Arterial stiffness and plasma creatinine in untreated hypertensive patients

Spironolactone Reduces Aortic Stiffness in Patients With Resistant Hypertension Independent of Blood Pressure Change

Background

Aortic stiffness is an independent predictor of cardiovascular events in patients with arterial hypertension. Resistant hypertension is often linked to hyperaldosteronism and associated with adverse outcomes. Spironolactone, a mineralocorticoid receptor antagonist, has been shown to reduce both the arterial blood pressure (BP) and aortic stiffness in resistant hypertension. However, the mechanism of aortic stiffness reduction by spironolactone is not well understood. We hypothesized that spironolactone reduces aortic stiffness in resistant hypertension independently of BP change.

Methods and Results

Patients with uncontrolled BP (≥140/90 mm Hg) despite use of ≥3 antihypertensive medications (including diuretics) were prospectively recruited. Participants were started on spironolactone at 25 mg/d, and increased to 50 mg/d at 4 weeks while other antihypertensive medications were withdrawn to maintain constant mean BP. Phase‐contrast cardiac magnetic resonance imaging of the ascending aorta was performed in 30 participants at baseline and after 6 months of spironolactone treatment to measure aortic pulsatility, distensibility, and pulse wave velocity. Pulse wave velocity decreased (6.3±2.3 m/s to 4.5±1.8 m/s, P<0.001) and pulsatility and distensibility increased (15.9%±5.3% to 22.1%±7.9%, P<0.001; and 0.28%±0.10%/mm Hg to 0.40%±0.14%/mm Hg, P<0.001, respectively) following 6 months of spironolactone.

Conclusions

Our results suggest that spironolactone improves aortic properties in resistant hypertension independently of BP, which may support the hypothesis of an effect of aldosterone on the arterial wall. A larger prospective study is needed to confirm our findings.

Impact of Arteriovenous fistula creation on estimated glomerular filtration rate decline in Predialysis patients

BACKGROUND

Arteriovenous fistula (AVF) is the vascular access of choice for patients on hemodialysis. Recent evidence suggests that AVF creation may slow estimated glomerular filtration rate (eGFR) decline. The study objective was to assess the impact of the AVF creation on eGFR decline, after controlling for key confounding factors.

METHODS

This retrospective cohort study included adult patients followed in a single-center predialysis clinic between 1999 and 2016. Patients with a patent AVF were followed up to 2 years pre- and post-AVF creation. Estimated GFR trajectory was reported using linear mixed models adjusted for demographic characteristics, comorbidities and use of renin-angiotensin-aldosterone blockade.

RESULTS

A total of 146 patients were studied with a median age 68.7 (60.5-75.4) years and a median eGFR at time of AVF creation of 12.8 (11.3-13.9) mL/min/1.73m2. The crude annual eGFR decline rates were - 3.60 ± 4.00 mL/min/1.73 m2 pre- and - 2.28 ± 3.56 mL/min/1.73 m2 post-AVF, resulting in a mean difference of 1.28 mL/min/1.73 m2 (95% CI 0.49, 2.07). In a mixed effect linear regression model, monthly eGFR decline was - 0.63 (95% CI -0.81, - 0.46; p <  0.001) mL/min/1.73m2/month. The period after AVF creation was associated with a relatively higher eGFR (β 0.94, 95% CI 0.61-1.26, p <  0.001). There was a significant association between follow-up time and the period pre/post AVF (β 0.19, 95% CI 0.16, 0.22; p <  0.001) such that eGFR decline was more attenuated each month after AVF creation.

CONCLUSIONS

In this cohort, AVF creation was associated with a significant reduction of eGFR decline. Further prospective studies are needed to confirm this association.

Arteriovenous fistula creation may slow estimated glomerular filtration rate trajectory

BACKGROUND

We practice the timely placement of an arteriovenous fistula (AVF) in patients facing chronic hemodialysis. We have anecdotally observed after AVF creation that there appears to be a slowing of the decline in kidney function as measured by the estimated glomerular filtration rate (eGFR). There are physiologically plausible explanations as to how an AVF might alter kidney function, but this clinical observation has been attributed to improved compliance and/or other practices. The present retrospective observational analysis was performed to assess the possibility that a successfully created AVF could be associated with the slowing of the eGFR trajectory.

METHODS

We identified 123 patients between 2005 and 2010 with at least two eGFR determinations for 2 years before and up to 2 years after AVF creation. Inclusion eligibility was that the fistula was maturing by the nephrologists' initial post-creation examination. Termination events were death, starting dialysis or transplantation. Each subject served as their own control for the pre- and post-AVF-creation eGFR measurements.

RESULTS

Subjects' median age was 68 years and 56% were diabetic. The rate of change of the eGFR for the 2 years prior to AVF creation was -5.9 mL/min/year (95% CI: -5.3, -6.5) and after AVF creation -0.5 mL/min/year (95% CI: -1.1, 0.1) (interaction (P < 0.001).

CONCLUSIONS

A functioning AVF may be associated with a slowing of the eGFR decline. Agreeing to timely AVF creation selects patients in an otherwise typical population and other confounders have not yet been eliminated. To do so a thorough prospective observational study is indicated.

Associations between blood pressure responses to acute stress and impaired renal function and serum uric acid level

The study aimed to examine correlations between blood pressure (BP) responses to direct laryngoscopy and tracheal intubation and parameters of renal function, serum uric acid (SUA) level, and mean preoperative BP. Fifty-four patients (≥ 40 years) who were scheduled for oral surgery were analyzed. General anesthesia was induced by the rapid sequence method without opioid analgesics. Systolic and diastolic BP (SBP, DBP) in the operation room were measured when an electrocardiogram, a BP cuff, and a pulse oximetry probe were attached to the patients (T1) and immediately after the trachea was intubated (T2). The ΔSBP was defined as the difference between SBP at T2 and T1. The increasing rate of SBP (ΔSBPr) was defined as ΔSBP/SBP at T1. SBP at T2 was associated with increasing age (R = 0.44), serum creatinine (R = 0.32), SUA (R = 0.30), mean preoperative SBP and DBP (R = 0.54 and 0.37, respectively), and reduced estimated glomerular filtration rate (eGFR) (R = -0.44). Serum creatinine and SUA were positively associated, and eGFR was negatively associated with ΔSBP (R = 0.36, 0.34, and -0.29) and ΔSBPr (R = 0.39, 0.37, and -0.29). Multivariate regression analysis revealed that age and mean preoperative SBP was independently associated with SBP at T2, and serum creatinine was independently associated with ΔSBP and ΔSBPr. These findings suggested that elevated serum creatinine level, as well as elevated preoperative BP level, was associated with enhanced BP responses to acute stress in middle-aged to elderly patients.

Arterial stiffness, pulse pressure, and the kidney

Classical studies indicate that the contribution of kidneys to hypertension is almost exclusively related to the association between mean arterial pressure (MAP) and vascular resistance. Recent reports including estimates of glomerular filtration rate (GFR) have shown that pulse pressure (PP) and pulse wave velocity, 2 major indices of arterial stiffness, now emerge as significant predictors of cardiovascular risk and age-associated decline in GFR. Such findings are mainly observed in patients with hypertension and renal failure and in atherosclerotic subjects undergoing coronary angiography. In such patients, amplification of PP between ascending and terminal aorta at the renal site is constantly increased over 10mm Hg (P < 0.001), whereas MAP level remains continuously unmodified. This PP amplification is significantly associated with presence of proteinuria. Furthermore, increases in plasma creatinine and aortic stiffness are independently and positively correlated (P < 0.001) both in cross-sectional and longitudinal studies. All these relationships associating PP, arterial stiffness, and renal function are mainly observed in patients 60 years of age or older. Furthermore, in renal transplant patients and their donors, subjects have been recruited for evaluations of arterial stiffness and posttransplant decline in GFR. Determinants of GFR decline were evaluated 1 and 9 years after transplantation. The first year GFR decline was related to smoking and acute rejection, whereas the later was significantly and exclusively associated with donor age and aortic stiffness. Thus, in hypertensive humans, the observed association between PP and GFR suggests that the 2 parameters are substantially mediated by arterial stiffness, not exclusively by vascular resistance.

Lower glomerular filtration rate is associated with higher systemic vascular resistance in patients without prevalent kidney disease

The authors examined the association between estimated glomerular filtration rate (eGFR), calculated using the Chronic Kidney Disease Epidemiology Collaboration creatinine-cystatin C equation, and hemodynamics in 556 normotensive or never-treated hypertensive patients without kidney disease (mean age, 46 years). Hemodynamic variables were recorded using pulse wave analysis and whole-body impedance cardiography. The mean eGFR was 98 mL/min/1.73 m(2) (range, 64-145 mL/min/1.73 m(2) and one third of the patients had values below 92, while none had proteinuria. In linear regression analyses adjusted for differences in age, weight:height ratio, low-density lipoprotein cholesterol, and sex, significant associations were found between lower eGFR and higher systolic (P=.001) and diastolic blood pressure (P<.001) and higher systemic vascular resistance (P=.001). There was no association between eGFR and cardiac output or extracellular volume. In the absence of clinical kidney disease, lower eGFR was associated with higher blood pressure and systemic vascular resistance. Therefore, early impairment in kidney function may be involved in the pathogenesis of essential hypertension.

The ambulatory arterial stiffness index and target-organ damage in Chinese patients with chronic kidney disease

Background

The ambulatory arterial stiffness index (AASI) can be used to predict cardiovascular morbidity and mortality in hypertensive patients. However, data on AASI in Chinese patients with chronic kidney disease (CKD) is not available.

Methods

This cross-sectional study enrolled 583 CKD patients. Univariate and multivariate analyses were used to evaluate the relationship between AASI and renal function and parameters of cardiovascular injury.

Results

Patients with a higher AASI had a higher systolic blood pressure, a lower estimated glomerular filtration rate (eGFR), a higher serum cystatin C, a higher left ventricular mass index (LVMI) and carotid intima-media thickness (cIMT). Univariate analyses showed that AASI was positively correlated with serum cystatin C (r=0.296, P < 0.001), serum creatinine (r=0.182, P < 0.001), and LVMI (r = 0.205, P < 0.001) and negatively correlated with the eGFR (r = –0.200, P < 0.001). Multivariate analyses revealed that serum cystatin C, eGFR, serum creatinine and LVMI were independently correlated with AASI.

Conclusions

These data suggest that AASI was closely correlated with renal function and parameters of cardiovascular injury in Chinese CKD patients. Good quality, long-term, large longitudinal trials to validate the role of AASI in clinical practice for Chinese CKD patients.

Large arteries and the kidney

In subjects with chronic renal disease, high systolic blood pressure (SBP) is the most modifiable cardiovascular (CV) risk factor that enables prevention of the progression of chronic kidney disease renal failure and the occurrence of CV events. Although large-artery stiffness and wave reflections are the principal hemodynamic determinants of SBP, their precise role in the progression of chronic renal disease has been poorly investigated. However, in subjects with mild to severe renal insufficiency, increased arterial stiffness and reduced creatinine clearance are closely related, independently of age; mean arterial pressure level; and presence of other traditional risk factors, including atherosclerotic plaques. Through inflammatory mechanisms, as well as through the development of arterial calcifications (including microscopic) and sodium-related alterations in extracellular matrix composition, arterial stiffness is associated with significant SBP and increased pulse pressure (PP). In the presence of renal dysfunction, frequently observed in elderly hypertensive or diabetic subjects, or even in some living donors, the resulting increase in PP may be transmitted toward and across glomeruli, even when peripheral blood pressure values are maintained. This alteration alone may initiate glomerulosclerosis and/or tubulointerstitial damage, eventually leading to CV events. In subjects with end-stage renal disease and high CV risk, pharmacological modulation of the renin-angiotensin system has been shown to prevent independently such complications.

Ambulatory arterial stiffness index is higher in hypertensive patients with chronic kidney disease

Ambulatory arterial stiffness index (AASI) is a parameter obtained from ambulatory blood pressure monitoring (ABPM) that correlates with clinical endpoints. The aim of this study was to compare AASI in nondiabetic hypertensive patients with and without chronic kidney disease (CKD). Subjects with systemic arterial hypertension (SAH, n = 30) with normal renal function, aged 40 to 75 years, were compared to hypertensive patients with CKD (n = 30) presenting estimated glomerular filtration rate (eGFR) <60 mL/min by MDRD formula. ABPM was carried out in all patients. In CKD group, eGFR was 35.3 ± 2.8 ml/min. The mean 24-hour systolic and diastolic blood pressure (BP) was similar in both groups. AASI was significantly higher in CKD group (0.45 ± 0.03 versus 0.37 ± 0.02, P < 0.05), positively correlated to age (r = 0.38, P < 0.01) and pulse pressure (r = 0.43, P < 0.01) and negatively correlated to nocturnal BP fall (r = -0.28, P = 0.03). These findings indicate the presence of stiffer vessels in CKD hypertensive patients.

Glomerular hemodynamics and arterial function in normal individuals

OBJECTIVE

To determine the relationship between arterial function (stiffness and wave reflection) and glomerular hemodynamics.

METHODS

In 49 healthy normotensive individuals, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by urinary clearances of 99mTC-DTPA and 131I-hippuran, respectively. Filtration fraction was computed as GFR/ERPF. Arterial stiffness was estimated by carotid-femoral pulse wave velocity (PWV). Wave reflection was evaluated by carotid augmentation index (AIx), reflection magnitude and the round-trip travel time of the pressure wave.

RESULTS

PWV and round-trip travel time were not independently correlated with any renal hemodynamic parameter or urinary albumin-creatinine ratio (UACR). AIx and reflection magnitude were directly correlated with filtration fraction (r = 0.35 and 0.37, respectively) and UACR (r = 0.43 and 0.53, respectively). When the population was divided into quartiles of reflection magnitude, filtration fraction and UACR progressively increased from the lowest to the highest quartile and after adjustment for age, mean arterial pressure, heart rate but also sex for UACR (P linear trend = 0.031 and 0.001, respectively).

CONCLUSION

It is suggested that in normal individuals, the amplitude of wave reflection but not arterial stiffness is associated with signs evocative of increased glomerular pressure (filtration fraction and UACR), independently of systemic blood pressure.

Aortic stiffness is independently associated with rate of renal function decline in chronic kidney disease stages 3 and 4

Aortic stiffness and chronic kidney disease are closely linked by shared risk factors and associated increased cardiovascular mortality. At lower levels of renal function, aortic stiffness is independently associated with glomerular filtration rate. However, the longitudinal impact of aortic stiffness on renal function has not been reported previously. A cohort of 133 patients with chronic kidney disease stages 3 and 4 (estimated glomerular filtration rate: 15 to 59 mL/min per 1.73 m(2)) underwent prospective measurement of arterial stiffness parameters and monitoring of renal function. Aortic pulse wave velocity measurement was performed in 120 patients. The mean age was 69+/-12 years (mean+/-SD; 103 men, 30 women, and 23.3% diabetic). Mean systolic blood pressure was 155+/-21 mm Hg, and mean diastolic blood pressure was 83+/-11 mm Hg. The mean Modification of Diet in Renal Disease estimated glomerular filtration rate was 32+/-11 mL/min per 1.73 m(2). Change in renal function was measured using reciprocal creatinine plots and the dichotomous combined end point of > or = 25% decline in renal function or start of renal replacement therapy. After stepwise multivariate analysis, aortic pulse wave velocity was independently associated with gradient of reciprocal creatinine plot (r=0.46; P=0.014). In multivariate analysis of the end point of > or = 25% decline in renal function or start of renal replacement therapy, independent predictors were aortic pulse wave velocity (r=0.48; P=0.002), systolic blood pressure (r=0.17; P=0.039), and urine protein:creatinine ratio (r=0.20; P=0.021). We, therefore, conclude that aortic stiffening is independently associated with rate of change in renal function in patients with chronic kidney disease stages 3 and 4.

Inverse relationship between ambulatory arterial stiffness index and glomerular filtration rate in arterial hypertension

BACKGROUND

Arterial stiffness and mild-to-moderate renal dysfunction are predictors of cardiovascular (CV) morbidity and mortality. Recently, the ambulatory arterial stiffness index (AASI) has been proposed as a surrogate index of arterial stiffness. It has been associated with an enhanced risk of stroke. The aim of our study was to assess the relationship between AASI and glomerular filtration rate (GFR) in a group of hypertensive patients with no CV complications.

METHODS

A total of 143 untreated hypertensive subjects (mean age: 44 +/- 12 years; men 57%), with serum creatinine <1.5 mg/dl, were enrolled. AASI was calculated as one minus the regression slope of diastolic on systolic blood pressure (BP) obtained by individual 24-h BP recordings. GFR was computed from the scintigraphic determination of the technetium-99m diethylenetriaminepentaacetic acid uptake within the kidneys, by the Gates' method.

RESULTS

Hypertensive patients with AASI above the median value (n = 71) had lower GFR than those with AASI below the median (n = 72) (98.3 +/- 31 vs. 122.4 +/- 32 ml/min/1.73 m(2); P < 0.001). This difference held even after adjustment for age and gender. The linear regression analysis disclosed a significant inverse correlation between GFR and AASI (r = -0.30; P < 0.001), that was replicated (beta = -0.19; P = 0.02) in a multiple regression model including, as independent variables (besides AASI), age, gender, high-density lipoprotein cholesterol, body mass index, 24-h pulse pressure (PP) and nocturnal reduction in BP.

CONCLUSIONS

AASI is inversely related to GFR in arterial hypertension. This may help to explain the increased CV risk associated with mild-to-moderate renal dysfunction.

Relationships among renal function loss within the normal to mildly impaired range, arterial stiffness, inflammation, and oxidative stress

BACKGROUND AND OBJECTIVES

This study was conducted to clarify whether individuals with mildly impaired renal function show increased arterial stiffness, microinflammation, and oxidative stress as compared with those with normal renal function and also to examine the association of these parameters with the degree of GFR loss in middle-aged Japanese men with a low cardiovascular risk.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The brachial-ankle pulse wave velocity and plasma levels of C-reactive protein and lipid peroxides were measured in 1873 men (42 +/- 9 yr of age).

RESULTS

The brachial-ankle pulse wave velocity but not the plasma C-reactive protein or lipid peroxides, was increased in individuals with mildly impaired renal function. The GFR was significantly correlated with the brachial-ankle pulse wave velocity but not with the log-transformed values of C-reactive protein or lipid peroxides. Multivariate linear regression analysis demonstrated a significant relationship between the brachial-ankle pulse wave velocity and the GFR, independent of the conventional atherosclerotic risk factors. This relationship was significant even in individuals with GFR values within the "normal renal function" range. Thus, GFR loss seems to be more closely associated with arterial stiffness than with microinflammation and/or oxidative stress.

CONCLUSIONS

A weak but significant relationship was observed between the degree of GFR loss and arterial stiffness, even in individuals with GFR values within the normal renal function range. Therefore, increased arterial stiffness may underlie, at least in part, the elevated cardiovascular risk in individuals with mildly impaired renal function.

The integrity of the blood-brain barrier in Alzheimer's disease

OBJECTIVE

To evaluate the integrity of the blood-brain barrier (BBB) in incident Alzheimer's disease (AD).

MATERIALS AND METHODS

The mean age of the 157 patients (45% men) was 69.7(9.4) years (range 51-88 years). The patients had undergone a thorough investigation including magnetic resonance imaging or computed tomography of the brain. The cerebrospinal(CSF)/plasma albumin ratio (albumin ratio) was used as a measure of BBB function.

RESULTS

There were gender differences with respect to albumin ratio and plasma creatinine with higher values in men (P < 0.001). 42% of the men and 13% of the women (P < 0.001) had a mild to moderate BBB dysfunction when applying the reference limit of the laboratory (<9.2). Both male gender (P = 0.002) and plasma creatinine (P = 0.009) were independently associated with the albumin ratio when controlling for putative confounders.

CONCLUSIONS

The BBB is dysfunctional in a portion of patients with AD, both women and, primarily, men. The dysfunction might influence the clearance of both harmful and beneficial substances across the barrier. Renal function might have an impact on the BBB.

Ambulatory arterial stiffness index and renal abnormalities in primary hypertension

OBJECTIVE

Arterial stiffness is a predictor of cardiovascular mortality in the general population as well as in hypertension and end-stage renal disease. We investigated the relationship between a recently proposed ambulatory blood pressure monitoring-derived index of arterial stiffness and early signs of renal damage in patients with primary hypertension.

DESIGN AND SETTING

A total of 168 untreated patients with sustained primary hypertension were studied. Ambulatory arterial stiffness index (AASI) was calculated based on 24-h ambulatory blood pressure readings. Albuminuria was measured as the albumin to creatinine ratio. Creatinine clearance was estimated using the Cockcroft-Gault formula, and the interlobar resistive index was evaluated by renal ultrasound and Doppler examination.

RESULTS

AASI was positively related to urinary albumin excretion and resistive index, and was negatively related to estimated creatinine clearance and renal volume to the resistive index ratio. Patients with AASI above the median (i.e. > 0.51) showed a higher prevalence of microalbuminuria and a mild reduction in creatinine clearance. Moreover, patients with microalbuminuria or a mild reduction in creatinine clearance had significantly higher AASI values compared with those without, and the greater the renal involvement, the greater the AASI. After adjusting for several potentially confounding variables, we found that each standard deviation increase in AASI (i.e. 0.16) entails an almost twofold greater risk of renal involvement.

CONCLUSION

Increased AASI is independently associated with early signs of renal damage in patients with sustained primary hypertension. These results strengthen the usefulness of AASI and ambulatory blood pressure monitoring in cardiovascular risk assessment.

Relation Between Renal Function Within the Normal Range and Central and Peripheral Arterial Stiffness in Hypertension

Chronic kidney disease is accompanied by increased large-artery stiffness, but the relation between glomerular filtration rate within the reference range and central or peripheral arterial stiffness has been understudied. The link between renal function and arterial stiffness was assessed in 305 patients with never-treated essential hypertension (men: 58%; age: 48±11 years, blood pressure: 151/95±20/11 mm Hg), free from overt cardiovascular disease and with serum creatinine values <1.4 mg/dL (men) and <1.2 mg/dL (women), who underwent noninvasive aortic and upper-limb pulse wave velocity (PWV) determination. Aortic PWV was strongly related to age ( r =0.55; P <0.001), whereas upper-limb PWV had a weaker nonlinear relation with age (β=1.392; P <0.001 for age; β=−1.312; P <0.001 for age squared) and a weak relation with aortic PWV ( r =0.22; P <0.001). Glomerular filtration rate (GFR), estimated according to the Mayo clinic equation for healthy subjects, was inversely correlated with large-artery stiffness, as assessed by aortic PWV ( r =−0.34; P <0.001), and with peripheral artery stiffness, as assessed by upper-limb PWV ( r =−0.25; P <0.001). In a multivariate linear regression, aortic PWV was independently predicted by age (β=0.48; P <0.001), mean arterial pressure (β=0.14; P =0.013), and GFR (β=−0.13, P =0.029). Upper-limb PWV was predicted by GFR (β=−0.24; P <0.001) and mean arterial pressure (β=0.20; P <0.001). We conclude that, in hypertensive patients with normal renal function, an inverse relationship exists between GFR and stiffness of both central elastic and peripheral muscular arteries. These relations are in part independent from the effect of several confounders, including age, sex, and blood pressure values.

Primary hypertension and nephropathy

PURPOSE OF REVIEW

The relationship between primary hypertension (formerly called essential hypertension) and hypertension-associated chronic kidney disease is complex and poorly understood. The strong association between hypertension-associated chronic kidney disease and cardiovascular disease supports the existence of common mediators. We will review data indicating common mediating mechanisms for cardiovascular disease and chronic kidney disease in primary hypertension.

RECENT FINDINGS

Chronic kidney disease develops in primary hypertension due to local and systemic inflammatory mediators that cause endothelial injury. This injury is an important early step in the development of hypertension-associated vasculopathy that causes nephron ischemia with nephrosclerosis. Similar mechanisms mediate endothelial injury in cardiovascular disease and its progression. Subjects with primary hypertension at increased risk for chronic kidney disease are at higher risk for cardiovascular disease, the major cause of mortality in primary hypertension.

SUMMARY

Primary hypertension is a modifiable risk factor for both cardiovascular disease and chronic kidney disease. Better understanding of how primary hypertension leads to these outcomes might help in the development of pharmacologic strategies that retard and/or prevent chronic kidney disease in primary hypertension. Because of the strong association between cardiovascular disease and chronic kidney disease in primary hypertension, this improved understanding will likely lead to better therapies to hinder the development and/or progression of cardiovascular disease, in addition to its benefits in preventing hypertension-associated chronic kidney disease.