Biventricular pacing is an excellent option for certain patients with advanced heart failure. Also known as “cardiac resynchronization therapy”, biventricular pacing has been shown to improve heart failure symptoms in a majority cases. The normal cardiac conduction system delivers the electrical impulse to both the right and left ventricles simultaneously, however in the presence of a left bundle branch block (LBBB) or right bundle branch block (RBBB), the electrical impulse will reach one ventricle first then slowly transmit to the other causing “cardiac dyssynchrony”. Remember that a LBBB and RBBB by definition prolong the QRS duration.

The indications for biventricular pacing are below:

1. Left ventricular ejection fraction < 35%, a QRS duration of > 120 ms and New York Heart Association (NYHA) functional class III or IV with optimal medical therapy.

2. Left ventricular ejection fraction < 35% and frequent reliance on right ventricular pacing (which significantly prolongs the QRS duration).

3. Left ventricular ejection fraction < 35% and NYHA functional class I or II who are undergoing pacemaker or implanted cardioverter defibrillator (ICD) insertion and may rely on frequent cardiac pacing.

*Note: Meta-analysis has shown a mortality benefit for those patients with a QRS duration of > 150 ms who receive biventricular pacing and not those with a QRS duration < 150 ms.

*Note: Many patients who are candidates for biventricular pacing also receive an implanted cardioverter defibrillator (ICD) at the same time.