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:
- Positive or equiphasic V1 indicates left free wall and left septal AP;
conversely, negative V1 indicates right free wall and right septal AP
- Precordial transition to positive/equiphasic QRS at V2 – V4 indicates
right septal AP; while precordial transition > V4 suggest
right free wall or Mahaim AP
- 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.
- 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.