Inclusion Criteria:  expectation of permanent right ventricular pacing with atrio-ventricular delay set to 150/180 ms (130/160 resp.) for sensed/paced atrial events during a follow-up, a good quality of images during echocardiography, willingness to attend clinical check-ups in the implanting center for at least two years. life expectancy of at least 2 years  Exclusion Criteria:  planned cardiac surgery or transcatheter aortic valve implantation hypertrophic cardiomyopathy an indication for implantable cardioverter-defibrillator, biventricular implantable cardioverter-defibrillator, or biventricular pacemaker active myocarditis cardiac surgery or coronary revascularization in the last ten days persistent/permanent atrial fibrillation during randomization severe aortic stenosis mitral valvular disease with an indication to intervention.