Clinical Resources
Step 1
Absence of an RS complex in all precordial leads (concordance)?
Step 2
R to S interval >100 ms in one precordial lead?
Step 3
Atrioventricular dissociation present?
Step 4
What is the QRS morphology?
Step 5 — RBBB
Morphology criteria present in V1 and V6?
V1: monophasic R, Rr', qR, RS with R>S; V6: rS or QS
Step 5 — LBBB
Morphology criteria present in V1–V2 and V6?
V1/V2: R >30ms, notched S downstroke, R to nadir S >70ms; V6: QR or QS
