IntroductionDegenerative mitral regurgitation (MR) results in left ventricular (LV) volume overload and LV dysfunction that contributes to prognosis [1]. RV function is also prognostically important [2]: tricuspid annular plane systolic excursion (TAPSE), a measure of systolic annular descent, is correlated with RV ejection fraction (RVEF) [3] and predicts survival after mitral valve repair [4].In patients with LV systolic dysfunction, beta-blockade improves prognosis [5] and reverses adverse LV remodelling [6], potentially mediated through a long-term reduction in myocyte strain, also seen with MR-related chronic LV volume overload [7]. Recently, we reported that short-term beta-blocker treatment did not change MR volume but decreased LV work in patients with moderate-severe MR [8]. The aim of this study was to investigate the influence of short-term beta-blocker on RV. Patients and MethodsThe methods have been reported elsewhere [8]. Briefly, patients with moderate-severe MR, normal LV systolic function (echo LV ejection fraction >55%) and sinus rhythm were recruited into this double-blind, randomised, crossover