Association between fibroblast growth factor 23 and left ventricular hypertrophy in maintenance hemodialysis patients. Comparison with B-type natriuretic peptide and cardiac troponin T.

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a novel bone-derived phosphate-regulating hormone, and serum FGF-23 levels are associated with mortality among hemodialysis (HD) patients. However, the pathophysiological role of FGF-23 in those patients remains unclear, so the association between serum FGF-23 levels and known cardiac biomarkers or echocardiographic measurements were investigated in long-term HD patients without cardiac symptoms. METHODS AND RESULTS: The 87 consecutive patients treated in a single HD center (51 males, 36 females; mean age 64 years, mean HD duration 5.8 years) were included in this study. Comprehensive echocardiography was performed after HD. Blood samples were obtained before HD. Serum FGF-23 levels in dialysis patients were 1,171±553pg/ml. In univariate analysis, serum phosphate (r=0.443, P<0.001) and calcium levels (r=0.256, P=0.04), left ventricular mass index (LVMI) (r=0.268, P=0.039) were significantly associated with FGF-23 levels. Neither the B-type natriuretic peptide (BNP) nor the cardiac troponin T level was correlated with FGF-23. In multivariate regression analysis, only LVMI (ß=0.287, P=0.031, confidence interval (CI) 0.390-8.040) and phosphate levels (ß=0.419, P=0.001, CI 57.12-207.7) and calcium levels (ß=0.277, P=0.025, CI 24.95-360.1) remained significantly correlated with FGF-23. CONCLUSIONS: Beside BNP, FGF-23 was identified as a factor that is significantly associated with LVMI. FGF-23 could be a novel biomarker of left ventricular overload, which is closely associated with the increased risk of death in HD patients.

Parametric detection and measurement of perfusion defects in attenuated contrast echocardiographic images.

OBJECTIVE: Attenuation of radio frequency (RF) signals limits the use of contrast echocardiography. The harmonic-to-fundamental ratio (HFR) of the RF signals compensates for attenuation. We tested whether HFR analysis measures the left ventricular nonperfused area under simulated experimental attenuation. METHODS: Radio frequency image data from short axis systolic projections were obtained from 11 open-chest dogs with left anterior descending or left circumflex coronary artery occlusion followed by left atrial bolus injection of a perflutren microbubble contrast agent. Clinical attenuation was simulated by calibrated silicone pads interposed between the epicardial surface and the transducer to induce mild (7-dB) and severe (14-dB) reduction of the backscattered RF signals. Harmonic-to-fundamental ratio values were calculated for each image pixel for 0-, 7-, and 14-dB attenuation conditions and reproducibly showed a "perfused area" and a "nonperfused area." A reference nonperfused area was obtained by manual delineation in high-quality contrast scans. RESULTS: Correlations of the HFR-detected and manually outlined perfusion defect areas were R = 0.92 for 0 dB, R = 0.94 for 7 dB, and R = 0.90 for 14 dB; the mean difference was less than 0.36 cm(2) (negligible) in all 3 attenuation settings. Conclusions. Attenuation compensation by our HFR method allows precise measurement of myocardial perfusion defect areas in contrast scans with simulated high level of attenuation.