[Estimation of cardiac function by plasma concentration of brain natriuretic peptide in patients with Duchenne muscular dystrophy].

We investigated the usefulness of the plasma concentration of brain natriuretic peptide (BNP) for evaluating cardiac function in patients with Duchenne muscular dystrophy (DMD). The plasma BNP concentration was measured by immunoradiometric assay in 55 patients with DMD and in 34 healthy subjects. Cardiac function was evaluated by the cardiothoracic ratio (CTR) on chest roentgenogram, left ventricular end-diastolic dimension (LVDd) and fractional shortening (FS) on echocardiogram, and the ratio of ejection time to pre-ejection period (ET/PEP) on mechanocardiogram. The function of skeletal muscle was evaluated in terms of the disability of lower limb function, serum creatine kinase (CK) activity and % vital capacity (% VC). The plasma concentration of BNP was increased in patients with DMD (32.7 +/- 14.8 pg/ml, mean +/- SEM) compared with that in normal subjects (4.3 +/- 0.5 pg/ml). Two of the DMD patients had symptoms of heart failure, with markedly increased plasma BNP concentrations. The other DMD patients with increased plasma BNP concentrations showed abnormal cardiac function but no symptoms of heart failure. In addition, in patients with DMD, the plasma BNP concentration showed significant positive correlations with CTR and LVDd (p < 0.01), and negative correlations with ET/PEP and FS (p < 0.01). In severe DMD patients who had advanced disability and decreased CK activity, the plasma BNP concentration tended to be elevated. There was no significant correlation between the plasma BNP concentration and % VC. These findings suggest that the plasma BNP concentration is useful for evaluating cardiac dysfunction, whether manifest or latent, in patients with DMD, in whom accurate evaluation of cardiac function by conventional methods is difficult due to severe muscle atrophy and deformity of the thorax.