Prognostic Value of Reverse Dipper Blood Pressure Pattern in Chronic Kidney Disease Patients not Undergoing Dialysis: Prospective Cohort Study

[Blood pressure patterns in pressurometry and their ralationship with cardiovascular events in follow-up]

Introducción

Nuestro objetivo fue determinar en una cohorte de pacientes de un hospital de la ciudad de Buenos Aires, cómo fue la distribución de ritmo circadiano y el impacto según el tipo de comportamiento circadiano en la tasa de eventos cardiovasculares en el seguimiento. Material y métodos: Estudio de cohorte retrospectiva que incluyó pacientes adultos que se realizaron una presurometría ambulatoria en un hospital de la ciudad de Buenos Aires, incorporados a un registro propio entre marzo de 2017 y julio de 2020, con seguimiento de hasta 36 meses de la presurometría índice.

Resultados

De 522 sujetos, se incluyeron 494 en el análisis final. El 48% eran de sexo masculino y la edad promedio fue de 58,9 años. El 62% (n = 308) presentó hipertensión arterial nocturna. El patrón dipper invertido fue el grupo que presentó más eventos cardiovasculares en el seguimiento (6% n: 24). Además, en el tiempo libre de evento globales, se evidencio menos tasas de supervivencia para el grupo con patrón dipper invertido (Log Rank test p: 0.0033).

Conclusión

En una cohorte contemporánea y de la ciudad de Buenos Aires, el grupo patrón dipper invertido se asoció con la aparición de desenlaces cardiovasculares. En base a estos hallazgos, se deben implementar medidas para incrementar su diagnóstico en nuestro medio.

Risk Factors of Chronic Kidney Disease Progression: Between Old and New Concepts

Chronic kidney disease (CKD) is a condition characterized by the gradual loss of kidney function over time and it is a worldwide health issue. The estimated frequency of CKD is 10% of the world's population, but it varies greatly on a global scale. In absolute terms, the staggering number of subjects affected by various degrees of CKD is 850,000,000, and 85% of them are in low- to middle-income countries. The most important risk factors for chronic kidney disease are age, arterial hypertension, diabetes, obesity, proteinuria, dyslipidemia, and environmental risk factors such as dietary salt intake and a more recently investigated agent: pollution. In this narrative review, we will focus by choice just on some risk factors such as age, which is the most important non-modifiable risk factor, and among modifiable risk factors, we will focus on hypertension, salt intake, obesity, and sympathetic overactivity.

Nocturnal systolic blood pressure dipping and progression of chronic kidney disease

The relationship between declining nocturnal blood pressure (BP) and adverse cardiovascular outcomes is well-recognized. However, the relationship between diurnal BP profile and the risk of chronic kidney disease (CKD) progression is unclear. Herein, we examined the association between nocturnal systolic SBP (SBP) dipping and CKD progression in 1061 participants at the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk (CMERC-HI). The main exposure was diurnal systolic BP (SBP) profile and diurnal SBP difference ([nighttime SBP-daytime SBP] × 100/daytime SBP). The primary outcome was CKD progression, defined as a composite of ≥ a 50% decline in the estimated glomerular filtration rate from baseline or the initiation of kidney replacement therapy. During 4749 person-years of follow-up (median, 4.8 years), the composite outcome occurred in 380 (35.8%) participants. Compared to dippers, the hazard ratios (HRs) for the risk of adverse kidney outcomes were 1.02 (95% confidence interval [CI], 0.64-1.62), 1.30 (95% CI, 1.02-1.66), and 1.40 (95% CI, 1.03-1.90) for extreme dipper, non-dipper, and reverse dipper, respectively. In a continuous modeling, a 10% increase in diurnal SBP difference was associated with a 1.21-fold (95% CI, 1.07-1.37) higher risk of CKD progression. Thus, decreased nocturnal SBP decline was associated with adverse kidney outcomes in patients with CKD. Particularly, patients with non-dipping and reverse dipping patterns were at higher risk for CKD progression than those with a dipping pattern.

Prognostic Value of Nighttime Double Product in Nondialysis Chronic Kidney Disease With Hypertension

BACKGROUND

Both nighttime systolic blood pressure and pulse rate are associated with adverse outcomes in patients with chronic kidney disease (CKD). However, nighttime double product (DP), which is the product of nighttime systolic blood pressure and pulse rate, has not yet been investigated in this context. The present study aimed to explore the prognostic value of nighttime DP for adverse outcomes in patients with CKD and hypertension.

METHODS AND RESULTS

This retrospective cohort study included a total of 1434 patients with nondialysis CKD complicated by hypertension. The patients were enrolled in Zhuhai and Guangzhou, China, with a median follow-up of 23.8 months. Patient enrollment for the high or low nighttime DP group was performed on the basis of the cutoff value determined by time-dependent receiver operator characteristic curve analysis. The primary end point was a composite of major cardiovascular and cerebrovascular events, and the secondary end point was all-cause death and composite renal end point. The 24-hour circadian DP rhythm was established via multiple-component cosinor analysis. Cox regression was used to explore the association between nighttime DP and adverse outcomes. The DP of nondialysis patients with CKD and hypertension showed a diurnal rhythm, which varied with renal function. After adjustment, high nighttime DP was associated with a higher risk for major cardiovascular and cerebrovascular events (hazard ratio [HR], 5.823 [95% CI, 2.382-14.233]), all-cause death (HR, 4.978 [95% CI, 2.205-11.240]), and composite renal event (HR, 1.661 [95% CI, 1.128-2.447]), compared with low nighttime DP. These associations were independent of nighttime systolic blood pressure and PR.

CONCLUSIONS

The present cohort study demonstrated that DP had diurnal fluctuations and nighttime DP was an important prognostic factor in nondialysis patients with CKD and hypertension, outperforming traditional risk factors, including systolic blood pressure and pulse rate.

Short-term blood pressure variability as a potential therapeutic target for kidney disease

Short-term blood pressure variability (BPV) measured with ambulatory blood pressure (BP) monitoring has been demonstrated to be significant in predicting various clinical outcomes. Short-term BPV is distinguished from long-term BPV based on the time interval in which BP fluctuations are measured. Increased short-term BPV has been linked to detrimental effects on the microvascular structure and contributes to subclinical organ damage in the heart, blood vessels, and kidneys, regardless of the average 24-h BP levels. Short-term BPV can be defined by various measures, including calculated metrics (standard deviation, coefficient of variation, average real variability, weighted standard deviation, variability independent of the mean) or dipping patterns. Nevertheless, the additional role of short-term BPV beyond the predictive value of average 24-h BPs or established risk factors for cardiovascular disease and kidney disease remains unclear. In particular, longitudinal studies that evaluate the association between short-term BPV and kidney function impairment are limited and no conclusive data exist regarding which short-term BPV indicators most accurately reflect the prognosis of kidney disease. The issue of how to treat BPV in clinical practice is another concern that is frequently raised. This paper presents a review of the evidence for the prognostic role of short-term BPV in kidney outcomes. Additionally, this review discusses the remaining concerns about short-term BPV that need to be further investigated as an independent risk modifier.

Effects of Nondipping Blood Pressure Changes: A Nephrologist Prospect

Blood pressure (BP) variations depend on various internal, environmental, and behavioral factors. BP fluctuations occur both in normotensive and hypertensive people. Although it fluctuates over the 24-hr day and night, the morning BP increases after waking up and declines throughout sleep. It is typical for BP to decrease by 10% to 20%, while sleeping, known as dipping BP. However, if there is no decrease in nighttime mean systolic BP or a drop of less than 10 mmHg, it is called nondipping BP. Conversely, reverse dipping BP means an increase in mean systolic BP instead of a drop during the night. Reverse dipping is observed in hypertension (HTN), diabetes mellitus (DM), chronic kidney disease (CKD), and obstructive sleep apnea (OSA) syndrome. The introduction of ambulatory BP monitoring (ABPM) led to the emergence of identifying normal and elevated BP patterns. Non-dipping BP increases the risk of cardiovascular system (CVS) complications such as left ventricular hypertrophy, proteinuria, glomerular filtration rate (GFR) reduction, and CKD progression. A loss or blunting of the normal BP profile is recognized as a deleterious variant, and restoring abnormal BP patterns has been reported to significantly impact end-organ damage, morbidity, and mortality. In this non-systematic clinically-oriented, comprehensive review, we aim to update the BP variables and the pathophysiology of nondipping BP and point out the areas which need more investigation from a nephrology perspective because the nondipping BP increases the risk of proteinuria, GFR reduction, and CKD progression. A literature search of PubMed, Google, EMBASE, and Google Scholar was conducted. Checks of selected papers and relevant reviews complemented the electronic search. With improved BP measurement methods, the physiology of BP profile variations is readily detectable during the day and night. A nondipping BP profile is a distinct BP pattern that may have significant end-organ damage effects and therapeutic importance for nephrologists. The pathophysiology of the nondipping BP variant must be clarified to prevent complications, and further investigations are required. Furthermore, there is debate about the best BP index to utilize: systolic BP, diastolic BP, mean arterial pressure, or a mixture of all. All these areas are important and need new research projects.

Reduced Blood Pressure Dipping Is A Risk Factor for the Progression of Chronic Kidney Disease in Children

Background: Elevated blood pressure and proteinuria are well-established risk factors for chronic kidney disease (CKD) progression in children. This study aimed to analyze risk factors for CKD progress, emphasizing detailed ambulatory blood pressure (ABPM) data. Methods: In 55 children with CKD II−V, observed for ≥1 year or until initiation of kidney replacement therapy, we analyzed ABPM, clinical, and biochemical parameters. Results: At the beginning, the glomerular filtration rate (eGFR) was 66 (interquartile range—IQR: 42.8−75.3) mL/min/1.73 m2, and the observation period was 27 (16−36) months. The mean eGFR decline was 2.9 ± 5.7 mL/min/1.73 m2/year. eGFR decline correlated (p < 0.05) with age (r = 0.30), initial proteinuria (r = 0.31), nighttime systolic and mean blood pressure (r = 0.27, r = 0.29), and systolic and diastolic blood pressure dipping (r = −0.37, r = −0.29). There was no relation between mean arterial pressure during 24 h (MAP 24 h Z-score) and eGFR decline and no difference in eGFR decline between those with MAP 24 h < and ≥50 th percentile. In multivariate analysis, systolic blood pressure dipping (beta = −0.43), presence of proteinuria (beta = −0.35), and age (beta = 0.25) were predictors of eGFR decline. Conclusions: Systolic blood pressure dipping may be a valuable indicator of CKD progression in children.

Nocturnal heart rate rising is a risk factor for poor renal outcomes in patients with chronic kidney disease and hypertension

The association of heart rate (HR) dipping pattern with renal outcomes in chronic kidney disease (CKD) patients with hypertension has never been investigated. In order to demonstrate if HR dipping pattern is a risk factor for renal outcomes, cardiovascular (CV) diseases, and mortality in hypertensive patients with CKD, we conducted the prospective longitudinal observational study. Patients were divided into three groups according to their nocturnal HR: HR dippers (night-day HR ratio ≤ 0.9), HR non-dippers (0.9 < night-day HR ratio ≤ 1.0), and HR risers (night-day HR ratio > 1.0). The primary outcome was renal endpoint, a composite outcome of progression to end-stage renal disease (ESRD) or estimated glomerular filtration rate (eGFR) decline ≥ 50%; the secondary outcomes included poor renal outcomes, CV events, and death. A total of 34 (11.3%) patients reached renal endpoint after a follow-up of 34 ± 17 months. Both HR non-dippers and HR risers were predictive to renal endpoint (hazard ratio 2.58, 95% confidence interval (CI) 1.04- 6.4, P = .04; hazard ratio 3.95, 95% CI 1.33- 11.79, P = .01, respectively), while only HR risers was shown to be correlated with a decline in eGFR≥ 50% (hazard ratio 5.28, 95% CI 1.45-19.16, P < .05), and decline in eGFR (β -0.17, 95% CI -0.33- -0.01, P = .04). No predictive value was found for HR dipping pattern to mortality and CV events. In conclusion, our study provided the first evidence that HR non-dippers, especially risers were a risk factor for poor renal outcomes in hypertensive patients with CKD.

Differences in estimated glomerular filtration rate are associated with different patterns of 24-h ambulatory blood pressure in the general population

BACKGROUND

Alterations of the circadian blood pressure rhythm are associated with cardiovascular and chronic kidney diseases. We investigated the relationship between 24-h ambulatory blood pressure monitoring (ABPM) patterns and eGFR differences in participants without chronic kidney disease.

METHOD

This cross-sectional study was conducted using data from the ongoing Korean Genome and Epidemiology Study, which involves 1733 participants (age, 60 ± 7 years; 938 women) with an eGFR >60 ml/min per 1.73 m2. The blood pressure dipping status was stratified as reverse-dipper (<0%), nondipper (0 to <10%), and dipper (≥10%). They were also categorized into eGFR quartiles (Q4, 128.6-101.6; Q3, 101.5-95.7; Q2, 95.6-87.4; and Q1, 87.3-60.5), and Q4 was fixed as the reference.

RESULTS

The proportion of dippers progressively decreased and the proportions of reverse and nondippers significantly increased from the highest to the lowest eGFR quartile (P < 0.001). In the univariate analyses, the Q1 and Q2 groups were significantly associated with increasing odds ratios (ORs) for the nondipper, reverse-dipper, and nondipper plus reverse-dipper groups. After adjustment, the lowest eGFR group was significantly associated with the reverse-dipper and nondipper plus reverse-dipper patterns in comparison with the highest eGFR group [OR = 1.685, 95% confidence interval (CI), 1.002-2.834; OR = 1.422, 95% CI, 1.023-1.978, respectively). The significant linear trend for an association of the nondipper plus reverse-dipper pattern with a decrease in eGFR was confirmed with the test for trend (P = 0.023).

CONCLUSION

Differences in eGFR are associated with different 24-h ABPM patterns in non-CKD individuals. ABPM can identify individuals with a nondipper status in this population.

Association Between Nocturnal Blood Pressure Dipping and Chronic Kidney Disease Among Patients With Controlled Office Blood Pressure

BACKGROUND

Although abnormal blood pressure (BP) patterns are associated with adverse cardiorenal outcomes, their associations are yet unquantified by nocturnal dipping status. We examined the association of nocturnal BP dipping pattern with albuminuria and kidney function among participants with controlled hypertension without prior advanced kidney disease.

METHODS

Ambulatory BP (ABP) measurements were collected from 995 middle-aged, cardiology clinic patients with controlled office BP (OBP) (<140/90 mm Hg). The magnitude of dipping was calculated as the difference between daytime and nighttime systolic BP (SBP) divided by daytime SBP. Accordingly, the participants were categorized as extreme-dipper (≥20%), dipper (10% to <20%), non-dipper (0% to <10%), or reverse-dipper (<0%). We analyzed the cross-sectional associations of dipping with albuminuria (urine albumin-to-creatinine ratio ≥30 mg/g) and decreased estimated glomerular filtration rate (<60 ml/min/1.73 m2), adjusting for OBP/ABP, antihypertensive class, body mass index, total cholesterol, fasting glucose, socioeconomic status, and health behavior.

RESULTS

The participants (mean age 60.2 years; 52.9% male) consisted of 13.5% extreme-dippers, 43.1% dippers, 34.7% non-dippers, and 8.7% reverse-dippers. In reference to dippers, odds ratios [95% confidence interval] for albuminuria were 1.73 [1.04-2.60] in reverse-dippers, 1.67 [1.20-2.32] in non-dippers, and 0.62 [0.38-1.04] in extreme-dippers. Likewise, abnormal dipping profile was associated with decreased kidney function: reverse-dipping, 2.02 [1.06-3.84]; non-dipping, 1.98 [1.07-3.08]; extreme-dipping, 0.69 [0.20-1.17]. The associations persisted among participants with more conservatively controlled OBP (<130/80 mm Hg).

CONCLUSIONS

Monitoring diurnal and nocturnal BP may identify chronic kidney disease otherwise overlooked based on OBP.

Abnormal diurnal blood pressure profile and hypertension-mediated organ damage in nondiabetic chronic kidney disease G1-G3b patients

OBJECTIVE

Chronic kidney disease (CKD) is associated with high cardiovascular risk. Prevalence of hypertension and hypertension-mediated organ damage (HMOD) increases with CKD progression. Nocturnal blood pressure (BP) is a strong predictor of cardiovascular complications. This cross-sectional study investigated the link between the diurnal BP profile and HMOD in nondiabetic CKD G1-G3b patients.

METHODS

We investigated 109 CKD patients and 41 apparently healthy persons as controls. All subjects underwent 24-ambulatory blood pressure monitoring (ABPM), echocardiography with left ventricular mass index (LVMI) calculation and pulse wave velocity (PWV) measurement.

RESULTS

Hypertension was present in 84% of CKD patients. SBP-24 and DBP-24, SBP-day and DBP-day did not differ between CKD and controls. Significant differences were found in SBP-night and DBP-night. The nondipping BP profile (SBP-night/SBP-day ratio ≥0.9) was found in 62% of CKD patients and 32% of controls (P < 0.005). Nocturnal hypertension was found in 56% of CKD patients. LVMI was higher in CKD compared to controls, higher in nondipping than dipping CKD patients, and higher in patients with nocturnal hypertension than without nocturnal hypertension. Abnormal left ventricular geometry was found in 72% nondipping and 43% dipping CKD patients. PWV was higher in CKD than in controls, in patients with nocturnal hypertension than without nocturnal hypertension but did not differ between CKD nondippers and dippers.

CONCLUSION

The nondipping BP profile and nocturnal hypertension are associated with HMOD in G1-G3b CKD patients. Hence, there is a need for more extensive use of ABPM for individual risk assessment and personalization of antihypertensive treatment in CKD patients.

Practical application of ABPM in the pediatric nephrology clinic

The use of 24-h ABPM has become commonplace when diagnosing and managing hypertension in the pediatric population. Multiple clinical guidelines recommend ABPM as the preferred method for identifying white-coat hypertension, masked hypertension, and determining degree of blood pressure (BP) control. Accurate, timely diagnosis and optimal management are particularly important in certain populations, such as children with chronic kidney disease (CKD), diabetes, and other conditions with increased risk for cardiovascular disease. Understanding how best to utilize ABPM to achieve these goals is important for pediatric nephrologists and other hypertension specialists. This review will provide practical information on the equipment, application, interpretation, and documentation of ABPM in the specialty clinic.

Nocturnal blood pressure is associated with sympathetic nerve activity in patients with chronic kidney disease

Elevated nocturnal blood pressure (BP) and nocturnal non-dipping are frequently observed in patients with chronic kidney disease (CKD) and are stronger predictors of cardiovascular complications and CKD progression than standard office BP. The sympathetic nervous system (SNS) is thought to modulate diurnal hemodynamic changes and the vascular endothelium plays a fundamental role in BP regulation. We hypothesized that SNS overactivity and endothelial dysfunction in CKD are linked to elevated nocturnal BP and non-dipping. In 32 CKD patients with hypertension (56 ± 7 years), office BP, 24-hr ambulatory BP, muscle sympathetic nerve activity (MSNA) and endothelial function via flow-mediated dilation (FMD) were measured. Participants were subsequently divided into dippers (nighttime average BP > 10% lower than the daytime average BP, n = 8) and non-dippers (n = 24). Non-dippers had higher nighttime BP (p < .05), but not office and daytime BP, compared to dippers. MSNA burst incidence (81 ± 13 versus 67 ± 13 bursts/100 HR, p = .019) was higher and brachial artery FMD (1.7 ± 1.5 versus 4.7 ± 1.9%, p < .001) was lower in non-dippers compared to dippers. MSNA and FMD each predicted nighttime systolic (β = 0.48,-0.46, p = .02, 0.07, respectively) and diastolic BP (β = 0.38,-0.47, p = .04, 0.03, respectively) in multivariate-adjusted analyses. Our novel findings demonstrate that unfavorable nocturnal BP profiles are associated with elevated SNS activity and endothelial dysfunction in CKD. Specifically, CKD patients with higher nighttime BP and the non-dipping pattern have higher MSNA and lower FMD. These support our hypothesis that SNS overactivation and endothelial dysfunction are linked to the dysregulation of nighttime BP as well as the magnitude of BP lowering at nighttime in CKD.

Nocturnal blood pressure changes in Parkinson's disease: correlation with autonomic dysfunction and vitamin D levels

Nocturnal blood pressure (BP) changes are an indicator of autonomic dysfunction. We aim to investigate the correlation between nocturnal blood pressure (BP) variability, vitamin D levels and Parkinson's disease severity (PD) in this study. Thirty-five patients with PD participated in the study. Disease severity was evaluated by United Parkinson's Disease Rating Scale (UPDRS) and Hoehn and Yahr Scale (HYS). Equivalent levodopa dose was calculated and 25-hydroxyvitamin D levels were measured. The Non-Motor Symptom Questionnaire (NMSQ) was applied to all patients. Ambulatory BP monitoring for 24 h was established. Patients were divided into three groups according to nocturnal BP results: dippers (normal finding-a decline in mean nighttime BP of more than 10%); non-dippers (pathological-a decline in mean nighttime BP of less than 10%); reverse dippers (pathological-an increase in mean nighttime BP) .The mean score of the NMSQ was higher in the group with HYS > 2 (p = 0.050). Four patients were dipper, 17 patients were non-dipper and 16 patients were reverse dipper. There was no significant difference between the three groups in terms of age, gender, disease duration, age of the disease onset, disease stage, disease duration, dopamine agonist usage, levodopa equivalent dose, vitamin D level and NMSQ scores. NMSQ scores are high in advanced PD. Ambulatory BP monitoring is useful in detecting autonomic dysfunction. The number of patients with non-dipping and reverse dipping is high in PD, independent from PD severity, drug dose, vitamin D and the other NMS symptoms.

Ambulatory blood pressure monitoring-based analysis of long-term outcomes for kidney disease progression

Non-dipping nocturnal blood pressure (BP) pattern is a predictor of the future decline of renal function; however, it is unclear whether it is still a risk for chronic kidney disease (CKD) patients with normal BP. To solve this question, a retrospective cohort study was conducted, and 1107 CKD patients who underwent ambulatory blood pressure monitoring (ABPM) were enrolled. We divided patients into 4 groups based on their nocturnal BP dipping pattern (dipper or non-dipper) and average 24-hour BP (hypertension or normotension). The cumulative incidence of composite renal outcomes, including a 40% reduction in eGFR, the induction of renal-replacement therapy, or death from renal causes, was analyzed. Overall, 86.1% of participants were non-dippers and 48.2% of them were normotensive. During the median follow-up period of 4.72 years, the incidence of renal composite outcomes was highest in hypertensive non-dipper patients, and was similar between normotensive dipper and non-dipper patients. Multivariate regression analysis revealed that the 24-hour systolic BP, amount of urinary protein, and hemoglobin values were associated with the incidence of renal outcomes. In conclusion, our ABPM-based analysis revealed that a non-dipping BP pattern with normotension does not predict the future incidence of composite renal outcomes in CKD patients.

Ambulatory Blood Pressure at Sea Level and High Altitude in a Climber with a Kidney Transplant and Hypertension

Background and Objectives: High altitude may increase blood pressure (BP) and the kidney plays an important role in acclimatization. Little is known about how transplanted kidneys respond to the hypoxic stress at high altitude. We compared 24 hour ambulatory BP in a climber with a kidney transplant and hypertension at sea level and at high altitude (2860-4300 m). Methods: Welch-Allyn ABPM 6100 monitor was used to collect heart rate, systolic BP (SBP), and diastolic BP every 30 minutes while awake, and hourly while asleep. BP was monitored for 49 hours at sea level and for 53 hours at 2860-4300 m. Results: Overall mean SBP did not differ between altitudes. At high altitude, the participant's mean nocturnal BP increased, but this "reverse dipping" pattern was not observed at sea level. The participant had no evidence of altitude illness or infectious complications at high altitude. Conclusions: This case builds on previous reports that kidney transplant recipients may safely travel to high altitude. Further study is required to determine the generalizability to other travelers with kidney transplant and/or underlying hypertension, and the clinical significance of short-term elevated nocturnal BP at high altitude.

Blood pressure and heart rate variability are linked with hyperphosphatemia in chronic kidney disease patients

Hyperphosphatemia is a common complication of chronic kidney disease (CKD) and is associated with cardiovascular disease (CVD), which has contributed to an increase in mortality of CKD patients. The onset of CVD often varies by time-of-day. Acute myocardial infarction or ventricular arrhythmia occurs most frequently during early morning. Blood pressure (BP) and heart rate circadian rhythms account for the diurnal variations in CVD. Preservation of normal circadian time structure from the cardiomyocyte level to the whole organ system is essential for cardiovascular health and CVD prevention. Independent risk factors, such as reduced heart rate variability (HRV) and increased BP variability (BPV), are particularly prevalent in patients with CKD. Analysis of HRV is an important clinical tool for characterizing cardiac autonomic status, and reduced HRV has prognostic significance for various types of CVD. Circadian BP rhythms are classified as extreme dipper, dipper, non-dipper or riser. It has been reported that nocturnal riser BP pattern contributes to cardiovascular threats. Previous studies have indicated that the circadian rhythm of serum phosphate in CKD patients is consistent with the general population, with the highest diurnal value observed in the early morning hours, followed by a progressive decrease to the lowest value of the day, which occurs around 11:00 am. Rhythm abnormalities have become the main therapeutic target for treating CVD in CKD patients. It has been reported that high levels of serum phosphate are associated with reduced HRV and increased BPV in CKD patients. However, the mechanisms related to interactions between hyperphosphatemia, HRV and BPV have not been fully elucidated. This review focuses on the evidence and discusses the potential mechanisms related to the effects of hyperphosphatemia on HRV and BPV.

Role and prognostic value of individual ambulatory blood pressure components in chronic kidney disease

Hypertension is a key risk factor for chronic kidney disease (CKD), but can also be a detrimental consequence of established CKD. Unsurprisingly, the majority of subjects with abnormal creatinine in the general population are also hypertensive, with a huge toll on national health care systems worldwide due to a staggering increase in the risk of cardiovascular complications and end-stage renal disease requiring renal replacement therapy. In this setting, a comprehensive and careful assessment of the whole 24-h blood pressure (BP) profile could be of paramount importance in ensuring a timely diagnosis of hypertension and an optimal therapeutic control. Hence, ambulatory BP monitoring (ABPM) has the potential to become the preferred method for optimal clinical management of CKD patients. ABPM might better define the relationship between BP, target organ damage (TOD), and clinical outcomes. Current evidence suggests that specific day-night BP components, along with average BP values, may have clinical relevance in such patients, despite the suboptimal statistical power of available studies and inconsistencies on the prognostic value of individual BP components. The main aim of our review is to scrutinize the evidence for the usage of ABPM in CKD patients, including the relationship between ambulatory BP recordings and cardiovascular events, and the distinctive features of ABPM in these subjects.

Renal denervation attenuates hypertension but not salt sensitivity in ETB receptor-deficient rats

Hypertension is a prevalent pathology that increases risk for numerous cardiovascular diseases. Because the etiology of hypertension varies across patients, specific and effective therapeutic approaches are needed. The role of renal sympathetic nerves is established in numerous forms of hypertension, but their contribution to salt sensitivity and interaction with factors such as endothelin-1 are poorly understood. Rats deficient of functional ET_B receptors (ET_B-def) on all tissues except sympathetic nerves are hypertensive and exhibit salt-sensitive increases in blood pressure. We hypothesized that renal sympathetic nerves contribute to hypertension and salt sensitivity in ET_B-def rats. The hypothesis was tested through bilateral renal sympathetic nerve denervation and measuring blood pressure during normal salt (0.49% NaCl) and high-salt (4.0% NaCl) diets. Denervation reduced mean arterial pressure in ET_B-def rats compared with sham-operated controls by 12 ± 3 (SE) mmHg; however, denervation did not affect the increase in blood pressure after 2 wk of high-salt diet (+19 ± 3 vs. +16 ± 3 mmHg relative to normal salt diet; denervated vs. sham, respectively). Denervation reduced cardiac sympathetic-to-parasympathetic tone [low frequency-high frequency (LF/HF)] during normal salt diet and vasomotor LF/HF tone during high-salt diet in ET_B-def rats. We conclude that the renal sympathetic nerves contribute to the hypertension but not to salt sensitivity of ET_B-def rats.