EFFECT OF BODY POSITION ON ELECTROCARDIOGRAPHIC RECORDINGS OF RHESUS MONKEYS (Macaca mulatta)

Abstract

Electrocardiogram (ECG or EKG) is an invaluable technique used to detect the electrical activity and rhythms of the heart. Several cardiovascular diseases can be easily detected through ECG. In non-human primates, ECG is used to evaluate standard electrocardiographic data for cardiotoxicological studies and preclinical drug safety testing. As rhesus monkeys (Macaca mulatta) are the most suitable models for investigating heart diseases due to close proximity with humans, high quality ECG tracings are physiologically valuable. Body positions may have profound effect on ECG, accordingly, the position that suits best for ECG tracings in non-human primates can also be applied to human subjects. The present study determined the effect of four different body positions, supine, ventral, sitting and standing on ECG parameters. For this purpose, we obtained limb lead electrocardiogram of ketamine sedated rhesus macaques (n=10) in all the four positions. Rhythm, Heart rate, RR Interval, PR, and QT Intervals, QRS duration, QRS axis, P wave duration, P, T and R wave amplitudes were calculated manually from rhythm lead II, using the interpretational methods. For calculating the QT interval correction, Bazett, Fridericia, Framingham and Hodge formulae were applied both manually and by using the QTc calculator. Results revealed significant changes (P<0.01) in all the parameters except the P wave amplitude that remained indifferent with change in body position. The study further revealed that RR, QT, QTc, and R wave amplitude depend on heart rate and vary with each position as the heart rate changes. Conversely, the PR and QRS durations were independent of heart rate. In addition, the rhythms were sinus and P waves were upright in all positions, while an inverted T wave was observed in sitting position as compared to other body positions. We further propose that supine position is ideal for obtaining electrocardiographic data from rhesus monkeys.