Echocardiographic reference ranges for sedated healthy cynomolgus monkeys (Macaca fascicularis)

Echocardiographic imaging has become the primary tool to evaluate cardiac structure and function in human and veterinary medicine. The cynomolgus monkey (Macaca fascicularis) is a nonhuman primate species frequently used in biomedical research, particularly for the study of human cardiovascular disease and toxicology, yet echocardiographic reference ranges are not available for this species. Using standard 2-dimensional and M-mode imaging, we performed echocardiographic evaluation of 118 female and 119 male cynomolgus monkeys under sedation with either ketamine hydrochloride (10 mg/ kg IM) alone or with a combination of tiletamine hydrochloride and zolazepam (4.0 mg/kg IM) and atropine sulfate (0.015 mg/kg IM). Reference ranges were developed (tolerance interval methodology) separately for each gender for heart rate, left ventricular (LV) size (interventricular septum in diastole, LV internal diameter in diastole and systole, LV free wall in diastole), left atrial diameter, and aortic diameter. LV functional parameters (fractional shortening, aortic peak flow velocity, LV ejection time, and LV preejection period) and mitral valve E point to septal separation were also measured. After normalization for body weight (1.7 to 6.3 kg), the data were analyzed for gender- and sedation-associated differences. Using a large number of healthy subjects (118 of each gender), we have developed gender-specific echocardiographic reference ranges for cynomolgus monkeys.