Effects of Reduced Kidney Function Because of Living Kidney Donation on Left Ventricular Mass

Risk for subsequent hypertension and cardiovascular disease after living kidney donation: is it clinically relevant?

The first successful live donor kidney transplant was performed in 1954. Receiving a kidney transplant from a live kidney donor remains the best option for increasing both life expectancy and quality of life in patients with end-stage kidney disease. However, ever since 1954, there have been multiple questions raised on the ethics of live kidney donation in terms of negative impacts on donor life expectancy. Given the close relationship between reduced kidney function in patients with chronic kidney disease (CKD) and hypertension, cardiovascular disease and cardiovascular mortality, information on the impact of kidney donation on these is particularly relevant. In this article, we review the existing evidence, focusing on the more recent studies on the impact of kidney donation on all-cause mortality, cardiovascular mortality, cardiovascular disease and hypertension, as well as markers of cardiovascular damage including arterial stiffness and uraemic cardiomyopathy. We also discuss the similarities and differences between the pathological reduction in renal function that occurs in CKD, and the reduction in renal function that occurs because of a donor nephrectomy. Kidney donors perform an altruistic act that benefits individual patients as well as the wider society. They deserve to have high-quality evidence on which to make informed decisions.

The impact of epicardial adipose tissue in patients with acute myocardial infarction

AIMS

Epicardial adipose tissue (EAT) has been linked to impaired reperfusion success after percutaneous coronary intervention (PCI). Whether EAT predicts myocardial damage in the early phase after acute myocardial infarction (MI) is unclear. Therefore, we investigated whether EAT in patients with acute MI is associated with more microvascular obstruction (MVO), greater ST-deviation, larger infarct size and reduced myocardial salvage index (MSI).

METHODS AND RESULTS

This retrospective analysis of a prospective observational study including patients with acute MI (n = 54) undergoing PCI and 12 healthy matched controls. EAT, infarct size and MSI were analyzed with cardiac magnetic resonance imaging, conducted 3-5 days and 12 weeks after MI. Patients with acute MI showed higher EAT volume than healthy controls (46 [25.;75. percentile: 37;59] vs. 24 [15;29] ml, p < 0.001). The high EAT group (above median) showed significantly more MVO (2.22 [0.00;5.38] vs. 0.0 [0.00;2.18] %, p = 0.004), greater ST-deviation (0.38 [0.22;0.55] vs. 0.15 [0.03;0.20] mV×10-1, p = 0.008), larger infarct size at 12 weeks (23 [17;29] vs. 10 [4;16] %, p < 0.001) and lower MSI (40 [37;54] vs. 66 [49;88] %, p < 0.001) after PCI than the low EAT group. After accounting for demographic characteristics, body-mass index, heart volume, infarct location, TIMI-flow grade as well as apnea-hypopnea index, EAT was associated with infarct size at 12 weeks (B = 0.38 [0.11;0.64], p = 0.006), but not with MSI.

CONCLUSIONS

Patients with acute MI showed higher volume of EAT than healthy individuals. High EAT was linked to more MVO and greater ST-deviation. EAT was associated with infarct size, but not with MSI.

Biomarkers of high salt intake

High salt intake is associated with hypertension, which is a leading modifiable risk factor for cardiovascular disease (CVD) and chronic kidney disease (CKD). International Guidelines recommend a large reduction in the consumption of sodium to reduce blood pressure, organ damage, and mortality. In its early stages, the symptoms of CKD are generally not apparent. CKD proceeds in a "silent" manner, necessitating the need for urinary biomarkers to detect kidney damage at an early stage. Since traditional renal biomarkers, such as serum creatinine, are not sufficiently sensitive, difficulties are associated with detecting kidney damage induced by a high salt intake, particularly in normotensive individuals. Several new biomarkers for renal tubular damage, such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), vanin-1, liver-type fatty acid-binding protein (L-FABP), and monocyte chemotactic protein-1 (MCP-1), have recently been identified. However, few studies have investigated early biomarkers for CKD progression associated with a high salt diet. This chapter provides insights into novel biomarkers for CKD in normo- and hypertensive individuals with a high salt intake. Recent studies using spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) fed a high salt diet identified urinary vanin-1 and NGAL as early biomarkers for renal tubular damage in SHR and WKY, whereas urinary KIM-1 was a useful biomarker for salt-induced renal injury in SHR only. Clinical studies are needed to confirm these findings.

Abnormal P-wave terminal force in lead V1 is a marker for atrial electrical dysfunction but not structural remodelling

Aims

There is a lack of diagnostic and therapeutic options for patients with atrial cardiomyopathy and paroxysmal atrial fibrillation. Interestingly, an abnormal P‐wave terminal force in electrocardiogram lead V₁ (PTFV₁) has been associated with atrial cardiomyopathy, but this association is poorly understood. We investigated PTFV₁ as a marker for functional, electrical, and structural atrial remodelling.

Methods and results

Fifty‐six patients with acute myocardial infarction and 13 kidney donors as control cohort prospectively underwent cardiac magnetic resonance imaging to evaluate the association between PTFV₁ and functional remodelling (atrial strain). To further investigate underlying pathomechanisms, right atrial appendage biopsies were collected from 32 patients undergoing elective coronary artery bypass grafting. PTFV₁ was assessed as the product of negative P‐wave amplitude and duration in lead V₁ and defined as abnormal if ≥4000 ms*μV. Activity of cardiac Ca/calmodulin‐dependent protein kinase II (CaMKII) was determined by a specific HDAC4 pull‐down assay as a surrogate for electrical remodelling. Atrial fibrosis was quantified using Masson's trichrome staining as a measure for structural remodelling. Multivariate regression analyses were performed to account for potential confounders. A total of 16/56 (29%) of patients with acute myocardial infarction, 3/13 (23%) of kidney donors, and 15/32 (47%) of patients undergoing coronary artery bypass grafting showed an abnormal PTFV₁. In patients with acute myocardial infarction, left atrial (LA) strain was significantly reduced in the subgroup with an abnormal PTFV₁ (LA reservoir strain: 32.28 ± 12.86% vs. 22.75 ± 13.94%, P = 0.018; LA conduit strain: 18.87 ± 10.34% vs. 10.17 ± 8.26%, P = 0.004). Abnormal PTFV₁ showed a negative correlation with LA conduit strain independent from clinical covariates (coefficient B: −7.336, 95% confidence interval −13.577 to −1.095, P = 0.022). CaMKII activity was significantly increased from (normalized to CaMKII expression) 0.87 ± 0.17 to 1.46 ± 0.15 in patients with an abnormal PTFV₁ (P = 0.047). This increase in patients with an abnormal PTFV₁ was independent from clinical covariates (coefficient B: 0.542, 95% confidence interval 0.057 to 1.027, P = 0.031). Atrial fibrosis was significantly lower with 12.32 ± 1.63% in patients with an abnormal PTFV₁ (vs. 20.50 ± 2.09%, P = 0.006), suggesting PTFV₁ to be a marker for electrical but not structural remodelling.

Conclusions

Abnormal PTFV₁ is an independent predictor for impaired atrial function and for electrical but not for structural remodelling. PTFV₁ may be a promising tool to evaluate patients for atrial cardiomyopathy and for risk of atrial fibrillation.

Prognostic values of left ventricular mass index in chronic kidney disease patients

BACKGROUND

Left ventricular hypertrophy is causally implicated in the high risk of death and heart failure (HF) in chronic kidney disease (CKD) patients. Whether the left ventricular mass index (LVMI) adds meaningful predictive power for mortality and de novo HF to simple risk models has not been tested in the CKD population.

METHODS

We investigated this problem in 1352 CKD patients enrolled in the Chronic Renal Insufficiency Cohort (CRIC). LVMI was measured by echocardiography and the risks for death and HF were estimated by the Study of Heart and Renal Protection (SHARP) score, a well-validated risk score in CKD patients.

RESULTS

During a median follow-up of 7.7 years, 326 patients died and 208 had de novo HF. The LVMI and the SHARP score and a cross-validated model for HF (CRIC model) were all significantly (P < 0.001) related to the risk of death and HF. LVMI showed a discriminatory power for death (Harrell's C index 66%) inferior to that of the SHARP score (71%) and the same was true for the risk of HF both in the test (LVMI 72%, CRIC model 79%) and in the validation cohort (LVMI 71%, CRIC model 74%). LVMI increased very little the discriminatory (2-3%) and the risk reclassification power (3.0-4.8%) by the SHARP score and the CRIC model for HF for the same outcomes.

CONCLUSIONS

In CKD, measurement of LVMI solely for the stratification of risk of death and perhaps for the risk of HF does not provide evident prognostic values in this condition.

Increased risk of ischemic heart disease after kidney donation

Background

Previous reports suggest increased risk of hypertension and cardiovascular mortality after kidney donation. In this study we investigate the occurrence of ischaemic heart disease and cerebrovascular disease, diabetes and cancer in live kidney donors compared with healthy controls eligible for donation.

Methods

Different diagnoses were assessed in 1029 kidney donors and 16 084 controls. The diagnoses at follow-up were self-reported for the controls and registered by a physician for the donors. Stratified logistic regression was used to estimate associations with various disease outcomes, adjusted for gender, age at follow-up, smoking at baseline, body mass index at baseline, systolic blood pressure at baseline and time since the donation.

Results

The mean observation time was 11.3 years [standard deviation (SD) 8.1] for donors versus 16.4 years (SD 5.7) for controls. The age at follow-up was 56.1 years (SD 12.4) in donors versus 53.5 years (SD 11.1) in controls and 44% of donors were males versus 39.3% in the controls. At follow-up, 35 (3.5%) of the donors had been diagnosed with ischaemic heart disease versus 267 (1.7%) of the controls. The adjusted odds ratio for ischaemic heart disease was 1.64 (confidence interval 1.10–2.43; P = 0.01) in donors compared with controls. There were no significant differences for the risks of cerebrovascular disease, diabetes or cancer.

Conclusions

During long-term follow-up of kidney donors, we found an increased risk of ischaemic heart disease compared with healthy controls. This information may be important in the follow-up and selection process of living kidney donors.

Cardiovascular Effects of Unilateral Nephrectomy in Living Kidney Donors at 5 Years

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Kidney donation reduces renal function by ≈30% allowing study of the cardiovascular effects of a reduced estimated glomerular filtration rate without comorbidities. We report 5-year results of a longitudinal, parallel-group, blinded end-point study of living kidney donors (n=50) and healthy controls (n=45). The primary end point, left ventricular mass, was measured using cardiac magnetic resonance. Secondary end points, 24-hour ambulatory blood pressure, and pulse wave velocity were measured using validated blood pressure monitors and the SphygmoCor device. Effect sizes were calculated as differences between change from baseline in the donor and control groups. In donors, estimated glomerular filtration rate was 95±15 mL/min per 1.73 m2 at baseline (predonation) and 67±14 mL/min per 1.73 m2 at 5 years. In controls, there was a −1±2 mL/min per 1.73 m2 decline per annum. Change in left ventricular mass at 5 years was not significantly different between donors and controls (mean difference, +0.40 g [95% CI, −4.68 to 5.49] P=0.876), despite an initial increase in mass in donors compared with controls at 12 months. Pulse wave velocity, which increased in donors at 12 months, returned to levels not different from controls at 5 years (mean difference, −0.24 m/s [95% CI, −0.69 to 0.21]). Change in ambulatory systolic blood pressure was not different in donors compared with controls (mean difference, +1.91 mm Hg [95% CI, −2.72 to 6.54]). We found no evidence that the reduction in estimated glomerular filtration rate after kidney donation was associated with a change in left ventricular mass detectable by magnetic resonance imaging at 5 years.

Coronary flow velocity reserve and inflammatory markers in living kidney donors

BACKGROUND

Coronary microvascular dysfunction is prevalent in chronic kidney disease (CKD), and may contribute to the development of myocardial dysfunction in CKD. Coronary flow velocity reserve (CFVR) is a marker of coronary microvascular function and falls with increasing CKD stage. Living kidney donors have renal function consistent with early stage CKD and concern has been raised about their cardiovascular risk. No studies to date have investigated the presence of coronary microvascular dysfunction in living kidney donors.

METHODS

25 healthy controls and 23 living kidney donors were recruited and underwent assessment with transthoracic echocardiography, Doppler CFVR, myocardial contrast echocardiography and serum multiplex immunoassay panels.

RESULTS

Doppler CFVR was significantly reduced in living kidney donors compared to controls (mean CFVR 3.4 ± 0.7 vs 3.8 ± 0.6, mean difference 0.4 95% confidence interval 0.03-0.8, p =.036). Quantitative myocardial contrast echocardiography showed a trend towards reduced coronary flow reserve in living kidney donors. Compared to controls, living kidney donors had higher serum high sensitivity C reactive peptide (hsCRP) and lower levels of uromodulin.

CONCLUSIONS

This is the first study of CFVR in living kidney donors. We have shown that the modest drop in estimated glomerular filtration rate in living kidney donors is associated with lower values of Doppler CFVR compared to controls, suggesting that isolated reductions in renal function may lead to altered microvascular function. The increase in hsCRP and reduction in uromodulin suggests that chronic subclinical inflammation may contribute to altered microvascular function in this population.

Aortic Stiffness and Heart Failure in Chronic Kidney Disease

Purpose of Review

To provide an update on the recent findings in the field of aortic stiffness and heart failure in patients with chronic kidney disease (CKD).

Recent Findings

Stratification of cardiovascular risk in CKD remains an open question. Recent reports suggest that aortic stiffness, an independent predictor of cardiovascular events in many patient populations, is also an important prognostic factor in CKD. Also, novel measures of myocardial tissue characterization, native T1 and T2 mapping techniques, have potential as diagnostic and prognostic factors in CKD.

Summary

Cardiovascular magnetic resonance has the ability to thoroughly evaluate novel imaging markers: aortic stiffness, native T1, and native T2. Novel imaging markers can be used for diagnostic and prognostic purposes as well as potential therapeutic targets in CKD population.

Cardiovascular rEmodelling in living kidNey donorS with reduced glomerular filtration rate: rationale and design of the CENS study

Purpose: Until recently, it has been believed that donating a kidney not represents any risk for development of cardiovascular disease. However, a recent Norwegian epidemiological study suggests that kidney donors have an increased long-term risk of cardiovascular mortality. The pathophysiological mechanisms linking reduced kidney function to cardiovascular disease are not known. Living kidney donors are screened for cardiovascular morbidity before unilateral nephrectomy, and are left with mildly reduced glomerular filtration rate (GFR) after donation. Therefore, they represent an unique model for investigating the pathogenesis linking reduced GFR to cardiovascular disease and cardiovascular remodelling. We present the study design of Cardiovascular rEmodelling in living kidNey donorS with reduced glomerular filtration rate (CENS), which is an investigator-initiated prospective observational study on living kidney donors. The hypothesis is that living kidney donors develop cardiovascular remodelling due to a reduction of GFR.Materials and methods: 60 living kidney donors and 60 age and sex matched healthy controls will be recruited. The controls will be evaluated to fulfil the Norwegian transplantation protocol for living kidney donors. Investigations will be performed at baseline and after 1, 3, 6 and 10 years in both groups. The investigations include cardiac magnetic resonance imaging, echocardiography, bone density scan, flow mediated dilatation, laser Doppler flowmetry, nailfold capillaroscopy, office blood pressure, 24-h ambulatory blood pressure, heart rate variability and investigation of microbiota and biomarkers for inflammation, cardiovascular risk and the calcium-phosphate metabolism.Conclusions: The present study seeks to provide new insight in the pathophysiological mechanisms linking reduced kidney function to cardiovascular disease. In addition, we aim to enlighten predictors of adverse cardiovascular outcome in living kidney donors. The study is registered at Clinical-Trials.gov (identifier: NCT03729557).

High plasma guanidinoacetate-to-homoarginine ratio is associated with high all-cause and cardiovascular mortality rate in adult renal transplant recipients

L-Arginine:glycine amidinotransferase (AGAT) is the main producer of the creatine precursor, guanidinoacetate (GAA), and L-homoarginine (hArg). We and others previously reported lower levels of circulating and urinary hArg in renal transplant recipients (RTR) compared to healthy subjects. In adults, hArg emerged as a novel risk factor for renal and cardiovascular adverse outcome. Urinary GAA was found to be lower in children and adolescents with kidney transplants compared to healthy controls. Whether GAA is also a risk factor in the renal and cardiovascular systems of adults, is not yet known. In the present study, we aimed to investigate the significance of circulating GAA and the GAA-to-hArg molar ratio (GAA/hArg) in adult RTR. We hypothesized that GAA/hArg represents a measure of the balanced state of the AGAT activity in the kidneys, and would prospectively allow assessing a potential association between GAA/hArg and long-term outcome in RTR. The median follow-up period was 5.4 years. Confounders and potential mediators of GAA/hArg associations were evaluated with multivariate linear regression analyses, and the association with all-cause and cardiovascular mortality or death-censored graft loss was studied with Cox regression analyses. The study cohort consisted of 686 stable RTR and 140 healthy kidney donors. Median plasma GAA concentration was significantly lower in the RTR compared to the kidney donors before kidney donation: 2.19 [1.77-2.70] µM vs. 2.78 [2.89-3.35] µM (P < 0.001). In cross-sectional multivariable analyses in RTR, HDL cholesterol showed the strongest association with GAA/hArg. In prospective analyses in RTR, GAA/hArg was associated with a higher risk for all-cause mortality (hazard ratio (HR): 1.35 [95% CI 1.19-1.53]) and cardiovascular mortality (HR: 1.46 [95% CI 1.24-1.73]), independent of potential confounders. GAA but not GAA/hArg was associated with death-censored graft loss in crude survival and Cox regression analyses. The association of GAA and death-censored graft loss was lost after adjustment for eGFR. Our study suggests that in the kidneys of RTR, the AGAT-catalyzed biosynthesis of GAA is decreased. That high GAA/hArg is associated with a higher risk for all-cause and cardiovascular mortality may suggest that low plasma hArg is a stronger contributor to these adverse outcomes in RTR than GAA.

Chronic kidney disease as a cardiovascular risk factor: lessons from kidney donors

Chronic kidney disease (CKD) is a major risk factor for cardiovascular disease but is often associated with other risks such as diabetes and hypertension and can be both a cause and an effect of cardiovascular disease. Although epidemiologic data of an independent association of reduced glomerular filtration rate with cardiovascular risk are strong, causative mechanisms are unclear.

Living kidney donors provide a useful model for assessing the “pure” effects of reduced kidney function on the cardiovascular system. After nephrectomy, the glomerular filtration rate ultimately falls by about one-third so many can be classified as having chronic kidney disease stages 2 or 3. This prompts concern based on the data showing an elevated cardiovascular risk with these stages of chronic kidney disease. However, initial data suggested no increase in adverse cardiovascular effects compared with control populations. Recent reports have shown a possible late increase in cardiovascular event rates and an early increase in left ventricular mass and markers of risk such as urate and albuminuria. The long-term significance of these small changes is unknown. More detailed and long-term research is needed to determine the natural history of these changes and their clinical significance.

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Subjects with chronic kidney disease (CKD) have an elevated risk of cardiovascular disease.

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Kidney donors have a reduced glomerular filtration rate and biochemical changes similar to CKD subjects.

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Most studies of donors have not shown an elevated risk of death or cardiac disease.

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Donors have structural and functional cardiovascular changes similar to early CKD.

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The clinical significance of these changes is currently unknown.