الفهرس 
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Abstract
Cardiac resynchronization therapy (CRT) is one of the most important therapeutic advancements in recent years for patients with heart failure with reduced ejection fraction (HFrEF). Throughout the past two decades, numerous trials and studies have repeatedly illustrated the efficacy of CRT to improve outcomes in carefully selected patients by eliminating the dyssynchrony which results from bundle branch block activation and restore the mechano-energetic efficiency of the heart. During CRT, both the left and right ventricles are stimulated in an attempt to re-coordinate cardiac electrical activation and produce a synchronous and efficient contraction. However, 20% to 40% of patients are non-responders to CRT therapy. Several variables, including cause of HF, pattern of mechanical dyssynchrony, and site of LV pacing, have been investigated as predictors of response.
Whether the right ventricular (RV) lead position may improve the response to CRT is a matter of debate. Apical position is conventional, especially in patients receiving a CRT-defibrillator (CRT-D) but long-term RV apical pacing may adversely affect cardiac function in intracardiac cardioverter defibrillator (ICD) recipients. Alternative RV pacing sites, mainly RV septal, have been recently proposed in CRT recipients.
We have studied the impact of different RV lead positions (apical versus septal) on QRS complex duration and the clinical response (NYHA functional class), we also evaluated the relationship between change of QRS complex duration and the improvement of clinical response, the study enrolled 100 patients presented for routine follow up and programming in electrophysiology clinic of Ain shams university hospitals. The patients divided into two groups, RV apex (RVA)group (n 54) and RV septum (RVS) group (n 46).
The study revealed no significant difference between the two groups regarding the age, sex, risk factors, and pre-CRT implantation parameters (clinical response, ECG and Echocardiography), we stated that there is no significant difference between RVA and RVS group regarding improvement of clinical response (NYHA), QRS complex duration (Delta QRS), and Echocardiographic parameters (LVEF, LVED diameter, and LVES diameter).
There was a significant correlation between delta QRS complex duration and both NYHA class and delta LVEF represented in the form of inverse relationship between delta QRS complex duration and NYHA class in both RVS and RVA groups and direct relationship between delta QRS complex duration and delta EF in both RVA and RVS groups.
In summary, our study concluded that There is no difference between Septal RV pacing in CRT to apical and apical pacing regarding the primary objective of the study regarding clinical outcome, ΔQRS or LV reverse remodelling, thus no recommendation for optimal RV lead position can hence be drawn from this study.
Delta QRS is inversely related to NYHA class (directly related to clinical response) and may be used as an indicator for CRT response.
Based on the result of this study no specific recommendations for optimal RV lead position could be obtained, further larger studies with longer follow up duration should be directed toward assessment of the impact of different RV lead positions regarding the risk of hospitalization due to heart failure, and mortality outcomes.