Classification of naturally occurring arterial disease in the dog

Ultrasound Evaluation of Extracranial Cerebral Circulation (The Common, External and Internal Carotid Artery) in Different Breeds of Dogs

Noninvasive Doppler ultrasonography (US) examination is a standard method for the clinical evaluation of the carotid arteries. Extracranial cerebral circulation includes the common carotid artery (CCA), the external carotid artery (ECA), and the extracranial part of the internal carotid artery (ICA). The present study was conducted with the objective of assessing physiological normative values and describing the appearance of spectral waveforms of extracranial arteries in 104 healthy dogs of eight breeds divided into four groups according to weight. We also focused on searching for correlations for carotid blood velocities with the resistive index (RI), body weight and diameter, and differences between observers and the influence of sex in the calculations of Doppler parameters. In the evaluated breeds, significant differences were found in the velocity of peak systolic velocity (PSV) and end diastolic velocity (EDV). There was a strong correlation between body weight and peak systolic velocity, the RI index and CCA diameter. The intra-observer agreement for the PSV and EDV parameters in each vessel was considered excellent reliability, and overall interobserver agreement showed very good reliability. This study could improve the descriptions of physiological values and waveforms recorded in carotid arteries. Defining the physiological values of velocity and the resistive index (RI) helps in the easier identification of pathology and diagnosis of disease. Our results may be used for further studies of vascular diseases in veterinary medicine that correlate with the pathology of neurological disorders of ischemic origin, further in thromboembolism, oncologic disease and degenerative, proliferative and inflammatory diseases of the arteries that lead to stenosis.

Renal Magnesium Handling: A Comparison Between Dogs With Chronic Kidney Disease and Healthy Elderly Dogs

Chronic kidney disease (CKD) and aging are known to possibly cause a progressive reduction in glomerular filtration rate, which may be associated with an increase in fractional excretion of electrolytes due to an adaptive response of the remaining functioning nephrons. However, the behavior of magnesium excretion has not been studied in CKD and healthy elderly dogs. The objective was to evaluate the fractional excretion of magnesium (FEMg) in dogs with (CKD) compared to healthy elderly dogs. Sixteen healthy elderly dogs and 43 dogs with CKD were divided into 3 groups (CKD 2 [n = 14], CKD 3 [n = 17], CKD 4 [n = 12]), in accordance with the current International Renal Interest Society (IRIS) criteria that were used in this study. Blood samples were obtained by jugular venipuncture and urine samples were obtained by cystocentesis. The FEMg was evaluated at a single time point in both urine and blood samples. FEMg was significantly higher in dogs with CKD compared to healthy elderly dogs, especially in advanced stages. This preliminary study demonstrates that FEMg may be altered in dogs with CKD. Further research is warranted to elucidate magnesium's potential role in cardiovascular and arterial calcification in dogs with CKD as observed in humans with CKD.

Spontaneously occurring cardiovascular lesions in commonly used laboratory animals

The search for new chemical entities which are clinically effective and do not adversely affect the cardiovascular system is an ongoing objective. In vivo studies designed to detect potential drug-induced cardiovascular toxicity typically utilize both rodent and non-rodent species. An important component of such studies includes the microscopic evaluation of tissues for histopathologic changes. A factor which could potentially complicate this type of evaluation relates to the potential for laboratory animals to develop natural or spontaneous pathological cardiovascular lesions. Some types of these naturally occurring alterations are similar to those induced by chemical compounds and thus could confound accurate interpretation. Accurate morphologic analysis becomes contingent upon the ability to distinguish spontaneous cardiovascular changes from actual drug-induced lesions. A summary of some of the more frequently reported spontaneous cardiovascular alterations in commonly-used laboratory animals is presented below. Special emphasis is given to the spectrum of spontaneous background myocardial pathology that might be encountered during preclinical studies conducted to identify potential cardiotoxic actions of anticancer agents.

Nonclinical Safety Biomarkers of Drug-induced Vascular Injury

Better biomarkers are needed to identify, characterize, and/or monitor drug-induced vascular injury (DIVI) in nonclinical species and patients. The Predictive Safety Testing Consortium (PSTC), a precompetitive collaboration of pharmaceutical companies and the U.S. Food and Drug Administration (FDA), formed the Vascular Injury Working Group (VIWG) to develop and qualify translatable biomarkers of DIVI. The VIWG focused its research on acute DIVI because early detection for clinical and nonclinical safety monitoring is desirable. The VIWG developed a strategy based on the premise that biomarkers of DIVI in rat would be translatable to humans due to the morphologic similarity of vascular injury between species regardless of mechanism. The histomorphologic lexicon for DIVI in rat defines degenerative and adaptive findings of the vascular endothelium and smooth muscles, and characterizes inflammatory components. We describe the mechanisms of these changes and their associations with candidate biomarkers for which advanced analytical method validation was completed. Further development is recommended for circulating microRNAs, endothelial microparticles, and imaging techniques. Recommendations for sample collection and processing, analytical methods, and confirmation of target localization using immunohistochemistry and in situ hybridization are described. The methods described are anticipated to aid in the identification and qualification of translational biomarkers for DIVI.

Arteriosclerotic changes in the myocardium, lung, and kidney in dogs with chronic congestive heart failure and myxomatous mitral valve disease

BACKGROUND

The occurrence of small vessel arteriosclerosis in the myocardium, kidney, and lung in dogs with naturally occurring myxomatous mitral valve disease has not been previously investigated systematically.

METHODS

Twenty-one dogs with naturally occurring congestive heart failure and 21 age-matched, sex-matched, and weight-matched control dogs underwent extensive pathological and histopathological examination. Morphometry and scoring of tissue sections were used to measure arterial narrowing and fibrosis in the myocardium, kidney, and lung; and intimal thickness and plaque formation in the aorta and pulmonary artery.

RESULTS

Dogs with congestive heart failure had significantly more arterial narrowing in the left ventricle (P < .003), lung (P < .0001), and kidney (P < .02); intimal-medial thickening in the pulmonary artery (P = .04); and fibrosis in the left ventricle (P < .0001) than control dogs. However, they did not have more plaque formation or intimal-medial thickening in the aorta than controls. There was significantly more arterial narrowing in papillary muscles than in all other locations in dogs with congestive heart failure (P < .002). In control dogs, arterial changes were less pronounced and did not differ in different locations.

CONCLUSIONS

Dogs with naturally occurring myxomatous mitral valve disease have significantly more arterial changes in the myocardium, lung, and kidney, and significantly more fibrosis in the myocardium than control dogs. This could have important implications in the management of myxomatous mitral valve disease and raises interesting questions about the occurrence and importance of intramural small vessel disease in humans with primary mitral valve prolapse.

A search for an animal model of the Spanish toxic oil syndrome

To date, pathology characteristics of toxic oil syndrome (TOS), a disease associated with consumption of a contaminated cooking oil in Spain in 1981, have not been reproduced in an animal model. As vasculitis, eosinophilia, and a rise in circulating IgE levels were features of the acute phase of TOS, leading to an autoimmune outcome, a review of predisposition to these aspects across species was conducted. The intent was to determine predisposed strains or species that potentially might be effective in testing the toxic oils and thus defining the precise identity of the toxic contaminant(s). A number of potential candidates emerge from this review. Among mice, these include the NZB mouse hybrids, the MRL/lpr and SJL/J strains, and a transgenic mouse model of eosinophilia. The Brown Norway may be the most appropriate rat strain, while beagle dogs inbred to be genetically predisposed to immune complex disease and vasculitis are also a candidate species. Of the more exotic species, the mink and ferret have characteristics that might make them suitable candidates for testing oil samples.

Ischaemic heart disease in the dog: a review of 65 cases

Sixty-five dogs are reviewed with histopathologically confirmed intramural arteriosclerosis. Clinical data (clinical signs, electrocardiographic findings and ultrasound parameters) on these animals were collected from nine small animal clinics in Sweden: 16 dogs had died suddenly, with few or no previous clinical signs; 13 dogs died or were euthanased during or shortly after general anaesthesia or sedation; 30 dogs developed acute (14) or chronic (16) congestive heart failure; and six dogs died or were euthanased for causes unrelated to cardiac disease. Electrocardiography of 23 of the dogs revealed several types of arrhythmias, with atrial fibrillation and sinus tachycardia being most commonly detected. Ultrasonographic examinations of 24 dogs found a relatively high number (19) with decreased indices of contractility. Dogs that had died suddenly and in relation to general anaesthesia or sedation had a higher incidence (25 of 29) of purely arteriosclerotic changes in the myocardial vessels, whereas just over half the dogs with congestive heart failure (16 of 30) had other concomitant heart lesions (in most cases endocardiosis). The incidence of myocardial infarcts was high (51 of 65 cases). It is postulated that arteriosclerosis in the dog may be an important reason for sudden death and death during general anaesthesia. Coronary arterial disease should also be a consideration in the clinical evaluation of dilated cardiomyopathy and may contribute to the decreased myocardial contractility when it is present in dogs with mitral regurgitation.

Vascular toxicity in dogs associated with overdoses of a novel benzodiazepine receptor partial agonist

Necrotizing arteritis and periarteritis were found in Beagle and German Shepherd dogs treated for 13 or 52 weeks with the novel benzodiazepine receptor (BZR) partial agonist Ro 16-6028 (generic name bretazenil). Eight male and one female out of a total of 20 dogs treated with 40-60 mg/kg/day Ro 16-6028 developed the arteritis, predominantly in the heart or the epididymis. Two of these animals died prematurely following treatment at the initial dosing levels of 80 and 55 mg/kg/day; one of these two dogs was asymptomatic and in good general condition until death. Clinically, all but one of the dogs showed sedation, ataxia, stiff gait, body weight-loss and a deterioration of the general condition as well as changes of some laboratory parameters. No signs of arteritis and untoward clinical or laboratory findings were seen at lower doses. Possible aetiologies, as well as the mechanisms involved in arteritis in general and the genetic disposition of beagles in particular for this type of effect, are discussed. Reflections on the potential risk to man of this so far unknown finding after oral treatment with 1,4-benzodiazepines (BZs) are presented.