Myocardial ischaemia is associated with an elevated brain natriuretic pepide level even in the presence of left ventricular systolic dysfunction

Aims
Plasma BNP and high-sensitivity cardiac troponin-T (hs-TnT) are elevated by both ischaemia and LV systolic dysfunction (LVSD). As a result, it is unknown whether BNP and/or hs-TnT could be useful biomarkers to identify ischaemia in the presence of LVSD.

Methods and results
Three separate patient populations were studied. Study A (n = 500) involved consecutive patients undergoing clinically indicated myocardial perfusion scintigraphy, study B (n = 100) included patients with vascular disease but no known cardiac disease, and study C (n = 300) recruited primary prevention patients with controlled risk factors. Levels of BNP and hs-TnT were measured prior to the stress testing to detect myocardial ischaemia. The prevalence of myocardial ischaemia was 28.2, 28, and 6.3% in study A, B, and C, respectively. For BNP, area under curve (AUC) values to identify ischaemia in the presence and absence of coincidental LVSD were: 0.73 vs. 0.63 (study A), 0.90 vs. 0.81 (study B), and 0.83 vs. 0.80 (study C). Equivalent figures for hs-TnT were: 0.64 vs. 0.60 (study A), 0.75 vs. 0.68 (study B), and 0.53 vs. 0.68 (study C). BNP and hs-cTnT, when combined together, performed better with an AUC of 0.75 vs. 0.65 (study A), 0.91 vs. 0.92 (study B), and 0.84 vs. 0.83 (study C).

Conclusion
In three separate populations a consistent finding is that BNP is increased further by myocardial ischaemia even in the presence of LVSD. A disproportionately high BNP for the degree of LVSD might be due to (unsuspected) ischaemia, and a disproportionately low BNP could be useful as a ‘rule out’ test for ischaemia even in the presence of LVSD.