Localization and characterization of atrial depolarizationwaves on the surface electrocardiogram in dogs with rapidsupraventricular tachycardiaStefano

Background:Supraventricular tachycardias (SVTs), despite having various anatomicalsubstrates and pathophysiological mechanisms, frequently show similar electrocar-diographic presentations.Objectives:To locate and characterize atrial deflections (ADs) on 12-lead electrocar-diograms in dogs with sustained rapid SVT and assess the utility of different electro-cardiographic variables in differentiating types of tachycardia.Animals:Ninety-two dogs with orthodromic atrioventricular reciprocating tachycar-dia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed byelectrophysiological study, and 40 dogs with sinus tachycardia.Methods:Atrial deflection position on the 12-lead surface electrocardiogram wasassessed according to the sequence of intracardiac activation. Its features were eval-uated together with the relationship between AD and QRS complex interval (AD-R)and QRS complex and AD interval (R-AD).Results:Orthodromic atrioventricular reciprocating tachycardia was characterized by anAD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of90 (90/78),R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter wascharacterized by an AD-AD interval of 199 ± 57 ms, MEA of 76(72/81), R-AD of120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was char-acterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (72/76),R-ADof160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was charac-terized by an AD-AD interval of 292±31ms, MEA of 66(52/73), R-AD of215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08).Conclusions and Clinical Importance:Analyzing AD on 12-lead electrocardiogram ishelpful in differentiating the most common SVTs in dogs.