Protocol pre-specified interim analysis showed that difference between groups was too small to reach significance.

Right ventricular apical pacing in patients treated with a pacemaker is unnecessary in cases where patients have stable atrioventricular (AV)-conduction. Recent findings demonstrate that pacing even might have unfavourable effects, especially if patients suffer from additional cardiac diseases such as heart failure. The Search AV+ algorithm was designed to avoid ventricular pacing and support intrinsic AV-conduction in order to avoid possible detrimental effects of right ventricular apical pacing. The goal of the EnTRINSIC study is to assess the amount of ventricular stimulation, the amount of hospitalizations, the occurrence of atrial fibrillation and the usage of drugs in patients treated with pacemakers with an activated Search AV+ algorithm versus patients treated with an individual optimization of the pacemaker settings to minimize the amount of right ventricular pacing.

Inclusion Criteria:

• Patients with sinus node disease and an intrinsic AV delay of maximal 260 ms
• Patients treated with a Medtronic pacemaker with Search AV+ algorithm

Exclusion Criteria:

• Patients with documented persistent atrial fibrillation within 6 months before implantation and slow AV-conduction
• New York Heart Association (NYHA) III/IV
• Instable angina pectoris
• Heart valve vitium
• Persistent AV-block II and III
• Early diastolic mitral regurgitation
• Implantable cardioverter defibrillator
• Participation in other clinical studies
• Pregnancy or unreliable birth control
• AV-block under strain