First description of the Burmeister porpoise (Phocoena spinipinnis) electrocardiogram

Abstract

The aim of this study was to make the first characterization of the electrocardiogram (ECG) of the Burmeister porpoise (Phocoena sipinipinnis). A total of three ECGs were made in one, wild juvenile female (body weight = 32.5 kg, Lt = 1.45 m), temporarily held in captivity for rehabilitation at Mar del Plata Aquarium (Argentina). For ECG recordings, the animal was removed from its pool on a stretcher under constant veterinary supervision. A traditional six-lead system in the frontal plane was used, with the typical four "extremities" electrodes positioned bilaterally. ECGs were readable and all waves were detectable. The QRS complexes were characterized by Q wave absence in all leads. The ECG characteristically displayed distinctly defined STs, with a T wave clearly differentiated from the QRS complex. An STs elevation was detected in leads II and III. The mean electrical axis was -79°, meaning a cranial left axis orientation. The animal showed normal sinus rhythm and heart rate (HR) showed a continuous oscillation between tachycardia and bradycardia. Mean HR from all recordings was 147.02 ± 24.95 bpm (range = 71-176, n = 178). Evidence of the occurrence of respiratory sinus arrhythmia was detected through HR variations and RR interval differences, which suggested an adequate cardiovascular system compensation to handling conditions. This study has reported ECG amplitude and duration measurements of a potentially healthy specimen, which represents the starting point for the determination of normal ECG values for this species. Also, it has confirmed that ECG is a valuable noninvasive tool for rapid cardiac health assessment in small cetaceans.

Keywords: Burmeister porpoise; cetaceans; electrocardiogram; heart rate; respiratory sinus arrhythmia.