Abstract 714: Lower Frequency of Worsening Left Ventricular Dyssynchrony and Myocardial Twisting Behavior During Optimal Right Ventricular Outflow Septal Pacing
[Background] Right ventircular apical pacing (RVA) is a traditional pacing method for patients with bradyarrhythmias, but this results in left ventricular (LV) asynchrony and thus occasionally, LV dysfunction. RV outflow tract septal pacing (RVS) is an alternative pacing method used to shorten LV electro-mechanical activation time particularly in cases where the pacing leads are attached to the RV outflow septum.
[Aim] This study was aimed to compare the effect of RV pacing on LV dyssynchrony and myocardial torsional behavior between RVA and RVS.
[Method] Thirty consecutive patients (16 female, 73+/−7 years) with symptomatic sick sinus syndrome without organic heart diseases were included. The patients were assigned into two groups according to the RV pacing sites (RVA: n= 15, RVS: n= 15). The optimal RVS method that was confirmed by fluoroscopic guidance was successfully performed in all the patients. All the patients underwent an echocardiographic study with GE Vivid 7 during AAI- and DDD-mode after the pacemaker implantation. The two indexes of LV dyssynchrony were estimated as follows:
Ts-Diff: max opposing wall delay in 4 LV models using tissue velocity imaging,
Tϵ-SD: standard deviation of time to peak longitudinal strain in 18 LV models using speckle tracking imaging. Myocardial peak torsion and untwisting rate were also evaluated using speckle tracking imaging.
[Results] The mean QRS width during DDD-mode was significantly longer in RVA compared to RVS (RVA: 158 ms, RVS: 134 ms, p< 0.05). Ts-Diff and Tϵ-SD values during the RV pacing were significantly greater in RVA compared to RVS (Ts-Diff: 65+/−45 ms vs 20+/−19 ms, Tϵ-SD: 87+/−20 vs 54+/−14, p< 0.01 for all). In addition, the myocardial torsion and untwisting rate were significantly deteriorated in RVA compared to RVS (torsion: 9+/−3 deg vs 13+/−4 deg, untwisting rate: −73+/−22 deg/s vs −100+/−33 deg/s). Furthermore, the change of Tϵ-SD from AAI- to DDD-mode was significantly associated with that of myocardial torsion in this study population (r= 0.354, p< 0.05).
[Conclusion] The optimal RV outflow septal pacing was shown to be a more effective method compared to RV apical pacing due to the lower frequency of left ventricular dyssynchrony and torsional abnormalities.