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- 60 bpm
- Regularly irregular
- Alternating Atrial (A) and Ventricular (V) pacing
- LAD for both A-paced & V-paced complexes
- QRS - Prolonged (160-180ms)
- Discordant ST segment and T wave changes
- Native ventricular complexes are Sgarbossa negative
Additional:
- A-pacing associated with native LBBB ventricular morphology
- V-pacing associated with RBBB morphology
- Frontal QRS axis ~-75 degrees with transition at V6
Interpretation:
- Alternating A & V pacing
- Native LBBB
- V-paced rhythm associated with RBBB morphology
Is RBBB morphology during right ventricular pacing always due to lead malposition ?
The short answer to this is no. There are cases in which an RBBB morphology can occur with appropriate right ventricular apical pacing.
In this case the patient had a chest x-ray which showed appropriate lead placement, for an example of RBBB morphology associated with lead malposition check out this case here.
Features which may assist in differentiating between lead malposition and correct placement are:
- Frontal plane axis
- Precordial transition point
- Repositioning of leads V1-2
I would recommend the following freely available papers which both include a review of RBBB morphology during right ventricular pacing.
- Erdogan O, Aksu F. Right bundle branch block pattern during right ventricular permanent pacing: Is it safe or not? Indian Pacing Electrophysiol J. 2007 Aug 1;7(3):187-91. PMID: 17684578 Full text here
- Almehairi M, Baranchuk. Right Bundle Branch Block Morphology During Apical Right Ventricular Pacing. The Journal of Innovations in Cardiac Rhythm Management, 4 (2013), 1303–1304. Full text here
References / Further Reading
Life in the Fast Lane
Textbook
- Chan TC, Brady WJ, Harrigan RA, Ornato JP, Rosen P. ECG in Emergency Medicine and Acute Care. Elsevier Mosby 2005.
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