Inverse relation of C-reactive protein levels to heart rate variability in patients after acute myocardial infarction.

ABSTRACT

INTRODUCTION: Inflammation has a major role in atherosclerosis and the acute phase C-reactive protein (CRP) is elevated after acute myocardial infarction. Inflammation is also implicated in autonomic nervous system control. Heart rate variability (HRV) has been used as a marker of abnormal autonomic activity after myocardial infarction. Our purpose was to investigate the relation between CRP levels and autonomic tone in patients after acute ST-segment elevation myocardial infarction. METHODS: We studied prospectively 98 patients. CRP and the cardiac enzymes CK, CK-MB, and troponin-I were measured for a total of 72 hours and 24-hour Holter ECG recordings for HRV analysis were acquired before hospital discharge. RESULTS: The natural logarithm of CRP levels was inversely correlated with the following logarithmic transformed indices of HRV in the time and in the frequency domain SDNN, standard deviation of all normal R-R intervals, (r = -0.40, p < 0.001); SDANN index, standard deviation of the average normal R-R intervals for 5-minute segments, (r = -0.46, p < 0.001); SDNN index, mean of the standard deviation of all normal R-R intervals for 5-minute segments (r = -0.41, p < 0.001); total power (TP) (r = -0.38, p < 0.001); high frequency power (HF) (r = -0.31, p < 0.01); low frequency power (LF) (r = -0.45, p < 0.001). The strong inverse relation between CRP and SDNN, SDANN, SDNN index, LF and TP persisted after adjustment for left ventricular function. CONCLUSIONS: Increased levels of circulating CRP after acute myocardial infarction are associated with attenuated HRV indices, suggesting a possible relationship between inflammation and cardiac autonomic balance.