VN April 2023

Vetnews | April 2023 17 Article Exotic companion mammals Due to the delicate nature of exotic mammal skin, alligator clips are not attached directly to the skin but instead the clips are attached to the tips of small-gauge hypodermic needles or stainless-steel suture that has been passed into the subcutaneous space and through the skin. 6 Alternatively, adhesive ECG patches or button electrodes can be placed on the foot pads. Large patches can easily be cut down to size but take care as the adhesive can be irritating to delicate skin. 5 The ECG can be used to detect and diagnose arrhythmias and conduction abnormalities: • A pronounced sinus arrhythmia is often observed in the normal ferret ( Mustela putorius furo ). Second-degree atrioventricular block canalsobe anormal finding in ferrets. 14 Sinus tachycardia, and atrial or ventricular premature complexes are commonly seen in ferrets with cardiac disease. Sinus bradycardia may develop secondary to hypoglycemia and insulinoma. • Rabbits ( Oryctolagus cuniculus ) can present with cardiovascular concerns related to thymoma, congestive heart failure, or valvular disease. An ECG can be used to detect abnormal rhythms associated with these conditions, including atrial fibrillation, ventricular premature complexes, ventricular tachycardia, and supraventricular tachycardia. 11 Birds Although the rapid heart rate of the bird can challenge most ECG equipment, electrocardiograms have been described in a number of avian species. 2,4,5 A bipolar ECG reading can be obtained by placing the right atrial lead (sometimes labeled “right arm” or RA) on the right side of the cranial sternum and the left atrial lead on the left side of the caudal sternum. 16 Alligator clips are typically attached to needles or stainless-steel suture as described above in exotic companion mammals. 17 The normal ECG tracing in the avianpatient canhave the appearance of ventricular tachycardia, primarily because of the large negative S wave (Fig 3). 13 This QRS morphology is caused by the high density of sympathetic and parasympathetic nerve fibers in the avian ventricles and atria when compared to mammals. 18 Reptiles The thick, scaly skin of snakes and lizards limits the sensitivity of ECG leads. Effective signal conduction requires alligator clips be attached to needles or stainless-steel suture. 17 Adhesive ECG patches can also be placed directly on smooth-scaled reptiles, like large snakes and chelonians (Fig 4). 3 Electrocardiograph leads can be placed in either a standard three-limb or base-apex configuration. 17 The latter simply requires the “right arm” lead be placed 10-12 scutes cranial to the heart (one-third to one-quarter down the length of the body) and the “left arm” lead is placed 10-12 scutes caudal to the heart. 17 Esophageal base-apex ECG lead configurations are also commercially available that can be combined within the tubing of an esophageal stethoscope. 17 The use of electrocardiography in reptiles is hampered by a lack of normal values, however the typical ECG tracing may include an SV wave that precedes the P wave. 1,3,12 The SV wave represents depolarization of the sinus venosus, which serves as a pacemaker of the three-chambered heart in most reptiles. 1 Figure 2: Electrocardiogram tracing in a rat (Rattus norvegicus). Photo credit: Katrina Lafferty, CVT, VTS. Figure 3: Monitoring screen from an anesthetized whooping crane (Grus americana). Note the prominent S wave and rapid rate (arrow), normal for many avian species. Photo credit: Ka- trina Lafferty, CVT, VTS. >>> 18