Assessment of Ventricular Dissynchrony in Right Ventricular Single Chamber Pacing using Echocardiografic Parameters

Background: Right ventricular apical pacing has been used since the early years of pace-makers, despite the fact that it determined nonphysiological ventricular depolarization. As medical technologies developed, septal lead implantation became feasible, in order to outrun the above mentioned inconveniences. The question whether the apical or septal lead position is better still gives rise to a lot of controversies. Different echocardiographic parameters are currently used to assess the impact of specific sites of stimulation on ventricular function. The aim of the study was to determine which of the followed synchronicity parameters varied significantly during apical stimulation, compared to septal stimulation in patients requiring single chamber pacing.
Material and method: Fifty-nine patients admitted between January 1st – December 31st 2012 either for battery replacement or for first implant of a single chamber pace-maker were included in this prospective study. Thirty-eight of them had the lead placed in the apex of the right ventricle and 21 on the interventricular septum. All were subjected to echocardiografic examination after device implantation. Measurements included complete chamber and valvular assessment, apart from the synchronicity evaluation, that comprised interventricular mechanical delay (IVMD), septal to posterior wall delay (SPWMD) and electro systolic delays (ESD), in order to assess the presence and compare the relevance of interventricular and intraventricular dissyncrony. All the investigations were in accordance with the Declaration of Helsinki.
Results: Although preejection times were significantly different, there were no statistically significant differences (p = 0.06) between the values of IVMD in the two groups, as well as regarding the longitudinal intraventricular dyssynchrony expressed by ESD. Significant differences appeared though, between the values of SPWMD, reflecting the fact that radial intraventricular dissyncrony is present in apical stimulation.
Conclusions: During apical right ventricular pacing, radial intraventricular dissyncrony appears, while in the case of septal pacing this parameter is close to normal. Surprisingly, although right ventricular pacing determines interventricular and longitudinal intraventricular dissincrony, we found no significant differences in this respect, between apical and septal pacing.