Address for correspondence:
Garry Robert Thomas
St. Joseph’s Health Centre
Unity Health Toronto
30 The Queensway
Toronto, Ontario, Canada
M6R1B5
Telephone: 416-766-1162
Fax: 416-766-0463
Email: garry.thomas@unityhealth.to
Manuscript word count: 420
Key words: Inferior lead discordance, Right sided accessory pathway
We read, with interest, the article by Deb et al. entitled“Positive QRS complex in limb lead 2 with negative QRS in lead 3
on surface electrocardiogram: A novel predictor for anterior location of
right sided accessory pathways.” 1 We would like to
raise a few concerns regarding the interpretation of the
electrocardiographic (ECG) sign they have highlighted.
- The authors propose that inferior lead discordance (ILD) with a
positive in Lead 2 and negative in Lead 3 is indicative of a right
anterior accessory pathway (AP); this relies on QRS polarity rather
than delta wave polarity. This would imply that this sign would have
the same implication as ventricular arrhythmia arising from the site
of AP insertion. Based on this assumption, one would conclude that ILD
would be an indicator of a “Para-Hisian” location of the AP rather
than being removed from it as the authors conclude.2
- Further analysis of the ECGs in Figure 2 shows us that the QRS
transition is beyond V3 in all ECGs except the third one (ECG c).D’Avila et. al. 3 and Taguchi et.
al. 4 have shown that a positive QRS in V2, or what
we recognize as an early transition from V1 to V2, is indicative of a
septal pathway while a late transition is indicative of a right sided
pathway. So, based on this ECG finding, one would diagnose a right
sided pathway away from the septum. This simple sign was not
highlighted in the article.
- D’Avila et. al .3 have already published that
a positive QRS in Lead II and a negative in Lead III is indicative of
a Right sided pathway, suggesting the sign described in this article
is not novel.. This makes intuitive sense too since right sided
pathways would be expected to have greater negativity in Lead III. The
authors of this author did not use the term “inferior lead
discordance”
- The authors use this sign as indicative of a right anterior location
while we believe a right lateral pathway may also have a negative Lead
III. Sternick et. al. 5 described the ECG
features of right sided pathways, especially atriofascicular pathways;
in their publication one can see an atriofascicular pathway with the
same discordance identified by the authors of this publication. We
have also observed this discordance in most of the posteroseptal
accessory pathways we have ablated from the right side. (unpublished)
In conclusion, we disagree with the authors and believe that this
proposed “discordance” is an oversimplification, and not reliably
indicative of a right anterior pathway.