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BackgroundA 5-year-old, healthy English Springer Spaniel died suddenly 4 months after delivering a litter of 7 puppies. Within 4 months of the dam's death, 3 offspring also died suddenly.HypothesisAbnormal cardiac repolarization, caused by an inherited long QT syndrome, is thought to be responsible for arrhythmias leading to sudden death in this family.AnimalsFour remaining dogs from the affected litter and 11 related dogs.MethodsPhysical examination and resting ECG were done on the littermates and 9 related dogs. Additional tests on some or all littermates included echocardiogram with Doppler, Holter monitoring, and routine serum biochemistry. Blood for DNA sequencing was obtained from all 15 dogs.ResultsThree of 4 littermates examined, but no other dogs, had prolonged QT intervals with unique T-wave morphology. DNA sequencing of the KCNQ1 gene identified a heterozygous single base pair mutation, unique to these 3 dogs, which changes a conserved amino acid from threonine to lysine and is predicted to change protein structure.Conclusions and clinical importanceThis family represents the first documentation in dogs of spontaneous familial QT prolongation, which was associated with a KCNQ1 gene mutation and sudden death. Although the final rhythm could not be documented in these dogs, their phenotypic manifestations of QT interval prolongation and abnormal ECG restitution suggested increased risk for sudden arrhythmic death. The KCNQ1 gene mutation identified is speculated to impair the cardiac repolarizing current IKs, similar to KCNQ1 mutations causing long QT syndrome 1 in humans.

Background: Activity of the circulating renin-angiotensin-aldosterone system (RAAS) has not been comprehensively characterized in cats with systemic hypertension (SH) or cardiomyopathy (CM), and the effects of furosemide or amlodipine treatment on the RAAS have not been fully evaluated in cats., Hypothesis/objectives: To document RAAS activity in cats with SH or CM compared to healthy cats and determine how RAAS profiles change with furosemide or amlodipine treatment., Animals: Sixty-six client-owned cats: 15 with SH (7 amlodipine-treated, 8 untreated), 17 with advanced CM (7 furosemide-treated, 10 not furosemide-treated), and 34 healthy cats., Methods: Equilibrium concentrations of RAAS peptides and aldosterone were quantified in serum samples by liquid chromatography-mass spectrometry. Variables were compared between groups using Kruskal-Wallis analysis with post hoc Holms-corrected Dunn's testing., Results: Compared with healthy cats, cats with CM had higher concentrations of angiotensin I, aldosterone, and plasma renin activity (all P < .01), and these differences remained significant (P < .03) after considering subgroups of untreated or furosemide-treated cats. Compared with healthy cats, untreated cats with SH showed no differences in RAAS biomarkers, whereas amlodipine-treated cats had higher concentrations of angiotensins I, II, III, IV, and 1-7, aldosterone, and plasma renin activity (all P < .03). Multivariable analysis determined that furosemide and amlodipine treatments were independent predictors of increased RAAS biomarker concentrations., Conclusions and Clinical Importance: Cats with CM had increased RAAS activity, whereas cats with untreated SH did not. Furosemide and amlodipine both led to nonspecific activation of both classical and alternative RAAS pathways in cats., (© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

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., (© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC. on behalf of the American College of Veterinary Internal Medicine.)

Background: Low vitamin D concentrations have been associated with advanced heart disease and poorer outcomes in people and dogs. Vitamin D status typically is assessed by serum 25(OH)D concentration. However, cats also produce notable amounts of a C-3 epimer of 25(OH)D (3-epi)., Hypothesis/objectives: Determine if vitamin D status, estimated by 25(OH)D 3 alone or combined with 3-epi (summation vitD), is lower in cats with cardiomyopathy (CM) compared to clinically normal (N) cats and if indicators of disease severity are associated with vitamin D status., Animals: Privately owned cats, 44 with CM and 56 N., Methods: Cross-sectional observational study using clinical and echocardiographic findings, diet history, and serum 25(OH)D 3 and 3-epi measurements., Results: Cat age was negatively related to vitamin D status. Summation vitD was lower in CM cats (median = 47.1 ng/mL) compared to N cats (median = 58.65 ng/mL) both before (P = .03) and after (P = .04) accounting for age. However, 25(OH)D 3 became nonsignificant between CM and N cats after age was included. Summation vitD was related positively to survival time and fractional shortening (FS), but negatively to left atrial enlargement (LAE) severity, both before and after accounting for age. For 25(OH)D 3 alone, only survival time and FS remained significant after including age., Conclusions and Clinical Importance: We report 25(OH)D 3 and 3-epi concentrations in CM and N cats. Age had an important (negative) relationship to vitamin D status. After accounting for age, summation vitD was lower in CM cats. Vitamin D status was related positively to survival time and FS, but negatively to LAE severity., (© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Epidemiologic knowledge regarding noncardiovascular and all-cause mortality in apparently healthy cats (AH) and cats with preclinical hypertrophic cardiomyopathy (pHCM) is limited, hindering development of evidence-based healthcare guidelines., Objectives: To characterize/compare incidence rates, risk, and survival associated with noncardiovascular and all-cause mortality in AH and pHCM cats., Animals: A total of 1730 client-owned cats (722 AH, 1008 pHCM) from 21 countries., Methods: Retrospective, multicenter, longitudinal, cohort study. Long-term health data were extracted by medical record review and owner/referring veterinarian interviews., Results: Noncardiovascular death occurred in 534 (30.9%) of 1730 cats observed up to 15.2 years. Proportion of noncardiovascular death did not differ significantly between cats that at study enrollment were AH or had pHCM (P = .48). Cancer, chronic kidney disease, and conditions characterized by chronic weight-loss-vomiting-diarrhea-anorexia were the most frequently recorded noncardiovascular causes of death. Incidence rates/risk of noncardiac death increased with age in AH and pHCM. All-cause death proportions were greater in pHCM than AH (65% versus 40%, respectively; P < .001) because of higher cardiovascular mortality in pHCM cats. Comparing AH with pHCM, median survival (study entry to noncardiovascular death) did not differ (AH, 9.8 years; pHCM, 8.6 years; P = .10), but all-cause survival was significantly shorter in pHCM (P = .0001)., Conclusions and Clinical Importance: All-cause mortality was significantly greater in pHCM cats due to disease burden contributed by increased cardiovascular death superimposed upon noncardiovascular death., (© 2019 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Objective: To characterize lung ultrasonography (LUS) findings in dogs with a primary clinical complaint of cough., Animals: 100 client-owned coughing dogs., Procedures: A standardized LUS examination was performed for all dogs to quantify the number of B lines and identify subpleural abnormalities at 4 sites on each hemithorax. The final clinical diagnosis (reference standard) was determined by medical record review, and sensitivity and specificity of LUS for the diagnosis of selected causes of cough was determined., Results: Common underlying causes of cough included dynamic airway collapse (n = 37), cardiogenic pulmonary edema (CPE; 12), and bronchitis (10). Compared with dogs with other causes of cough, dogs with bacterial pneumonia (n = 7) were more likely to have subpleural shred signs, whereas dogs with pulmonary neoplasia (4) were more likely to have subpleural nodule signs. Dogs with CPE had higher total B-line scores and higher numbers of LUS sites strongly positive for B lines (> 3 B lines/site) than other dogs. The LUS criteria of total B-line score ≥ 10 and presence of ≥ 2 sites strongly positive for B lines were each 92% sensitive and 94% specific for CPE diagnosis. Notably, 18% (16/88) of dogs with noncardiac causes of cough had been treated previously with diuretics because of prior CPE misdiagnosis., Conclusions and Clinical Relevance: LUS profiles in dogs with cough differed by the underlying cause. In dogs with a clinical history of cough, this imaging modality could be diagnostically useful, particularly to help exclude the possibility of underlying CPE.

Objective: To evaluate the clinicopathologic, hemodynamic, and echocardiographic effects of short-term administration of anti-inflammatory dosages of prednisolone to systemically normal cats., Animals: 10 cats with allergic dermatitis and 10 healthy control cats., Procedures: Cats with allergic dermatitis were randomly allocated to 2 groups and received 2 dosages of prednisolone (1 and 2 mg/kg/d, PO, for 7 days) in a crossover design followed by 9-day tapering and 14-day washout periods. Each prednisolone-treated cat was matched to a healthy control cat on the basis of sex, neuter status, age (± 1 year), and body weight (± 10%). Control cats received no treatment during the 35-day observation period. Clinicopathologic, echocardiographic, and hemodynamic variables were measured at baseline (day 0) and predetermined times during and after prednisolone administration and compared within and between the 2 treatment groups., Results: Prednisolone-treated cats had expected clinicopathologic alterations (mild increases in neutrophil and monocyte counts and serum concentrations of albumin, cholesterol, and triglycerides) but systolic arterial blood pressure; blood glucose, serum potassium, and cardiac biomarker concentrations; urinary sodium excretion; and echocardiographic variables did not differ significantly from baseline at any time. Statistically significant, albeit clinically irrelevant, increases in blood glucose and N-terminal pro-B-type natriuretic peptide concentrations were observed between baseline and the prednisolone pharmacokinetic steady state (7 days after initiation) only when the 2-mg/kg dosage was administered., Conclusions and Clinical Relevance: Results indicated short-term oral administration of anti-inflammatory dosages of prednisolone did not cause relevant hemodynamic, echocardiographic, or diabetogenic effects in systemically normal cats with allergic dermatitis.

CASE DESCRIPTION A 9-year-old spayed female Dalmatian was examined because of progressive pelvic limb paraparesis. CLINICAL FINDINGS The dog had a history of chronic urinary incontinence and had been treated with phenylpropanolamine (PPA) for almost 8.5 years. Intervertebral disk disease at T12-13 was diagnosed, and a hemilaminectomy was performed. Three days after surgery, the dog developed a ventricular tachyarrhythmia. Severe left and mild right ventricular hypertrophy were detected by echocardiography. TREATMENT AND OUTCOME The arrhythmia was controlled with sotalol. Phenylpropanolamine administration was discontinued immediately before surgery and was not resumed. Heart rate and rhythm and blood pressure were within reference limits, and the ventricular hypertrophy had almost completely resolved 5 months later. Sotalol administration was discontinued. Shortly after the 5-month recheck evaluation, PPA administration was resumed, albeit at a lower dosage than that before surgery, for control of urinary incontinence. At the 10-month recheck evaluation, the dog was hypertensive and ventricular hypertrophy had recurred. Discontinuation of PPA administration was recommended but not heeded. The dog developed marked azotemia 1.5 years after surgery, which was managed by the referring veterinarian, and was subsequently lost to follow-up. CLINICAL RELEVANCE The fact that the ventricular hypertrophy almost completely resolved when PPA administration was discontinued and then recurred after it was resumed strongly suggested the drug was an important contributing factor to the cardiac disease of this patient. Patients receiving PPA on a long-term basis should be frequently monitored for cardiac disease, and use of other adrenergic receptor agonists should be avoided in such patients.

Background: The diagnosis of congestive heart failure (CHF) in cats is challenging. Point-of-care (POC) thoracic ultrasound and NT-proBNP testing are emerging tools that may aid in diagnosis., Hypothesis/objectives: To assess the diagnostic accuracy of POC lung ultrasound (LUS), focused cardiac ultrasound (FCU), and NT-proBNP in predicting a final diagnosis of CHF., Animals: Fifty-one cats in respiratory distress., Methods: Blood NT-proBNP, LUS, and FCU evaluating left atrial (LA) size and presence of pericardial effusion (PCEFF) were performed in all cats. Lung ultrasound findings including pleural effusion (PLEFF), number of B-lines, and sub-pleural abnormalities were noted. Medical records were evaluated for final diagnosis., Results: Thirty-three of 51 (65%) cats were diagnosed with CHF. Lung ultrasound and blood NT-proBNP were significant predictors of CHF in a multivariate model. The LUS criterion that maximized accuracy for CHF diagnosis was presence of >1 site strongly positive for B-lines (>3 B-lines per site), resulting in sensitivity of 78.8%, specificity of 83.3%, and area under the curve (AUC) of 0.833. Subjective LA enlargement was 97.0% sensitive and 100% specific for CHF (AUC 0.985). Presence of PCEFF also was 100% specific, but only 60.6% sensitive, for CHF (AUC 0.803). A positive blood NT-proBNP test was 93.9% sensitive and 72.2% specific for the diagnosis of CHF (AUC 0.831)., Conclusions and Clinical Importance: Point-of-care diagnostic techniques of LUS, FCU, and NT-proBNP are useful to diagnose CHF in cats with respiratory distress., (Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Hypertrophic cardiomyopathy is the most prevalent heart disorder in cats and principal cause of cardiovascular morbidity and mortality. Yet, the impact of preclinical disease is unresolved., Hypothesis/objectives: Observational study to characterize cardiovascular morbidity and survival in cats with preclinical nonobstructive (HCM) and obstructive (HOCM) hypertrophic cardiomyopathy and in apparently healthy cats (AH)., Animals: One thousand seven hundred and thirty client-owned cats (430 preclinical HCM; 578 preclinical HOCM; 722 AH)., Methods: Retrospective multicenter, longitudinal, cohort study. Cats from 21 countries were followed through medical record review and owner or referring veterinarian interviews. Data were analyzed to compare long-term outcomes, incidence, and risk for congestive heart failure (CHF), arterial thromboembolism (ATE), and cardiovascular death., Results: During the study period, CHF, ATE, or both occurred in 30.5% and cardiovascular death in 27.9% of 1008 HCM/HOCM cats. Risk assessed at 1, 5, and 10 years after study entry was 7.0%/3.5%, 19.9%/9.7%, and 23.9%/11.3% for CHF/ATE, and 6.7%, 22.8%, and 28.3% for cardiovascular death, respectively. There were no statistically significant differences between HOCM compared with HCM for cardiovascular morbidity or mortality, time from diagnosis to development of morbidity, or cardiovascular survival. Cats that developed cardiovascular morbidity had short survival (mean ± standard deviation, 1.3 ± 1.7 years). Overall, prolonged longevity was recorded in a minority of preclinical HCM/HOCM cats with 10% reaching 9-15 years., Conclusions and Clinical Importance: Preclinical HCM/HOCM is a global health problem of cats that carries substantial risk for CHF, ATE, and cardiovascular death. This finding underscores the need to identify therapies and monitoring strategies that decrease morbidity and mortality., (Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

OBJECTIVE To investigate mechanisms by which anti-inflammatory doses of orally administered intermediate-acting glucocorticoids (prednisone) could predispose dogs to progression of heart disease or congestive heart failure. ANIMALS 11 client-owned dogs with allergic dermatitis and 11 matched healthy control dogs. PROCEDURES Clinicopathologic, echocardiographic, and hemodynamic variables were measured. Dogs with allergic dermatitis then received prednisone (1 mg/kg, PO) once daily for 14 consecutive days beginning on day 0 (baseline), followed by a tapering and washout period; control dogs received no treatment. Measurements were repeated on days 7, 14, and 35. Linear mixed modeling was used to compare changes in variables across measurement points and between dog groups. RESULTS Prednisone administration caused no significant changes in serum sodium or potassium concentration, blood glucose concentration, or target echocardiographic variables. The change from baseline in systolic arterial blood pressure at day 7 was significantly greater in prednisone-treated dogs than in control dogs. Expected changes in hematologic and serum biochemical values with prednisone administration (neutrophilia, eosinopenia, isosthenuria, and high serum alkaline phosphatase and alanine aminotransferase activities) also occurred in the prednisone-treated dogs. CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that anti-inflammatory doses of orally administered glucocorticoids have the potential to adversely impact cardiac function in dogs by causing an increase in blood pressure and thus increased cardiac afterload.

Background: Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is a morbid infection with mortality benefit from receipt of parenteral β-lactam therapy. A substantial portion of MSSA bacteremia patients report penicillin allergy, but infrequently have true allergy., Objective: To determine the frequency and predictors of optimal and adequate therapy in patients with MSSA bacteremia., Design: Retrospective cohort., Participants: Adult inpatients with MSSA bacteremia, January 2009 through October 2013., Main Measures: The primary measure was a trial of optimal therapy (OT), defined as ≥3 inpatient days or discharge on any first-line agents (nafcillin, oxacillin, cefazolin, or penicillin G, if susceptible). The secondary measure was completion of adequate therapy (AT), defined as ≥10 inpatient days or discharge on an agent appropriate for MSSA bacteremia. Data were electronically gathered with key variables manually validated through chart review. Log-binomial regression models were used to determine the frequency and predictors of outcomes., Key Results: Of 456 patients, 346 (76%) received a trial of OT. Patients reporting penicillin allergy (13%) were less likely to receive OT trial than those without penicillin allergy (47% vs. 80%, p <0.001). Adjusting for other factors, penicillin allergy was the largest negative predictor of OT trial (RR 0.64 [0.49, 0.83]). Infectious Disease (ID) consultation was the largest positive predictor of OT trial across all patients (RR 1.34 [1.14, 1.57]). Allergy/Immunology consultation was the single most important predictor of OT trial among patients reporting penicillin allergy (RR 2.33 [1.44, 3.77]). Of 440 patients, 391 (89%) completed AT, with ID consultation the largest positive predictor of the outcome (RR 1.28 [1.15, 1.43])., Conclusions: Nearly 25% of patients with MSSA bacteremia did not receive OT trial and about 10% did not receive AT completion. Reported penicillin allergy reduced, and ID consult increased, the likelihood of OT. Allergy evaluation, coupled with ID consultation, may improve outcomes in MSSA bacteremic patients.

Ractopamine, a synthetic β(2)-adrenoceptor agonist, is widely used as a feed additive in the United States to promote a reduction in body fat and enhance muscle growth in cattle, pigs, and turkeys. It has the potential for illegal use in show and racing animals because it may affect performance via its β-adrenergic agonist properties or anabolic activities. Nine greyhounds were orally administered 1 mg/kg of ractopamine to investigate the ability to detect the drug in urine. Postdosing, 7 of 9 dogs developed cardiac arrhythmias and had elevated troponin levels indicating myocardial damage. One dog necropsied 4 days postdosing had massive myocardial necrosis, mild to focally moderate skeletal muscle necrosis, and widespread segmental arterial mediolysis. A second dog necropsied 17 days postdosing had mild myocardial necrosis and fibrosis. Scattered arteries exhibited segmental medial and perimedial fibromuscular dysplasia. This is the first reported case of arterial, cardiac, and skeletal muscle damage associated with ractopamine.

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease caused by loss of activity of α-l-iduronidase and attendant accumulation of the glycosaminoglycans dermatan sulfate and heparan sulfate. Current treatments are suboptimal and do not address residual disease including corneal clouding, skeletal deformities, valvular heart disease, and cognitive impairment. We treated neonatal dogs with MPS I with intravenous recombinant α-l-iduronidase replacement therapy at the conventional 0.58 mg/kg or a higher 1.57 mg/kg weekly dose for 56 to 81 weeks. In contrast to previous results in animals and patients treated at a later age, the dogs failed to mount an antibody response to enzyme therapy, consistent with the induction of immune tolerance in neonates. The higher dose of enzyme led to complete normalization of lysosomal storage in the liver, spleen, lung, kidney, synovium, and myocardium, as well as in the hard-to-treat mitral valve. Cardiac biochemistry and function were restored, and there were improvements in skeletal disease as shown by clinical and radiographic assessments. Glycosaminoglycan levels in the brain were normalized after intravenous enzyme therapy, in the presence or absence of intrathecal administration of recombinant α-l-iduronidase. Histopathological evidence of glycosaminoglycan storage in the brain was ameliorated with the higher-dose intravenous therapy and was further improved by combining intravenous and intrathecal therapy. These findings argue that neonatal testing and early treatment of patients with MPS I may more effectively treat this disease.

A 5-year-old, 29-kg, female Labrador retriever developed tachypnea, tachycardia, and ataxia following ingestion of approximately 48 mg/kg of phenylpropanolamine. Initial diagnostic tests showed multiform ventricular tachycardia, left ventricular dilatation with a focal dyskinetic region in the dorsal interventricular septum, and elevations in creatinine kinase and cardiac troponin I. All abnormalities resolved within 6 months. The transient electrocardiographic, echocardiographic, and biochemical abnormalities were consistent with myocardial necrosis from infarction or direct catecholamine-induced myocardial toxicity.

The purpose of this study was to assess the effects of systemic hypertension (SHT) on echocardiographic and radiographic cardiovascular variables in affected cats compared with healthy geriatric cats. Secondary objectives were to determine whether there were any relationships between these findings and age or systolic blood pressure (SBP). Fifteen healthy cats (>8 years of age with normal SBP) and 15 hypertensive cats (SBP > 180 mm Hg) were studied. Each cat was evaluated for standard echocardiographic parameters and 4 different aortic root dimensions. Seventeen variables were measured from right lateral and dorsoventral radiographic views. Left ventricle wall thickness was greater in the SHT group (5.1 +/- 0.9 mm) than in the healthy cats (4.2 +/- 0.5 mm). Left ventricular hypertrophy in the SHT cats often was not severe, and mean measures were considered normal. Some cats had asymmetrical septal hypertrophy (ASH) in the basilar portion of the septum as determined from the 2-dimensional view of the left ventricular outflow tract. ASH was greater in cats with SHT. Comparisons of the proximal ascending aorta indicated the presence of dilatation in the SHT cats, and comparison of the ascending aorta to the aortic annulus was helpful in differentiating between the 2 groups. The distal aortic root measurements and ratios evaluated by echocardiography were significantly different between the 2 groups of cats (P = .0001) and were significantly correlated with SBP (P = .0001) but not age (P > .3).

Objective: To develop a clinically useful model for predicting QT interval duration as a function of heart rate in healthy cats., Animals: 20 healthy cats., Procedure: For all cats, results of a physical examination, electrocardiography, and echocardiography were normal. Twenty-four hour heart rate and rhythm data were collected by means of ambulatory electrocardiography. Hourly ECG segments were obtained from the 24-hour recordings. Mean heart rate and the mean of 5 QT interval measurements were calculated for each of 479 usable ECG segments. Analysis of covariance was used to develop models to describe variability in QT interval duration., Results: Prediction equations (R2 = 0.81) including terms for heart rate, (heart rate)2, age group (1 to 4 vs 8 to 14 years old), and their interactions were developed. Sex, individual cat, and time of day were of little value in predicting QT interval duration. A simplified prediction equation without age group (R2 = 0.71) also was developed and had better predictive ability than reported correction formulas for QT interval duration., Conclusions and Clinical Relevance: Prediction equations with 95% prediction intervals for expected QT interval duration in healthy cats were generated. Abnormal QT interval duration can be associated with cardiac electrical instability, yet QT interval duration is greatly influenced by heart rate. Results of the present study provide reference ranges for expected QT interval duration as a function of heart rate in healthy cats.

Twenty-four-hour ambulatory electrocardiograms were recorded in two age groups of 10 normal cats each: group 1 (1 to 4 years) and group 2 (8 to 14 years), with equal numbers of males and females in each group. Average heart rates over the 24-hour recording period ranged from 114 to 202 beats/minute (bpm). The mean 24-hour average rate did not differ between group 1 and group 2 (157.6 vs. 156.3+/-5.3 bpm, respectively); however, females (both groups combined) had higher average heart rates than males (166.8 vs. 147.1+/-5.3 bpm, respectively). Females also had a higher mean minimum heart rate than males (116.9 vs. 96.5+/-4.2 bpm, respectively); but there were no gender or age group differences in maximum heart rate. Results of hourly analyses of average, minimum, and maximum heart rates were similar. Mean heart rates rose from mid-afternoon to about 9:00 PM and were lowest just after midnight. Although regular sinus rhythm predominated, periods of sinus arrhythmia were evident in most cats, especially in early morning hours. Supraventricular extrasystoles were uncommon. Isolated ventricular extrasystoles occurred more frequently in group 2 cats; multiform configuration was observed in both groups. Repetitive ventricular extrasystoles, which usually consisted of occasional couplets, occurred more frequently in group 2 cats. One older cat had 2 short runs of ventricular tachycardia. Another older cat appeared to have a recurrent accelerated idioventricular rhythm.

A Veterinary Medical Database search from 1982 to 1995 identified 1,383 dogs with tumors of the heart from a total population of 729,265 dogs (0.19% incidence). Hemangiosarcoma (HSA) was the most common cardiac tumor identified. In the subset of dogs with specific histologic diagnoses, the number with HSA was almost 10-fold that of the 2nd most common tumor, aortic body tumor. Primary heart tumors were more common than cardiac metastases. When biologic behavior was noted, most heart tumors were classified as malignant. Cardiac tumors (excluding lymphoma) occurred most often in dogs between the ages of 7 and 15 years. In very old dogs (>15 years), the frequency of cardiac tumors was the same or lower than that of the youngest age group. Tumors occurred with similar frequency in males and females, but the relative risk for spayed females was >4 times that for intact females. For HSA, spayed females had >5 times greater relative risk than did intact females. The risk for castrated males was slightly greater than that for intact males, which had 2.4 times the relative risk of intact females. Thus, neutering appeared to increase the risk of cardiac tumor in both sexes. Intact females were least likely to develop a cardiac tumor, whereas spayed females were most likely to develop a tumor. Twelve breeds had greater than average risk of developing a cardiac tumor, whereas 17 had lower risk.

Objectives: To determine the pharmacokinetics of atenolol (AT) after i.v. and oral administrations in cats, to assess duration of beta-blocking effect, and to determine whether AT can be effectively used once per day., Animals: 9 clinically normal cats., Procedure: Single doses of 1 (i.v.) or 3 (oral) mg of AT/kg of body weight were administered to each cat on different occasions, and serial blood samples were collected. Plasma concentrations of AT were subsequently determined, using high-performance liquid chromatography. The plasma concentration data were analyzed, using noncompartmental analysis. An isoproterenol challenge test was used to determine the beta-blocking effect of AT on heart rate after 3 consecutive days of oral treatment (3 mg/kg, once a day)., Results: After i.v. administration, mean +/- SD apparent volume of distribution at steady state and systemic clearance values were 1,088 +/- 148 ml/kg and 259 +/- 72 ml/h/kg, respectively. Bioavailability was 90 +/- 9% after oral administration. The half-life values were 3.44 +/- 0.5 and 3.66 +/- 0.39 hours after i.v. and oral administrations, respectively. Compared with baseline values prior to AT administration, heart rates at 6 and 12 hours after administration of AT were significantly reduced., Conclusions: AT has high oral bioavailability in cats, resulting in small interindividual variability in its kinetics in this species. The drug has beta-blocking effect in cats, as indicated by the attenuated heart rate response to isoproterenol; this effect persists for at least 12 hours in clinically normal cats.

Mitral stenosis was diagnosed in 15 young to middle-aged dogs. There were 5 Newfoundlands and 4 bull terriers affected, suggesting a breed predisposition for this disorder. Clinical signs included cough, dyspnea, exercise intolerance, and syncope. Soft left apical diastolic murmurs were heard only in 4 dogs, whereas 8 dogs had systolic murmurs characteristic of mitral regurgitation. Left atrial enlargement was the most prominent radiographic feature. Left-sided congestive heart failure was detected by radiographs in 11 dogs within 1 year of diagnosis. Electrocardiographic abnormalities varied among dogs and included atrial and ventricular enlargement, as well as atrial and ventricular arrhythmias. Abnormalities on M-mode and two-dimensional echocardiograms included abnormal diastolic motion of the mitral valve characterized by decreased leaflet separation, valve doming, concordant motion of the parietal mitral valve leaflet, and a decreased E-to-F slope. Increased mitral valve inflow velocities and prolonged pressure half-times were detected by Doppler echocardiography. Cardiac catheterization, performed in 8 dogs, documented a diastolic pressure gradient between the left atrial, pulmonary capillary wedge, or pulmonary artery diastolic pressures and the left ventricular diastolic pressure. Necropsy showed mitral stenosis caused by thickened, fused mitral valve leaflets in 5 dogs and a supramitral ring in another dog. The outcome in affected dogs was poor; 9 of 15 dogs were euthanatized or died by 2 1/2 years of age.

The effects of IV administered amiodarone, a class-III antiarrhythmic agent, on myocardial contractility, early myocardial relaxation, and hemodynamic variables were evaluated in normal canine hearts and those with infarcts. In the normal canine heart, amiodarone had important, but relatively mild, depressant effects on left ventricular contractility (assessed by maximal positive first derivative of left ventricular pressure (+dP/dtmax) and maximal elastance (Emax)) and heart rate when given IV at a dose of 10 mg/kg of body weight. An effect on contractility or active relaxation (assessed by maximal negative first derivative of left ventricular pressure (-dP/dtmax) and the time constant of isovolumic pressure decrease) was not identified with smaller doses. Myocardial infarction itself caused a predictable and marked depressant effect on myocardial contractility, as indicated by decreases in +dP/dtmax, ejection fraction, Emax, and -dP/dtmax, and elevation in end diastolic pressure. Additional depressive effects on contractility and active relaxation resulted when 10 mg of amiodarone/kg was administered to dogs with myocardial infarction and these effects were sufficient to worsen acute myocardial infarction-induced heart failure. Significant changes attributable to heart rate alone could not be identified. On the basis of our findings, we suggest that amiodarone administered IV should be used with caution in dogs with compromised ventricular function.

Baseline plasma norepinephrine (NE) and epinephrine (EPI) concentrations were measured in dogs with naturally acquired heart failure (HF) caused by either degenerative mitral valve disease and mitral regurgitation (MR) or idiopathic dilated cardiomyopathy (DCM). Compared with controls (clinically normal), dogs with HF had increased plasma NE concentration, which was correlated positively with clinical severity of HF. Dogs with the most severe degree of HF (New York Heart Association functional class IV) had mean NE concentration significantly (P less than 0.05) greater than that of dogs with all other functional classes of HF. Overall, mean NE concentration in dogs with DCM was greater than that in dogs with MR. Plasma EPI concentration was not different between control dogs and dogs with HF or between dogs with DCM or MR. Correlations were not found between the echocardiographically derived end systolic volume index (used as an estimate of myocardial function) and plasma NE and EPI concentrations or serum sodium or potassium concentration. Dogs with DCM, as a group, had a small but significant (P less than 0.05) decrease in serum sodium concentration, compared with dogs with MR. This difference was maintained only for class-IV HF when dogs were separated according to functional HF class. In dogs with DCM, significant inverse correlation was found between plasma NE and serum sodium concentrations. When grouped together, all dogs with HF maintained this relationship; however, dogs with MR did not have correlation between plasma NE and serum sodium concentrations. Plasma EPI and serum sodium concentrations were not correlated for any group. It was concluded that in dogs, plasma NE, but not EPI, concentration is high in relation to the clinical severity of naturally acquired HF.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracardiac rhabdomyosarcoma was diagnosed in a 14-month-old Golden Retriever referred for evaluation of syncope. The dog was weak, with irregular heart rate, pulse deficit, heart murmur, and hepatomegaly. Thoracic radiography revealed generalized cardiomegaly, and electrocardiography revealed sinus rhythm with multiform ventricular premature complexes and intermittent ventricular tachycardia. Two-dimensional echocardiography revealed extensive soft-tissue density masses in both ventricles. An intracardiac neoplasm seen at postmortem examination was identified histologically as rhabdomyosarcoma, an uncommon intracardiac tumor in dogs.

A 5-year-old cow developed signs of bacterial endocarditis subsequent to parturition and mastitis. Massive vegetative lesions on the pulmonic valve were imaged with 2-dimensional echocardiography.

An 8-year-old mixed-breed dog was evaluated for caudal paresis. Transient lameness of the left hind and left forelimbs had developed during the preceding week. Clinical findings included conscious proprioceptive deficits, hyporeflexive tendon reflexes and decreased pain perception, coolness in the hind limbs and left forelimb, and absence of femoral pulses. A fluid-dense mass was radiographically identified adjacent to the left atrium. Echocardiography revealed a mass in the left atrium and spontaneous contrast in the left ventricular lumen and aortic root. The dog was euthanatized because of its deteriorating condition. A large mass was adhered to the dorsal left atrial wall and had eroded into the atrial lumen. A sterile blood clot was attached to this site, and sterile thrombi were in the terminal portion of the aorta. Histologically, the mass was found to be hilar lymph node with chronic pyogranulomatous inflammation containing organisms characteristic of Blastomyces dermatitidis.

Chylothorax associated with congestive cardiomypathy was diagnosed in a 10-year-old male castrated domestic shorthair cat via analysis of pleural fluid. The triglyceride concentration in the pleural fluid was high (579 mg/dl), compared with that in serum (87 mg/dl), and the fluid cleared with ether. Evidence of atrial and left ventricular enlargement was found via electrocardiography and thoracic radiography. Left-sided cardiac dilatation and reduced systolic motion of the left ventricle were revealed by echocardiography. The cat was treated with digoxin, furosemide, and aspirin. Two months after initiation of treatment, fluid (265 ml) was aspirated from the pleural cavity. Two months after this procedure, the cat was doing well, with minimal pleural fluid production.

An adult cat with vague signs of gastrointestinal dysfunction was found to have a congenital portosystemic shunt. There were no signs of hepatoencephalopathy, which is in contrast to what has been reported in other cats with the disease.