Plasma sodium and subclinical left atrial enlargement in chronic kidney disease

Kidney Function, Albuminuria, and Risk of Incident Atrial Fibrillation: A Systematic Review and Meta-Analysis

RATIONALE & OBJECTIVE

Atrial fibrillation (AF) and chronic kidney disease (CKD) often coexist. However, it is not known whether CKD is an independent risk factor for incident AF. Therefore, we evaluated the association between markers of CKD-estimated glomerular filtration rate (eGFR) and albuminuria-and incident AF.

STUDY DESIGN

Systematic review and meta-analysis of cohort studies and randomized controlled trials.

SETTING & STUDY POPULATIONS

Participants with measurement of eGFR and/or albuminuria who were not receiving dialysis.

SELECTION CRITERIA FOR STUDIES

Cohort studies and randomized controlled trials were included that reported incident AF risk in adults according to eGFR and/or albuminuria.

ANALYTICAL APPROACH

Age- or multivariate-adjusted risk ratios (RRs) for incident AF were extracted from cohort studies, and RRs for each trial were derived from event data. RRs for incident AF were pooled using random-effects models.

RESULTS

38 studies involving 28,470,249 participants with 530,041 incident AF cases were included. Adjusted risk of incident AF was greater among participants with lower eGFR than those with higher eGFR (eGFR<60 vs≥60mL/min/1.73m2: RR, 1.43; 95% CI, 1.30-1.57; and eGFR<90 vs≥90mL/min/1.73m2: RR, 1.42; 95% CI, 1.26-1.60). Adjusted incident AF risk was greater among participants with albuminuria (any albuminuria vs no albuminuria: RR, 1.43; 95% CI, 1.25-1.63; and moderately to severely increased albuminuria vs normal to mildly increased albuminuria: RR, 1.64; 95% CI, 1.31-2.06). Subgroup analyses showed an exposure-dependent association between CKD and incident AF, with the risk increasing progressively at lower eGFR and higher albuminuria categories.

LIMITATIONS

Lack of patient-level data, interaction between eGFR and albuminuria could not be evaluated, possible ascertainment bias due to variation in the methods of AF detection.

CONCLUSIONS

Lower eGFR and greater albuminuria were independently associated with increased risk of incident AF. CKD should be regarded as an independent risk factor for incident AF.

PLAIN-LANGUAGE SUMMARY

Irregular heartbeat, or atrial fibrillation (AF), is the commonest abnormal heart rhythm. AF occurs commonly in people with chronic kidney disease (CKD), and CKD is also common in people with AF. However, CKD in not widely recognized as a risk factor for new-onset or incident AF. In this research, we combined data on more than 28 million participants in 38 studies to determine whether CKD itself increases the chances of incident AF. We found that both commonly used markers of kidney disease (estimated glomerular filtration rate and albuminuria, ie, protein in the urine) were independently associated with a greater risk of incident AF. This finding suggests that CKD should be recognized as an independent risk factor for incident AF.

Impact of Renal Dysfunction on Left Atrial Low-Voltage Areas in Patients With Atrial Fibrillation

BACKGROUND

The presence of residual left atrial low-voltage areas (LVA) has been shown to be strongly associated with atrial fibrillation (AF) recurrence after pulmonary vein isolation. A preliminary study showed that concomitant chronic kidney disease (CKD) increased the rate of AF recurrence. The association between CKD and LVA, however, has not been elucidated. In the present study, we investigated the association between CKD severity and LVA prevalence. Methods and Results: In total, 183 consecutive AF patients who underwent initial ablation for AF were enrolled in this retrospective observational study. Serum cystatin C before ablation was measured, and the estimated glomerular filtration rate (eGFR) was calculated. LVA were defined as sites of left atrial electrogram amplitude <0.5 mV. Of 183 patients, 76 (42%) had LVA. Patients with LVA had lower eGFR calculated using cystatin C (74±22 vs. 86±24 mL/min/1.73 m², P=0.001). The optimal cut-off of the calculated eGFR was 71.5 mL/min/1.73 m², corresponding to a 79.4% sensitivity, 50% specificity, and 67.2% predictive accuracy. LVA occurred more frequently in patients with more severe categories of CKD. On multivariate analysis, eGFR <71.5 mL/min/1.73 m²was an independent predictor of LVA (odds ratio, 3.3; 95% CI: 1.4-7.8; P=0.006).

CONCLUSIONS

CKD severity was correlated with left atrial LVA prevalence in patients with AF undergoing catheter ablation.

Association between pre hemodialysis serum sodium concentration and blood pressure: results from a retrospective analysis from the international monitoring dialysis outcomes (MONDO) initiative

A recent study from the United Kingdom indicates an association between pre hemodialysis (HD) serum sodium (SNa(+)) and systolic and diastolic blood pressure (SBP and DBP) in chronic HD patients. We extend this analysis to an international cohort of incident HD patients. The Monitoring Dialysis Outcomes initiative encompasses patients from 41 countries. Over 2 years monthly pre-HD SNa(+) levels were used as predictors of pre-HD SBP and DBP in a linear mixed model (LMM) adjusted for age, gender, interdialytic weight gain, diabetes, serum albumin and calcium. Similar models were constructed with DBP as outcome. Analyses were carried out stratified by continent (North and South America; Europe and Asia). LMMs were also constructed for the entire observation period of 2 years, and separately the first and the second year after HD initiation. We studied 17 050 incident patients and found SNa(+) to have a significant slope estimate in the LMM predicting pre-HD SBP and DBP (ranging from 0.22 to 0.29 and 0.10 to 0.21 mm Hg per mEq l(-1), respectively, between the continents). The findings were similar in subsets of SBP and SNa(+) tertiles, and separately analyzed for the first and second year. Our analysis shows an independent association between SNa, SBP and DBP in a large intercontinental database, indicating that this relation is a profound biological phenomenon in incident and prevalent HD patients, generalizable to an international level and independent of SBP and DBP magnitude.

Lower plasma sodium is associated with a microinflammatory state among patients with advanced chronic kidney disease

BACKGROUND/AIMS

Lower serum sodium levels have been associated with increased mortality among patients with chronic kidney disease (CKD). Our aim was to analyze the independent factors associated with lower sodium levels among nondialysis patients with advanced CKD and to evaluate the evolution of these patients in comparison to those with higher plasma sodium over a 1-year period.

METHODS

We included 72 patients with CKD stages 4 and 5 without clinically evident cardiopathy or liver disease. Bioelectrical impedance and echocardiography were performed to analyze the possible relation between plasma sodium and volume status and subclinical left ventricular (LV) dysfunction. During follow-up, we compared the evolution of patients with lower baseline plasma sodium (low quartile: <138 mEq/l) with that of patients with higher levels over a 1-year period.

RESULTS

At baseline, the independent predictors of lower plasma sodium were C-reactive protein (CRP; OR 0.96; 95% CI 0.91-0.99) and body mass index (OR 0.89; 95% CI 0.78-0.99). An inverse correlation between plasma sodium and CRP was observed (r = -0.32; p = 0.01). Plasma sodium did not correlate with extracellular water and was not different between patients with or without echocardiographic data of LV dysfunction (p = 0.7). During follow-up, patients with lower sodium at baseline showed persistently lower sodium values (p = 0.04), higher CRP (p = 0.05), lower serum albumin (p < 0.01) and higher erythropoietin-stimulating agent resistance index (p = 0.05).

CONCLUSIONS

Our results suggest an association between lower plasma sodium and a microinflammatory state among patients with advanced CKD. Inflammation could be an underlying confounding factor explaining the increased mortality in these patients.

Cardiovascular remodeling during long-term nocturnal home hemodialysis

BACKGROUND

Cardiovascular disease is the leading cause of morbidity and mortality in patients with kidney failure. Nocturnal home hemodialysis (NHD) is a form of kidney replacement therapy whereby hemodialysis is performed for at least 6-h overnight, at least 4 days per week. Little is known about the effects of NHD on cardiovascular remodeling as assessed by transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR).

OBJECTIVES

The primary objective of the study was to determine the long-term effects of NHD on cardiovascular remodeling using different imaging modalities over a one-year follow-up.

METHODS AND RESULTS

A total of 11 patients were included in the study (6 males, mean age 48 ± 16 years) between 2009 and 2011 inclusive at a single tertiary care center. All patients underwent TTE and CMR at baseline and after 1 year of NHD. Left ventricular mass index decreased significantly at 1 year by both TTE (152 ± 7-129 ± 8 g/m(2), p < 0.05) and CMR (162 ± 4-124 ± 4 g/m(2), p < 0.05). There was also a significant decrease in both left and right atrial volume as well as in right ventricular mass index over 1 year of follow-up. Diastolic dysfunction, graded from 0 to 4, improved from a baseline grade of 3.4 to 1.2 at 1-year follow-up.

CONCLUSIONS

Long-term nocturnal hemodialysis leads to favorable cardiovascular remodeling with a reduction in cavity dimensions, regression of left ventricular hypertrophy, and an improvement in diastolic function, as assessed by both TTE and CMR.

Blood pressure and amiloride-sensitive sodium channels in vascular and renal cells

Sodium transport in the distal nephron is mediated by epithelial sodium channel activity. Proteolytic processing of external domains and inhibition with increased sodium concentrations are important regulatory features of epithelial sodium channel complexes expressed in the distal nephron. By contrast, sodium channels expressed in the vascular system are activated by increased external sodium concentrations, which results in changes in the mechanical properties and function of endothelial cells. Mechanosensitivity and shear stress affect both epithelial and vascular sodium channel activity. Guyton's hypothesis stated that blood pressure control is critically dependent on vascular tone and fluid handling by the kidney. The synergistic effects, and complementary regulation, of the epithelial and vascular systems are consistent with the Guytonian model of volume and blood pressure regulation, and probably reflect sequential evolution of the two systems. The integration of vascular tone, renal perfusion and regulation of renal sodium reabsorption is the central underpinning of the Guytonian model. In this Review, we focus on the expression and regulation of sodium channels, and we outline the emerging evidence that describes the central role of amiloride-sensitive sodium channels in the efferent (vascular) and afferent (epithelial) arms of this homeostatic system.

A look at the upper heart chamber: the left atrium in chronic kidney disease

Altered left ventricular (LV) mass and function are classical hallmarks of cardiomyopathy in chronic kidney disease (CKD). The left atrium (LA), a heart chamber exquisitely sensitive to volume overload and diastolic function, is an independent predictor of death and adverse cardiovascular (CV) events in high-risk patients such as those with hypertension and/or with heart failure. In this review we focus on the relationship of LA size with LV diastolic function, and the association between LA enlargement and CV and renal outcomes in patients with CKD, including patients with end-stage renal disease. Increased LA size emerges as a powerful predictor of mortality and major adverse CV events in both end-stage and early CKD, and some studies also show a close association between enlarged LA and renal disease progression. Secondary analyses of clinical trials suggest that the LA has the potential to be elected as a surrogate end point in CKD patients but the issue remains to be tested in specifically designed clinical studies.