Correlation of 24‐Hour Blood Pressure and Heart Rate Variability to Renal Function Parameters in Hypertensive Patients. The Effect of Smoking

Abstract

Intrarenal hemodynamics depend on blood pressure (BP), heart rate (HR), and smoking. Although BP levels have been associated with kidney function, the effect of HR levels, BP, and HR variability on renal function are less well clarified. This cross-sectional study sought to determine the association of 24-hour BP and HR variability with kidney function in hypertensive patients, stratified by smoking. The study comprised 9600 nondiabetic, never-treated hypertensive individuals without evident renal impairment examined from 1985 to 2014 (aged 53.3AE13.4 years, 55.3% males). The 24-hour systolic BP (SBP) and HR variability were estimated via their coefficient of variation (C V =standard deviation9100/ mean value) derived from ambulatory recording. The C V SBPto-C V HR ratio (C V R) was used as a marker of the interplay between 24-hour SBP and HR variability. Renal function was estimated via 24-hour urine creatinine clearance (CrCl), estimated glomerular filtration rate (eGFR), albumin-to-creatinine ratio (ACR), and 24-hour urine a 1 -microglobulin. After adjustment for age, sex, and smoking, C V SBP was found to be weakly correlated to eGFR (r=À0.017, P=.1) and somewhat more strongly to CrCl, ACR, and a 1 -microglobulin (r=À0.032, 0.072, and 0.065; P=.002, <.001 and <.001, respectively). C V HR was much better related to renal function, with stronger adjusted correlations to CrCl, eGFR, ACR, and a 1 -microglobulin (r=0.185, 0.134, À0.306, À0.247; all P<.001, respectively). C V R also showed equally good adjusted correlations (r=À0.175, À0.125, 0.336, 0.262; all P<.001, respectively). Most adjusted correlations for C V HR and C V R were even better in smokers (r=0.213, 0.158, À0.332, À0.272 and À0.183, À0.118, 0.351, 0.275, respectively; all P<.001). C V HR and C V R emerge as better related to kidney function than C V SBP, especially in smokers. The correlation of C V HR and C V SBP to renal function is inverse to each other. ACR and a 1 -microglobulin are better related to variability indices than CrCl and eGFR. However, causal relations cannot be proved. J Clin Hypertens (Greenwich). 2015;17:938-943. ª 2015 Wiley Periodicals, Inc.

Twenty‐Four–Hour Urine α1‐Microglobulin as a Marker of Hypertension‐Induced Renal Impairment and Its Response on Different Blood Pressure–Lowering Drugs

“…These results seem to be in agreement with the current literature. Urine α 1 ‐microglobulin has been previously significantly correlated with office SBP (but not DBP) in hypertensive patients . Recently, it has been closely associated with office SBP (but not DBP) in patients with white‐coat hypertension as well .…”

“…Recently, it has been closely associated with office SBP (but not DBP) in patients with white‐coat hypertension as well . Moreover, significant correlations have been reported between urine α 1 ‐microglobulin and 24‐hour SBP variability, after adjustment for age, sex, and smoking …”

“…Urine a 1 -microglobulin has been previously significantly correlated with office SBP (but not DBP) in hypertensive patients. 11,12 Recently, it has been closely associated with office SBP (but not DBP) in patients with white-coat hypertension as well. 13 Moreover, significant correlations have been reported between urine a 1 -microglobulin and 24-hour SBP variability, after adjustment for age, sex, and smoking.…”

Blood Pressure, Heart Rate Variability, and Renal Function in Nonsmoker and Smoker Hypertensive Patients

“…In this issue of the Journal, Liakos and coworkers report the results of a cross‐sectional study aimed at investigating the correlation of 24‐hour blood pressure (BP) and heart rate (HR) variability, as assessed by a single session of 24‐hour ambulatory BP monitoring, with renal function in a large cohort of untreated, uncomplicated essential hypertensive patients. In particular, the authors examined the influence of smoking status on the relationship between BP/HR variability and renal parameters including creatinine clearance, estimated glomerular filtration rate, albumin‐to‐creatinine ratio and urinary α 1 ‐microglobulin.…”

“…The report by Liakos and coworkers provides a new piece of evidence on the association between BP, HR, and renal function in a large sample of adult untreated essential hypertensive patients without diabetes and renal insufficiency, stratified according to cigarette smoking status. The prevalence of active smokers at the time of examination was approximately 38%, and about two thirds were men.…”