An Even More Physiological Pacing: Changing the Sequence of Ventricular Activation

Summary

Physiological pacing includes preservation of A -V sequential stimulation and adaptation of heart rate to body requirements. However the sequence of ventricular activation (VA) is also important. In four patients with aortic valvular disease, LBBB and HV ~ 70 msec a Medtronic Versatrax DDD pacemaker was implanted at the time of aortic valve surgery. The ventricular electrode was placed in the free wall of the LV. With ditTerents pulse generator A-V intervals (PG-A V), we obtained: A) LBBB morphology when PG-AV was > A-V conducted interval (C-AV); B) “RBBB” morphology when PG-A V < C-A V, and C) intermediate (“fusion”) morphology when PG-A V ⋍ CAV. A mean delay of 70 ± 5 msec between beginning of the spontaneous activation of RV and arrival of stimulation to ventricular electrode in LV favoured these fusion beats. The sequence of mechanical ventricular emptying was non-invasively assessed by radioisotopic (Tc-99 m Pyp labelled red blood cells) study of the “wave of emptying” and of phase histograms, using the Fourier’s analysis. The most “normal” pattern was found in C. LV ejection fraction (radioisotopic cineangiogram) was 0.59 ± 0.035 in C versus 0.51 ± 0.047 in B (p < 0.001) and 0.47 ± 0.045 in A (p < 0.001). We conclude than an appropriate placement of ventricular electrode besides a correct programation of A-V delay in DDD pacemakers allows for a more synergistic ventricular activation in patients with LBBB, improving their ventricular performance.