Echocardiography is a non-invasive method to help evaluate cardiac function and anatomy, and there is limited information available regarding cardiovascular parameters in non-domestic felids, including tigers (Panthera tigris). Previously reported echocardiographic studies in non-domestic felids are limited to Panthera pardus orientalis, Panthera uncia, Neofelis nebulosi and Acinonyx jubatus, while cardiac abnormalities in tigers diagnosed antemortem using echocardiography include tetralogy of Fallot, patent ductus arteriosus, and endocardial fibroelastosis.1-4 This study obtained blood pressure measurements and echocardiographic parameters of tigers under sedation, following the use of medetomidine, midazolam, ketamine and isoflurane (phase 1), and compared those measurements performed after administration of the alpha-2 antagonist, atipamezole (phase 2). Eight adult tigers were anesthetized, and echocardiograms performed in right and left lateral recumbency during each anesthetic phase. A single animal was excluded from analyses due to the finding of a ventricular septal defect. Physiological regurgitation of both the tricuspid (6/7) and pulmonic (7/7) valves was commonly seen in both phases. A statistically significant decrease in left ventricular internal dimension at end-diastole (p=0.0321), and increase for interventricular septum thickness at end-systole (p=0.0612) and mean arterial pressure (p=0.0002) was found in phase 2 when compared to phase 1. Fractional shortening increased in phase 2, but did not reach statistical significance (p=0.0586). These values can be used as guidelines for clinicians performing future cardiac examinations in adult tigers, and provides information on the effects of medetomidine on echocardiographic measurements and blood pressure readings.
The authors wish to thank the staff at Tiger Haven for their continued care and dedication to these animals, and the technicians, interns, and residents of the anesthesia, cardiology and zoological medicine services at the University of Tennessee for their assistance in data acquisition.
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