N02 - Electrical Impedance Myography in Healthy Dogs: Reference Values and Impact of Age

Abstract: Background: Electrical impedance myography (EIM) is a tool for muscle assessment based on voltages obtained with application of high-frequency, low-intensity electrical current. The phase value metric is calculated based on resistance and reactance values.



Hypothesis/Objectives: To assess normal EIM values in healthy dogs and determine an age dependence to the metric.



Animals: 73 healthy dogs (62 males, 49 females) were sampled for a total of 111 muscle observations. Mean age was 5.1 years (0.63 - 13.48 years), and mean body condition score was 5 (4 to 6).



Methods: EIM measurements were performed on bilateral craniotibialis, gastrocnemius, and sartorius muscles and assessed at 100 kHz phase. A second-degree polynomial regression was used to fit for phase with age and extract the lower limit of prediction for sex.



Results: Lower limits of normal were established across a range of ages. Data suggested modest reduction in phase values with age, consistent with expected decline in muscle condition. The average value decreased from 16.6° in 2-year-old male dogs to 12.7° in 13-year-old male dogs (23.4% reduction) and decreased from 15.4° in 2-year-old female dogs to 12.1° in 13-year-old female dogs (21.4% reduction).



Conclusions and Clinical Importance: EIM is a non-invasive, quantitative measure of muscle pathology utilized to track muscle condition in healthy dogs. There is a small but consistent reduction in EIM values with increased age. The normal EIM values established here can serve as reference for future studies in disease.