G. Rapoport

Cardiomyopathy and Right-sided Congestive Heart Failure in a Red-tailed Hawk (Buteo jamaicensis)

Abstract A 15-year-old female red-tailed hawk (Buteo jamaicensis) was evaluated because of dyspnea, anorexia, and coelomic distension. Diagnostic imaging results confirmed severe coelomic effusion and revealed a markedly dilated right ventricle. The diagnosis was right-sided congestive heart failure. Results of measurements of vitamin E, selenium, lead, zinc, and cardiac troponin levels were normal or nondiagnostic. The hawk was treated with furosemide, antifungal and antimicrobial agents, and supplemental fluids and oxygen, but euthanasia was elected because of the poor prognosis and the practical difficulties associated with intensive case management. To our knowledge, this is the first described case of cardiomyopathy and congestive heart failure in a captive red-tailed hawk.

Doppler and Volumetric Echocardiographic Methods for Cardiac Output Measurement in Standing Adult Horses

BACKGROUNDnCardiac output (CO) is not routinely measured in critically ill adult horses because of invasiveness of currently validated methods. Noninvasive CO monitoring would complement clinical assessment of hemodynamic status in adult horses.nnnHYPOTHESISnVolumetric methods for measuring CO will have better agreement with lithium dilution than Doppler-based methods.nnnANIMALSnEight healthy adult horses.nnnMETHODSnProspective study. CO was manipulated with continuous rate infusions of dobutamine and romifidine to achieve high and low CO states, respectively. At each level, CO was measured by lithium dilution and various echocardiographic methods. Images stored as video loops were reviewed by an individual blinded to the lithium dilution results.nnnRESULTSnLithium dilution determinations of CO ranged between 16.6 and 63.0xa0L/min. There was a significant effect of method of CO measurement (Pxa0<xa0.001), but no significant effect of CO level (Pxa0=xa0.089) or interaction between level and method (Pxa0=xa0.607) on the absolute value of the bias. The absolute values of the bias of the right ventricular outflow tract (RVOT) Doppler, Simpson, 4-chamber area-length, and bullet methods [5.5, 6.1, 6.5, 8.8xa0L/min, respectively] were significantly lower than that of the left ventricular outflow tract (LVOT) Doppler or cubic methods [14.8, 24.3xa0L/min, respectively].nnnCONCLUSIONS AND CLINICAL IMPORTANCEnThe 4-chamber area-length, Simpson, bullet, and RVOT Doppler provided better agreement with lithium dilution than the other methods evaluated. These methods warrant further investigation for use in critically ill adult horses.

Pharmacodynamic Evaluation of 4 Angiotensin‐Converting Enzyme Inhibitors in Healthy Adult Horses

BACKGROUNDnAngiotensin-converting enzyme (ACE) inhibitors are used in horses with cardiovascular disorders despite the paucity of available data regarding their efficacy.nnnHYPOTHESISnThe degree of serum ACE inhibition varies considerably between drugs.nnnANIMALSnEight healthy adult horses.nnnMETHODSnRandomized prospective study. Horses were fasted overnight prior to receiving one of 4 ACE inhibitors intragastrically, administered at one of 2 dosages, using a randomized Latin square design (benazepril: 0.5 and 0.25 mg/kg; ramipril: 0.3 and 0.1 mg/kg; quinapril: 0.25 and 0.125 mg/kg; perindopril: 0.1 and 0.05 mg/kg). Serum ACE activity was measured using a kinetic spectrophotometric method.nnnRESULTSnThere was a significant effect of drug and dosage on maximum ACE inhibition (I(max)), ACE inhibition 24 hours after administration (I(24h)), and area under the curve (AUC(0-48h)). Benazepril at 0.5 mg/kg resulted in significantly higher I(max) (86.9 ± 7.0%) and I(24h) (60.3 ± 7.9%) compared to the other drugs. There was a significant decrease in indirect blood pressure (BP) over time after administration of each drug, but differences in BP were not significantly different between drugs. Pharmacodynamic variables measured after administration of benazepril to horses with free access to hay were not significantly different from those obtained after fasting. Administration of benazepril orally once daily for 7 days did not result in a cumulative effect on ACE inhibition.nnnCONCLUSIONS AND CLINICAL IMPORTANCEnOf the ACE inhibitors tested, oral benazepril (0.5 mg/kg) is the most effective at inhibiting serum ACE activity in healthy horses.

A survey of southeastern United States veterinarians’ preferences for managing cats with diabetes mellitus

This study evaluated primary practitioners’ perceptions of managing feline diabetics. Surveys distributed during local continuing education events achieved a response rate of 46% (90/195). A mean of 74% feline diabetics required chronic insulin; 26% were transient diabetics. Choice of insulin was most influenced by duration of action: human recombinant protamine zinc insulin was ranked first (42%) and glargine second (27%). Dietary management was always/usually recommended by 97% respondents, with prescription or proprietary low-carbohydrate, high-protein diets recommended in 93% responses. More recent graduates (P = 0.0419), those who worked in larger practices (P = 0.0315), and those who saw more transient diabetics (P = 0.0288) were more likely to recommend dietary change. In-house blood glucose curves (BGCs) were the most popular method of assessing glycemic control, while at-home BGCs were least popular, although their use correlated positively with annual diabetic caseload (r = 0.43, P = 0.0239). Owners mishandling insulin was cited as the most common cause of poor glycemic control, while clinical signs of acromegaly were rarely recognized.

Heart rate variability in horses with acute gastrointestinal disease requiring exploratory laparotomy.

Objective n nTo describe heart rate variability (HRV) in horses with acute gastrointestinal disease that undergo exploratory laparotomy. We hypothesized that horses with ischemic gastrointestinal disease will have reduced HRV compared to horses with nonischemic lesions. We further hypothesized that a reduction in HRV will be associated with nonsurvival. n n n nDesign n nProspective, clinical, observational study. n n n nSetting n nUniversity veterinary teaching hospital. n n n nAnimals n nHorses presented for acute colic (n = 57) or elective surgical procedures (n = 10) were enrolled. n n n nInterventions n nAdmission heart rate (HR) was recorded and within 2 hours of recovery from general anesthesia continuous telemetry was placed, monitored and recorded for 48-52 hours postoperatively. Stored electrocardiograms were manually inspected and R-to-R intervals were extracted and uploaded into HRV software for analysis. Time domain and frequency spectral analysis were investigated at Times 1 (2–10 h), 2 (16–24 h), 3 (30–38 h), and 4 (44–52 h) postoperatively. A two-way ANOVA for repeated measures was used for group comparisons. Logistic regression analysis was used to detect potential associations between admission HR, time and frequency domain variables, and nonsurvival. n n n nMeasurements and Main Results n nHorses diagnosed with an ischemic gastrointestinal lesion (n = 22) at the time of surgery had significantly higher postoperative heart rates and reduced time domain-derived measures of HRV than horses with nonischemic gastrointestinal lesions (n = 35) or control horses (n = 10). Horses that survived to discharge had significantly lower postoperative HRs, higher time domain, and lower low frequency spectral measures of HRV compared to nonsurvivors. The multivariable logistic regression model had a receiver operating characteristic area under the curve (AUC) of 0.95 and was significantly better at predicting nonsurvival than admission HR (P = 0.0124). n n n nConclusions n nReduced HRV was strongly associated with ischemic gastrointestinal disease and nonsurvival. HRV analysis is a noninvasive technique that may provide diagnostic and prognostic information pertinent to the management of postoperative horses with severe gastrointestinal disease.OBJECTIVEnTo describe heart rate variability (HRV) in horses with acute gastrointestinal disease that undergo exploratory laparotomy. We hypothesized that horses with ischemic gastrointestinal disease will have reduced HRV compared to horses with nonischemic lesions. We further hypothesized that a reduction in HRV will be associated with nonsurvival.nnnDESIGNnProspective, clinical, observational study.nnnSETTINGnUniversity veterinary teaching hospital.nnnANIMALSnHorses presented for acute colic (n = 57) or elective surgical procedures (n = 10) were enrolled.nnnINTERVENTIONSnAdmission heart rate (HR) was recorded and within 2 hours of recovery from general anesthesia continuous telemetry was placed, monitored and recorded for 48-52 hours postoperatively. Stored electrocardiograms were manually inspected and R-to-R intervals were extracted and uploaded into HRV software for analysis. Time domain and frequency spectral analysis were investigated at Times 1 (2-10 h), 2 (16-24 h), 3 (30-38 h), and 4 (44-52 h) postoperatively. A two-way ANOVA for repeated measures was used for group comparisons. Logistic regression analysis was used to detect potential associations between admission HR, time and frequency domain variables, and nonsurvival.nnnMEASUREMENTS AND MAIN RESULTSnHorses diagnosed with an ischemic gastrointestinal lesion (n = 22) at the time of surgery had significantly higher postoperative heart rates and reduced time domain-derived measures of HRV than horses with nonischemic gastrointestinal lesions (n = 35) or control horses (n = 10). Horses that survived to discharge had significantly lower postoperative HRs, higher time domain, and lower low frequency spectral measures of HRV compared to nonsurvivors. The multivariable logistic regression model had a receiver operating characteristic area under the curve (AUC) of 0.95 and was significantly better at predicting nonsurvival than admission HR (P = 0.0124).nnnCONCLUSIONSnReduced HRV was strongly associated with ischemic gastrointestinal disease and nonsurvival. HRV analysis is a noninvasive technique that may provide diagnostic and prognostic information pertinent to the management of postoperative horses with severe gastrointestinal disease.

Pharmacokinetic and pharmacodynamic evaluation of oral rivaroxaban in healthy adult cats.

OBJECTIVESnTo determine the pharmacodynamics and pharmacokinetics of rivaroxaban (RVX), in healthy cats and to evaluate the clinicopathologic effects of various plasma RVX concentrations within target therapeutic ranges established for people.nnnDESIGNnProspective randomized cross-over study performed between July 2013 and November 2014.nnnSETTINGnVeterinary university teaching hospital.nnnANIMALSnSix healthy adult domestic shorthair cats (3 males, 3 females).nnnINTERVENTIONSnCats were treated with oral RVX at single, fixed doses (1.25, 2.5, 5 mg PO), q 12 h for 3 days (1.25 mg); q 24 h for 7 days (2.5 mg); and q 24 h for 28 days (1.25 mg). Blood samples were collected for complete blood count, blood chemistry, and RVX anticoagulant activity based on prolongation of dilute prothrombin time, activated partial thromboplastin time (aPTT), activated Factor X (FXa) inhibition (anti-Xa activity [aXa]) and high-pressure liquid chromatography tandem mass spectrometry determination of drug concentration.nnnMEASUREMENTS AND MAIN RESULTSnTreated cats had no signs of hemorrhage or clinicopathologic off-target adverse effects. There were dose-dependent prolongations of coagulation times and increase in aXa, with peak effect at 3 hours postadministration. There was a direct correlation between plasma RVX concentration and dilute prothrombin time and aXa. Coagulation parameters returned to baseline by 24 hours after the last dose.nnnCONCLUSIONSnOral RVX was well tolerated by healthy cats with predictable pharmacokinetics and anticoagulant effects. Clinical studies of RVX are warranted in cats with heart disease.

Microdose computed tomographic cardiac angiography in normal cats.

OBJECTIVESnTo determine if microdose contrast-enhanced multi-detector computed tomographic angiography (MDCTA) allows characterization of cardiac chambers in lightly sedated normal cats.nnnANIMALSnSeven healthy domestic cats.nnnMETHODSnLightly sedated normal cats were imaged pre-contrast and with microdose (0.22 ml/kg of non-ionic iodinated contrast medium, 300 mg I/ml) triple-phase MDCTA in a motion restriction device.nnnRESULTSnOn pre-contrast images, the aorta (median: 52.43 Hounsfield units [HU], range 27.35-76.74 HU) was outlined by significantly (p = 0.015) lower attenuating periaortic fat (-66.16 HU, -42.62 to -92.77 HU). On post-contrast images, median peak contrast enhancement in the right ventricle (111.77 HU, 36.09-141.60 HU) was achieved in 3.1 s (range 2.9-7.3 s), in the aorta (149.30 HU, 99.43-319.60 HU) and left atrium (180.83 HU, 88.53-266.84 HU) in 6.4 s (range 5.6-7.7 s) and in the left ventricle (147.89 HU, 57.23-245.77 HU) in 7.10 s (range 6.2-11.2 s). Significantly higher attenuation was measured between all chambers and walls, the right ventricular lumen and interventricular septum (median ratio 53.78 HU, range 0.21-83.20 HU), left ventricular lumen and left ventricular free wall (89.32 HU, 38.81-185.95 HU) and aorta and periaortic fat (190.43 HU, 143.22-425.44 HU) on post-contrast images.nnnCONCLUSIONSnSufficient biological contrast is available on survey CT to discriminate between the aorta and the left atrium, and microdose MDCTA provides sufficient contrast enhancement for adequate visualization of the heart chambers in normal cats.

Attenuation of the blood pressure response to exogenous angiotensin I after oral administration of benazepril to healthy adult horses

BACKGROUNDnBenazepril has been shown to inhibit circulating angiotensin-converting enzyme (ACE) activity in horses but the optimal dosage is unknown.nnnOBJECTIVESnTo determine the lowest tested dose of benazepril that results in ≥75% attenuation in the response of arterial blood pressure (BP) to exogenous angiotensin I (ANG-I) administration.nnnSTUDY DESIGNnProspective experimental study.nnnMETHODSnA total of 5 healthy horses were instrumented for the direct measurement of BP. Each horse received 4 intragastric doses of benazepril (0.5, 1, 2 and 4 mg/kg bwt) with a washout period of 7 days between doses. Prior to and 2, 12 and 24 h after benazepril administration, each horse received intravenous (i.v.) boluses of ANG-I at 20, 60 and 200 ng/kg. Attenuation of the systolic arterial pressure (SBP) response to ANG-I and serum ACE activity were quantified and expressed as percentage of inhibition.nnnRESULTSnThere was a significant effect of benazepril dose (P = 0.004) and time (P = 0.004) on the percentage of inhibition of the systolic pressor response to ANG-I. Regardless of benazepril dose, the percentage of inhibition was significantly greater 2 h after administration of benazepril compared with 12 and 24 h. At an ANG-I dose of 20 ng/kg, the percentage of inhibition after administration of benazepril at 1 mg/kg bwt (46.6 ± 18.9%) was significantly greater than that achieved after 0.5 mg/kg bwt (19 ± 14%) but not significantly different from that achieved at higher doses of benazepril. Benazepril doses ≥1 mg/kg bwt resulted in serum ACE inhibition of at least 90%.nnnMAIN LIMITATIONSnSmall sample size and resulting low statistical power.nnnCONCLUSIONSnAttenuation of the rise in SBP in response to ANG-I after administration of benazepril is modest in horses despite adequate serum ACE inhibition. A dose of 1 mg/kg bwt would be recommended for future investigations of benazepril for the management of cardiovascular diseases in horses.

Cardiovascular effects of pimobendan in healthy mature horses

REASONS FOR PERFORMING STUDYnPimobendan is an inodilator used in dogs for the management of heart failure due to myxomatous valve disease or dilated cardiomyopathy. The lack of data regarding the effects of pimobendan in horses prevents the rational use of this drug.nnnOBJECTIVEnTo determine the cardiovascular effects of pimobendan in healthy mature horses.nnnSTUDY DESIGNnRandomised experimental study.nnnMETHODSnFive horses were fasted overnight prior to receiving i.v. pimobendan (0.25 mg/kg bwt), intragastric (i.g.) pimobendan (0.25 mg/kg bwt) or i.g. placebo with a washout period of one week between each administration. Horses were instrumented for the measurement of right ventricular (RV) minimum pressure, RV maximum pressure, RV end diastolic pressure, and maximum rate of increase and decrease in RV pressure before and 0.5, 1, 2, 4, and 8 h after drug administration. Arterial blood pressure, central venous pressure, cardiac output and heart rate were measured at the same time points. Data were expressed as a maximum percentage of change over baseline values.nnnRESULTSnThere were no adverse effects associated with administration of pimobendan. The percentage increase in heart rate was significantly greater for horses given pimobendan i.g. (33 ± 4%) and i.v. (36 ± 14%) than for those given a placebo (-2 ± 7%). The percentage increase in maximum rate of increase in RV pressure (35 ± 36%) and the percentage decrease in minimum pressure (47 ± 24%) and end diastolic pressure (34 ± 13%) were significantly greater in horses given pimobendan i.v. than in those given placebo. Other variables measured were not significantly different between treatment groups.nnnCONCLUSIONnPimobendan administered i.v. has positive chronotropic and inotropic effects in healthy mature horses and warrants further investigation for the treatment of heart failure in horses.

Pulmonary edema secondary to a cardiac schwannoma in a dog

A 4-year-old castrated labrador retriever presented for cardiac evaluation to determine the etiology of cardiogenic pulmonary edema diagnosed 1 month prior. A large pedunculated mass involving the ventral aspect of the mural mitral valve leaflet and the endocardial surface of the left ventricular free wall, resulting in severe mitral regurgitation, was identified on echocardiogram. Histopathology and immunohistochemistry of this mass and other endocardial masses identified at necropsy for S-100 protein were consistent with a diagnosis of schwannoma. To the authors knowledge, this is the first case of a benign intracardiac schwannoma described in the left heart of a dog.