Objectives: Left ventricular function and synchrony may be altered by right ventricular (RV) apical pacing. Septal pacing might be a better alternative. We compared effects on cardiac synchrony and function, between the 2 pacing sites, in chronically implanted patients.
Material and methods: 40 pacing-dependent patients (74±9 years, 21 men), 20 paced at the apex, were studied 11±4 months after implantation (baseline); 32 of them were re-examined after 1 year. Systolic function was assessed from ejection fraction (EF), cardiac index (CI), mean longitudinal systolic strain (MLSS), and strain rate (MLSR); diastolic function from E/A, E/E', and E/Vp ratios. Intraventricular dyssynchrony from standard deviation (SSD) and maximal difference (MAXS) of the 12 LV myocardial systolic timings, and sum of all times from the aortic valve closure to peak strain (SUMTAVC) for those segments with post-systolic shortening; interventricular synchrony from the aorto-pulmonary delay (APD).
Outcomes: Four patients died, all of them from the apical group. NYHA functional class was not different. Cardiac synchrony was not significantly different between the two pacing sites at baseline, and after 1 year follow-up. Although at baseline there was a greater dyssynchrony for the septal site, this did not progress at follow-up, whereas this increased for the apical site. Meanwhile, there was a higher LV filling pressure (E/E' ratio) for the apical site at 1 year (13±6 vs.18±6; p=0.04).
Conclusions: Both septal and apical pacing sites affect negatively LV mechanical activation timings and synchrony. Apical, but not septal site, affects LV synchrony at 1 year, associated with increased filling pressure.
Keywords: dyssynchrony; left ventricular function; septal pacing.