Localization and characterization of atrial depolarization waves on the surface electrocardiogram in dogs with rapid supraventricular tachycardia

Abstract

Background: Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations.

Objectives: To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia.

Animals: Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia.

Methods: Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated 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 an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of -90 (-90/-78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (-72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (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 is helpful in differentiating the most common SVTs in dogs.

Keywords: atrial flutter; electrocardiography; electrophysiology; focal atrial tachycardia; orthodromic atrioventricular reciprocating tachycardia; sinus tachycardia.

FIGURE 1

Example of a 12‐lead surface ECG and intracardiac recording printed at a speed of 150 mm/s and amplitude of 1 mV/cm and obtained during the mapping of a crista terminalis focus (A). All these traces had to be simultaneous on one sheet to correctly identify AD on a 12‐lead surface ECG by referring to the sequence of intracardiac activation, as shown by the gray stripe, which highlights AD duration in the 12‐surface ECG leads. Recordings included all 12 leads of the surface ECG and intracardiac recordings from the distal to the proximal portion of the CS (CSp and CSd), from the distal to the proximal His bundle area (HBED and HBEp), from the distal to the proximal portion of the different atrial ectopic foci (ABLd and ABLp), and a unipolar recording (unip). The presystolic, fractioned potential at atrial potential (A) recorded with the ablation catheter's distal pairs and sharp and negative with QS morphology of atrial potential of unipolar recording at the target area is visible. A, atrial potential; H, potential; V, ventricular potential. In the same tracing, an example of the measurements of the ventriculoatrial interval (R‐AD interval) and atrioventricular interval (AD‐R interval) on the 12‐lead surface ECG, by referring to the sequence of intracardiac activation, is shown (B).

FIGURE 2

Box and whisker plots comparing atrial deflection (AD) duration (A), atrial deflection cycle length (B), RR cycle length (C), R‐AD interval (D), AD‐R interval (E), and R‐AD/AD‐R ratio (F) in dogs affected by orthodromic atrioventricular reciprocating tachycardia (OAVRT), focal atrial tachycardia (FAT), atrial flutter (AFL), and sinus tachycardia (ST). The lower quartiles, medians, and upper quartiles are represented. Black circles represent outliers. Statistically significant differences between groups (P < .05) are represented by capital letters. Different letters indicate a statistical significance. For each plot, the specific statistical report is indicated (exact P value and effect size).

FIGURE 3

Receiver operating characteristic (ROC) curves of the R‐AD interval (A) and of the R‐AD/AD‐R ratio (B) to differentiate focal atrial tachycardia (FAT) from orthodromic atrioventricular reciprocating tachycardia (OAVRT). ROC curves of the R‐AD interval (C) and of the R‐AD/AD‐R ratio (D) to differentiate sinus tachycardia (ST) and focal atrial tachycardia (FAT). The intersection between the yellow line and the AUC graph indicates the point with the best statistical performance (sensitivity and specificity). The suggested cut‐off values and the area under the curve (AUC) for each ROC curve are reported.

FIGURE 4

Schematic depiction of the position and features of atrial deflections in orthodromic atrioventricular reciprocating tachycardia (OAVRT), focal atrial tachycardia (FAT), atrial flutter (AFL), and sinus tachycardia (ST). Given that atrial deflection position is variable in most cases of AFL, it is represented as a continuous line throughout the ECG tracing.