Conventional right ventricular apical pacing may result in asynchronous ventricular contraction with delayed left ventricular activation, interventricular motion abnormalities, and worsening of left ventricular ejection fraction. His pacing is preserving a synchronous contraction and may prevent a decrease in left ventricular ejection fraction.~The aims of our crossover, double-blinded, randomized study is to evaluate the feasibility and long-term safety of permanent His pacing and to compare the effects on left ventricular ejection fraction of permanent His pacing with those of conventional right septal stimulation after 12 months treatment in patients with 2nd or 3rd degree AV-block.
Conventional right ventricular (RV) apical pacing may result in asynchronous ventricular contraction with delayed left ventricular activation, interventricular motion abnormalities, and worsening of left ventricular ejection fraction. His pacing is preserving a synchronous contraction and may prevent a decrease in left ventricular ejection fraction.~Hypothesis: His-pacing preserves left ventricular function and is a feasable alternative compared to RV septal septal pacing in patients with AV-block.