Assessment of left ventricular electromechanical activation during right ventricular apical and outflow tract pacing

Background: Right ventricular (RV) apical pacing, induces asynchronous ventricular contraction and impairs cardiac function. Alternative sites of pacing particularly right ventricular outflow tract (RVOT) may have a more favorable hemodynamic profile, physiological left ventricular (LV) activation and normal ventricular contraction pattern. The Aim of the study was to find out the best alternative sites to RV apex for permanent pacemaker (PM) lead fixation in the RVOT, based on the width of the QRS in the surface ECG. Patients and methods: The study included 69 patients with pacemaker-dependent complete heart block; 35 with active pacemaker lead fixation in the site which achieved narrowest max. QRS duration in the RVOT (group 1) and 34 with active pacemaker lead fixation in RV apex (group 2). Results: High RVOT septum was the site which achieved the narrowest QRS duration on surface ECG (117.86 +/- 8.43 ms) when compared with RV apex (140.29 +/- 13.14) (p < 0.001). There was a marked LV asynchrony after 3 months in group 2; IVMD (51.67 +/- 14.06 ms), LVPEP (191.55 +/- 36.56 ms), RVPEP (142.45 +/- 23.11 ms) and SPWMD (125.64 +/- 34.15 ms) when compared to group 1; IVMD (26.93 +/- 12.44 ms), LVPEP (107.32 +/- 45.28 ms), RVPEP (76.11 +/- 27.66 ms) and SPWMD (78.15 +/- 36.45 ms) (p < 0.001). Tissue Doppler Imaging revealed marked difference on the opposing LV segments mainly between mid-septal and mid-lateral in group 2. The 6 MWT was much better in group 1 patients (473 +/- 240 m) than in group 2 patients (308 +/- 221 m) (p < 0.001). Conclusion: High RVOT septum is the ideal site for PM lead implantation. Compared with RV apical pacing, it is associated with improvement in functional and hemodynamic parameters over medium-term follow-up. (C) 2016 Egyptian Society of Cardiology. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.