الفهرس 
AcknowledgementsOnly 14 pages are availabe for public view
 |  | from | 110 |  |  |
| | | from | 110 | | |
Abstract
In our study we aimed to assess the LV systolic function and mechanical dyssynchrony by 2D and RT3D echocardiography in patients with either single or dual chamber pacemakers implanted for not less than one-year duration with normal pre-implantation LV systolic function.Our study was conducted as a cross-sectional observational study over nine-month duration (from April 2018 to December 2018), and included 46 patients with either single chamber pacemaker 28 patients (60.0%) or dual chamber pacemaker 18 patients (39.1%), implanted for a period not less than one-year duration presenting to the pacemaker outpatient clinic of Assuit University Heart Centre who met the study inclusion criteria with normal pre-implantation LV dimensions and EF on conventional echocardiography and no identifiable causes of cardiomyopathy that would hinder them excluded. All patients included in our study were subjected to full history and clinical examination assessing for symptoms and signs of HF, assessment of exercise capacity by standardized six-minute walk test, assessment of pacemaker parameters and lead position as well as 2D and 3D echocardiographic assessment of LV systolic function and dyssynchrony. Studying patients with permanent RV apical pacing either single or dual chamber pacemakers implanted for at least one-year duration with more than 90% RV pacing, showed that despite a normal baseline LVEF, 15 patients (32.6%) developed LV dysfunction while 24 patients (52.2%) had LV mechanical dyssynchrony. All patients having LV dysfunction had concomitant LV mechanical dyssynchrony as well, but not those having dyssynchrony necessarily had concomitant LV dysfunction. Despite being statistically insignificant, yet higher proportion of patients having VVI pacemakers 15 patients (62%) were among the dyssynchronous group than those having a DDD 9 patients (37.5%). Patients having LV mechanical dyssynchrony had significantly higher RV pacing threshold, significantly larger 3D-ESV and hence significantly lower 3D-EF. They also had increased number of delayed segments. Univariate regression analysis revealed that hypertension, presence of HF symptoms, both biplane and 3D EF as well as 3D LV ESV were significant predictors for LV dyssynchrony, with lower 3D LV EF being a significant independent predictor of LV mechanical dyssynchrony on a multivariate logistic regression analysis model.Interestingly, among the different pacemaker parameters, RV pacing threshold showed a significantly moderate negative correlation with 3D LVEF and positive correlation with LV SDI. RV pacing threshold was the only independent predictor of LV mechanical dyssynchrony. Conclusion Permanent RV apical pacing with either single or dual chamber pacemakers is associated with a high prevalence of LV mechanical dyssynchrony. Lower 3D LV EF and high RV pacing threshold were significant independent predictors of LV mechanical dyssynchrony. Whether alternative RV ventricular site or biventricular pacing, with reduction of RV pacing threshold, can prevent LV dysfunction and dyssynchrony in patients requiring long-term pacing needs further investigation.