30-year old female presenting with sudden onset of palpitations. Normally well. Describe the ECG.
Describe and interpret this ECG
ECG ANSWER and INTERPRETATION
- Regular broad-complex tachycardia.
- No atrial activity seen.
- Typical LBBB morphology in aVR, V1 and V6.
- No obvious diagnostic features for VT — compare this with ECG 047.
However, there is one feature here that is unusual for LBBB, can you spot it?
There is an inferior axis (+90 degrees), which is atypical for Left Bundle branch block. LBBB normally has a leftward axis.
This combination of…
- Broad complex tachycardia with typical LBBB morphology.
- Inferior axis (+90 degrees).
… is suggestive of a specific type of VT known as right ventricular outflow-tract tachycardia (RVOT).
RVOT is a relatively common form of right ventricular VT, occurring in two main groups:
- Patients with structurally normal hearts (= 70% of idiopathic VT).
- Patients with arrhythmogenic right ventricular cardiomyopathy.
It may be very difficult to differentiate RVOT from SVT with LBBB.
Tips for Spotting RVOT
- Suspect RVOT when you see LBBB morphology + inferior axis.
- Record a long rhythm strip looking for fusion and capture beats.
I have diagnosed this only a couple of times in the past. Each time I had to stand by the monitor with my finger on the “print” button waiting for a fusion or capture beat to appear before anyone would believe me!