Adrenergic Receptor Polymorphism and Maximal Exercise Capacity after Orthotopic Heart Transplantation.

ABSTRACT

BACKGROUND: Maximal exercise capacity after heart transplantion (HTx) is reduced to the 50-70% level of healthy controls when assessed by cardiopulmonary exercise testing (CPET) despite of normal left ventricular function of the donor heart. This study investigates the role of donor heart ß1 and ß2- adrenergic receptor (AR) polymorphisms for maximal exercise capacity after orthotopic HTx. METHODS: CPET measured peak VO2 as outcome parameter for maximal exercise in HTx recipients ≥9 months and ≤4 years post-transplant (n = 41; mean peak VO2 57±15% of predicted value). Donor hearts were genotyped for polymorphisms of the ß1-AR (Ser49Gly, Arg389Gly) and the ß2-AR (Arg16Gly, Gln27Glu). Circumferential shortening of the left ventricle was measured using magnetic resonance based CSPAMM tagging. RESULTS: Peak VO2 was higher in donor hearts expressing the ß1-Ser49Ser alleles when compared with ß1-Gly49 carriers (60±15% vs. 47±10% of the predicted value; p = 0.015), and by trend in cardiac allografts with the ß1-AR Gly389Gly vs. ß1-Arg389 (61±15% vs. 54±14%, p = 0.093). Peak VO2 was highest for the haplotype Ser49Ser-Gly389, and decreased progressively for Ser49Ser-Arg389Arg > 49Gly-389Gly > 49Gly-Arg389Arg (adjusted R2 = 0.56, p = 0.003). Peak VO2 was not different for the tested ß2-AR polymorphisms. Independent predictors of peak VO2 (adjusted R2 = 0.55) were ß1-AR Ser49Gly SNP (p = 0.005), heart rate increase (p = 0.016), and peak systolic blood pressure (p = 0.031). Left ventricular (LV) motion kinetics as measured by cardiac MRI CSPAMM tagging at rest was not different between carriers and non-carriers of the ß1-AR Gly49allele. CONCLUSION: Similar LV cardiac motion kinetics at rest in donor hearts carrying either ß1-AR Gly49 or ß1-Ser49Ser variant suggests exercise-induced desensitization and down-regulation of the ß1-AR Gly49 variant as relevant pathomechanism for reduced peak VO2 in ß1-AR Gly49 carriers.