Proposed steps of ECG assessment to localize AP
Optimized steps for ECG analysis were added to the WPW24.com app to increase its functionality. These steps were developed on the basis of the classic rules of ECG interpretation and the personal experience of over 1000 APs ablated by the first author. Most of these criteria, in various modifications, can be found in the literature, (10-17) the only authorial criterion is QRS notch/slur/plateau (Figure 2 ) to differentiate right free wall pathways from septal pathways. The steps for ECG analysis were optimized by post-hoc assessment - if a step did not result in an expected differentiating change of AP distribution pattern – it was abandoned and other were explored. Following rules were tested to build the pathways for analysis of preexcited ECG:
  1. Positive or equiphasic V1 indicates left free wall and left septal AP; conversely, negative V1 indicates right free wall and right septal AP
  2. Precordial transition to positive/equiphasic QRS at V2 – V4 indicates right septal AP; while precordial transition > V4 suggest right free wall or Mahaim AP
  3. Negative II, III, aVF indicate posterior AP, positive II, III, AVF indicate anterior AP, while mixed polarity in these leads suggest sites in-between (i.e. lateral free-wall or midseptal). In such scenario, right free wall pathways are favored by the presence of a notch/slur/plateau in leads I, aVL, aVF or V6.
  4. Completely positive lead I indicates right or septal AP. Contrarywise, the more negative the QRS in lead I (the deeper the S wave) the more to the left is the AP, with completely negative complex (QS morphology) indicating the most left sided region – i.e. left lateral location.