Time-domain signal-averaged electrocardiogram in healthy German Shepherd and Boxer dogs

P.P.C Chamas,V.M.C Oliveira,F.L Yamaki,M.H.M.A Larsson

doi:10.1590/1678-41626148

Abstract

Signal-averaged electrocardiogram (SAECG) identifies ventricular late potentials (LP), low-amplitude electrical signals that are markers of slow cardiac conduction in fibrous myocardium, consisting in a predictive factor for sudden death in dogs at risk of sustained ventricular tachycardia. The aim of this study was to establish reference values of SAECG for German Shepherd and Boxer dogs. SAECG was performed in 19 German Shepherd and 28 Boxer client-owned dogs, and parameters analyzed were QRSd (duration of filtered QRS), LAS<40μV (duration of low-amplitude signals in terminal portion of filtered QRS) and RMS40 (root square of mean voltage over the last 40 milliseconds of filtered QRS), with two different filters (25-250 Hz and 40-250 Hz). Statistical analyses was achieved by T Student test (p<0.05) to identify differences between the two groups and between the values obtained with the two filters. No statistical difference was found in SAECG variables between the two breeds with the two different filters (p>0.05). Achieving normal values of SAECG in German Shepherd and Boxer dogs is important to further research late potentials in animals of these breeds with hereditary ventricular tachycardia or arrhythmogenic cardiomyopathy and identification of individuals at high risk of cardiac-related sudden death.

Highlights

Time-domain signal-averaged electrocardiogram (SAECG) is an applied, noninvasive diagnostic technique that detects the presence of late potentials (LP), high-frequency and low-amplitude signals that occur at the end of the QRS complex
Forty-seven apparently healthy dogs were used, where 19 were German Shepherds and 28 were Boxer dogs of both genders, with ages ranging from 2 to 10 years. The selection of these breeds was based on the applicability of this examination, since animals of these breeds are prone to developing ventricular arrhythmias that may be associated with presence of LP in SAECG
Separately analyzing the animals grouped according to age, we noted that using the filter 25 to 250 Hz there was, in the German Shepherd dog group, statistically significant difference between the values of QRSd (p=0.048), LAS (p=0.0023) and RMS (p=0.001) obtained for dogs up to 4 years and dogs over 4 years, while for the Boxer dog group only LAS (p=0.0145) differed among the age groups

Summary

Introduction

Time-domain signal-averaged electrocardiogram (SAECG) is an applied, noninvasive diagnostic technique that detects the presence of late potentials (LP), high-frequency and low-amplitude signals that occur at the end of the QRS complex. By using high-gain amplification of up to 100 times and by increasing the speed of signal acquisition, the LP can be recorded. These signals are considered markers of slow and heterogeneous cardiac conduction between myocardial cells interspersed with fibrous tissue, which provides a substrate for the appearance and maintenance of ventricular tachycardia by a re-entry mechanism. Besides being used to identify patients at risk of developing ventricular tachycardia (VT) and sudden death after myocardial infarction, the SAECG is performed to identify LP prior to electrophysiological study in patients with nonsustained VT, as well as in patients with a history of syncope, Duchenne muscular dystrophy (Corrado et al, 2002), ventricular aneurysms, tachycardia and ventricular fibrillation, arrhythmogenic right ventricular cardiomyopathy (ARVC), and nonischemic congestive cardiomyopathies (Poll et al, 1985; Kinoshita et al, 1995)

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