Reduced low-frequency heart rate variability relates to greater intimal-medial thickness of the carotid wall in two samples.

INTRODUCTION We investigated the relationship between heart rate variability and preclinical carotid intima-media thickening, a putative index of atherosclerosis. METHODS A sample of 350 men and women (mean age 56.8 years) selected for the presence or absence of untreated hypertension was assessed for heart rate variability at rest and separately for carotid intima-media thickness using duplex ultrasonography (Pittsburgh study). Findings from this sample were cross-validated in a subsample of 68 men drawn from the Kuopio Ischemic Heart Disease Risk Factor trial and selected for the presence or absence of angina. RESULTS In both samples, regression analyses, controlling for known risk factors, showed a significant negative relationship between mean carotid intima-media thickness and low-frequency (0.05-0.15 Hz) heart rate variability, but not high-frequency variability. DISCUSSION The mechanism underlying this relationship remains unclear. The absence of difference in high-frequency variation questions any interpretation in terms of vagal function; the difference in low-frequency variation may implicate vessel wall characteristics or decreased sympathetic nervous system influence. CONCLUSION Decreased amplitude of low-frequency heart rate variability seems associated with a preclinical atherosclerotic index.