Is blunted heart rate decrease at night associated with prevalent organ damage in essential hypertension?

Abstract

The association between a blunted decrease in day–night heart rate and subclinical organ damage has not been investigated earlier in human hypertension. Therefore, we assessed such an association in a cohort of 658 untreated essential hypertensive patients. All patients underwent procedures including cardiac and carotid ultrasonography, 24-h urine collection for microalbuminuria, ambulatory blood pressure monitoring with simultaneous assessment of heart rate over two 24-h periods within 4 weeks. Nondipping heart rate was defined as a mean heart rate reduction at night lower than 10% compared with daytime values. A reproducible nocturnal dipping (heart rate decrease >10% in both the ambulatory blood pressure monitoring periods) and nondipping profile was found in 513 (78%) and 76 patients (12%), respectively; 69 hypertensive patients (10%) had a variable dipping profile. The three groups did not differ with regard to age, sex, body size, metabolic variables, office and ambulatory blood pressures, left ventricular mass, carotid intima-media thickness, carotid plaque and microalbuminuria. In a univariate analysis, the decrease in nocturnal heart rate did not correlate with any parameter of subclinical organ damage. Our findings from a cross-sectional study do not support the view that a flattened heart rate circadian rhythm is related to a prevalent organ damage in essential hypertension and that this altered pattern is a marker for subclinical cardiovascular disease. The prognostic significance of this finding should be defined by prospective studies.