Objective: We sought to determine the effect of long-term right ventricular (RV) pacing on left ventricular (LV) mechanical dyssynchrony in children and young adults with congenital and acquired heart block.
Methods: Eighteen patients aged 19.5±7.0 years with congenital heart block (group I), 9 aged 20.7±11.1 years with acquired heart block post congenital heart surgery (group II), and 15 healthy control subjects (group III) were studied. The LV volumes, ejection fraction, and systolic dyssynchrony index (SDI), as determined by three-dimensional echocardiography, were compared among groups.
Results: Groups I (6.68±2.44%) and II (9.43±4.44%) had significantly greater SDI compared with group III (3.88±0.63%, p=0.011 and <0.001, respectively). The prevalence of LV mechanical dyssynchrony (SDI>5.14%, mean+2SD of controls) in group I and II was 72.2% and 66.7%, respectively. In 27 patients with RV pacing, the LV SDI correlated negatively with LV ejection fraction (r=-0.744, p<0.001). The times-to-minimum regional volume were significantly longer in lateral, posterior, and inferior segments in group I and septal and inferior segments in group II compared with those in group III (p<0.05). Compared to patients without LV dyssynchrony, patients with LV dyssynchrony had lower LV ejection fraction (p<0.001), shorter R-R interval (p<0.001), and tended to have dual chamber pacing (p=0.088), but had similar duration of pacing, QRS duration, and position of pacing wire (epicardial vs endocardial).
Conclusions: Permanent RV pacing in childhood has a negative effect on LV systolic dysfunction through induction of mechanical dyssynchrony, the magnitude and pattern of which differ between congenital and acquired heart block.