ABSTRACT
Permanent cardiac pacing has been proposed for the treatment of atrioventricular and intraventricular conduction defects and related hemodynamic alterations which may worsen the performance of the failing heart. The initial positive results of right sided atrioventricular synchronous pacing have not been confirmed in later studies involving a larger number of patients with different clinical characteristics. The reason of these conflicting results may be related to the poor understanding of the complex interaction between the adopted pacing mode and the different type, grade and hemodynamic significance of conduction defects. The negative hemodynamic effects of the altered sequence and synchrony of ventricular activation during right sided pacing may outweigh the benefits of an optimal atrioventricular synchrony. Biventricular stimulation has been proposed to improve the electromechanical activation of the left ventricle in patients with left bundle branch block. Ongoing prospective studies are evaluating the potential benefits of biventricular stimulation versus alternative treatments. Although there are no standard indications to cardiac pacing in heart failure it seems that this therapeutic tool may be of value in selected patients with conduction defects which unfavorably affect the cardiac function and that are amenable to be corrected by an appropriate pacing modality. Doppler echocardiography, in its different applications, emerges has a key technique for the selection of patients who may benefit from permanent pacing and for the selection of the best pacing modality. Doppler echocardiography criteria may also be useful in the selection of homogeneous groups of patients to be enrolled in prospective studies aimed at assessing the potential benefits of permanent pacing versus alternative treatments.