Beta-blockers in i-PAH

The main question of this study is: \'Is selective beta-blocker treatment safe and effective in reducing sympathetic overdrive, thereby improving RV function and remodeling in patients with iPAH?\'. In addition to the determination of RVEF, the investigators will explore how beta-blocker therapy affects sympathetic overdrive, remodeling of the RV, single beat elastance, exercise capacity and mechanical efficiency. 30 iPAH patients will be randomized to either Bisoprolol- or placebo-treatment in a double-blinded fashion. A cross-over trial design will be used to increase the power of the study and to assess long-term effects of Bisoprolol-treatment and -withdrawal. The medication will be given in an escalating dose regimen (as described in the \'farmacotherapeutisch kompas\', www.fk.cvz.nl) and treatment will be monitored along the guidelines of the American Heart Association.