Heart rate recovery after exercise and its relation with neutrophil-to-lymphocyte ratio in patients with cardiac syndrome X

Abstract

The neutrophil-to-lymphocyte ratio (NLR) and the platelet-to-lymphocyte ratio (PLR) are measures of systemic inflammation. Heart rate recovery (HRR) after exercise is influenced by autonomic function. The aim of this study was to ascertain whether HRR and the Duke Treadmill Score (DTS) values are related to NLR and PLR in patients with cardiac syndrome X (CSX). A total of 350 participants were enrolled in the study. Complete blood counts and high-sensitivity C-reactive protein (hsCRP) were obtained. All participants underwent an exercise test. HRR and DTS were calculated after exercise. Abnormal HRR was defined as 12 beats/min or less. CSX and coronary artery disease (CAD) groups had higher NLR, PLR, and hsCRP, and lower HRR and DTS values than the control group (for all, P<0.05). In both CSX and CAD groups, HRR was positively correlated with DTS (r=0.468, P<0.001 and r=0.491, P<0.001, respectively) and negatively correlated with NLR (r=-0.519, P<0.001 and r=-0.612, P<0.001, respectively), PLR (r=-0.422, P<0.001 and r=-0.438, P<0.001, respectively), and hsCRP (r=-0.553, P<0.001 and r=-0.521, P<0.001, respectively). NLR and hsCRP were important two predictors of the presence of lower HRR in both CSX [NLR: odds ratio (OR), 0.395; 95% confidence interval (CI), 0.168-0.925; P=0.032 and hsCRP: OR, 0.748; 95% CI, 0.591-0.945; P=0.015], and CAD groups (NLR: OR, 0.115; 95% CI, 0.026-0.501; P=0.004 and hsCRP: OR, 0.637; 95% CI, 0.455-0.892; P=0.009). CSX patients have higher NLR and PLR and slower HRR and lower DTS, similar to CAD patients, suggesting that CSX patients may be at a higher risk for developing cardiovascular events in the future. NLR may predict autonomic imbalance assessed by HRR in CSX.