Data collection
Data were obtained on clinical history, and venous blood samples at the
time of echocardiography. In the hospital, values for eGFR, a measure of
glomerular filtration function, were calculated using the Chronic Kidney
Disease Epidemiology Collaboration Formula, and serum brain natriuretic
peptide (BNP) levels were measured by an enzyme immunoassay (E test
TOSOH II (BNP), TOSOH Corporation, Tokyo, Japan) with a coefficient of
variation <15%.