This study is a long-term, prospective, and controlled evaluation of the mechanical dyssynchrony induced by right ventricular apical pacing, both in acute (spontaneous and stimulated) and chronic (12 and 24 months); the study also evaluates the benefit of an alternative pacing site through measures of dyssynchrony in acute and chronic.

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.

Inclusion Criteria:

• indication for a dual chambers cardiac pacemaker device (DDD/DR) according to current guidelines
• Patients who are able to understand and sign an informed written consent
• Patients who will conduct the follow-up in the center for at least 24 months
• Patients age ≥ 18

Exclusion Criteria:

• Patients with chronic atrial fibrillation or atrial arrhythmias not controlled within 90 days before enrollment
• Pre-existing permanent cardiac pacemaker (PM), defibrillator (ICD) or cardiac resynchronization therapy device (CRT)
• Unplanned or emergency access to the hospital and / or inability to measure the dyssynchrony for the absence of spontaneous rhythm
• Patients participating in other studies that clearly impact the clinical practice of the center or whose protocol would conflict or affect the outcome of this study
• Patient not expected to survive for the duration of the study follow-up due to co-morbid medical condition