Abstract 423: Reduction of Wasted Left Ventricular Contractility During Right Ventricular Septal Pacing in Comparison With Apical Pacing
[Background] Right ventricular apical pacing (RVA) creates left ventricular (LV) dyssynchrony, and longstanding RVA occasionally promotes LV dysfunction. RV septal pacing (RVS) is an alternative method to shorten the QRS complex width, which may lessen the degree of LV dyssynchrony in comparison with RVA.
[Aim] This study aimed to clarify the difference of wasted LV contractility between RVA and RVS using the longitudinal strain delay index by speckle tracking imaging.
[Methods] Eighty-two consecutive patients with symptomatic bradyarrhythmia and preserved LV function who were scheduled for permanent pacemaker insertion were included in the analysis. Patients were assigned to two groups according to RV pacing sites (RVA: n = 40, RVS: n = 42). Twenty age- and gender-matched control subjects without cardiac diseases were also included. Echocardiographic equipment was used with GE Vivid 7 Dimension in all the patinets and control subjects, and patients underwent echocardiographic study after pacemaker implantation. The indexes of LV dyssynchrony were estimated as the standard deviation of the time from QRS onset to peak longitudinal strain in 18 LV models using speckle tracking imaging. In addition, the LV longitudinal strain delay index was analyzed as the parameter of wasted contractility, which was estimated by the sum of the differences between the peak systolic and end-systolic longitudinal strain per each segment in 16 LV models.
[Results] The mean QRS width was significantly longer in RVA compared to both the RVS and control subjects (RVA: 161 ms, RVS: 141 ms, P< 0.01 vs RVA; Control: 93 ms, P< 0.01 vs RVA). The LV dyssynchrony index during the RV pacing was found to be significantly greater in RVA compared to both the RVS and control subjects (RVA: 91±22 ms, RVS: 52±14 ms, P< 0.001 vs RVA; Control: 52±12 ms, P< 0.001 vs RVA). In addition, the LV strain delay index was also significantly greater in RVA compared to both the RVS and control subjects (RVA: 38±15 ms, RVS: 23±8 ms, P< 0.001 vs RVA; Control: 22±7 ms, P< 0.001 vs RVA).
[Conclusion] According to the analysis of the longitudinal strain delay index using speckle tracking imaging, RV septal pacing reduces LV wasted energy by attenuating asynchronous wall motion in comparison with apical pacing.