Abstract 241: Asynchronous Twist During Right Ventricular Pacing-Comparison Between Apical and Septal Pacing
Background: Right ventricular apical pacing (RVA) causes left ventricular (LV) electromechanical dyssynchrony. Experimental studies have demonstrated that LV dyssynchrony induced by RVA may alter normal physiological twist. However, rotational dynamics during RV pacing have not been fully studied in a clinical setting.
[Aim] This study aimed to elucidate the rotational alterations such as twist, asynchronous rotation and untwisting rate in patients receiving RV apical and septal pacing (RVS).
Methods: Seventy-three consecutive patients with symptomatic bradyarrhythmias and preserved LV function who were scheduled for permanent pacemaker insertion were included. Patients were assigned to two groups according to RV pacing sites (RVA: n= 35, RVS: n= 38). Twenty age- and gender-matched control subjects were also included. All the patients underwent an echocardiographic study with GE Vivid 7 Dimension after the pacemaker implantation. The LV twist and the untwisting rate were estimated using speckle tracking imaging. The global twist gap was also evaluated as the parameter of asynchronous rotation, which was defined as the standard deviation of the QRS onset to peak rotation in 12 LV segments from both basal and apical short axial views.
[Results] The mean QRS width was significantly longer in RVA compared to both the RVS and control (RVA: 161 ms, RVS: 142 ms, P< 0.01 vs RVA, Control: 93 ms, P< 0.01 vs RVA). The LV twist, global twist gap and untwisting rate during the RV pacing were significantly worse in RVA compared to both the RVS and control (Twist: RVA 7±3 degrees, RVS 14±5 degrees, P< 0.05 vs RVA; Control 13±5 degrees, P< 0.05 vs RVA; Twist gap: RVA 85±45 ms, RVS 53±35 ms, P< 0.05 vs RVA; Control 53±28 ms, P< 0.05 vs RVA; Untwisting rate: RVA −85±37 degrees/sec, RVS −116±45 degrees/sec, P< 0.05 vs RVA; −107±31 degrees/sec, P< 0.05 vs RVA). In addition, the degree of LV twist and the magnitude of the global twist gap were significantly associated with the untwisting rate among 73 patients receiving RV pacing (Twist: r= 0.572, Twist gap: r= 0.549, P< 0.0001 for both).
Conclusion: RV septal pacing preserved the physiological LV twist and synchronous rotation compared to RV apical pacing, which were proportionately associated with better untwisting properties.