title: Effects of 0.5% Timolol Maleate Ophthalmic Solution on Heart Rate and Selected Echocardiographic Indices in Apparently Healthy Cats.
abstract: BACKGROUND
  Echocardiographic assessment of diastolic function is challenging in cats, partially because of transmitral flow pattern fusion associated with high heart rates. With heart rate (HR) reduction, transmitral flow waveforms separate, allowing identification of diastolic dysfunction. Timolol, an ophthalmic, nonselective beta-blocker used in glaucoma is safe and transiently decreases HR in clinical trials.
  
  
  OBJECTIVE
  Administration of timolol ophthalmic solution decreases HR and facilitates echocardiographic assessment of diastolic function in cats without inducing clinically relevant adverse effects.
  
  
  METHODS
  Twenty-five apparently healthy cats.
  
  
  METHODS
  Electrocardiograms and echocardiograms including transmitral flow patterns were evaluated before and 20 minutes after ocular administration of 1 drop of timolol 0.5% solution. Twenty cats underwent treatment with timolol, and 5 different cats served as untreated controls to evaluate the effects of acclimation to the hospital environment on HR.
  
  
  RESULTS
  Acclimation to the hospital had no effect on HR in control cats. After timolol administration, a significant median HR reduction of 25 bpm was observed (P < .0001). Timolol had no effect on E/A ratio in cats without E/A fusion (7/20, P = .44). Of the 13 cats with E and A waves that were fused before timolol application, separation of these waves was identified in 8 cats (62%) after timolol treatment. No bradyarrhythmias were noted after timolol administration, but 2 cats had first-degree atrioventricular block. Timolol resulted in resolution of dynamic outflow tract obstruction in 6 of 6 cats.
  
  
  CONCLUSIONS
  Ocular administration of timolol safely decreases HR in cats and could facilitate assessment of diastolic function.
authors.affiliation: Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA.
authors.forename: C T
authors.initials: CT
authors.lastname: Gunther-Harrington
authors.affiliation: Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA.
authors.forename: E S
authors.initials: ES
authors.lastname: Ontiveros
authors.affiliation: Veterinary Medical Center, University of California, San Diego, CA.
authors.forename: T E
authors.initials: TE
authors.lastname: Hodge
authors.affiliation: Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA.
authors.forename: L C
authors.initials: LC
authors.lastname: Visser
authors.affiliation: Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA.
authors.forename: J A
authors.initials: JA
authors.lastname: Stern
mesh_terms: D060433:Administration, Ophthalmic / Q000662:veterinary; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002371:Cat Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D002415:Cats; D003971:Diastole; D004562:Electrocardiography / Q000662:veterinary; D006337:Heart Murmurs / Q000503:physiopathology / Q000662:veterinary; D006339:Heart Rate / Q000187:drug effects*; D013999:Timolol / Q000008:administration & dosage / Q000494:pharmacology*; D016277:Ventricular Function, Left
chemical_list: D000319:Adrenergic beta-Antagonists; D013999:Timolol
keywords: Cardiomyopathy; Doppler; Echocardiography; Feline