C-reactive protein is associated with heart rate variability

Background: The aim of this study was to investigate the relation between low-grade inflammation and autonomic dysfunction, both of which may be risk markers for sudden cardiac death. Methods: A total of 269 subjects referred for elective coronary angiography because of clinically suspected coronary heart disease were included in the study. Of these 27% had a previous myocardial infarction and 70% had significant coronary stenoses. A 24-hour Holter-recording was obtained from all subjects, and time-domain heart rate variability indices were analyzed. C-reactive protein was measured using a high-sensitivity assay. Results: Mean SDNN was significantly higher in the lower compared to the upper hs-CRP quartile (140 +/- 34 ms vs 113 +/- 29 ms; P < 0.001). Similar results were found for SDNNindex (54 +/- 16 ms vs 46 +/- 12 ms; P = 0.002) and SDANN (125 +/- 33 ms vs 101 +/- 31 ms; P < 0.001). The association was strongest for subjects with a previous myocardial infarction, subjects with significant coronary stenoses, and males. In a linear regression analysis, hs-CRP remained an independent determinant of each of these three heart rate variability indices (all P < 0.001). Conclusion: C-reactive protein and heart rate variability are independently associated. This may support a link between low-grade inflammation and autonomic dysfunction.