Introduction:

Studies to determine usefulness of QRS duration and its dispersion in patients undergoing permanent cardiac pacing from different sites are scarce. A objective was to demonstrate the relationship between mechanical synchrony of the heart evaluated by echocardiography with QRS dispersion in patients with cardiac pacing stimulated from different cardiac sites.

Methods:

Three groups were studied. First group: 82 patients submitted to right ventricular apical pacing; second group, 27 patients with systolic dysfunction secondary to right ventricular apical pacing taken to high septal pacing. Third group: 19 patients undergoing cardiac resynchronization therapy. Electrocardiographic and echocardiographic variables were studied to determine if there is electromechanical synchrony relationship.

Results:

First group: QRS duration and its dispersion showed significant increases correlation when decreases left ventricular ejection fraction at follow-up. Second group: Ejection fraction increased from 31% ± 3,1% to 45% ± 12% (p = 0,0041) with septal pacing; this showed a better degree of mechanical synchrony when it was evaluated by echocardiography, with significant and inverse correlation between QRS dispersion and ejection fraction. Third group: Linear correlation between ejection fraction and QRS dispersion at six months of follow-up was significant (r = 0,34 and p = 0,02); women showed greater QRS dispersion (48,0 ± 24,0 vs. 37,14 ± 13,8) ms; p = 0,04 and better response to resynchronization. As some conclusions right ventricular apical pacing is related to cardiac contractile deterioration; increased QRS dispersion could be an electrocardiographic variable to predict a decreased left ventricular ejection fraction. Patients underwent septal stimulation improved electromechanical synchrony; decreased QRS dispersion could predict this improvement. Finally, decreased QRS dispersion may predict a good response to resynchronization therapy.

        · resumo em Espanhol     · texto em Espanhol     · Espanhol ( pdf )