Aims: Reciprocating atrioventricular tachycardia can be categorized into common slow-fast atrioventricular node re-entrant (AVNRT) and orthodromic atrioventricular reciprocating tachycardia (AVRT). The electrocardiogram (ECG) during tachycardia is useful in distinguishing these two mechanisms. The presence of a pseudo-R'-wave in lead V1 or pseudo-S-wave in the inferior leads has been widely used, although the value of an isolated aVL lead has not been evaluated yet. To determine whether an isolated aVL lead of the surface 12-lead ECG is useful for the differential diagnosis between AVNRT and AVRT.
Methods and results: Consecutive patients referred for paroxysmal regular supraventricular tachycardia radiofrequency ablation were prospectively evaluated. Patients with atrial tachycardia, bundle branch block, manifested pre-excitation, and those undiagnosed after electrophysiology study were excluded. We compared the standard criteria with the value of an isolated aVL lead to distinguish between AVNRT and AVRT. One hundred and one patients were included; 73.3% were AVNRT and 26.7% AVRT. Patients with AVNRT were older (49.4 +/- 16.4 vs. 36.0 +/- 18.7 years, P = 0.001). The aVL notch and the standard criteria were found more frequently in AVNRT than in AVRT (aVL notch: 51.3 vs. 7.4%, P< or = 0.001; pseudo-S-wave 45 vs. 8.6% P = 0.001; and pseudo-R'-wave in V1 39.7 vs. 11.5%, P = 0.008, respectively). The aVL notch sensitivity and specificity to determine the final diagnosis were higher than the standard criteria (aVL notch 48.6 and 92.6%; pseudo-S-wave 45 and 91.3%; and pseudo-R'-wave in V1 39.7 and 88.5%, respectively).
Conclusion: The presence of a notch in aVL lead appeared to be as sensitive and specific as the standard electrocardiographic criteria for the differential diagnosis of AVNRT.