Effect of amlodipine on the circulating renin-angiotensin-aldosterone system in healthy cats.

BACKGROUND: Systemic hypertension (SH) is a common cardiovascular disease in older cats that is treated primarily with the calcium channel blocker amlodipine besylate (AML). The systemic effect of AML on the classical and alterative arms of the renin-angiotensin-aldosterone system (RAAS) in cats is incompletely characterized. HYPOTHESIS/OBJECTIVES: To determine the effect of AML compared to placebo on circulating RAAS biomarkers in healthy cats using RAAS fingerprinting. ANIMALS: Twenty healthy client-owned cats. METHODS: Cats were administered amlodipine besylate (0.625 mg in toto) or placebo by mouth once daily for 14 days in a crossover design with a 4-week washout period. Plasma AML concentrations and RAAS biomarker concentrations were measured at multiple timepoints after the final dose in each treatment period. Time-weighted averages for RAAS biomarkers over 24 hours after dosing were compared between treatment groups using Wilcoxon rank-sum testing. RESULTS: Compared to placebo, AML treatment was associated with increases in markers of plasma renin concentration (median 44% increase; interquartile range [IQR] 19%-86%; P = .009), angiotensin I (59% increase; IQR 27-101%; P = .006), angiotensin II (56% increase; IQR 5-70%; P = .023), angiotensin IV (42% increase; -19% to 89%; P = .013); and angiotensin 1-7 (38% increase; IQR 9-118%; P = .015). CONCLUSIONS AND CLINICAL IMPORTANCE: In healthy cats, administration of AML resulted in nonspecific activation of both classical and alternative RAAS pathways.

A randomised, controlled trial to determine the effect of levothyroxine on Standardbred racehorses.

BACKGROUND: The use of thyroid supplement is pervasive in athletic horses although its effects on measures of performance are not known. OBJECTIVES: One purpose of this study was to determine whether supra-physiologic doses of levothyroxine affect the velocities at which blood lactate was greater than 4 mmol/L (VLa4 ) and heart rate was over 150 (V150 ) and 200 (V200 ) beats per minute respectively. Additionally, a survey of post-race blood samples was also conducted to determine whether high thyroxine concentrations were common in racehorses. STUDY DESIGN: A randomised, crossover, trial was performed in six healthy Standardbred racehorses. METHODS: Study 1: T4 was determined in 50 post-race samples from a single Standardbred meet. Study 2: Research horses were trained to fitness and then randomised to one of three treatments: carrier, 0.1 mg/kg thyroxine or 0.25 mg/kg thyroxine for 2 weeks. Horses completed a standardised exercise treadmill test (SET) to fatigue on the last day of treatment. Serum free and total thyroxine and triiodothyronine were determined on the day of SET testing. Blood lactate and ECG data were collected during the SET at 6, 8, 10, 11, and 12 m/s and during recovery. The effect of treatment and SET on heart rate and blood lactate was examined using generalised linear mixed models. Post hoc analysis was adjusted for multiple comparisons using Tukey's Test. Data were expressed as mean ± standard deviation and P < .05 was considered significant. RESULTS: Study 1: The median T4 value in this population of horses was 2.00 µg/dL (laboratory's normal range 1.5-4.5 µg/dL) and 3 of 50 racehorses had values above the laboratory reference range. Study 2: Levothyroxine at 0.25 mg/kg resulted in higher heart rates during SET (199 ± 30, 223 ± 17 and 239 ± 9 bpm at 6, 8 and 10 m/s respectively) and recovery (144 ± 20 and 119 ± 15 at 5 and 15 min) as compared to placebo (176 ± 18, 203 ± 10 and 219 ± 6 bpm at 6, 8, and10 m/s and 126 ± 5, 102 ± 11 at 5-15 minutes respectively). Three of six horses developed cardiac arrhythmias including atrial fibrillation. MAIN LIMITATIONS: A relatively small number of animals were used and a SET is not identical to actual racing conditions. CONCLUSIONS: Supra-physiologic thyroxine supplementation caused a decreased V200 during a standard exercise test and may result in cardiac arrhythmias.

Comparison of curvilinear-array (microconvex) and phased-array transducers for ultrasonography of the lungs in dogs.

OBJECTIVES: To compare the use of curvilinear-array (microconvex) and phased-array transducers for ultrasonographic examination of the lungs in dogs. ANIMALS: 13 client-owned dogs with left-sided congestive heart failure. PROCEDURES: In a prospective methods comparison study, 24 ultrasonographic examinations of the lungs (4 sites/hemithorax) were performed with both curvilinear-array and phased-array transducers at 3 clinical time points. Two observers independently assessed the number of B lines (scored per site and in total), number of sites strongly positive for B lines (ie, those with > 3 B lines/site), and image quality (scored on a 5-point scale). Analyses included assessment of interobserver agreement with κ analysis, comparison of quality scores between transducers with mixed-effects modeling, and investigation of agreement and bias for B-line data and quality scores between transducers with Passing-Bablok regression. RESULTS: Interobserver agreement for total B-line scores and number of strong-positive sites was excellent (κ > 0.80) for both transducers. There was no evidence of analytic bias for the number of B lines or strong-positive sites between transducers. Interobserver agreement for image quality scores was moderate (κ, 0.498 and 0.517 for the curvilinear-array and phased-array transducers, respectively). Both observers consistently assigned higher-quality scores to curvilinear-array images than to phased-array images. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated both curvilinear-array (microconvex) and phased-array transducers can be used by experienced sonographers to obtain diagnostic ultrasonographic images of the lungs in dogs with acute or resolving left-sided congestive heart failure and suggested the former transducer may be preferred, particularly to aid identification of anatomic landmarks for orientation.

Focused ultrasound of the caudal vena cava in dogs with cavitary effusions or congestive heart failure: A prospective, observational study.

INTRODUCTION: Ultrasonographic indices of the inferior vena cava are useful for predicting right heart filling pressures in people. OBJECTIVES: To determine whether ultrasonographic indices of caudal vena cava (CVC) differ between dogs with right-sided CHF (R-CHF), left-sided CHF (L-CHF), and noncardiac causes of cavitary effusion (NC). MATERIALS AND METHODS: 113 dogs diagnosed with R-CHF (n = 51), L-CHF (30), or NC effusion (32) were enrolled. Seventeen of the R-CHF dogs had pericardial effusion and tamponade. Focused ultrasound was performed prospectively to obtain 2-dimensional and M-mode subxiphoid measures of CVC maximal and minimal size (CVCmax and CVCmin), CVCmax indexed to aortic dimension (CVC:Ao), and CVC collapsibility index (CVC-CI). Variables were compared between study groups using Kruskal-Wallis and Dunn's-Bonferroni testing, and receiver operating characteristics curves were used to assess sensitivity and specificity. RESULTS: All sonographic CVC indices were significantly different between R-CHF and NC dogs (P < 0.001). Variables demonstrating the highest diagnostic accuracy for discriminating R-CHF versus NC were CVC-CI <33% in 2D (91% sensitive and 96% specific) and presence of hepatic venous distension (84% sensitive and 90% specific). L-CHF dogs had higher CVC:Ao and lower CVC-CI compared to NC dogs (P = 0.016 and P = 0.043 in 2D, respectively) but increased CVC-CI compared to the R-CHF group (P < 0.001). CONCLUSIONS: Ultrasonographic indices of CVC size and collapsibility differed between dogs with R-CHF compared to NC causes of cavitary effusions. Dogs with L-CHF have CVC measurements intermediate between R-CHF and NC dogs.

A Multi-Institutional Retrospective Analysis of Toceranib Phosphate for Presumed or Confirmed Canine Aortic Body Chemodectomas.

Aortic body tumors, specifically chemodectomas, are the second most common type of canine cardiac tumor; however, information about treatment is currently lacking. This study included dogs with a presumptive or definitive diagnosis of an aortic body chemodectoma that underwent treatment with toceranib phosphate. Cases were solicited via the American College of Veterinary Internal Medicine Cardiology, Internal Medicine, and Oncology listservs using an electronic survey. Cox multivariate analysis of factors potentially impacting survival time was completed. Twenty-seven (27) cases were included in analysis. The clinical benefit rate (complete remission, partial remission, or stable disease >10 weeks) was 89%. A median survival time of 478 days was found for those receiving toceranib alone (n = 14), which was not statistically different from those treated with additional modalities (521 days). No factors evaluated statistically impacted outcome. Further, prospective studies are warranted to evaluate the use of toceranib for the treatment of canine aortic body chemodectomas.

Utility of point-of-care lung ultrasound for monitoring cardiogenic pulmonary edema in dogs.

BACKGROUND: Point-of-care lung ultrasound (LUS) is an effective tool to diagnose left-sided congestive heart failure (L-CHF) in dogs via detection of ultrasound artifacts (B-lines) caused by increased lung water. HYPOTHESIS/OBJECTIVES: To determine whether LUS can be used to monitor resolution of cardiogenic pulmonary edema in dogs, and to compare LUS to other indicators of L-CHF control. ANIMALS: Twenty-five client-owned dogs hospitalized for treatment of first-onset L-CHF. METHODS: Protocolized LUS, thoracic radiographs (TXR), and plasma N-terminal pro-B-type natriuretic peptide were performed at hospital admission, hospital discharge, and recheck examinations. Lung ultrasound findings were compared between timepoints and to other clinical measures of L-CHF. RESULTS: From time of hospital admission to discharge (mean 19.6 hours), median number of LUS sites strongly positive for B-lines (>3 B-lines per site) decreased from 5 (range, 1-8) to 1 (range, 0-5; P < .001), and median total B-line score decreased from 37 (range, 6-74) to 5 (range, 0-32; P = .002). Lung ultrasound indices remained improved at first recheck (P < .001). Number of strong positive sites correlated positively with respiratory rate (r = 0.52, P = .008) and TXR edema score (r = 0.51, P = .009) at hospital admission. Patterns of edema resolution differed between LUS and TXR, with cranial quadrants showing more significant reduction in B-lines compared to TXR edema score (80% vs 29% reduction, respectively; P = .003). CONCLUSIONS AND CLINICAL IMPORTANCE: Lung ultrasound could be a useful tool for monitoring resolution of pulmonary edema in dogs with L-CHF.

Retrospective evaluation of the safety and tolerability of pimobendan in cats with obstructive vs nonobstructive cardiomyopathy.

BACKGROUND: Pimobendan is frequently used off-label for treatments of cats with congestive heart failure (CHF). Concern exists regarding the safety of pimobendan in cats with outflow tract obstruction (OTO). OBJECTIVES: In cats treated with pimobendan, incidence of adverse effects will not differ between cats with OTO vs cats with nonobstructive cardiomyopathy. ANIMALS: Two-hundred sixty cats with CHF (57 with OTO, 203 with nonobstructive disease). METHODS: Retrospective medical record review. Groups were compared using 2-sample t-tests, Wilcoxon rank-sum tests, and Fisher exact tests. RESULTS: Compared to cats with nonobstructive cardiomyopathy, cats with OTO were younger (8.9 [interquartile range (IQR) 6.6] vs 10.8 [6.3] years, P = .0036), more likely to have a heart murmur (51/57 [90%] vs 76/203 [37.8%] cats, P < .0001), more likely to manifest CHF as pulmonary edema (53/57 [83%] vs 144/203 [70.9%] cats, P = .0004), and less likely to have pleural effusion (19/57 [33%] vs 122/203 [60.1%] cats, P = .0005). Adverse effects suspected to be related to pimobendan administration occurred in 12/260 cats (4.6%), including 11/203 cats (5.4%) with nonobstructive cardiomyopathy and 1/57 cat (2%) with OTO (P = .7). Pimobendan was discontinued due to adverse effects in 4/260 cats (1.5%), 3 with nonobstructive disease and 1 with OTO (P = 1.0). Acute adverse hemodynamic effects after pimobendan administration were not detected in any cats. CONCLUSIONS AND CLINICAL IMPORTANCE: Pimobendan is well tolerated in cats with cardiomyopathy and CHF, regardless of the presence of OTO.

Mucinous Pleural Effusion in a Dog with a Pulmonary Adenocarcinoma and Carcinomatosis.

An 11 yr old castrated male greyhound presented to the Washington State University's Veterinary Teaching Hospital (WSU VTH) for evaluation of a 4 day history of pleural effusion. The pleural effusion had a gelatinous appearance, suggestive of mucus, and was characterized cytologically as a pyogranulomatous exudate with some features suggestive of a carcinoma. Postmortem examination identified a pulmonary mass with evidence of carcinomatosis. Pulmonary papillary adenocarcinoma with carcinomatosis was the histologic diagnosis. Abundant mucin production was present, consistent with a mucinous pulmonary adenocarcinoma. To the authors' knowledge, this is the first report of a mucinous pulmonary adenocarcinoma with mucus pleural effusion in a dog.