The 12-lead electrocardiogram in midseptal, anteroseptal, posteroseptal and right free wall accessory pathways

The 12-lead electrocardiograms of 50 patients with 1 anterogradely conducting accessory pathway were analyzed to obtain characteristics of electrocardiographic findings in the midseptal, anteroseptal, true posteroseptal and right free wall accessory pathway locations. Locations were confirmed by surgery (33 patients) or radiofrequency catheter ablation (17 patients). This study analyzed (1) QRS in the frontal plane, (2) delta wave axis in the frontal plane, (3) the angle between QRS and delta wave axes, (4) the rmR S ratio in lead III, (5) negativity of delta wave in inferior leads, and (6) the rmR S ratio in precordial leads. Results were (1) QRS axis in the frontal plane in the right free wall — range from +15 to −65 ° (−32 ± 19 °); true posteroseptal pathways — range from +30 to −60 ° (−38 ± 22 °); midseptal pathways range from +15 to +60 ° (+49 ± 11 °); anteroseptal pathways range from 0 to +75 ° (+46 ± 22 °); (2) delta wave axis in the right free wall −0 to −60 ° (−32 ± 22 °); true posteroseptal − 0 to −60 ° (−43 ° 18 °); midseptal −0 to +45 ° (+24 ± 15 °), and anteroseptal −0 to +60 ° (+45 ± 17 °); (3) QRS/delta wave axis angle in the right free wall − 7 ± 6 °, true posteroseptal −9 ± 7 °; midseptal − 22 ± 6 °, and anteroseptal accessory pathways − 3 ± 5 °; (p = 0.006); (4) the rmR S ratio lead III was 1 in anteroseptal and equal to 1 in midseptal accessory pathways; (5) delta negativity in ≥2 inferior leads was observed in the right free wall −90%; in true posteroseptal −90%, in midseptal − 0%, and anteroseptal accessory pathways −0% (p rmR S ratio >1 in lead V 2 was right free wall −20%, true posteroseptal −100%, midseptal — 12%, anteroseptal −0% (p rmR S ratio in lead III. A QRS/delta wave axis angle of ≥20 ° and an rmR S ratio equal to 1 in lead III favor a midseptal accessory pathway location.