AIMS: To analyze the paced QRS duration in various septal positions of the right ventricular leads and with different paced QRS vectors. To use the results to assess parameters suggesting the optimal site for right ventricular pacing. METHODS AND RESULTS: A total of 609 patients with leads implanted in the right ventricular septum were classified using fluoroscopy in the lateral view (the primary pacing site), and in the anteroposterior view (the secondary pacing site), according to the QRS vector in leads I and III. Significantly shortened paced QRS was found in the primary pacing site with the true septal compared with the anteroseptal site, with the vector being negative or isoelectric in lead I plus positive in lead III. In secondary pacing sites, no significant difference in pacing QRS duration was found between RVOT-HS, RVOT-LS, mid-septum and inferior-septum. CONCLUSIONS: For optimization of the pacing site in the ventricular septum, the following are significant: the primary site based on the lateral view, and the paced QRS vector in leads I and III.

Department od Medicine 1st Faculty of Medicine Charles University Prague and Central Military Hospital Prague Czech Republic

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