Right Ventricular Lead Placement in a Pacemaker Population: Evaluation of Apical and Alternative Position

Permanent cardiac pacing plays an important role in cardiac disease management. Since early studies on right ventricular pacing, apex has been the preferred implant site for transvenous endocardial ventricular leads for several reasons: ease of placement, lead stability as well as the design characteristics of the electrode and the fixation system. It is now also accepted, however, that right ventricle pacing causes a long term deterioration of left ventricular function through complex effects, both at the structural level of the heart wall and at the hemodynamic level in left ventricular load conditions. It is possible that this deterioration is due to a dyssynchrony of contraction induced by pacing at the right ventricular apex. Some authors suggest to pace the right ventricle at alternative sites, i.e. the medium septum (RVS) region, to guarantee a more physiological activation pattern, especially in patients expected to receive high pacing percentages. However, unequivocal evidences that stimulation of the right ventricular septum is more physiological than the apical pacing are still missing. Nonetheless, it should be noted that, although a number of studies refer to RV septum as the alternative site for pacing , poor attention has been paid to the unambiguous definition of RV septum region itself. A clear definition and a proper evaluation of the alternative site is therefore important. Furthermore, from a procedural point of view, it has been demonstrated that acute and chronic electrical performances of the leads positioned at alternative sites, in particular in the region of mid septum, are equivalent to those of the leads positioned at the apical site. The purpose of this study is to perform a comprehensive assessment of the electrical and mechanical measures obtained by pacing standard RV site (Right ventricular apex, RVA) and alternative RV site (right ventricular septum, RVS). Specifically, the two pacing sites will be compared in terms of electrical dyssynchrony, as assessed by ECG criteria, and in terms of mechanical dyssynchrony, as assessed by echocardiographic criteria. The primary end point of the study is defined through the evaluation of dyssynchrony measured both in spontaneous rhythm (Vs) and paced rhythm (Vp). The delay between the time to peak systolic velocity of the septum and the LV free wall will be used to define the degree of dyssynchrony; this measurement will be obtained by TDI echocardiographic technique. Patients will receive any commercially available dual-chamber implantable pacemakers, according to current standard indications. At the end of the implantation and at follow-up visits (12 and 24 months) device programming will follow the clinical practice of the center.