Selective or non-selective high-dose betablockade – evaluation of exercise capacity in children and adolescents with hypertrophic cardiomyopathy

  • Ewa-Lena Bratt, Sahlgrenska Academy, Institute of Clinical Sciences, Department of pediatrics, University of Gothenburg, Sweden
  • Prof Ingegerd Östman-Smith, Sahlgrenska Academy, Institute of Clinical Sciences, Department of pediatrics, University of Gothenburg, Sweden
  • PhD RN Åsa Axelsson, Sahlgrenska Academy, Institute of Health and Care Sciences, University of Gothenburg, Sweden

    • Background
    Hypertrophic cardiomyopathy (HCM) is a common medical cause of sudden death during exercise. High-dose therapy with metoprolol or propanolol reduces risk of sudden death. There is a perception that exercise ability will be drastically curtailed, with non-selective beta-blockade being worse, but on the other hand beta-blockade improves diastolic function in HCM. This study evaluates the exercise capacity in HCM-patients with metoprolol- or propranolol-therapy compared to HCM-patients without treatment.

    Methods
    20 HCM patients have >one year follow-up, 12 in treatment-group (6 metoprolol and 6 propanolol), median age 15 years (range 9-25), and 8 randomised controls, median age 14.5 years (range 7-24), with no therapy but same life-style modifications. Before study entry, and after one year, they underwent incremental bicycle exercise tests with a ramp protocol starting at 1W/kg, with 10W increments each minute. We monitored 12 lead ECG, blood pressure and respiratory rate every minute.

    Results
    Maximum exercise capacity in W/kg in metoprolol-group before treatment, median 2.85W/kg (range 2.2-3.3) was not different from controls, median 2.6W/kg (2.1-3.3; p=0.51). After one year of metoprolol-therapy the median exercise capacity was 2.55W/kg (range 2.1-3.0) and no different from the controls, median 2.4W/kg (1.4-2.9; p=0.51). Maximum exercise capacity in propranolol-group before treatment was 2.65W/kg (2.1-3.8), no different from controls (p=0.79). After one year of propanolol-therapy the exercise capacity was 2.35 W/kg (1.6-2.8), still no different from controls (p=0.95).

    Conclusion
    Neither selective nor non-selective beta-blockade causes significant reduction in exercise capacity in HCM-patients, probably because improvement in diastolic filling increases the stroke volume to compensate.