Plasma TMAO, Cardiac Biomarkers in Hospitals

Peripheral blood samples were collected before heparinization using vacutainer tubes containing ethylenediamine tetra-acetic acid, maintained at 4°C and processed within 3 h. Then, plasma samples were stored at −80°C and thawed once for analysis. Plasma levels of TMAO were quantified by stable isotope dilution high performance liquid chromatography with online tandem electrospray ionization mass spectrometry using an API 3200 triple quadrupole mass spectrometer (AB SCIEX, Framingham, MA) with a d9-(trimethyl)-labeled internal standard as described previously (37 (link)). In addition, cardiac troponin I (cTnI) and NT-proBNP were measured as routine biochemical work-up during the hospital stay. As a standard care, cTnI was measured at least 3 times within 24 h after admission and daily until normalization and then every 2 days before discharge; NT-proBNP was measured on admission, immediately after and on the second day after the index procedure and then up to physicians. Results of cTnI and NT-proBNP during hospitalization were retrieved from electronic medical records and baseline values and peak values were reported.