N-TERMINAL PRO BRAIN NATRIURETIC PEPTIDE PREDICTS EXERCISE TOLERANCE IN HEART TRANSPLANT RECIPIENTS

The diagnostic value of N-terminal pro-brain natriuretic peptide (NT-proBNP) after heart transplantation (HTx) is still incompletely understood. As certain graft factors (eg. diastolic dysfunction) may affect both, cardiac synthesis of BNP and functional performance) we hypothesized a relationship between exercise variables and NT-proBNP levels after HTx.
Patients and Methods: 105 asymptomatic HTx recipients (92 m, 13 f; aged 59±10 yrs; donor age 33±11 yrs; 88±52 months after HTx; body mass index 27±4 kg/m2; cyclosporin/sirolimus/tacrolimus 68/19/13%) were studied. From 2004 april to 2005 june 120 graded symptom-limited bicycle exercise tests and NT-proBNP assays (by Roche Diagnostics) were performed
Results: Mean exercise tolerance was 74±17 percent predicted normal (0-49%: n=10; 50-69%: n=37; 70-84%: n=38; 85-115%: n=35). Peak systolic blood pressure and heart rate were 184±27mmHg and 140±19 bpm, respectively. Median resting NT-proBNP level was 282 pg/ml (25th – 75th percentile 132-584; range 29 – 4143 pg/ml). Log-transformed NT-proBNP levels correlated inversely with exercise tolerance (r= - 0.23; p=0.011), peak systolic blood pressure (r= - 0.38, p=0.0001) and peak heart rate (r= - 0.25; p=0.004) and directly with time after HTx (r= +0.30; p=0.001). 
Conclusion: Our data –confirming  earlier results of a time dependent rise in NT-proBNP levels late after HTx- demonstrate that increased endocrine activity of the transplanted heart is associated with limited exercise tolerance, and hence, corresponding key exercise variables. By that a role of myocardial versus extracardiac factors in limiting fitness in HTx recipients is suggested.