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  • Author or Editor: Virginia Luis Fuentes x
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Abstract

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 years old.

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 variables.

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)

Full access
in American Journal of Veterinary Research

Abstract

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.

Full access
in American Journal of Veterinary Research

Abstract

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).

Full access
in American Journal of Veterinary Research

Abstract

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 age).

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 analyses.

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)

Full access
in American Journal of Veterinary Research

Abstract

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)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine optimal sample preparation conditions with potassium triiodide (I2KI) and optimal imaging settings for microfocus CT (micro-CT) of excised cat hearts.

SAMPLE

7 excised hearts (weight range, 10 to 17.6 g) obtained from healthy adult cats after euthanasia by IV injection of pentobarbital sodium.

PROCEDURES

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.

RESULTS

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.

Full access
in American Journal of Veterinary Research

Abstract

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)

Full access
in American Journal of Veterinary Research