Low-energy ablation of anteroseptal accessory pathways in two dogs

In humans, accessory pathways (APs) in an anteroseptal and midseptal position are often challenging to ablate because of their close proximity with the conduction pathways of the atrioventricular junction. The use of low-energy ablation techniques can be useful to reduce the risk of permanently damaging the atrioventricular node and the His bundle. This report describes the use of low-energy radiofrequency catheter ablation to successfully and permanently ablate anteroseptal APs in two dogs with orthodromic atrioventricular reciprocating tachycardia. In the first dog, a transient first degree atrioventricular block persisted for 30 s after radiofrequency energy delivery. In the second dog, transient paroxysmal atrioventricular conduction block was observed during the procedure but resolved within 3 days. First degree atrioventricular block was again identified 2 months later. In conclusion, anteroseptal APs can be effectively treated by low-energy radiofrequency catheter ablation with minimal and transient damage to the atrioventricular junction.     

Hemodynamic and electrophysiologic effects of ontazolast in dogs

OBJECTIVE: To determine whether QT interval is prolonged or sudden death is caused by ventricular fibrillation resulting from torsades de pointes and to identify hemodynamic effects of ontazolast. ANIMALS: 28 Beagles. PROCEDURE: Physiologic variables were measured for 2 hours in conscious dogs given ontazolast (0, 1, or 3 mg/kg of body weight, IV) and for 1 hour in anesthetized dogs given cumulative doses of ontazolast (0, 1, 3, 6, or 8 mg/kg, IV). RESULTS: Ontazolast prolonged QT interval and QT interval corrected for heart rate (QTc) at doses of 6 mg/kg in anesthetized dogs. At 8 mg/kg, both variables remained prolonged but tended to decrease. In conscious dogs, ontazolast increased QT interval and QTc 15 minutes after administration, but both variables returned to reference ranges by 60 minutes. In conscious dogs, ontazolast increased maximum rate of increase of left ventricular pressure and maximal velocity of fiber shortening, indicators of inotropy, and increased tau, indicating a decreased rate of relaxation. One conscious dog receiving 3 mg/kg developed nonfatal torsades de pointes, but another conscious dog developed ventricular fibrillation. Two anesthetized dogs receiving 6 mg/kg developed early afterdepolarizations, and all dogs developed secondary components in theirT waves. CONCLUSION AND CLINICAL RELEVANCE: Ontazolast possesses potent class-III antiarrhythmic properties and induces prolongation of QTc in a dose-dependent fashion. Because there was a clear dose-dependent prolongation of QT interval in all instances, ontazolast may serve as a positive-control compound for studying other compounds that are believed to prolong the QT interval.     

Heart rate distribution in dogs with third degree atrioventricular block and rate responsive pacemakers

IntroductionIn dogs, single lead ventricular pacing, ventricular sensing, inhibition response, rate adaptive (VVIR) pacemakers are routinely used to treat third degree atrioventricular block. The objectives of this study were to investigate the heart rate distribution in dogs with VVIR pacemakers, and report changes when activity settings were adjusted.AnimalsEighteen client-owned dogs with VVIR pacemakers for third degree atrioventricular block.Materials and methodsThis observational study consisted of a review of medical records of dogs with VVIR pacemakers. For dogs with >50% of paced beats at the lower pacing rate, the activity daily living (ADL) and exertion responses were increased. Re-evaluations were performed after 6–12 months.ResultsHeart rate distribution similar to healthy dogs was absent for all dogs. In nine dogs, the ADL and exertion responses were increased to the highest level. Of these, three dogs showed no improvement in heart rate distribution; for two dogs, one with an epicardial pacemaker, several activity settings were adjusted and pacing at higher heart rates was observed at re-evaluation. Four dogs died or were lost to follow-up. Clinical signs had resolved for all dogs after pacemaker implantation.ConclusionDefault activity settings of VVIR pacemakers do not result in heart rate distribution equivalent to healthy dogs. Increasing the ADL and exertion response settings to the highest levels did not improve the pacemaker rate response. Further investigations into the role of dog size, generator positioning, pacemaker settings, and whether rate responsiveness is required for dogs' quality and quantity of life are warranted.     

Anatomic distribution and clinical findings of intermuscular lipomas in 17 dogs (2005-2010)

Intermuscular lipomas (IML) in dogs can be associated with ominous clinical signs, especially in the thoracic limb. However, the prognosis is excellent following surgical excision. There is a paucity of information in the veterinary literature regarding IML. Our objective was to describe the anatomical location, imaging techniques, and clinical findings in a series of dogs that were diagnosed and treated for IML. The prevalence of thoracic versus pelvic limb IML was not different. Most IML of the thoracic limb were located in the axilla. Operative time for IML of the thoracic and pelvic limb averaged 60 minutes. Complications were rare after marginal surgical excision and recurrence was not seen in any of the cases in this report. Intermuscular lipomas of the axilla are as common as IML of the caudal thigh. Surgical treatment of both axillary and caudal-thigh IML is associated with an excellent prognosis in dogs.     

Frequency of second-degree atrioventricular heart blocks in dogs.

Clinically normal adult dogs and pups 8 to 24 weeks of age were monitored for 2nd-degree atrioventricular (AV) heart block. Radiotelemetry was used to obtain the electrocardiogram (ECG) of resting, unanesthetized, unrestrained dogs. Second-degree AV heart block was detected in 64% of 11 adult dogs and 100% of 12 pups between 8 and 11 weeks of age. The dropped beats, prolonged P-R intervals, and prolonged P-P intervals appeared to be associated with the respiratory cycle. Atropine quickly reduced the frequence of dropped beats. It was concluded that occasional dropped ventricular beats due to 2nd-degree AV heart block may be normal in dogs, especially young dogs.     

Haemodynamic, electrocardiographic, electrophysiologic and pharmacokinetic activity of 4'-hydroxypropranolol in dogs

We determined the haemodynamic, electrocardiographic and electrophysiologic effects, and the pharmacokinetic properties of 4′-hydroxypropranolol (4′-OHP) by conducting three different experiments in dogs. In experiment 1 the plasma concentrations of 4′-OHP (mg/kg, i.v.) in pentobarbital anaesthetized dogs were determined by HPLC and pharmacokinetic parameter values were estimated. The terminal elimination half-life (t1/2) for 4′-OHP was 69.4 min, the apparent volume of distribution (V_d) was 3.39 L/kg and the total clearance (Cl_t) was 53.6 mL/min·kg. These data were subsequently used to calculate the loading and maintenance doses of 4′-OHP required to produce targeted steady-state plasma concentrations for 4′-OHP of 30, 60, 120, 240 and 480 ng/mL. In experiment 2 the haemodynamic and electrocardiographic effects for target plasma concentrations of 4′-OHP were determined in two groups of pentobarbital anaesthetized dogs, and beta-blocking activity was assessed by infusion or bolus doses of isoproterenol. The haemodynamic and electrocardiographic effects of the target plasma concentrations (30, 60, 120 ng/mL) of 4′-OHP were first determined in seven pentobarbital anaesthetized dogs (Group 1). Beta blocking activity was assessed by the infusion of 0.1 μg/kg/min isoproterenol. The infusion of 4′-OHP produced dose dependent decreases in heart rate, cardiac output, dP/dt_max, mean arterial pressure and left ventricular diastolic pressure. The PR interval of the lead II electrocardiogram increased and the QT_c interval decreased. These haemodynamic and electrocardiographic changes became apparent at plasma 4′-OHP concentrations equal to or greater than 30 ng/mL. Plasma concentrations of 4′-OHP equal to or greater than 30 ng/mL prevented the haemodynamic and electrocardiographic effects of isoproterenol infusion. In group 2 dogs, (seven dogs) the haemodynamic and electrocardiographic effects of target plasma concentrations (30, 60, 120, 240, 480 ng/mL) of 4′-OHP were evaluated and beta-blocking activity was assessed by the i.v. bolus administration of 1 and 4 μg/kg of isoproterenol. The infusion of 4′-OHP produced haemodynamic and electrocardiographic changes similar to those in group 1 dogs. In addition, the QRS duration of the electrocardiogram increased at plasma concentrations of 4′-OHP equal to or greater than 240 ng/mL. The haemodynamic and electrocardiographic effects of i.v. bolus dose administrations of 1 and 4 μg/kg isoproterenol were abolished by plasma concentrations of 4′-OHP equal to or greater than 240 ng/mL. In experiment 3 we determined the electrophysiologic effects of 10^?9 to 10^?5 mmol/L 4′-OHP on Tyrodes superfused bundles of canine Purkinje fibres. Action potential duration and the effective refractory period decreased at superfusate concentrations of 4′-OHP equal to or greater than 10^?7 mmol/L. Action potential overshoot, action potential total amplitude, the rate of rise of phase O (dV/dt) and spontaneous rate decreased at superfusage concentrations of 4′-OHP equal to or greater than 800 ng/mL. These studies demonstrate that: 1) 4′-OHP produces haemodynamic, electrocardiographic and electrophysiologic effects similar to those of other beta-blocking drugs in pentobarbital anaesthetized dogs; 2) the haemodynamic and electrocardiographic effects produced by 4′-OHP are     

Anatomic and radiologic observations of the clavicle of adult dogs

In an anatomic and radiologic study of the clavicle of 50 adult dogs of 10 breeds, the clavicle had ossified in 96% of the dogs. The clavicles studied had various shapes, and each clavicle was attached to the caudomedial part of the clavicular intersection of the brachiocephalic muscle, to the mastoid part of the cleidocephalic muscle, and to 4 radiating bands of connective tissue fasciculi. One band was attached to the caudal border of the scapula and fascia deep to the latissimus dorsi muscle, 1 was attached to the manubrium of the sternum, and 1 each was attached to the epimysia of the superficial pectoral and sternocephalic muscles. We concluded that, during movements of the thoracic limb, the clavicle and the 4 fasciculated connective tissue bands associated with it stabilize the position of the brachiocephalic muscle with relation to the crest of the greater tubercle of the humerus. Also, the fasciculated band attached to the caudal border of the scapula provides protection for nerves from the brachial plexus and axillary blood vessels that supply the thoracic limb.     

Frequency of an accessory popliteal efferent lymphatic pathway in dogs

Staging and therapeutic planning for dogs with malignant disease in the popliteal lymph node are based on the expected patterns of lymphatic drainage from the lymph node. The medial iliac lymph nodes are known to receive efferent lymph from the popliteal lymph node; however, an accessory popliteal efferent pathway with direct connection to the sacral lymph nodes has also been less frequently reported. The primary objective of this prospective, anatomic study was to describe the frequency of various patterns of lymphatic drainage of the popliteal lymph node. With informed client consent, 50 adult dogs with no known disease of the lymphatic system underwent computed tomographic lymphography after ultrasound‐guided, percutaneous injection of 350 mg/ml iohexol into a popliteal lymph node. In all 50 dogs, the popliteal lymph node drained directly to the ipsilateral medial iliac lymph node through multiple lymphatic vessels that coursed along the medial thigh. In 26% (13/50) of dogs, efferent vessels also drained from the popliteal lymph node directly to the internal iliac and/or sacral lymph nodes, coursing laterally through the gluteal region and passing over the dorsal aspect of the pelvis. Lymphatic connections between the right and left medial iliac and right and left internal iliac lymph nodes were found. Based on our findings, the internal iliac and sacral lymph nodes should be considered when staging or planning therapy for dogs with malignant disease in the popliteal lymph node.     

Anatomic and biologic role of the movement of the thorax in dogs and cats

Development of the gonometrical measuring method has allowed the respiratory movement of the lateral chest wall and the sternum to be investigated. The mobility of a single rib varies enormously in gradual transitions. There are distinct differences between species. For a number of reasons, the cat can achieve more intense thoracic respiration than the dog.     

Caudal thigh intermuscular lipomas in dogs: Anatomic review and approach to surgical excision

The surgical approach for excision of caudal thigh intermuscular lipomas (IML) in dogs is described with relevant anatomy and short-term outcomes reported. Medical records were reviewed to identify dogs that underwent IML excision between 2015 to 2019. Signalment, location of the lipoma, pre-operative diagnostic tests, histopathology results, use of a closed-suction drain, and follow-up information including drain and suture removal were recorded. Mean age of patients in this study was 8.7 years. Multiple breeds were affected and there was no predilection for either left or right hind limb. Pre-operative diagnostic tests included fine-needle aspirate, radiography, peripheral ultrasonography, and/or computed tomography scan. In 45% (5/11) of the cases, a closed suction drain was placed. All masses removed were deemed grossly consistent with a lipoma by the attending clinician and 5 were confirmed by histopathology. No complications were noted in any case. Removal of caudal thigh IML requires careful identification of and dissection around the sciatic nerve, which is easily achieved with appropriate knowledge of the relevant anatomy and surgical approach.     

Follow-up of troponin I concentration in dogs with atrioventricular block and dual-chamber pacing in a case-matched study

Background

Increased cardiac troponin I (cTnI) concentration has been reported in dogs with atrioventricular (AV) block before and shortly following pacemaker implantation. The role of AV dyssynchrony, age, or concurrent cardiac disease on cTnI concentration remains unknown.

犬门静脉造影肝内影像的分布

手术肠系膜静脉、门静脉造影对诊断各种门静脉异常具有很大的临床意义,尤其是在门静脉短路血管结扎手术治疗之前,能对分流血管进行准确定位[1-2].造影X线片上正常肝内门静脉分布的研究有助于对门静脉异常进行鉴别及定位.本试验通过门静脉血管铸型做参照对不同体位投照的门静脉影像进行研究,旨在对各个肝叶门静脉的影像分支进行定位.     

Regional distribution of ten common skin diseases in dogs

We investigated the regional distributions of the most commonly diagnosed skin diseases in dogs from 17 North American veterinary teaching hospitals. Between January 1983 and December 1983, 11,456 diagnoses of skin disease were made. The 10 most common diagnoses were fleabite allergic dermatitis, skin cancer, pyoderma, seborrhea, allergy, demodectic acariasis (demodicosis), sarcoptic acariasis, immune-mediated skin disease, endocrine related skin disease, and acral lick dermatitis. Regional differences in the frequency of skin diseases were apparent. The northeast region had high frequencies of fleabite allergic dermatitis, allergy, and immune-mediated disease, and a low frequency of seborrhea. The midwest had a high frequency of seborrhea, and low frequencies of demodectic acariasis and allergy. In the plains region, low frequencies of fleabite allergic dermatitis, pyoderma, seborrhea, allergy, and demodectic acariasis were detected. In the west, the frequencies of fleabite allergic dermatitis, skin cancer, pyoderma, seborrhea, and acral lick dermatitis were high, whereas few dogs had allergic disease and sarcoptic acariasis. The southwest had high frequencies of fleabite allergic dermatitis and demodectic and sarcoptic acariasis. Fleabite allergic dermatitis, pyoderma, and demodectic and sarcoptic acariasis were frequently diagnosed in the southeast, but the number of dogs with seborrhea was low.