The effects of medetomidine on cardiac function in normal cats measured by radionuclide ventriculography

To assess the effects of medetomidine, an α₂-adrenoceptor agonist, on cardiac function, radionuclide ventriculograms (RNV) were performed in 7 normal anesthetised cats before and after im administration of the drug. Ejection fraction (EF), peak ventricular ejection rate (PVER), peak ventricular filling rate (PVFR), time to peak ejection (TPE) and time to peak filling (TPF) were determined. Medetomidine caused significant reductions in EF (baseline 55.0 ± 10.8%, post medetomidine 43.3 ± 10.7%), PVER (baseline 4.38 ± 0.83 EDV/s, post medetomidine 3.28 ± 0.73 EDV/s) and PVFR (baseline 4.46 ± 1.42 EDV/s, post medetomidine 3.05 ± 1.27 EDV/s). There was also a significant decrease in heart rate following medetomidine administration (baseline 115 ± 27.2 bpm, post medetomidine 100 ± 21.2 bpm). The TPE and TPF did not change significantly following medetomidine. The observed decrease in cardiac function may have been caused by a drug-induced increase in systemic vascular resistance, and the bradycardia due to central nervous system depression.