Dr.S.Venkatesan MD

We expect LBBB in RV pacing . . .but if RBBB is recorded we are worried ! (Often times it may be neither  LBBB nor RBBB )

Is it really a panic situation ?

• Not necessarily. The only issue is septal perforation .It is rare , can be recognised by echo or fluro .
• In true RV apical pacing with tined leads , RBBB  is extremely uncommon .
• If the lead  is fixed  in the septum and para hisian  area ,  there is  definite  possibility of  deviation from typical LBBB pattern . Screwing leads  that faces high septum  or outflow , RBBB  can be noted occasionally.
• The commonest cause for RBBB pattern in RV pacing ,  is due to  screw tip going deeper into septal planes  and activating the fibers of left bundle early .
• For LBBB pattern to occur right  bundle should be morphologically intact .In diffuse CHB  with bilateral bundle branch blocks  the relative contribution ( Impulse conduction ) will determine the QRS morphology . If right bundle is more damaged than left bundle ,RBBB pattern  may prevail  even in the midst of RV pacing !
• In elderly men with sigmoid septum typical LBBBs are not observed.
• Anther plausible mechanism would be , even though RV is paced , the pacemaker current’s  exit route may be from LV side .
• Finally , always  think about coronary  sinus pacing .It is extremely common in blind temporary pacing.

What should we do if we encounter RBBB morphology after PPM ?

• Analyse the ECG meticulosuly for capture or sensing failure .
• Do an echocardiography in RV inflow view.
• Screen the lead by fluroscopy
• Check the pacing  parameters.
• Do a holter if  you are really anxious .

If everything is fine , just forget the RBBB.Don’t split your hair for this apparent paradox. In medicine  impossibilities will always  galore !

This paper from Taiwan would vouch for this