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  • Author or Editor: Kensuke Nakamura x
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Abstract

OBJECTIVE To assess the use of contrast-enhanced ultrasonography (CEUS) of the hepatic vein for the detection of hemodynamic changes associated with experimentally induced portal hypertension in dogs.

ANIMALS 6 healthy Beagles.

PROCEDURES A prospective study was conducted. A catheter was surgically placed in the portal vein of each dog. Hypertension was induced by intraportal injection of microspheres (10 to 15 mg/kg) at 5-day intervals via the catheter. Microsphere injections were continued until multiple acquired portosystemic shunts were created. Portal vein pressure (PVP) was measured through the catheter. Contrast-enhanced ultrasonography was performed before and after establishment of hypertension. Time-intensity curves were generated from the region of interest in the hepatic vein. Perfusion variables measured for statistical analysis were hepatic vein arrival time, time to peak, time to peak phase (TTPP), and washout ratio. The correlation between CEUS variables and PVP was assessed by use of simple regression analysis.

RESULTS Time to peak and TTPP were significantly less after induction of portal hypertension. Simple regression analysis revealed a significant negative correlation between TTPP and PVP.

CONCLUSIONS AND CLINICAL RELEVANCE CEUS was useful for detecting hemodynamic changes associated with experimentally induced portal hypertension in dogs, which was characterized by a rapid increase in the intensity of the hepatic vein. Furthermore, TTPP, a time-dependent variable, provided useful complementary information for predicting portal hypertension.

IMPACT FOR HUMAN MEDICINE Because the method described here induced presinusoidal portal hypertension, these results can be applied to idiopathic portal hypertension in humans.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To determine the relationship between acute volume overload and echocardiographic indices of right ventricular (RV) function and dyssynchrony in healthy dogs.

ANIMALS 7 healthy Beagles.

PROCEDURES Right heart catheterization and echocardiography were performed in 7 healthy anesthetized Beagles at baseline and after induction of volume overload. Volume overload was induced by IV infusion of lactated Ringer solution (150 mL/kg/h for 90 minutes). Echocardiographic indices of RV function, including peak velocity of systolic tricuspid annular motion, tricuspid annulus plane systolic excursion, fractional area change, RV Tei index, RV longitudinal strain (RVLS), and systolic RV longitudinal strain rate (RVLSR), were obtained by use of speckle tracking echocardiography (STE). In addition, SD of the systolic shortening time of the right ventricle for the 6 segments (RV-SD6) was determined with STE.

RESULTS Volume overload significantly increased the RV end-diastolic pressure, compared with the baseline value. Echocardiographic indices of RV function, except for septal RVLSR, were significantly enhanced by volume overload. In contrast, RV-SD6 did not change with volume overload. Although echocardiographic indices of RV function, except for septal RVLSR, were correlated with RV end-diastolic pressure, RV-SD6 was not correlated.

CONCLUSIONS AND CLINICAL RELEVANCE Echocardiographic indices of RV function, including RVLS and RVLSR, were affected by acute short-term volume overload. Therefore, results for assessment of RV function by use of STE in dogs with clinical conditions associated with right-sided chronic volume overload, such as tricuspid and pulmonic regurgitation, should be interpreted with caution.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To elucidate the relationship between acute volume overload and left atrial phasic function in healthy dogs.

ANIMALS 6 healthy Beagles.

PROCEDURES Dogs were anesthetized. A Swan-Ganz catheter was placed to measure mean pulmonary capillary wedge pressure (PCWP). Cardiac preload was increased by IV infusion with lactated Ringer solution at 150 mL/kg/h for 90 minutes. Transthoracic echocardiography was performed before (baseline) and at 15, 30, 45, 60, 75, and 90 minutes after volume loading began. At each echocardiographic assessment point, apical 4-chamber images were recorded and analyzed to derive time–left atrial area curves. Left atrial total (for reservoir function), passive (for conduit function), and active (for booster-pump function) fractional area changes were calculated from the curves.

RESULTS Volume overload resulted in a significant increase from baseline in PCWP from 15 to 90 minutes after volume loading began. All fractional area changes at 15 to 90 minutes were significantly increased from baseline. In multiple regression analysis, quadratic regression models were better fitted to the relationships between PCWP and each of the total and active fractional area changes than were linear regression models. A linear regression model was better fitted to the relationship between PCWP and passive fractional area change.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that left atrial phasic function assessed on the basis of left atrial phasic areas was enhanced during experimental cardiac volume loading in healthy dogs. The effect of volume load should be considered when evaluating left atrial phasic function by indices derived from left atrial phasic sizes.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To determine the effects of IV administration of pimobendan on hemodynamic indices and indices of left atrial (LA) longitudinal strain by speckle-tracking echocardiography in healthy dogs.

ANIMALS

6 healthy Beagles.

PROCEDURES

After the dogs were anesthetized, the right heart was catheterized and 2-D conventional and speckle-tracking echocardiography were performed before and after IV administration of 0.15 mg of pimobendan/kg. Speckle-tracking echocardiography was performed to assess the 3 LA phasic functions through LA deformation (longitudinal strain and strain rate) and volumetric analyses.

RESULTS

Pimobendan significantly increased stroke volume and cardiac output and decreased systemic vascular resistance. Pimobendan significantly improved left ventricular function assessed by the Tei index and LA booster pump function assessed by LA longitudinal strain and change in fractional volume during atrial systole. Indices of LA reservoir and conduit function were unchanged.

CONCLUSIONS AND CLINICAL RELEVANCE

In healthy dogs, IV administration of pimobendan improved the indices of LA booster pump function but had no effect on the indices of LA reservoir and conduit functions. Further studies are needed to validate whether these results can be extrapolated to dogs with myxomatous mitral valve disease.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate the effects of dobutamine, esmolol, milrinone, and phenylephrine on left atrial phasic function of healthy dogs.

ANIMALS 9 healthy Beagles.

PROCEDURES Following sedation with propofol on each of 4 experimental days, dogs were administered a constant rate infusion of dobutamine (5 μg/kg/min), esmolol (500 μg/kg/min), milrinone (25 μg/kg, IV bolus, followed by 0.5 μg/kg/min), or phenylephrine (2 μg/kg/min). There was at least a 14-day interval between experimental days. Each drug was administered to 6 dogs. Conventional and 2-D speckle tracking echocardiography were performed before (baseline) and after administration of the cardiovascular drug, and time–left atrial area curves were derived to calculate indices for left atrial reservoir, conduit, and booster pump functions (left atrial phasic function) and left ventricular contractility and lusitropy.

RESULTS Compared with baseline values, indices for left atrial reservoir and booster pump functions and left ventricular contractility and lusitropy were significantly increased following dobutamine administration; indices for left atrial phasic function and left ventricular lusitropy were changed insignificantly, and indices for left ventricular contractility were significantly impaired following esmolol administration; indices for left atrial phasic function and left ventricular relaxation were changed insignificantly, and indices for left ventricular systolic function were significantly augmented following milrinone administration; and indices for left atrial phasic function and left ventricular lusitropy were changed insignificantly, and indices of ventricular contractility were significantly impaired following phenylephrine administration.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that, following administration of dobutamine, esmolol, milrinone, or phenylephrine to healthy dogs, left atrial phasic function indices were fairly stable and did not parallel changes in left ventricular function indices.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine dose dependency of tranexamic acid–induced emesis and the time course of the antifibrinolytic potency of tranexamic acid in dogs.

Animals—10 Beagles.

Procedures—In a dose-escalating experiment, ascending doses of tranexamic acid (10, 20, and 30 mg/kg, IV) were administered at 5-minute intervals until vomiting was observed. In a separate single-dose experiment, ascending doses of tranexamic acid (20, 30, 40, and 50 mg/kg, IV) were administered at 1-week intervals until vomiting was observed. Time to onset of vomiting and number of vomiting episodes were measured in both experiments. In a coagulation experiment, a single 50 mg/kg bolus of tranexamic acid was administered, and blood was obtained 1 hour before and 20 minutes, 3 hours, and 24 hours after administration. Antifibrinolytic potency of tranexamic acid was evaluated by use of a modified rotational thromboelastography method.

Results—Tranexamic acid induced vomiting in a dose-dependent manner. Vomiting frequency was < 2 episodes, and vomiting concluded < 250 seconds after administration. Antifibrinolytic potency of tranexamic acid was significantly higher at 20 minutes following administration, but not different by 24 hours, when compared with the potency measured before administration. No adverse effects were observed in any experiment.

Conclusions and Clinical Relevance—IV administration of tranexamic acid induced emesis in a dose-dependent manner. The antifibrinolytic potency of tranexamic acid decreased in a time-dependent manner and was resolved < 24 hours after administration. Further studies are warranted to investigate the emetic and other adverse effects of tranexamic acid in dogs of various breeds and ages.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To examine the expression and distribution of tight junction (TJ) and adherens junction (AJ) proteins in canine duodenal and colonic mucosa.

Sample—Mucosa obtained from 4 healthy Beagles.

Procedures—Biopsy specimens of the duodenum and colon were obtained via endoscopy from 4 healthy dogs. The expression patterns and subcelluar localization of claudin-1, -2, -3, -4, -5, -7, and -8; E-cadherin; and β-catenin in the duodenum and colon were analyzed by use of immunoblotting and immunofluorescence microscopy.

Results—In the duodenum, there was clear expression of claudin-3 and -5, E-cadherin, and β-catenin proteins and weak expression of claudin-7 protein. In contrast, there was clear expression of claudin-2 and -3, E-cadherin, and β-catenin proteins and weak expression of claudin-5 and -7 proteins in the colon, as determined by use of immunoblotting. As determined by the use of immunofluorescence microscopy, the duodenum and colon had staining for claudin-3 and -5, E-cadherin, and β-catenin in the most apical region and staining for claudin-7 in the basolateral region. Staining for claudin-2 was also observed in the colon.

Conclusions and Clinical Relevance—Information was provided about the expression patterns of TJ and AJ proteins in the duodenum and colon of clinically normal dogs. These results may provide valuable information for use in evaluating the importance of these TJ and AJ proteins in the pathogenesis of inflammatory bowel disease in dogs.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the expression of tight junction and adherens junction proteins in duodenal mucosa samples of dogs with inflammatory bowel disease (IBD).

Animals—12 dogs with IBD and 6 healthy control Beagles.

Procedures—Duodenal mucosa biopsy samples were endoscopically obtained from dogs with IBD and healthy control Beagles. The expression of claudin-1, -2, -3, -4, -5, -7, and -8; E-cadherin; and β-catenin in the duodenal mucosa samples was determined by means of immunoblotting. The subcellular localization of E-cadherin in the duodenal mucosa samples was determined with immunofluorescence microscopy.

Results—The expression of each claudin and β-catenin was not significantly different between control dogs and dogs with IBD. However, expression of E-cadherin was significantly lower in duodenal mucosa samples of dogs with IBD than it was in samples obtained from healthy control dogs. Results of immunofluorescence microscopy indicated decreased intensity of E-cadherin labeling in the tips of villi in duodenal mucosa samples obtained from 6 dogs with IBD, compared with staining intensity for other dogs.

Conclusions and Clinical Relevance—Results of this study indicated expression of claudin-1, -2, -3, -4, -5, -7, and -8 and β-catenin was not significantly different between duodenal mucosa samples obtained from control dogs and those obtained from dogs with IBD. However, E-cadherin expression was significantly lower in the villus epithelium in duodenal mucosa samples obtained from dogs with IBD versus samples obtained from control dogs, which suggested that decreased expression of that protein has a role in the pathogenesis of IBD in dogs.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate left atrial phasic function in healthy dogs by means of 2-D speckle tracking echocardiography with time-left atrial area curve analysis and to assess repeatability and reproducibility of obtained measurements.

Animals—6 healthy Beagles.

Procedures—Each dog underwent echocardiography twice on different days (3 nonconsecutive examinations/d). Images were analyzed with offline software; area of the left atrium was automatically calculated in each frame throughout the cardiac cycle to derive time-left atrial area curves. Variables used to assess left atrial phasic function (total, passive, and active emptying area and emptying fractions and mean active and total emptying rates) were calculated. Agreement between variables measured via speckle tracking echocardiography and a manual tracing method was assessed with modified Bland-Altman analysis. Within-day and between-day coefficients of variation were determined.

Results—Mean ± SD total, passive, and active emptying fractions of the left atrium were 49.8 ± 3.5%, 277 ± 4.0%, and 30.5 ± 4.3%, respectively. Mean ± SD total and active emptying rates were 16.0 ± 2.5 cm2/s and 25.1 ± 4.9 cm2/s, respectively. Within-day and between-day coefficients of variation were < 20% (range, 0.41% to 16.4%) for all variables except mean active emptying rate (between-day coefficient of variation, 29.2%). Agreement between variables measured via speckle tracking echocardiography and the manual tracing method was good, and differences between methods were nonsignificant.

Conclusions and Clinical Relevance—Evaluation of left atrial phasic function via speckle tracking echocardiography was feasible; repeatability and reproducibility of measurements were adequate in healthy dogs. Studies are needed to determine clinical applicability in canine patients.

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate repeatability and reproducibility of right ventricular Tei index (RTX) values derived from dual pulsed-wave Doppler, conventional pulsed-wave Doppler, and tissue Doppler echocardiography and to investigate relationships and repeatability among the 3 methods in healthy dogs.

ANIMALS 6 healthy adult Beagles.

PROCEDURE Echocardiography was performed on each dog on different days for 2 weeks (3 times/d) by 2 echocardiographers. Intraobserver within- and between-day and interobserver coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) for RTXs derived from dual pulse-waved Doppler (RTXDPD), conventional pulsed-wave Doppler (RTXPD), and tissue Doppler (RTXTD) methods were determined. Degrees of agreement among RTX values derived from the 3 methods were assessed by modified Bland-Altman analysis.

RESULTS Least squares mean (95% confidence interval) RTXtd was 0.50 (0.46 to 0.54), which was significantly higher than that for RTXDPD (0.27 [0.23 to 0.31]) and RTXPD (0.25 [0.21 to 0.29]). Agreement between RTXDPD and RTXPD was good (bias [mean difference], 0.04 [95% confidence interval, −0.03 to 0.10]). The RTXdpd had high within-day (CV, 6.1; ICC, 0.77) and interobserver (CV, 3.5; ICC, 0.83) repeatability, but between-day repeatability was not high. The RTXtd had high within-day repeatability (CV, 6.0; ICC, 0.80), but between-day and interobserver repeatability were not high. Within-day, between-day, and interobserver repeatability of RTXPD were not high.

CONCLUSIONS AND CLINICAL RELEVANCE RTXdpd measurement was a repeatable and reproducible method of cardiac evaluation in healthy dogs. The RTXTD values were significantly higher than the RTXDPD and RTXPD values; therefore, RTX values derived from different echocardiographic methods should be interpreted with caution.

Full access
in American Journal of Veterinary Research