Objectives Different cardiac site pacing may lead to different changes in the mechanics of left ventricular (LV) function, but how it affects LV rotation and twist is unknown. In this study, we evaluated the acute impact of different cardiac site pacing on LV rotation and twist using two-dimensional speckle-tracking imaging (STI).
Methods Ten dogs were anaesthetised and a 6F introducer sheath was inserted percutaneously into a vein and an artery. A cardiography catheter was placed in the LV chamber for LV pressure monitoring. The steerable pacing electrodes was positioned at different cardiac sites for pacing. LV short-axis images were acquired at the apical and basal level (mitral valve level) during sinus rhythm (SR) and all pacing rhythms. Analysis based on STI was performed offline to compute the rotation, twist, time to peak rotation (TPR), time to peak twist (TPT), and apical-basal rotation delay (rotational synchronisation index, RSI), and then they were compared.
Results Compared to SR and right atrium (RA) pacing, the apical rotation, basal rotation and twist were significantly decreased during pacing at right ventricular apex (RVA), RV outflow tract (RVOT), His bundle (HB), LV apex (LVA), LV septum (LVS), LV lateral (LVL) wall, RARV (RA + RVA), and RVLV (RVA + LVL) (all P < 0.05). The apical rotation, basal rotation and twist decreased significantly at other ventricular pacing sites other than HB (all P < 0.05, except basal rotation at RVA pacing). Apical TPR, TPT, and RSI were significantly longer during pacing at RVA, RVOT, HB, LVA, LVS, LVL, RVLV, and RARV than at RA pacing and SR. The apical TPR and the RSI during HB pacing were shorter than pacing at RVOT and RVA (both P < 0.05). After adjustment of the R-R interval, the basal TPR during SR was shorter than pacing at RVA, RVOT, HB, LVA, LVS, LVL, RVLV, or RARV, and the basal TPR of HB pacing was shorter than pacing at RVLV or LVA (all P < 0.05). The LVESP was lower at SR than at any pacing.
Conclusions Ventricular pacing not only reduced LV rotation and twist acutely, but also prolonged the apical TPR, TPT, and rotational dyssynchrony. RA and HB pacing was better than other ventricular pacings at other sites in terms of acute changes in rotation and twist.