C-Type Natriuretic Peptide as a Surrogate Marker in Variant Angina Pectoris

Background and Objectives: The purpose of this study was to assess the value of C-type natriuretic peptide (CNP) as a surrogate marker for detection of coronary artery spasm in variant angina pectoris (VAP). Subjects and Methods: Sixty-six patients (mean age: $51{\pm}11$ years, M : F=40 : 26) who underwent coronary angiography on suspicion of angina and who were diagnosed with VAP by the acetylcholine-induced spasm provocation test (SPT) were enrolled and divided into a SPT (-) group (n=23) and a SPT (+) group (n=43). Concentrations of CNP and other markers were determined by immunoassay in both groups. Results: Plasma CNP and creatine kinase myoglobin band (CK-MB) concentrations were significantly increased in the SPT (+) group relative to the SPT (-) group (CNP, $5.268{\pm}1.800pg/mL$ vs. $3.342{\pm}1.150pg/mL$, p=0.002; CK-MB, $2.54{\pm}1.03ng/dL$ vs. $1.86{\pm}0.96ng/dL$, p=0.019, respectively) while plasma high sensitivity C-reactive protein (hs-CRP) and N-terminal pro-brain natriuretic peptide (NT pro-BNP) concentrations were not significantly different between the SPT (-) group and SPT (+) group (hs-CRP, $2.76{\pm}4.99mg/L$ vs. $3.13{\pm}4.88mg/L$, p=0.789; NT pro-BNP, $49{\pm}47pg/mL$ vs. $57{\pm}63pg/mL$, p=0.818, respectively). Plasma CNP concentration was independently associated with the VAP via SPT {odds ratio: 2.014 (95% confidence interval: 1.016-3.992), p=0.045}. A CNP cut-off value of 4.096 pg/mL was found to have a sensitivity of 68.2% and a specificity of 40.0% for predicting the probability of VAP via SPT. Conclusion: Increased plasma CNP concentration in patients with VAP may have an impact on the regulation of endothelial function in accordance with the progression of atherosclerosis. Further analysis is warranted to develop clinical applications of this finding.