High-Sensitivity Cardiac Troponin Concentrations in Patients with Chest Discomfort: Is It the Heart or the Kidneys As Well?

BACKGROUND: High-sensitivity cardiac troponins (hs-cTn) are the preferred biomarkers to detect myocardial injury, making them promising risk-stratifying tools for patients with symptoms of chest pain. However, circulating hs-cTn are also elevated in other conditions like renal dysfunction, complicating appropriate interpretation of low-level hs-cTn concentrations. METHODS: A cross-sectional analysis was performed in 1864 patients with symptoms of chest discomfort from the cardiology outpatient department who underwent cardiac computed tomographic angiography (CCTA). Serum samples were analyzed using hs-cTnT and hs-cTnI assays. Renal function was measured by the estimated glomerular filtration rate (eGFR), established from serum creatinine and cystatin C. On follow-up, the incidence of adverse events was assessed. RESULTS: Median hs-cTnT and hs-cTnI concentrations were 7.2(5.8-9.2) ng/L and 2.6(1.8-4.1) ng/L, respectively. Multivariable regression analysis revealed that both assay results were more strongly associated with eGFR (hs-cTnT:stß:-0.290;hs-cTnI:stß:-0.222) than with cardiac imaging parameters, such as coronary calcium score, CCTA plaque severity score and left ventricular mass (all p<0.01). Furthermore, survival analysis indicated lower relative risks in patients with normal compared to reduced renal function for hs-cTnT [HR(95%CI), 1.02(1.00-1.03) compared to 1.07(1.05-1.09)] and hs-cTnI [1.01(1.00-1.01) compared to 1.02(1.01-1.02)] (all p<0.001). CONCLUSION: In patients with chest discomfort, we identified an independent influence of renal function on hs-cTn concentrations besides CAD, that affected the association of hs-cTn concentrations with adverse events. Estimating renal function is therefore warranted when interpreting baseline hs-cTn concentrations.

The value of clinical and laboratory diagnostics for chest pain patients at the emergency department.

BACKGROUND: The focus during the diagnostic process for patients with acute chest pain is to discriminate patients who can be safely discharged from those who are at risk for an acute coronary syndrome (ACS). In this study the diagnostic value of the clinical examination is compared with laboratory testing of troponin. METHODS: This study included 710 chest pain patients who presented at the ED of two hospitals in the Netherlands. Clinical examination and laboratory testing were combined in the recently developed HEART-score. The diagnostic values of clinical presentation, troponin and the HEART-score for a major adverse coronary event (MACE) and an ACS within 6 weeks were assessed. Furthermore, the improvement of HEART with the second troponin measurement after 6 h was assessed using the net reclassification improvement (NRI). RESULTS: The use of HEART (AUCMACE: 0.77; AUCACS: 0.82) obtains a higher diagnostic value than troponin (AUCMACE: 0.72; AUCACS: 0.74) or clinical evaluation (AUCMACE: 0.69; AUCACS: 0.74). Statistical significant different AUCs were obtained when HEART is compared to troponin or clinical evaluation (p<0.01). The use of the second troponin test (after 6 h of admission) within HEART resulted in an improvement of 8.0%. CONCLUSIONS: The HEART-score combines clinical evaluation and results from laboratory testing, which should be used together, to discriminate patients at risk of a cardiac event from patients who can be safely discharged. In addition, it is shown that a second troponin measurement slightly improves the discriminative ability of the HEART-score.

Tunable hydrodynamic chromatography of microparticles localized in short microchannels.

This paper describes a new way to perform hydrodynamic chromatography (HDC) for the size separation of particles based on a unique recirculating flow pattern. Pressure-driven (PF) and electro-osmotic flows (EOF) are opposed in narrow glass microchannels that expand at both ends. The resulting bidirectional flow turns into recirculating flow because of nonuniform microchannel dimensions. This hydrodynamic effect, combined with the electrokinetic migration of the particles themselves, results in a trapping phenomenon, which we have termed flow-induced electrokinetic trapping (FIET). In this paper, we exploit recirculating flow and FIET to perform a size-based separation of samples of microparticles trapped in a short separation channel using a HDC approach. Because these particles have the same charge (same zeta potential), they exhibit the same electrophoretic mobility, but they can be separated according to size in the recirculating flow. While trapped, particles have a net drift velocity toward the low-pressure end of the channel. When, because of a change in the externally applied PF or electric field, the sign of the net drift velocity reverses, particles can escape the separation channel in the direction of EOF. Larger particles exhibit a larger net drift velocity opposing EOF, so that the smaller particles escape the separation channel first. In the example presented here, a sample plug containing 2.33 and 2.82 microm polymer particles was introduced from the inlet into a 3-mm-long separation channel and trapped. Through tuning of the electric field with respect to the applied PF, the particles could be separated, with the advantage that larger particles remained trapped. The separation of particles with less than 500 nm differences in diameter was performed with an analytical resolution comparable to that of baseline separation in chromatography. When the sample was not trapped in the separation channel but located further downstream, separations could be carried out continuously rather than in batch. Smaller particles could successfully pass through the separation channel, and particles were separated by size. One of the main advantages of exploiting FIET for HDC is that this method can be applied in quite short (a few millimeters) channel geometries. This is in great contrast to examples published to date for the separation of nanoparticles in much longer micro- and nanochannels.