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in Journal of the American Veterinary Medical Association

Abstract

Objectives

To assess baseline cardiac electrophysiologic (EP) measurements in dogs undergoing a clinically used anesthetic protocol, and to study the effects of IV administered atropine and propranolol on these EP variables.

Animals

15 adult dogs with cardiac function within reference ranges, as assessed by physical examination, electrocardiography, and echocardiography.

Procedure

13 cardiac EP variables were measured in isofluorane-anesthetized dogs before and after IV administration of atropine and propranolol. Multipolar electrode catheters were positioned against the endocardium of the dorsal portion of the right atrium, His bundle region, and right ventricular apex. Incremental pacing and pacing-extrastimulus techniques were used to obtain EP measurements of the sinoatrial node, atrioventricular node, and atrial and ventricular myocardia in the control state and after IV administration of 0.04 mg of atropine and 0.2 mg of propranolol/kg of body weight.

Results

Only the atrial effective refractory period changed significantly after muscarinic and β-adrenergic receptor antagonism. Marked individual variation in response to these agents, however, was apparent. Two dogs had substantial decreases in sinoatrial and/or atrioventricular nodal measurements, and 7 dogs had notable increases in atrioventricular nodal measurements.

Conclusions

Cardiac EP measurements vary widely among clinically normal, isofluorane-anesthetized dogs. Individual dogs can have variable degrees of autonomic tone, which can be minimized by pharmacologic receptor antagonism.

Clinical Relevance

Although effects of receptor antagonism at clinically applicable dosages were not significant for 12 of 13 measurements, withdrawal of vagal tone can induce marked EP changes and may be important during a clinical study. (Am J Vet Res 1996;57:1695–1701)

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Objective

To determine signalment, diagnoses, presence of effusions in multiple sites, and outcome in cats with peritoneal effusion.

Design

Retrospective case series.

Animals

65 cats.

Procedure

Medical records from 1981 to 1997 were reviewed to obtain information on cats with peritoneal effusion identified on physical examination, radiographs, abdominal ultrasonograms, or at necropsy.

Results

Conditions most commonly associated with peritoneal effusion in cats, in order of frequency, were cardiovascular disease, neoplasia, hepatic disease, renal disease, feline infectious peritonitis, peritonitis attributable to other causes, and urinary tract trauma. Dilated cardiomyopathy (DCM) was the most common disease associated with peritoneal effusion; however, DCM was diagnosed in most of these cats before taurine deficiency was found to be a primary cause of this form of cardiomyopathy in cats. Neoplasia was the most common cause after 1987. Right-sided congestive heart failure was the most commonly associated disorder in cats < 1 year old, whereas neoplastic disease was more common with increasing age. Most effusions were detected during the initial physical examination and were modified transudates. Peritoneal effusion was commonly accompanied by fluid accumulation elsewhere, particularly pleural effusion. The prognosis for a cat with abdominal effusion in this study was poor (mean survival time, 21 days; range, 1 to 350 days; median, 2.5 days).

Clinical Implications

The primary differential diagnosis for peritoneal effusion in cats is neoplastic disease in older cats and right-sided heart failure in kittens. Diseases associated with peritoneal effusion generally have poor prognoses. (J Am Vet Med Assoc 1999;214:375–381)

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in Journal of the American Veterinary Medical Association

Abstract

Objective

To develop a protocol for reliably inducing atrioventricular (AV) block (ideally first- or second-degree), using radiofrequency energy.

Design

An electrosurgical unit was coupled to an ammeter, which was connected to the distal pole of an electrode catheter positioned at the AV node. Control settings had previously been calibrated to the power output in a circuit with a 100-ohm resistance.

Animals

10 clinically normal dogs.

Procedure

Transcatheter AV nodal modification was attempted, using progressive power applications of 10 to 20 W for progressive durations of 10 to 30 seconds. Atrioventricular nodal conduction and refractivity were measured before and 20 minutes and 1 month after ablation. Electrocardiograms were monitored throughout the 1-month period.

Results

Eight of the 10 dogs developed complete AV block, 1 developed stable 2:1 AV block, and another had no long-term change in AV nodal conduction. Four dogs attained their maximal degree of AV block in 2 to 5 days. Three of these had no AV nodal conduction changes until 2 to 4 days after ablation.

Conclusions

An electrosurgical unit can be economically modified for radiofrequency transcatheter ablation. Stable, incomplete AV block was rarely induced using this protocol, whereas complete AV block often developed. A major finding was frequent delay between energy delivery to the AV nodal region and induction of AV block.

Clinical Relevance

Induction of complete AV block using this technique, followed by permanent pacemaker placement, is an effective alternative to long-term antiarrhythmic treatment in animals with chronic atrial arrhythmias. Transcatheter ablation could be used to treat other forms of tachycardia, as it is in human medicine.

Free access
in American Journal of Veterinary Research