Rebound hyperkalemia in a dog with albuterol toxicosis after cessation of potassium supplementation.

OBJECTIVE: To describe the presentation of rebound hyperkalemia as a delayed side effect of albuterol toxicity in a dog. CASE SUMMARY: A 3-year-old female neutered mixed-breed dog was presented for albuterol toxicosis that led to a severe hypokalemia, hyperlactatemia, and hyperglycemia. The dog also experienced sinus tachycardia and generalized weakness. Treatment was instituted with intravenous fluid therapy and potassium supplementation, and the dog was monitored with a continuous electrocardiogram. Resolution of hypokalemia was documented 12 hours after initial presentation, at which time fluid therapy and potassium supplementation were discontinued. There were no further periods of sinus tachycardia, but instead the dog developed ventricular ectopy with rapid couplets (instantaneous rates of 300/min). An echocardiogram revealed normal cardiac size and function. Twenty-four hours after presentation, the patient developed severe hyperkalemia, despite discontinuation of fluids and potassium supplementation for 12 hours. Serial venous and urinary electrolytes were performed for determination of the fractional excretion of electrolytes. These data confirmed rebound hyperkalemia (7.0 mmol/L), consistent with a markedly increased fractional excretion of potassium, and secondary to the release of potassium from inside the cells. Fluid therapy with dextrose supplementation was provided until 36 hours postpresentation. The hyperkalemia resolved, and the dog was discharged after 44 hours of hospitalization. NEW OR UNIQUE INFORMATION PROVIDED: This case documents rebound hyperkalemia following treatment of albuterol toxicosis in a dog. This case highlights the importance of understanding the distribution of total body potassium when treating serum hypokalemia. Transcellular shifts of potassium, as in the case of albuterol toxicosis, can lead to rebound hyperkalemia even after discontinuation of potassium supplementation. This case further explores the utility of fractional excretion of electrolytes in elucidating the etiology and management of electrolyte disturbances.

Localization and characterization of atrial depolarization waves on the surface electrocardiogram in dogs with rapid supraventricular tachycardia.

BACKGROUND: Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations. OBJECTIVES: To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia. ANIMALS: Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia. METHODS: Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated together with the relationship between AD and QRS complex interval (AD-R) and QRS complex and AD interval (R-AD). RESULTS: Orthodromic atrioventricular reciprocating tachycardia was characterized by an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of -90 (-90/-78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (-72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08). CONCLUSIONS AND CLINICAL IMPORTANCE: Analyzing AD on 12-lead electrocardiogram is helpful in differentiating the most common SVTs in dogs.

Conventional and Holter Electrocardiographic Assessment of Dogs Infected Naturally With Acute Canine Monocytic Ehrlichiosis.

Canine Monocytic Ehrlichiosis (CME) is a disease of worldwide distribution caused by the bacteria Ehrlichia canis, appearing primarily in hot climates due to the massive prevalence of its vector, the tick Rhipicephalus sanguineus. Previous studies have shown that dogs afflicted by CME in the chronic phase can develop infectious myocarditis, arrhythmias, and alterations in heart rate variability (HRV), but there are few studies correlating cardiac diseases with the acute phase of CME. This study aims at assessing electric cardiac alterations and HRV in the time and frequency domains during the acute phase of CME. This study assessed 22 animals divided into 2 distinct groups: the control group, comprised by 10 healthy dogs, and the sick group, comprised of 12 dogs infected naturally with ehrlichiosis which presented clinical and hematological signs compatible with the acute phase of the disease. The animals underwent conventional and Holter electrocardiographic evaluations, systolic blood pressure measurement, complete blood count and biochemical assays (urea, creatinine, alanine aminotransferase (ALT), alkaline phosphatase (AP), and gamma glutamyl transferase (GGT)). The sick group presented higher activity in the sympathetic nervous system than in the parasympathetic nervous system, manifest as a significant increase in mean heart rate and a reduction in the HRV indexes for the time and frequency domains. The frequency-domain HRV indexes presented sympathetic prevalence during the sleep and vigilance states. Sinus tachycardia was the predominant heart rhythm in 58.33% of the animals. The mean systolic blood pressure diverged between the groups and no significant arrhythmias were observed during monitoring. The serum concentrations of urea, creatinine, AP, ALT, and GGT were within the established reference values for the species. We observed no indication that there was enough time during the acute phase for the disease to evolve in a way that resulted in arrhythmias, as is common in the chronic phase, but we observed that animals in the acute phase already present reduced HRV indexes.

Electrocardiographic parameters of the American Miniature Horse: influence of age and sex / Parâmetros eletrocardiográficos de equinos Mini Horse: influência da idade e sexo

The veterinary cardiology has growing importance in equine medicine. There are studies of standardization of electrocardiographic parameters of many races, according to their stature and ability. However, no studies are in the literature with the American Miniature Horse. To evaluate the electrocardiogram (ECG) tracing configuration of this breed at rest and to verify the influence of age and sex on ECG parameters, 203 horses including 143 females and 60 males were divided into four age groups (foals, yearlings, adults and elderly). Electrocardiographic parameters were performed by computerized electrocardiogram (TEB), and the parameters were evaluated in six leads of frontal plane (Lead I, II, III, aVR, aVL and aVF) and base-apex (BA). Heart rates (HR) decreased with increasing age were higher in males than in females. Sinus tachycardia followed by sinus arrhythmia was dominant in both sexes. The cardiac axis was higher in males and ranged between 120° and 150° for foals, 30° and 60° for yearlings and adults, and 60° and 90° for the elderly. The P wave was bifid in several animals. The P-wave amplitude and T-wave duration from lead II and BA were larger in males than in females. The majority of the animals exhibited ST segment depression and a negative T-wave. The most common QRS complex morphology was Qr. Differences were observed between the electrocardiographic tracings of males and females, and age influenced the ECG parameters. Therefore, this study established the ECG patterns for the American Miniature Horse breed and could be used to determine the influence of age and sex on several of the studied variables.(AU)

A cardiologia veterinária possui crescente importância na medicina equina. Existem estudos de padronização dos parâmetros eletrocardiográficos de muitas raças, de acordo com sua estatura e aptidão. No entanto, não há na literatura trabalhos com os equinos da raça Miniature Horse. Os objetivos deste trabalho foram avaliar a configuração do traçado do eletrocardiograma (ECG) em repouso, de equinos desta raça, além de verificar a influência do sexo e da idade sobre os parâmetros eletrocardiográficos desses animais. Foram utilizados 203 equinos desta raça, hígidos, sendo 143 fêmeas e 60 machos, classificados em quatro faixas etárias (potros, sobreanos, adultos e idosos). Os exames eletrocardiográficos foram realizados por eletrocardiograma computadorizado (TEB), e os parâmetros foram avaliados em seis derivações do plano frontal (DI, DII, DIII, aVR, aVL e aVF) e base-ápice (BA). A frequência cardíaca (FC) diminuiu com a progressão da idade, e foi maior nos machos do que nas fêmeas. O ritmo mais comum em ambos os sexos foi taquicardia sinusal, seguido de arritmia sinusal. O eixo cardíaco foi maior nos machos do que nas fêmeas, e nos potros ficou entre 120 e 150o, nos sobreano e adultos permaneceu entre 30 e 60o, e nos idosos entre 60 e 90o. A amplitude da onda P e a duração da onda T foram maiores nos machos do que nas fêmeas na DII e BA. A maioria dos animais apresentou segmento ST infradesnivelado e onda T negativa. A morfologia do complexo QRS mais encontrada em todos os casos foi Qr. Este estudo permitiu estabelecer os padrões eletrocardiográficos para a raça Mini Horse e conseguiu verificar a influência da progressão da idade nas diversas variáveis estudadas, bem como a diferença entre os sexos.(AU)

Suspected exercise-induced seizures in a young dog.

A 12-month-old female neutered crossbreed was referred for investigation of seizure-like episodes occurring only at intense exercise. Thorough medical, neurological and cardiac investigations were performed and excluded the most commonly known causes of seizure-like activity. The dog was fitted with an ambulatory electrocardiography device and underwent another exercise-induced seizure. The electrocardiogram during the episode revealed a sinus tachycardia at approximately 300 beats/minute. A video recording of the episode revealed generalised tonic clonic limb activity with jaw chomping and frothing at the mouth typical of seizure activity. Antiepileptic medications were not prescribed and the owner was advised not to exercise the dog intensely. The dog responded well and did not seizure after 12 months of mild-moderate off-lead exercise. As all the seizures in this case were triggered by intense physical activity, it is suggested that this may be a new form of reflex seizure activity.

Estudo eletrocardiográfico de equinos de salto sadios / Electrocardiographic study in healthy showjumping horses

Avaliou-se o eletrocardiograma de 100 equinos sadios praticantes de hipismo clássico modalidade salto, com idades entre 4 e 19 anos, sendo 61 machos e 39 fêmeas, com média de 516,3 kg. Observou-se frequência cardíaca média de 40,20 ±13,33 bpm, sendo o ritmo cardíaco mais freqüente o sinusal (56 por cento). As alterações de ritmo cardíaco estiveram presentes em 38 por cento dos animais estudados, sendo a mais presente o marcapasso migratório (22 por cento), seguido de bloqueio atrioventricular de 2º grau (4 por cento), bloqueio atrioventricular de 1º grau (3 por cento), contração ventricular prematura (2 por cento), contração atrial prematura (1 por cento). Não se observou correlação entre as variáveis estudadas (freqüência cardíaca, ritmo e arritmias) e a capacidade atlética, a idade e o sexo. O escore cardíaco após analise estatística não diferiu entre os grupos quanto ao desempenho atlético, a faixa etária e o sexo. O escore cardíaco, nesta amostra, não se mostrou um parâmetro confiável para se predizer o futuro atlético ou o nível de treinamento do eqüino.

The electrocardiographic study was made in 100 healthy showjumping horses, with ages between 4 and 19 year-old, being 61 males and 39 females, with mean bodyweight of 516.3 kg. A mean heart rate of 40.20 ± 13.33 bpm was observed, and the most common cardiac rhythm was sinus rhythm (56 percent). Alterations in cardiac rhythm were observed in 38 percent of the animals, as wandering pacemaker (22 percent), second degree atrioventricular block (4 percent), first degree atrioventricular block (3 percent), ventricular premature contraction (2 percent), atrial premature contraction (1 percent). There was no relationship between the variables (heart rate, rhythm and arrhythmias) and the athletic performance, age and sex. The heart score data obtained after statistical analysis were not different concerning the athletic performance, age or sex. Therefore, heart score, in this sample, did not appear to be a confident parameter to predict the athletic future or the training level of the individual horse.

Successful treatment of hyperkalaemic periodic paralysis in a horse during isoflurane anaesthesia.

HISTORY: A 3-year-old, 400 kg, gelding Quarter Horse was presented for investigation of epistaxis. PHYSICAL EXAMINATION: The horse was bright, alert and responsive with rectal temperature, heart rate and respiration rate within normal limits. MANAGEMENT: During a second general anaesthetic for surgical treatment of guttural pouch mycosis by balloon-tipped catheter occlusion of the right major palatine artery and ligation of the right external carotid artery, signs consistent with hyperkalaemic periodic paralysis (HYPP) were exhibited. These included concurrent hyperkalaemia, hypercapnoea, sinus tachycardia, and muscle fasciculations in the presence of normothermia. Stress associated with an acute haemorrhage pre-operatively, and intra-operative hypercapnoea may have precipitated the episode. There were no signs of HYPP during a general anaesthetic, 1 week earlier, when an initial attempt at surgical treatment of guttural pouch mycosis was performed. Treatment consisted of fluid therapy and administration of calcium gluconate (0.1-0.2 mg kg(-1) minute(-1)), dextrose 5% (5 mL kg(-1) hour(-1)) and insulin (0.05 IU kg(-1)). Treatment resulted in the resolution of clinical signs and an uneventful recovery. FOLLOW-UP: The diagnosis of HYPP was confirmed by DNA analysis post-operatively. CONCLUSIONS: Clinical cases of intra-operative HYPP can present despite a previous history of uneventful general anaesthesia. Rapid diagnosis and treatment can result in the successful management of HYPP. This report documents an unusual presentation of HYPP, a disease that remains present in the Quarter Horse population.

Cardiovascular manifestations of iatrogenic hyperthyroidism in two dogs.

Two dogs were diagnosed with iatrogenic thyrotoxicosis (1 definitive, 1 presumptive). Both showed physical examination findings of agitation, tachypnea, and tachycardia. Sinus tachycardia with supraventricular ectopy was diagnosed in one case, and syncope and atrial flutter was present in the other. Both dogs had concurrent cardiac disease that might have contributed to the severity of their clinical signs. Excessive thyroid hormone supplementation in humans causes supraventricular arrhythmias including sinus tachycardia, supraventricular tachycardia, atrial fibrillation, and atrial flutter. Clinical signs and rhythm abnormalities resolved in both dogs with resolution of the thyrotoxicosis.

Twenty-four hour Holter monitoring of unsedated healthy cats in the home environment.

OBJECTIVE: To determine the heart rate, rhythm, number of ventricular premature complexes (VPCs) and atrial premature complexes (APCs) in unsedated cats using Holter monitoring. ANIMALS, MATERIALS AND METHODS: Twenty-three healthy client owned cats were used. Clinical examination, blood pressure measurements, echocardiographic examination and serum biochemical analysis were performed. A lightweight Holter was used in the home environment. RESULTS: Three-lead electrocardiographic registrations of good quality were obtained from all cats. Normal sinus rhythm was present in all cats. The median heart rate was 165 beats per minute (bpm), range 70-303 bpm. Mean heart rate varied significantly with age and gender. Sinus arrhythmia occurred intermittently in 18 cats (78%). Uncommon ventricular premature complexes occurred in 18 (78%) of the cats. The median number of VPCs per cat was 3 complexes/24 h period, range 0-146. Cats 7-15 years of age had significantly more VPCs than cats 1-6 years of age (median 6 versus 1 per 24 h period, p=0.04). A single APC occurred in one cat (4%). CONCLUSIONS: Cats commonly have intermittent sinus arrhythmia. Many healthy cats have rare single VPCs per 24 h period. Old cats have significantly more VPCs than young cats. The heart rate varies significantly with age and gender.