Ventricular Pace Suppression Versus Intrinsic Rhythm Support Study

Inclusion Criteria: * Patients over 18 years of age; * Patient has proven informed consent; * Subject with indication of dual chamber pacemaker due to Sinus Node Dysfunction; * Subjects with a dual chamber pacemaker already implanted within six months from enrollment, provided that ventricular pacing percentage ≤ 40% and with the right ventricular lead in the apical position; * Stable medical situation; * Stable geographical situation; Exclusion Criteria: * Permanent or paroxysmal AV block ≥ II; * Permanent Atrial fibrillation/Atrial flutter; * Device Replacement; * Patient with a poor echocardiographic window; * Patient already implanted with the right ventricular lead not in the apical position; * Subjects with a dual chamber pacemaker, implanted later than six months; * Subjects with a dual chamber pacemaker with ventricular pacing percentage ≥ 40%; * Contraindication for DDD(R)-ADI(R) or DDD(R) pacing modes; * VpS or IRSplus algorithm contraindications; * Age \< 18 years; * Life expectancy \< 12 months; * Cardiac surgery planned within the FU period; * Participation to another clinical investigation;