Early and asymptomatic cardiac dysfunction in chronic kidney disease

Bilateral nephrectomy impairs cardiovascular function and cerebral perfusion in a rat model of acute hemodilutional anemia

Anemia and renal failure are independent risk factors for perioperative stroke, prompting us to assess the combined impact of acute hemodilutional anemia and bilateral nephrectomy (2Nx) on microvascular brain Po2 (PBro2) in a rat model. Changes in PBro2 (phosphorescence quenching) and cardiac output (CO, echocardiography) were measured in different groups of anesthetized Sprague-Dawley rats (1.5% isoflurane, n = 5-8/group) randomized to Sham 2Nx or 2Nx and subsequently exposed to acute hemodilutional anemia (50% estimated blood volume exchange with 6% hydroxyethyl starch) or time-based controls (no hemodilution). Outcomes were assessed by ANOVA with significance assigned at P < 0.05. At baseline, 2Nx rats demonstrated reduced CO (49.9 ± 9.4 vs. 66.3 ± 19.3 mL/min; P = 0.014) and PBro2 (21.1 ± 2.9 vs. 32.4 ± 3.1 mmHg; P < 0.001) relative to Sham 2Nx rats. Following hemodilution, 2Nx rats demonstrated a further decrease in PBro2 (15.0 ± 6.3 mmHg, P = 0.022). Hemodiluted 2Nx rats did not demonstrate a comparable increase in CO after hemodilution compared with Sham 2Nx (74.8 ± 22.4 vs. 108.9 ± 18.8 mL/min, P = 0.003) that likely contributed to the observed reduction in PBro2. This impaired CO response was associated with reduced fractional shortening (33 ± 9 vs. 51 ± 5%) and increased left ventricular end-systolic volume (156 ± 51 vs. 72 ± 15 µL, P < 0.001) suggestive of systolic dysfunction. By contrast, hemodiluted Sham 2Nx animals demonstrated a robust increase in CO and preserved PBro2. These data support the hypothesis that the kidney plays a central role in maintaining cerebral perfusion and initiating the adaptive increase in CO required to optimize PBro2 during acute anemia.NEW & NOTEWORTHY This study has demonstrated that bilateral nephrectomy acutely impaired cardiac output (CO) and microvascular brain Po2 (PBro2), at baseline. Following acute hemodilution, nephrectomy prevented the adaptive increase in CO associated with acute hemodilution leading to a further reduction in PBro2, accentuating the degree of cerebral tissue hypoxia. These data support a role for the kidney in maintaining PBro2 and initiating the increase in CO that optimized brain perfusion during acute anemia.

Cardiac transcriptomic changes induced by early CKD in mice reveal novel pathways involved in the pathogenesis of Cardiorenal syndrome type 4

Background

Cardiorenal syndrome (CRS) type 4 is prevalent among the chronic kidney disease (CKD) population, with many patients dying from cardiovascular complications. However, limited data regarding cardiac transcriptional changes induced early by CKD is available.

Methods

We used a murine unilateral ureteral obstruction (UUO) model to evaluate renal damage, cardiac remodeling, and transcriptional regulation at 21 days post-surgery through histological analysis, RT-qPCR, RNA-seq, and bioinformatics.

Results

UUO leads to significant kidney injury, low uremia, and pathological cardiac remodeling, evidenced by increased collagen deposition and smooth muscle alpha-actin 2 expression. RNA-seq analysis identified 76 differentially expressed genes (DEGs) in UUO hearts. Upregulated DEGs were significantly enriched in cell cycle and cell division pathways, immune responses, cardiac repair, inflammation, proliferation, oxidative stress, and apoptosis. Gene Set Enrichment Analysis further revealed mitochondrial oxidative bioenergetic pathways, autophagy, and peroxisomal pathways are downregulated in UUO hearts. Vimentin was also identified as an UUO-upregulated transcript.

Conclusions

Our results emphasize the relevance of extensive transcriptional changes, mitochondrial dysfunction, homeostasis deregulation, fatty-acid metabolism alterations, and vimentin upregulation in CRS type 4 development.

What Links Chronic Kidney Disease and Ischemic Cardiomyopathy? A Comprehensive Bioinformatic Analysis Utilizing Bulk and Single-Cell RNA Sequencing Data with Machine Learning

Chronic kidney disease (CKD) emerges as a substantial contributor to various cardiovascular disorders, including ischemic cardiomyopathy (ICM). However, the underlying molecular mechanisms linking CKD and ICM remain elusive. Our study aims to unravel these connections by integrating publicly available bulk and single-cell RNA sequencing (scRNA-seq) data. Expression profiles from two ICM datasets obtained from heart tissue and one CKD with Peripheral Blood Mononuclear Cell (CKD-PBMC) dataset were collected. We initiated by identifying shared differentially expressed genes (DEGs) between ICM and CKD. Subsequent functional enrichment analysis shed light on the mechanisms connecting CKD to ICM. Machine learning algorithms enabled the identification of 13 candidate genes, including AGRN, COL16A1, COL1A2, FAP, FRZB, GPX3, ITIH5, NFASC, PTN, SLC38A1, STARD7, THBS2, and VPS35. Their expression patterns in ICM were investigated via scRNA-seq data analysis. Notably, most of them were enriched in fibroblasts. COL16A1, COL1A2, PTN, and FAP were enriched in scar-formation fibroblasts, while GPX3 and THBS2 showed enrichment in angiogenesis fibroblasts. A Gaussian naïve Bayes model was developed for diagnosing CKD-related ICM, bolstered by SHapley Additive exPlanations interpretability and validated internally and externally. In conclusion, our investigation unveils the extracellular matrix's role in CKD and ICM interplay, identifies 13 candidate genes, and showcases their expression patterns in ICM. We also constructed a diagnostic model using 13 gene features and presented an innovative approach for managing CKD-related ICM through serum-based diagnostic strategies.

A systematic review and meta-analysis of the clinical impact of stopping renin-angiotensin system inhibitor in patients with chronic kidney disease

Although renin-angiotensin system (RAS) inhibitors reduce the risk of cardiovascular diseases and end-stage kidney disease (ESKD) in chronic kidney disease (CKD) patients, they are often discontinued in clinical practice due to drug-related adverse events. However, limited evidence is available about the clinical impact of RAS inhibitor discontinuation in CKD patients. A comprehensive search of publications investigating the effect of discontinuing RAS inhibitors on clinical outcomes in CKD patients in PubMed, the Cochrane Library, and Web of Science was conducted (inception to November 7, 2022), and potentially relevant studies were searched by hand (through November 30, 2022). Two reviewers independently extracted data according to the PRISMA and MOOSE guidelines and assessed the quality of each study with risk-of-bias tools, RoB2 and ROBINS-I. The pooled hazard ratio (HR) for each outcome was integrated with a random-effect model. A total of 1 randomized clinical trial and 6 observational studies involving 248,963 patients were included in the systematic review. The meta-analysis of observational studies showed that discontinuation of RAS inhibitors was associated with a higher risk of all-cause mortality (HR, 1.41 [95% CI, 1.23-1.62]; I² = 97%), ESKD (1.32 [95% CI, 1.10-1.57]; I² = 94%) and MACE (1.20 [95% CI 1.15-1.25]; I² = 38%), but not with hyperkalemia (0.79 [95% CI 0.55-1.15]; I² = 90%). Overall risk of bias was moderate-to-serious, and quality of evidence (GRADE system) was low-to-very low. The present study suggests that CKD patients would benefit from continuing RAS inhibitors.

Effects of renin-angiotensin system inhibitors on the incidence of unplanned dialysis

Unplanned dialysis initiation is associated with poor outcomes. It is controversial whether patients with advanced chronic kidney disease (CKD) should receive renin-angiotensin system (RAS) inhibitor therapy. The aim of this study was to evaluate the effect of RAS inhibitor therapy in patients with advanced CKD on the incidence of unplanned dialysis initiation. This single-center, retrospective study included patients who started maintenance dialysis at our hospital between April 2014 and March 2021. Patients who initiated dialysis within 6 months of nephrology referral or after kidney transplant were excluded. Among 334 patients (aged 70.0 [59.0-79.0] years; 28.4% women), 186 (55.7%) and 148 (44.3%) had planned and unplanned dialysis initiation, respectively. Multivariate logistic regression analysis revealed that the use of RAS inhibitors was significantly associated with a lower incidence of unplanned dialysis initiation (odds ratio [OR], 0.36; P < 0.01). Female sex (OR, 0.41; P < 0.05), use of potassium binders (OR, 0.28; P < 0.001), earlier referral to nephrology (OR, 0.39; P < 0.01), and earlier discussion of renal replacement therapy (OR, 0.33; P < 0.001) were also significantly associated with a lower incidence, whereas older age (OR, 1.28; P < 0.05), higher Charlson Comorbidity Index (OR, 1.24; P < 0.05), and faster decline in kidney function (OR, 1.29; P < 0.01) were associated with a higher risk of unplanned dialysis initiation. RAS inhibitor therapy in patients with advanced CKD is associated with a lower risk of unplanned dialysis initiation.

Cardiopulmonary reserve examined with cardiopulmonary exercise testing in individuals with chronic kidney disease: A systematic review and meta-analysis

BACKGROUND

Patients with chronic kidney disease (CKD) often present reduced physical activity and exercise tolerance due to factors relevant to co-existing disturbances of the cardiac, nervous and muscular systems. Cardiopulmonary exercise testing (CPET) is used for clinical evaluation of exercise limitation and related symptoms (i.e., dyspnea, fatigue) in several medical fields.

OBJECTIVES

This is a systematic review and meta-analysis of studies using CPET technology to examine cardiopulmonary reserve in individuals with versus without CKD.

METHODS

Literature search involved PubMed, Web of Science and Scopus databases; manual search of article references and of gray literature was also performed. Observational studies and randomized trials that used CPET for patients with CKD stage 1-5 versus controls were eligible. The primary outcome was peak oxygen uptake (VO₂peak). The Newcastle-Ottawa Scale was used to evaluate the quality of retrieved studies.

RESULTS

From an initial 4944 literature records, we identified 29 studies fulfilling the inclusion criteria; of these, 25 studies (2,213 participants) with complete data were included in the final meta-analysis. VO₂peak was significantly lower in CKD patients than controls without CKD [standardized mean difference (SMD) -1.40, 95% confidence interval (CI) -1.68; -1.13)]. Values were lower for CKD than non-CKD individuals for oxygen consumption at anaerobic threshold (SMD -1.06, 95% CI -1.34; -0.79) and maximum workload [weighted mean difference (WMD) -58.26, 95% CI 74.14; -42.38]. In 3 studies, CKD patients had higher VO₂peak than controls with heart failure without CKD (WMD 6.60, 95% CI 3.02; 10.18). Sensitivity analyses confirmed the robustness of these findings.

CONCLUSIONS

VO₂peak and other commonly analyzed CPET variables were lower in patients with CKD than controls, which indicates reduced functional cardiopulmonary reserve in CKD. In contrast, patients with CKD performed better than controls with heart failure without CKD. Overall, rehabilitation programs should be more widely applied to individuals with CKD.

PROSPERO REGISTRATION NUMBER

CRD42021227805.

Cardiorespiratory fitness assessed by cardiopulmonary exercise testing between different stages of pre-dialysis chronic kidney disease: A systematic review and meta-analysis

AIM

The burden of several cardiovascular risk factors increases in parallel to renal function decline. Exercise intolerance is common in patients with chronic kidney disease (CKD) and has been associated with increased risk of adverse outcomes. Whether indices of cardiorespiratory capacity deteriorate with advancing CKD stages is unknown.

METHODS

We conducted a systematic review and meta-analysis of studies assessing cardiorespiratory capacity in adult patients with pre-dialysis CKD using cardiopulmonary exercise testing (CPET) and reporting data for different stages. Our primary outcome was differences in peak oxygen uptake (VO₂ peak) between patients with CKD Stages 2-3a and those with Stages 3b-5(pre-dialysis). Literature search was undertaken in PubMed, Web of Science and Scopus databases, and abstract books of relevant meetings. Quality assessment was undertaken with Newcastle-Ottawa-Scale.

RESULTS

From 4944 records initially retrieved, six studies with 512 participants fulfilling our inclusion criteria were included in the primary meta-analysis. Peak oxygen uptake (VO₂ peak) was significantly higher in patients with CKD Stages 2-3a versus those with Stages 3b-5(pre-dialysis) [weighted-mean-difference, WMD: 2.46, 95% CI (1.15, 3.78)]. Oxygen consumption at ventilatory threshold (VO₂ VT) was higher in Stages 2-3a compared with those in Stages 3b-5(pre-dialysis) [standardized-mean-difference, SMD: 0.59, 95% CI (0.06, 1.1)], while no differences were observed for maximum workload and respiratory-exchange-ratio. A secondary analysis comparing patients with CKD Stages 2-3b and Stages 4-5(pre-dialysis), yielded similar results [WMD: 1.78, 95% CI (1.34, 2.22)]. Sensitivity analysis confirmed the robustness of these findings.

CONCLUSION

VO₂ peak and VO₂ VT assessed with CPET are significantly lower in patients in CKD Stages 3b-5 compared with Stages 2-3a. Reduced cardiorespiratory fitness may be another factor contributing to cardiovascular risk increase with advancing CKD.

Impact of chronic kidney disease in chronic total occlusion management and clinical outcomes

BACKGROUND

Data on the impact of chronic kidney disease (CKD) on clinical outcomes in chronic total occlusion (CTO) patients is scarce, and the optimal treatment strategy for this population is not well established. This study aims to compare differences in CTO management and long-term clinical outcomes, including all-cause and cardiac mortalities, according to baseline glomerular filtration rate (GFR).

METHODS

All patients with at least one CTO diagnosed in our center between 2010 and 2014 were included. Demographic and clinical data were registered. All-cause and cardiac mortalities were assessed during a median follow-up of 4.03 years (IQR 2.6-4.8). Clinical outcomes were compared between patients with CKD (GFR < 60 mL/min/1.73 m²) and without CKD (GFR ≥ 60 mL/min/1.73 m²).

RESULTS

A total of 1248 patients (67.3 ± 10.9 years; 32% CKD) were identified. CKD patients were older and had a higher prevalence of hypertension, type 2 diabetes, peripheral arterial disease, and severe left ventricular dysfunction compared to patients with normal renal function (p < 0.05). Subjects with renal dysfunction were more often treated with MT alone, compared to patients without CKD (63% vs 45%; p < 0.001), who were more likely to undergo PCI or surgery. During follow-up, 386 patients [31%] died. CKD patients had a higher rate of all-cause and cardiac mortalities compared to patients without CKD (p < 0.001). The independent predictors for all-cause mortality were age, GFR < 60 mL/min/1.73 m², Syntax Score I, and successful revascularization of the CTO (CABG or PCI-CTO). Among patients with CKD, advanced age, eGFR <30 mL/min/1.73 m², and CTO successful revascularization were predictors of all-cause mortality.

CONCLUSIONS

Patients with CKD were more often treated with MT alone. At long-term follow-up, revascularization of the CTO is associated with lower all-cause and cardiac mortalities in this population.

Cardiac and Noncardiac Determinants of Exercise Capacity in CKD

BACKGROUND

Impaired exercise capacity is a significant symptom of CKD and is associated with poor survival. Furthermore, there is a growing interest in applying exercise as a diagnostic tool or as therapy in CKD. However, an in-depth understanding of exercise physiology in CKD is still lacking.

METHODS

To evaluate the role of cardiac (central) and noncardiac (peripheral) determinants of exercise capacity in CKD, we conducted a cross-sectional study of 70 male patients with CKD (stages 2-5) without diabetes or cardiac disease, 35 healthy controls, and 25 patients with heart failure. An integrated cardiopulmonary exercise test using a CO₂ rebreathing technique was used to measure peak O₂ consumption (VO_2peak) and peak cardiac output simultaneously, and to calculate peak peripheral O₂ extraction (C[a-v]O₂), the peripheral determinant (the ability of exercising skeletal muscles to extract oxygen). We performed multiple regression analysis and used Bayesian information criteria (BIC) changes to quantitatively assess the individual contribution of central and peripheral factors.

RESULTS

Compared with healthy controls, in patients with CKD, the VO_2peak was impaired proportionate to its severity. Peak cardiac output was the predominant determinant of VO_2peak in healthy controls and patients with heart failure, whereas C(a-v)O₂ played a more significant role in determining VO_2peak in CKD (β=0.68, P<0.001) compared with cardiac output (β=0.63, P<0.001). In addition, the magnitude of BIC reduction was greater for C(a-v)O₂ compared with cardiac output (BIC, 298.72 versus 287.68) in CKD.

CONCLUSIONS

In CKD, both peak cardiac output and peak C(a-v)O₂ are independent predictors of VO_2peak, and the more significant roleplayed by peak C(a-v)O₂ highlights the importance of noncardiac factors in determining exercise capacity in CKD.

Association between social frailty as well as early physical dysfunction and exercise intolerance among older patients receiving hemodialysis

BACKGROUND

Recently, social frailty has been increasingly recognized as a factor associated with adverse health outcomes, including physical disability and mortality. However, there are no studies about the importance of this factor among hemodialysis patients. Therefore, we investigated the relationship between social frailty and early physical dysfunction in this group of patients.

METHODS

This was a two-center cross-sectional study. Older patients receiving hemodialysis were prospectively enrolled. Moreover, participants were evaluated for social frailty based on the definition of previous study and for physical function, peak oxygen uptake (peak VO₂ ), ventilatory equivalent for carbon dioxide (VE/VCO₂ ) slope and heart rate reserve. Then, they were divided into two groups based on the presence of physical frailty.

RESULTS

Data collected from 158 individuals were statistically analyzed. The prevalence rate of social frailty was 59.5%. In the non-physical frailty group, social frailty was found to be independently associated with reduced gait speed (P = 0.007), leg strength (P = 0.040) and peak VO₂ (P = 0.023), but not with hand grip strength (P = 0.36). In the physical frailty group, there was no association between social frailty and physical function. Moreover, in patients without physical and social frailty, physical function was maintained at above accepted threshold levels, whereas peak VO₂ (14.1 ± 3.3 mL/kg/min), VE/VCO₂ slope (32.3 ± 5.5) and heart rate reserve (50.8% ± 21.7%) were substantially impaired.

CONCLUSIONS

Patients receiving hemodialysis can present with social frailty and exercise intolerance with cardiac dysfunction in the early phase, which may contribute to subsequent dysfunction. Geriatr Gerontol Int 2021; 21: 664-669.

Cardiac Ultrasound for the Nephrologist: Know Thy Heart to Know Thy Kidneys

Kidney disease patients have a high prevalence of cardiovascular morbidity and mortality. It can be challenging to adequately assess their cardiovascular status based on physical examination alone. Cardiac ultrasound has proven to be a powerful tool to accomplish this objective and is increasingly being adopted by noncardiologists to augment their skills and expedite clinical decision-making. With the advent of inexpensive and portable ultrasound equipment, simplified protocols, and focused training, it is becoming easier to master basic cardiac ultrasound techniques. After a short course of training in focused cardiac ultrasound, nephrologists can quickly and reliably assess ventricular size and function, detect clinically relevant pericardial effusion and volume status in their patients. Additional training in Doppler ultrasound can extend their capability to measure cardiac output, right ventricular systolic pressure, and diastolic dysfunction. This information can be instrumental in effectively managing patients in inpatient, office, and dialysis unit settings. The purpose of this review is to highlight the importance and feasibility of incorporating cardiac ultrasound in nephrology practice, discuss the principles of basic and Doppler ultrasound modalities and their clinical utility from a nephrologist's perspective.

Assessment of Exercise Intolerance in Patients with Pre-Dialysis CKD with Cardiopulmonary Function Testing: Translation to Everyday Practice

BACKGROUND

Chronic kidney disease (CKD) is often characterized by increased prevalence of cardiovascular risk factors and increased incidence of cardiovascular events and death. Reduced cardiovascular reserve and exercise intolerance are common in patients with CKD and are associated with adverse outcomes.

SUMMARY

The gold standard for identifying exercise limitation is cardiopulmonary exercise testing (CPET). CPET provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise. It is useful in clinical setting for differentiation of the causes of exercise intolerance, risk stratification, and assessment of response to relevant treatments. A number of recent studies have used CPET in patients with pre-dialysis CKD, aiming to assess the cardiovascular reserve of these individuals, as well as the effect of interventions such as exercise training programs on their functional capacity. This review provides an in-depth description of CPET methodology and an overview of studies that utilized CPET technology to assess cardiovascular reserve in patients with pre-dialysis CKD. Key Messages: CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk. Potential clinical applications of CPET in CKD patients range from objective diagnosis of exercise intolerance to preoperative and long-term risk stratification and providing intermediate endpoints for clinical trials. Future studies should delineate the association of CPET indexes, with cardiovascular and respiratory alterations and hard outcomes in CKD patients, to enhance its diagnostic and prognostic utility in this population.

Aerobic exercise capacity is maintained over a 5-year period in mild-to-moderate chronic kidney disease: a longitudinal study

Background

Aerobic exercise capacity is reduced in non-dialysis chronic kidney disease (CKD), but the magnitude of changes in exercise capacity over time is less known. Our main hypothesis was that aerobic ExCap would decline over 5 years in individuals with mild-to-moderate CKD along with a decline in renal function. A secondary hypothesis was that such a decline in ExCap would be associated with a decline in muscle strength, cardiovascular function and physical activity.

Methods

We performed a 5-year-prospective study on individuals with mild-to-moderate CKD, who were closely monitored at a nephrology clinic. Fiftytwo individuals with CKD stage 2–3 and 54 age- and sex-matched healthy controls were included. Peak workload was assessed through a maximal cycle exercise test. Muscle strength and lean body mass, cardiac function, vascular stiffness, self-reported physical activity level, renal function and haemoglobin level were evaluated. Tests were repeated after 5 years. Statistical analysis of longitudinal data was performed using linear mixed models.

Results

Exercise capacity did not change significantly over time in either the CKD group or controls, although the absolute workloads were significantly lower in the CKD group. Only in a CKD subgroup reporting low physical activity at baseline, exercise capacity declined. Renal function decreased in both groups, with a larger decline in CKD (p = 0.05 between groups). Peak heart rate, haemoglobin level, handgrip strength, lean body mass and cardiovascular function did not decrease significantly over time in CKD individuals.

Conclusions

On a group level, aerobic exercise capacity and peak heart rate were maintained over 5 years in patients with well-controlled mild-to-moderate CKD, despite a slight reduction in glomerular filtration rate. In line with the maintained exercise capacity, cardiovascular and muscular function were also preserved. In individuals with mild-to-moderate CKD, physical activity level at baseline seems to have a predictive value for exercise capacity at follow-up.

Post-PCI acute heart failure is an independent predictor of long-term mortality in patients with chronic kidney disease

BACKGROUND

This study aimed to clarify the association of post-percutaneous coronary intervention (PCI) acute heart failure (AHF) with all-cause long-term mortality in patients with chronic kidney disease (CKD).

METHODS

In this prospective, observational study, 610 patients with CKD and coronary artery disease (CAD) undergoing PCI were included in the final analysis. Patients were divided to the non post-PCI AHF group (n = 557) and the post-PCI AHF group (n = 53). The diagnosis of post-PCI AHF was based on symptoms, prior cardiovascular history, and potential cardiac and noncardiac precipitants.

RESULTS

The overall incidence of post-PCI AHF was 53/610 (8.7%). The incidence of all-cause long-term mortality was significantly higher in the post-PCI AHF group than in the non post-PCI AHF group (50.9% vs 23.2%, P < .01). The median follow-up period was 7.3 years (interquartile range: 3.7-8.4). After adjusting for left ventricular ejection fraction <40% at discharge, CKD stage, acute myocardial infarction, age and smoking, post-PCI AHF was the strongest predictor of all-cause long-term mortality (hazard ratio: 8.08; 95% CI: 3.04-21.48; P < .01).

CONCLUSIONS

In patients with CKD and CAD undergoing PCI, post-PCI AHF is the strongest predictor of all-cause long-term mortality.

Impaired Systolic and Diastolic Left Ventricular Function in Children with Chronic Kidney Disease - Results from the 4C Study

Children with chronic kidney disease suffer from excessive cardiovascular mortality and early alterations of the cardiovascular system. Tissue doppler imaging is a validated echocardiographic tool to assess early systolic and diastolic cardiac dysfunction. We hypothesized that tissue Doppler velocities would reveal reduced cardiac function in children with chronic kidney disease compared to healthy children. A standardized echocardiographic exam was performed in 128 patients of the Cardiovascular Comorbidity in Children with Chronic Kidney Disease (4C) Study aged 6–17 years with an estimated glomerular filtration rate (eGFR) below 60 ml/min/1.73 m². Tissue Doppler measurements included early (E’) and late (A’) diastolic and systolic (S’) velocity at the mitral and septal annulus of the left ventricle. Measured values were normalized to z-scores using published reference data. Predictors of E’/A’, E/E’, S’ and left ventricular mass index (LVMI) were assessed by multiple linear regression analyses. Tissue Doppler E’ was reduced and tissue Doppler A’ increased, resulting in a reduced tissue Doppler E’/A’ ratio (z-score −0.14, p < 0.0001) indicating reduced diastolic function compared to healthy children. Reduced tissue Doppler E’/A’ Z-Scores were independently associated with lower eGFR (p = 0.002) and increased systolic blood pressure (p = 0.02). While E/E’ Z-Scores were increased (Z-score 0.57, p < 0.0001), patients treated with pharmacological RAS blockade but not with other antihypertensive treatments had significantly lower E/E’ and higher E’/A’ Z-Scores. Systolic tissue Doppler velocities were significantly decreased (Z-score −0.24, p = 0.001) and inversely correlated with E/E’ Z-Scores (r = −0.41, p < 0.0001). LVMI was not associated with systolic or diastolic tissue Doppler velocities. Concentric left ventricular hypertrophy showed a tendency to lower S’ in multivariate analysis (p = 0.13) but no association to diastolic function. Concentric left ventricular geometry was significantly associated with lower midwall fractional shortening. In summary, systolic and diastolic function assessed by tissue Doppler is impaired. eGFR, systolic blood pressure and the type of antihypertensive medications are significant predictors of diastolic function in children with CKD. Left ventricular morphology is largely independent of tissue Doppler velocities. Tissue Doppler velocities provide sensitive information about early left ventricular dysfunction in this population.

Gradual reduction in exercise capacity in chronic kidney disease is associated with systemic oxygen delivery factors

Background

The cause of reduced exercise capacity (ExCap) in chronic kidney disease (CKD) is multifactorial. The aim of this study was to investigate determinants of aerobic ExCap in patients with mild to severe CKD not undergoing dialysis.

Methods

We included 52 individuals with CKD stage 2–3, 47 with stage 4–5, and 54 healthy controls. Peak workload and peak heart rate (HR) were assessed by a maximal cycle exercise test. Cardiac function including stroke volume (SV) and vascular stiffness were evaluated by ultrasound at rest. Handgrip strength, body composition, haemoglobin level and self-reported physical activity were assessed.

Results

Peak workload (221±60, 185±59, 150±54 W for controls, CKD 2–3 and CKD 4–5 respectively), peak HR (177±11, 161±24, 144±31 beats/min) and haemoglobin level (14.2±1.2, 13.5±1.4, 12.2±1.3 g/dL) were all three significantly lower in CKD 2–3 than in controls, (p = 0.001, 0.001 and 0.03 respectively) and were even lower in stages 4–5 CKD than in CKD 2–3 (p = 0.01, 0.001 and <0.001 respectively). Resting SV and lean body mass did not differ between groups and handgrip strength was significantly lower only in CKD 4–5 compared to controls (p = 0.02). Peak workload was strongly associated with the systemic oxygen delivery factors: SV, peak HR and haemoglobin level. These three factors along with age, sex and height² explained 82% of variation in peak workload. Peak HR contributed most to the variation; the peripheral variables handgrip strength and vascular stiffness did not improve the explanatory value in regression analysis.

Conclusions

In this cross-sectional study of CKD patients not on dialysis, aerobic ExCap decreased gradually with disease severity. ExCap was associated mainly with systemic oxygen delivery factors, in particular peak HR. Neither muscle function and mass, nor vascular stiffness were independent determinants of aerobic ExCap in this group of CKD patients.

Association between Protein-Bound Uremic Toxins and Asymptomatic Cardiac Dysfunction in Patients with Chronic Kidney Disease

Although the relationship between protein-bound uremic toxins (PBUTs) and cardiac structure and cardiac mortality in chronic kidney disease (CKD) has been studied in the past, the association between cardiac dysfunction and PBUTs has not yet been studied. We therefore evaluated the association between impaired peak cardiac performance and the serum free and total concentrations of potentially cardiotoxic PBUTs. In a cross-sectional study of 56 male CKD patients (stages 2–5 (pre-dialysis)) who were asymptomatic with no known cardiac diseases or diabetes we measured peak cardiac power (CPO_max), aerobic exercise capacity (VO_2max), and echocardiographic parameters of cardiac morphology and evaluated their association with PBUTs. The serum total and free concentrations of indoxyl sulfate (IXS), p-cresyl sulfate (PCS), p-cresyl glucuronide, indole acetic acid, and hippuric acid showed significant negative correlation with CPO_max and VO_2max. IXS and PCS were independently associated with CPO_max and VO_2max even after controlling for eGFR. No correlation between left ventricular mass index (LVMI) and PBUTs was seen. The present study for the first time has demonstrated the association between subclinical cardiac dysfunction in CKD and serum levels of a panel of PBUTs. Further studies are required to evaluate the mechanism of cardiotoxicity of the individual uremic toxins.

Pathological cardiac remodeling occurs early in CKD mice from unilateral urinary obstruction, and is attenuated by Enalapril

Cardiovascular disease constitutes the leading cause of mortality in patients with chronic kidney disease (CKD) and end-stage renal disease. Despite increasing recognition of a close interplay between kidney dysfunction and cardiovascular disease, termed cardiorenal syndrome (CRS), the underlying mechanisms of CRS remain poorly understood. Here we report the development of pathological cardiac hypertrophy and fibrosis in early stage non-uremic CKD. Moderate kidney failure was induced three weeks after unilateral urinary obstruction (UUO) in mice. We observed pathological cardiac hypertrophy and increased fibrosis in UUO-induced CKD (UUO/CKD) animals. Further analysis indicated that this cardiac fibrosis was associated with increased expression of transforming growth factor β (TGF-β) along with significant upregulation of Smad 2/3 signaling in the heart. Moreover early treatment of UUO/CKD animals with an angiotensin-converting-enzyme inhibitor (ACE I), Enalapril, significantly attenuated cardiac fibrosis. Enalapril antagonized activation of the TGF-β signaling pathway in the UUO/CKD heart. In summary our study demonstrates the presence of pathological cardiac hypertrophy and fibrosis in mice early in UUO-induced CKD, in association with early activation of the TGF-β/Smad signaling pathway. We also demonstrate the beneficial effect of ACE I in alleviating this early fibrogenic process in the heart in UUO/CKD animals.

The effect of sildenafil on rats with adenine-Induced chronic kidney disease

The erectile dysfunction drug sildenafil has cardiopulmonary protective actions, and a nephroprotective action in cisplatin and ischemia-reperfusion-induced acute kidney injury. Here, we assessed its possible ameliorative action in a model of chronic kidney disease (CKD) using adenine feeding. Eight groups of rats were treated with saline (controls), adenine (0.25% w/w in feed daily for 5 weeks), and oral sildenafil (0.1, 0.5 or 2.5 mg/kg), either alone, or concomitantly with adenine. Urine was collected 24 h after the end of the treatments from all rats and blood pressure measured, followed by collection of blood and kidneys for the measurement of several functional, biochemical and histopathological parameters. Adenine treatment reduced body weight, creatinine renal clearance, and increased water intake and urine output, as well as the plasma concentrations of urea and creatinine, neutrophil gelatinase-associated lipocalin, and N-acetyl-β-D-glucosaminidase activity, and albumin in urine. Adenine also increased the concentrations of the uremic toxins indoxyl sulfate, uric acid and phosphate, and a number of proteins and inflammatory cytokines, and decreased that of several anti - oxidant indices. Renal histopathological markers of damage (inflammation and fibrosis) were significantly increased by adenine. Sildenafil, given simultaneously with adenine, induced a dose - dependent improvements in most of the above parameters, suggesting its possible use as adjunct treatment for CKD in humans.

The complex relationship among arteriovenous access, heart, and circulation

There are currently near 400 000 patients on hemodialysis in the United States. More than 50% of those treated by chronic hemodialysis die because of a cardiovascular (CV) event. The majority of these patients have functional arteriovenous fistulas (AVFs). AVFs have an adverse effect on cardiac function, but their exact contribution to CV morbidity is not clear. It has long been known that a vascular access with an inappropriately high-flow rate may cause high-output heart failure. Paradoxically, there may be hemodynamic and cardiopulmonary benefits conferred by AVF particularly in severe chronic obstructive pulmonary disease. While Brescia-Cimino`s basic idea of the AVF has saved millions of lives, we would like to stress that there are dangers from their often high blood flow rates, which unfortunately have proved difficult to evaluate.