PACING SITE SELECTION BASED UPON TRANS-VALVULAR IMPEDANCE RECORDING

Background:  Trans-Valvular Impedance (TVI) is derived between right atrium and ventricle with either tip or ring electrodes. The study was aimed at comparing TVI properties in apical (RVA) versus septal position (IVS), to test the hypothesis that TVI could be helpful in the selection of the optimal pacing site.

Methods: TVI was recorded in 17 patients, on implantation of the dual-chamber pacemaker Sophòs 155 (Medico, Padova, Italy) with active fixation pacing leads. At least two different ventricular positions were tested in each patient before the final placement.

Results: A physiological TVI waveform (increasing throughout the QT and decreasing during passive and active filling) was recorded in 16/17 cases in IVS and 15/17 cases in RVA. The two patients who did not show a normal TVI waveform in both positions also had the poorest pump performance in the group (35 and 40% LVEF). With intrinsic AV conduction, TVI excursion from diastole to systole was higher in RVA than IVS if the signal was recorded with the tip ventricular electrode (67±38 and 41±11 Ohm, respectively), while no difference was observed using the ring (31±21 vs 35±15 Ohm). TVI waveform deterioration (amplitude reduction and extra-peaks in the QT) was more frequently observed with RVA than IVS pacing (75 vs 50% and 38 vs 17% of cases, respectively, with V-tip and V-ring TVI recording).

Conclusions: Right ventricular midseptal pacing was less detrimental to ventricular mechanics comparing to the right ventricular apical lead position. IVS pacing should be performed as a standard approach esp. in patients with already impaired left ventricular systolic function.