size). Images were obtained from 6 ponies 1 time and from 1 pony 6 times. Independent analysis of images was performed by 2 investigators, 1 of whom analyzed images on 2 occasions.
Results—Mean ± SD FMD in 6 ponies (1 time) was 12.57 ± 4.28% and in 1 pony (6 times) was 7.30 ± 2.11%. Between-pony and within-pony coefficients of variation were 34.09% and 28.84%, respectively. Interobserver agreement was fair (intraclass correlation coefficient, 0.47); intraobserver agreement was poor (intraclass correlation coefficient, 0.30).
Conclusions and Clinical Relevance—FMD was identified and measured in ponies. Measurement of FMD is used to assess endothelial function in humans and has been investigated in dogs. Measurement of FMD in ponies appeared to be feasible and could be used to assess endothelial function (to determine predisposition for development of laminitis or cardiovascular diseases).
Objective—To compare Doppler echocardiographic
variables of left ventricular (LV) function with those
obtained invasively via cardiac catheterization under
a range of hemodynamic conditions.
Animals—7 healthy anesthetized cats (1 to 3 years of
Procedure—Cats were anesthetized and instrumented
to measure the time constant of isovolumic
relaxation (tau ), LV end-diastolic pressure
(LVEDP), peak negative and positive rate of change
of LV pressure, arterial blood pressure, and cardiac
output. Echocardiographic variables of diastolic function
(isovolumic relaxation time [IVRT], early LV flow
propagation velocity [Vp], transmitral and pulmonary
venous flow velocity indices, and LV tissue Doppler
imaging indices) were measured simultaneously
over a range of hemodynamic states induced by
treatments with esmolol, dobutamine, cilobradine,
and volume loading. Correlation between invasive
and noninvasive measures of LV filling was determined
by univariate and multivariate regression
Results—Significant correlations were found
between and IVRT, peak Vp, peak late transmitral
flow velocity, and peak systolic pulmonary venous
flow velocity. A significant correlation was found
between LVEDP and early diastolic transmitral flow
velocity (peak E) and the ratio of peak E to peak Vp,
but not between LVEDP and peak Vp.
Conclusion and Clinical Relevance—IVRT and Vp
can be used as noninvasive indices of LV relaxation;
Vp was independent of preload and heart rate in
this study. The E:Vp ratio may be useful as an indicator
of LV filling pressure. (Am J Vet Res 2003;64:93–103)
Objective—To evaluate the between- and within-dog repeatability of a flow-mediated vasodilation (FMD) measurement technique in healthy dogs.
Animals—43 male and female dogs of various breeds (weight range, 6.9 to 31.7 kg; age range, 11 months to 11 years).
Procedures—5 dogs were used to refine the technique; other dogs were classified as large (> 15 kg) or small (≥ 15 kg) before use in the main study. In each dog, a brachial artery was occluded for 5 minutes by inflating a blood pressure cuff (applied pressure was more than 50 mm Hg greater than that required to occlude flow). Two-dimensional ultrasonographic images of the artery were recorded during a 30-second period prior to cuff inflation (baseline) and during a 3-minute period after cuff deflation by each of 2 sonographers. Relative percentage increases in luminal size from baseline (ie, FMD) were calculated. Independent contributing factors to FMD (eg, body weight, age, and room temperature) were assessed.
Results—Median FMD was significantly greater in small dogs (77%; range, 0% to 19.3%) than it was in large dogs (2.2%; range, −2.2% to 10.6%); values were significantly greater in dogs < 6 years old, compared with dogs > 6 years old. Weight was the only independent contributing factor for FMD. Coefficients of variation for between- and within-dog repeatability were 99.7% and 62.8%, respectively.
Conclusions and Clinical Relevance—Application of the FMD measurement technique used in humans appears to be feasible in dogs and may provide a means of assessing canine endothelial function, although between and within-dog variations were large. (Am J Vet Res 2010;71:1154–1161)
To determine optimal sample preparation conditions with potassium triiodide (I2KI) and optimal imaging settings for microfocus CT (micro-CT) of excised cat hearts.
7 excised hearts (weight range, 10 to 17.6 g) obtained from healthy adult cats after euthanasia by IV injection of pentobarbital sodium.
Following excision, the hearts were preserved in 10% formaldehyde solution. Six hearts were immersed in 1.25% I2KI solution (n = 3) or 2.5% I2KI solution (3) for a 12-day period. Micro-CT images were acquired at time 0 (prior to iodination) then approximately every 24 and 48 hours thereafter to determine optimal sample preparation conditions (ie, immersion time and concentration of I2KI solution). Identified optimal conditions were then used to prepare the seventh heart for imaging; changes in voltage, current, exposure time, and gain on image quality were evaluated to determine optimal settings (ie, maximal signal-to-noise and contrast-to-noise ratios). Images were obtained at a voxel resolution of 30 μm. A detailed morphological assessment of the main cardiac structures of the seventh heart was then performed.
Immersion in 2.5% I2KI solution for 48 hours was optimal for sample preparation. The optimal imaging conditions included a tube voltage of 100 kV, current of 150 μA, and exposure time of 354 milliseconds; scan duration was 12 minutes.
CONCLUSIONS AND CLINICAL RELEVANCE
Results provided an optimal micro-CT imaging protocol for excised cat hearts prepared with I2KI solution that could serve as a basis for future studies of micro-CT for high resolution 3-D imaging of cat hearts.
Objective—To compare measurements of blood flow
in the common femoral artery obtained by duplex
Doppler ultrasonography (DDU) and a reference ultrasonic
transit-time flow (TTF) method and to examine
the impact of Doppler spectral waveform measurement
techniques on volumetric estimates.
Animals—5 healthy female pigs.
Procedure—Femoral arterial blood flow was measured
simultaneously in anesthetized pigs by use of a
TTF probe (left femoral artery) and transcutaneous
DDU (right femoral artery). A range of flow states was
induced pharmacologically by using xylazine,
bradykinin, dobutamine, and isoflurane. Volumetric
blood flow was calculated from DDU waveforms,
using the product of the flow velocity integral (FVI),
the cross-sectional vessel area, and heart rate. Three
calculations of FVI were obtained by manually tracing
the Doppler spectral envelopes at the outer envelope,
the modal, and the inner envelope of the spectral dispersion
pattern. Data analysis included calculation of
Pearson correlation coefficients and Bland-Altman
limits of agreement.
Results—Blood flow measured by DDU was more
closely correlated with TTF measurements when the
modal or inner envelope tracing method was used
( r, 0.76 and 0.78; limits of agreement, –100 to 54.2
and –48.5 to 77.0 mL/min, respectively). Limits of
agreement for the outer envelope tracing method
were –238.5 to 64 mL/min.
Conclusion and Clinical Relevance—Transcutaneous
DDU is a reliable noninvasive technique for
measuring blood flow in the femoral artery of pigs
over a range of flow states. Tracing the inner envelope
of the Doppler spectral dispersion pattern provided
the best estimate of blood flow in this study.
(Am J Vet Res 2003;64:43–50)