CARDIAC ASSESSMENTS AND IMPLANTABLE LOOP RECORDER PLACEMENT IN THREE MALE GELADAS (THEROPITHECUS GELADA)

Cardiac disease is a common cause of mortality in many primates housed in zoological settings. At the Bronx Zoo, between 2007 and 2018, there were ten incidences of sudden cardiac death in adult male geladas (Theropithecus gelada), none of which showed premonitory signs. Due to concerns of occult cardiac disease and fatal arrhythmogenic events, complete cardiac examinations were performed in three clinically normal, adult male geladas. Examinations included thoracic radiographs, transthoracic echocardiograms (echo), 12-lead ECG, and continuous ECG monitoring using an Implantable Loop Recorder (Reveal LINQ^TM Medtronic, Minneapolis, MN 55432, USA). Serum lipid profiles, vitamin E concentration, cardiac troponin I isoform (cTnI), and complete blood work were also performed. Wireless downloads from the implantable loop recorders were obtained intermittently for up to 2.5 years after placement. One male had an elevated cTnI level (210 ng/L), reduced ejection fraction (46%), and multiple episodes of supraventricular tachycardia and non-sustained ventricular tachycardia. Due to the abnormalities on ECG and echo, he was treated with metoprolol and lisinopril. Treatment was continued for nearly two years, until the animal had sudden cardiac death secondary to sustained ventricular fibrillation, which was confirmed by postmortem download of the loop recorder data and correlated with histologic evidence of cardiomyopathy. Implantable loop recorders greatly enhance the ability to diagnose and treat arrhythmias in primates and understand the mechanisms behind sudden cardiac deaths. Further studies are needed to establish cTnI, echocardiogram, and electrocardiogram reference ranges for this species, as well as appropriate treatment protocols.