Thread by @IkramHaqMD

🧵 on the Algorithmic Localisation of Accessory Pathways from ECG

A concept I’m getting to grips with made easier by a beautiful review by #Crinion & @adribaran in Card Electrophysiol Clinic (PMID 33161996)

#EPeeps #MedEd #Cardiology

🫀Considerations of AP localising algorithms:

A. Only apply to manifest antegrade AP & not concealed AP which conduct retrograde

B. Algorithms focused on atrioventricular AP & not other rarer AP

C. Depend on the degree of preexcitation with

D. Cautions with multiple APs

🩻 Anatomic Nomenclature

- AP locations is described in the LAO view
- Older algorithms use anatomical descriptions derived from the Valentine heart position & not attitudinally correct nomenclature which can be confusing

⚡️Arruda’s (1997)

- Delta wave polarity determined by measuring the initial 20ms of pre-excitation
- Algorithm based on determining delta wave polarity in leads I, II, AVF and V1, followed by the analysis of R/S ratio in leads III and V1

📰 Simplified 3 step approach:

1. Is AP Left Free wall?

- V1 is able to differentiate L vs R sided in 75% of cases (+ve Delta = L sided, -ve Delta = R sided)

- If V1 is positive, look at lateral leads (I, AVL):

Negative suggests L free wall APs
Isoelectric suggests Posterolat

2. Is AP Postero-septal?

- If at least 2/3 delta waves in II, III, AVF are negative = posters-septal AP

3. Is AP R antero-septal to free wall?

- V1 is -ve
- II, III, AVF +ve (Anterolateral: delta +ve; Posterolateral: delta -ve in at least one inferior lead)