Search Results

You are looking at 1 - 10 of 14 items for

  • Author or Editor: Janice M. Bright x
  • Refine by Access: All Content x
Clear All Modify Search
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

SUMMARY

Relaxation half-time (t½) was evaluated as a measure of isovolumic ventricular relaxation in clinically normal cats and cats with hypertrophic cardiomyopathy. Relaxation half-time was determined directly from the left ventricular pressure tracing as the time required for the left ventricular pressure at the beginning of isovolumic relaxation to decrease by half.

The value of t½ was unaffected by moderate changes in heart rate, inotropic state, and afterload in clinically normal cats. However, t½ increased significantly (P = 0.003) with increased preload. The value of t½ was significantly higher (P = 0.0003) in a group of cats with hypertrophic cardiomyopathy, compared with that of a group of clinically normal cats. Although t½ must be interpreted in the context of changes in loading conditions, the index is useful as a measure of relaxation in clinically normal cats and cats with hypertrophic cardiomyopathy.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the clinical usefulness of cardiac event recording in evaluating dogs and cats with unexplained syncope, episodic collapse, or intermittent weakness.

Design—Retrospective study.

Animals—58 dogs and 2 cats.

Procedure—Medical records and electrocardiographic rhythm strips obtained by cardiac event recordings were reviewed. Cardiac rhythm data from the event recordings were classified as diagnostic or nondiagnostic. Diagnostic yield was calculated by dividing the number of animals for which cardiac event recording was diagnostic by the total number of animals undergoing cardiac event recording.

Results—For 51 animals, cardiac event recording was classified as diagnostic; therefore, overall diagnostic yield was 85%. Diagnostic yield was lower for animals without underlying structural heart disease (75.5%) than for animals with structural heart disease (95.6%). A specific arrhythmia was identified as the cause of clinical signs in 18 of the 51 (35%) animals for which cardiac event recording was diagnostic. Cardiac arrhythmia was definitively excluded as the cause of clinical signs in the remaining 33 (65%) animals in which cardiac event recording was diagnostic.

Conclusions and Clinical Relevance—Results indicate that cardiac event recording had a high diagnostic yield in dogs and cats examined because of unexplained syncope, episodic collapse, or transient weakness and ataxia, regardless of whether animals did or did not have an underlying structural heart disease. Diagnostic yield of cardiac event recording was higher than that reported previously for Holter monitoring. (J Am Vet Med Assoc 2000;216:1110–1114)

Full access
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

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

Abstract

OBJECTIVE To determine pharmacokinetic and pharmacodynamic properties of the novel factor Xa inhibitor apixaban in clinically normal cats.

ANIMALS 5 purpose-bred domestic shorthair cats.

PROCEDURES A single dose of apixaban (0.2 mg/kg, PO) was administered to each cat (time 0), and blood samples were obtained at 0, 15, 30, 45, 60, 120, 240, 360, 480, and 1,440 minutes. After a 1-week washout period, another dose of apixaban (0.2 mg/kg, IV) was administered to each cat, and blood samples were obtained at 0, 5, 10, 15, 30, 45, 60, 120, 240, 360, 480, and 1,440 minutes. Apixaban concentrations in plasma were measured via liquid chromatography–tandem mass spectrometry. Pharmacodynamic effects of apixaban were determined with a commercial assay for factor × activity, which measures endogenous factor Xa activity chromogenically.

RESULTS Factor Xa was inhibited as a function of time after a single dose of apixaban administered orally or IV, and a direct inverse correlation with the plasma apixaban concentration was detected. Pharmacokinetic analysis revealed moderate clearance, short half-life, and high bioavailability for apixaban. A 2-compartment model was fit to the IV pharmacokinetic data; compartmental modeling could not be used to adequately describe the oral data because of substantial interindividual variability.

CONCLUSIONS AND CLINICAL RELEVANCE Results inticated that apixaban was an effective inhibitor of factor Xa in cats. Further studies will be needed to determine pharmacokinetics and pharmacodynamics after multidose administration, effects of cardiac disease on pharmacokinetics and pharmacodynamics, dosing recommendations, and efficacy of apixaban for use in the treatment and prevention of thromboembolic disease in cats.

Full access
in American Journal of Veterinary Research