Simultaneous pacing of both the left and right ventricles to resynchronize ventricular contraction.
Pacing leads are placed in the right and left ventricles to stimulate them both with each lead times to coordinate with electrical activation.
The right atrium is also paced with a short delay in atrioventricular pacing to consistently pace the ventricles.
If native sinus beats reach the ventricles the effect of biventricular pacing is lost.
Does not restore physiologic conduction but it does eliminate delay of electrical activation of the left ventricular free wall seen in left bundle branch block.
Duration of QRS interval on the surface electrocardiogram tends to decrease with biventricular pacing, although the effect does not correlate well with improvement in systolic function.
Mechanical improvements rather than electrical synchrony is the crucial factor in achieving benefit.
Is superior to right ventricular pacing in patients with AV block and left ventricular systolic dysfunction with NYHA classes I, II or III heart failure (Curtis AB et al).
The above BLOCK HF trial revealed biventricular pacing provided superior ventricular rate support compared with traditional right ventricular apical pacing in patients with AV block, mild to moderate heart failure, and abnormal left ventricular systolic function.