Quantification and Correlation of NTproBNP in High-risk Patients with Varying Severity of Myocardial Ischemia on Lexiscans

Background: Natriuretic peptides are released in increased myocardial wall stress, but myocardial ischemia or hypoxia may also contribute to natriuretic peptide release, independent of changes in left ventricular function. Objectives: In our study, we tried to check the impact of myocardial ischemia on the release of natriuretic peptides, and correlated it with cardiac troponins. Methods: We included all the patients with anginal chest pain or equivalents who underwent regadenoson single photon emission computed tomography myocardial perfusion imaging, commonly known as lexiscan, with positive stress results defined as reversible myocardial ischemia, and their corresponding myocardial markers and stress imaging findings were checked. The patients with reduced renal function (defined as glomerular filtration rate <60 ml/min/1.73 m 2 ) and heart failure (with LVEF <40%) were excluded from the study to remove the confounding factors that could contribute to the elevation in natriuretic peptides. Results: In total, 54 patients were studied. The NT-ProBNP levels were above the normal laboratory reference range of 450 ng/ml in 12 (44.4%) patients and >100 ng/ml in 18 (66.7%) patients. The median elevation (25–75 percentiles) of NTproBNP above the laboratory reference range was 1151.5 (645–1618) pg/ml. The combined cardiac troponin I and T (cTnI and cTnT, respectively) concentrations were above the detection level in 30 (55.6%) patients, and the median elevation of cTnI and cTnT was 0.135 (0.035–0.273) ng/ml, and 0.046 (0.021–0.221) ng/ml, respectively. There was a significant strong positive association between the rise of NTproBNP and cTnT elevation ( r = 0.687, P < 0.05), but there was no statistically significant difference in the elevation of NTproBNP across the increasing severity of myocardial ischemic categories on one-way ANOVA ( P > 0.05). Conclusions: The combined cardiac troponin elevation was still higher than NTproBNP elevation. There was no significant difference in the elevation of NTproBNP with increasing severities of myocardial ischemia on a lexiscan, but NTproBNP elevation correlated strongly with cTnT elevation.