Key result
Ophthalmic administration of 0.5% timolol significantly reduced median heart rate by 25 bpm and facilitated separation of fused transmitral E and A waves in 62% of affected cats.
Why the study?
Does 0.5% timolol maleate ophthalmic solution decrease heart rate and facilitate echocardiographic assessment of diastolic function in apparently healthy cats?
Does 0.5% timolol maleate ophthalmic solution decrease heart rate and facilitate echocardiographic assessment of diastolic function in apparently healthy cats?
Ocular administration of timolol safely decreases heart rate in cats, facilitating the echocardiographic assessment of diastolic function by separating fused E and A waves.
May aid echocardiographic assessment in tachycardic cats; leaves open confirmation of safety and benefit in prospective trials.
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. HYPOTHESIS: Administration of timolol ophthalmic solution decreases HR and facilitates echocardiographic assessment of diastolic function in cats without inducing clinically relevant adverse effects. ANIMALS: 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 AND CLINICAL IMPORTANCE: Ocular administration of timolol safely decreases HR in cats and could facilitate assessment of diastolic function.
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Gunther‐Harrington et al. (2016) studied Apparently healthy cats (n=25). Timolol maleate ophthalmic solution vs. Untreated controls (acclimation to hospital environment) was evaluated on Heart rate reduction (MD -25 bpm, p=<0.0001). Ophthalmic administration of 0.5% timolol significantly reduced median heart rate by 25 bpm and facilitated separation of fused transmitral E and A waves in 62% of affected cats.
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