Introduction Current NICE chest pain guidelines suggest coronary artery calcium scores (CACS), CT coronary angiography (CTCA), functional testing and invasive angiography depending on Diamond Forrester (DF) risk scores. Heart-type fatty acid-binding protein (H-FABP) has previously been assessed as an early ischaemic biomarker. Highly sensitive troponin T (hsTnT) is currently used for ACS diagnosis. Little work has been undertaken to assess early ischaemic biomarkers as predictors of coronary artery disease (CAD) in high risk patients following exercise stress testing (EST).
Methodology We prospectively evaluated if H-FABP and hsTnT following exercise could predict a primary outcome of obstructive CAD requiring coronary stenting or bypass surgery in high risk patients recruited from the rapid access chest pain clinic. Baseline demographics, cardiac risk factors and a DF risk score were recorded. Baseline blood samples were taken at 0, 2, 4 and 6 hours for H-FABP and hsTnT after exercising on a full Bruce EST protocol (Figure 2). Invasive angiography was undertaken if this was positive for ischaemia. If the EST was negative, patients had a CACS and if this was >0 patients had follow-on CTCA. Invasive angiography was performed if this showed obstructive CAD.
Results Of the 48 patients enrolled, 25 (52.1%) were male, 9 (18.8%) were smokers, 4 (8.3%) were diabetic, 31 (64.6%) had hypercholesterolaemia, 22 (45.8%) had hypertension and 33 (68.8%) had a positive family history of CAD. CAD was seen in 16 (33.3%) patients on CTCA or invasive angiography, 7 (14.6%) met primary outcome criteria (4 had coronary stenting and 3 had bypass surgery). Comparing those with and without intervention, there was no statistical difference in risk factors (p > 0.05), Table 1. Median DF score was 92% in the intervention and 92% in the non-intervention group, p = 0.82, AUC 0.53. Median CACS score was 55 versus 0 in the intervention versus non-intervention group, p = 0.27, AUC 0.72. However, median CACS was predictive of overall CAD, 122 versus 0 respectively, p ≤ 0.001, AUC 0.89. Table 2 compares median 6 hour hsTnT, H-FABP and TnI in intervention and non-intervention groups. There was no statistically significant difference in any biomarker, p > 0.05.
Conclusion In this cohort there was no statistical difference in risk factors or DF risk score between the intervention and non-intervention group. CACS (leading to CTCA) was statistically associated with CAD prediction but not predictive of patients requiring intervention. H-FABP and hsTnT are early ischaemic markers but were not predictive of obstructive CAD post EST in a high risk population.
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