Metoprolol therapy in patients with Eisenmenger syndrome (MINES) study. A single-centre, double-blinded, randomised, placebo-controlled trial

Abstract Background Prevalence of Eisenmenger syndrome is still common in developing countries where early neonatal screening and referral for surgery is seldom possible. Limited number of drugs are available for treatment of this condition. Beta-blockers may improve functional status in these patients. Observational study has shown beta blockers to be safe and effective in improving effort intolerance in patients with Eisenmenger syndrome. Purpose To study the safety and efficacy of metoprolol succinate therapy in patients with Eisenmenger syndrome. Methods In this double-blind, placebo-controlled study, we randomly assigned 60 patients with Eisenmenger syndrome to receive placebo or to receive 25 mg of metoprolol succinate once daily for 2 weeks followed by 25 mg twice daily for 14 weeks (total of 16 weeks). The primary outcome was mean difference in 6-minute walk test (6MWT) distance. Secondary outcomes were clinical composite outcome (all-cause death, heart failure hospitalization, worsening of heart failure, change in WHO functional class, and new onset syncope), change in resting saturation, Tricuspid Annular Plane Systolic Excursion (TAPSE) and NT Pro BNP level at 16 weeks. Results At 16 weeks, the mean difference in 6MWT distance between treatment group and placebo group as per protocol analysis was 6 meters (95% confidence interval, - 7.43 to 19.49; P 0.37), and the mean difference in 6MWT distance as per intention to treat analysis was -1.1 meters (95% confidence interval, - 16.97 to 14.77; P 0.89). Clinical composite outcome occurred more in the treatment group 5(17%) as compared to the placebo group 1(3%) (P 0.197) though it did not reach statistical significance. This was primarily driven by worsening of heart failure in the treatment group. Compared to baseline metoprolol group had 37% increase in NT pro BNP level while placebo group had 13% (-313.69, 88.80) reduction in NT Pro BNP level. There was no difference in TAPSE 0.05 (95% confidence interval -0.62 to 0.72; P 0.88) or resting saturation -0.06 (95% confidence interval -0.88 to 0.75; P 0.87) between the two groups at 16 weeks Conclusion Metoprolol succinate therapy did not improve 6-minute walk distance at 16 weeks among patients with Eisenmenger syndrome compared to placebo. Metoprolol succinate therapy was associated with increased clinical composite outcomes, primarily driven by worsening of heart failure.Graphic Abstract of MINES study