Sympathetic nerve activity in end-stage renal disease

Catecholamines regulate the activity, secretion, and synthesis of renalase

BACKGROUND

We previously identified renalase, a secreted novel amine oxidase that specifically degrades circulating catecholamines. Parenteral administration of either native or recombinant renalase lowers blood pressure, heart rate, and cardiac contractility by metabolizing circulating catecholamines. Renalase plasma levels are markedly reduced in patients with chronic kidney disease. It is not known whether endogenous renalase contributes to the regulation of catecholamines.

METHODS AND RESULTS

We show here that circulating renalase lacks significant amine oxidase activity under basal conditions (prorenalase) but that a brief surge of epinephrine lasting <2 minutes causes renalase activity to increase from 48+/-18 to 2246+/-98 arbitrary units (n=3; P<0.002). Enzyme activation is detectable within 30 seconds and sustained for at least 60 minutes. Analysis of epinephrine-mediated hemodynamic changes in normotensive rats indicates that prorenalase becomes maximally activated when systolic pressure increases by >5 mm Hg. The catecholamine surge also leads to a 2.8-fold increase in plasma renalase concentration. Cultured cells exposed to dopamine upregulate steady-state renalase gene expression by >10-fold. The time course of prorenalase activation is abnormal in rats with chronic kidney disease.

CONCLUSIONS

These data identify a novel mechanism for the regulation of circulating catecholamines. In the renalase pathway, excess catecholamine facilitates the conversion of prorenalase, an inactive plasma amine oxidase, to renalase, which can degrade catecholamines. Excess catecholamines not only regulate the activation of prorenalase but also promote its secretion and synthesis. Because chronic kidney disease is associated with a number of systemic abnormalities, including activation of the sympathetic nervous system, increased catecholamines levels, cardiac hypertrophy, and hypertension, renalase replacement is an attractive therapeutic modality owing to its role in catecholamine metabolism.

Do beta-blockers combined with RAS inhibitors make sense after all to protect against renal injury?

In chronic kidney disease (CKD) sympathetic overactivity is stimulated by signals from the diseased kidney activating hypothalamic centers. In addition, breakdown of circulating catecholamines is decreased. Indications for beta-blockers are cardio- and renoprotection. Cardioprotection is important because cardiovascular (CV) death is two- to 20-fold more likely in CKD than end-stage kidney disease; consequently, beta-blockers, with their adverse effect on CV risk profile, should be avoided. Controlled prospective evidence for renoprotection by beta-blockers in nondiabetic CKD with hard end points is lacking, but renoprotection by antihypertensive agents was first documented by administering beta-blockers in patients with diabetic nephropathy. Renoprotection by beta-blockers was seen experimentally. Furthermore, controlled studies documented a beneficial effect on albuminuria as a surrogate marker for renoprotection in diabetic and nondiabetic patients. Renin-angiotensin system blockade is the undoubted first-line treatment in CKD. Several points argue for ancillary treatment with beta-blockers: in CKD often four or more different antihypertensive drugs are required and cardiac indications are frequent.

Should β-Blockers Be Used to Control Hypertension in People With Chronic Kidney Disease?

Activation of the sympathetic nervous system is common in patients with chronic kidney disease, plays an important role in the genesis of hypertension, the rate of decrease of renal function, and is associated with the increased cardiovascular morbidity and mortality seen in these patients. beta-blockers are potent antihypertensive agents but differ in their hemodynamic effects on renal function. The cardioselective beta-blockers such as atenolol and metoprolol are known to retard the progression of renal diseases, but to a lesser degree compared with blockers of the renin-angiotensin-aldosterone system. However, the newer vasodilating beta-blockers such as carvedilol and nebivolol have different effects on renal hemodynamics and function primarily because of its greater adjunctive alpha1-blocking activity. Carvedilol decreases renal vascular resistance and prevents reductions in the glomerular filtration rate and renal blood flow in patients with hypertension with or without impaired kidney function. In addition, carvedilol may retard progression of albuminuria, and provide cardiorenal protection in chronic kidney disease patients with hypertension, congestive heart failure, and at high risk for sudden cardiac death.

Hypertension After Renal Transplant

Hypertension is common after renal transplant and is associated with adverse graft and patient outcomes. A thorough understanding of the unique factors that operate in renal transplant recipients is essential for the proper evaluation and management of this disorder. In this review, the authors outline the pathogenesis, diagnostic workup, and treatment of hypertension after renal transplant.

Renalase, a new renal hormone: its role in health and disease

PURPOSE OF REVIEW

Renalase is a secreted amine oxidase that metabolizes catecholamines. The approach used to identify this novel renal hormone will be discussed, as will the experimental data suggesting it regulates cardiovascular function, and its deficiency contributes to heightened cardiovascular risks in patients with chronic kidney disease.

RECENT FINDINGS

The sympathetic nervous system is activated in chronic kidney disease and end-stage renal disease, and patients have a significant increase in cardiovascular disease. Parenteral administration of either native or recombinant renalase lowers blood pressure and heart rate by metabolizing circulating catecholamines. Plasma levels are markedly reduced in patients with chronic kidney disease and end-stage renal disease. Renalase deficiency occurs in salt-sensitive Dahl rats as they develop hypertension. Renalase inhibition by antisense RNA increases baseline blood pressure, and leads to an exaggerated blood pressure response to adrenergic stress. Most recently, two single nucleotide polymorphisms in the renalase gene were found to be associated with essential hypertension in humans.

SUMMARY

The renalase pathway is a previously unrecognized mechanism for regulating circulating catecholamines, and, therefore, cardiac function, and blood pressure. Abnormalities in the renalase pathway are evident in animal models of chronic kidney disease and hypertension. Collectively, these data suggest that renalase replacement may be an important therapeutic modality.

Upregulation of the brain renin-angiotensin system in rats with chronic renal failure

AIM

We investigated how the brain renin-angiotensin system is involved in regulation of the sympathetic activity and arterial pressure in rats with chronic renal failure.

METHODS

Systolic arterial pressure, heart rate and diurnal urinary noradrenaline excretion were measured for 12 weeks in spontaneously hypertensive rats (SHR) with or without subtotal nephrectomy. Expression of mRNAs related to the brain renin-angiotensin system was measured using polymerase chain reaction. Effects of a 6-day intracerebroventricular infusion of a type 1 angiotensin II receptor antagonist (candesartan) or bilateral dorsal rhizotomy on these variables were also investigated.

RESULTS

Systolic arterial pressure and urinary excretion of noradrenaline were consistently higher in subtotally nephrectomized SHR than in sham-operated SHR (262 +/- 5 vs. 220 +/- 3 mmHg, P < 0.001; 2.71 +/- 0.22 vs. 1.69 +/-0.19 ng g(-1) body weight day(-1), P < 0.001). Expression of renin, angiotensin-converting enzyme and type 1 angiotensin II receptor mRNAs in the hypothalamus and lower brainstem was greater in subtotally nephrectomized SHR than in sham-operated SHR. Continuous intracerebroventricular infusion of candesartan attenuated hypertension and the increase in urinary noradrenaline excretion in subtotally nephrectomized SHR. Dorsal rhizotomy decreased arterial pressure, urinary excretion of noradrenaline and expression of renin-angiotensin system-related mRNAs in brains of subtotally nephrectomized SHR.

CONCLUSION

The brain renin-angiotensin system in subtotally nephrectomized SHR appears to be activated via afferent nerves from the remnant kidney, resulting in sympathetic overactivity and hypertension in this chronic renal failure model.

Tonic chemoreflex activation contributes to the elevated muscle sympathetic nerve activity in patients with chronic renal failure

OBJECTIVE

Sympathetic activation may contribute to both cardiovascular morbidity and the progression of chronic kidney disease. The role of the chemoreceptors in determining sympathetic nerve discharge in patients with chronic renal failure (CRF) is unknown. We tested the hypothesis that tonic activation of excitatory chemoreceptor afferents contributes to the elevated sympathetic activity in patients with CRF.

METHODS

Utilizing a double-blind, randomized, vehicle-controlled design, we examined the effects of chemoreflex deactivation on muscle sympathetic nerve activity (MSNA). We compared effects of breathing 100% oxygen for 15 min with effects of breathing room air for 15 min in 12 stable patients with CRF and in 12 control individuals with similar age, gender, blood pressure and body mass index.

RESULTS

The baseline MSNA was elevated significantly in the patients with CRF as compared with the control individuals (50 +/- 2 vs 42 +/- 2 bursts/min; P < 0.05). Reductions in systolic blood pressure and pulse pressure in response to the administration of 100% oxygen were significantly different from those observed during administration of room air in patients with CRF. In patients with CRF, MSNA decreased by 29 +/- 7% (P < 0.01) during hyperoxia but did not change during administration of room air (5 +/- 6%; P = NS). By contrast, neither 100% oxygen or room air changed any measures in control individuals.

CONCLUSIONS

Tonic activation of excitatory chemoreflex afferents contributes to increased efferent sympathetic activity to muscle circulation and to blood pressure control in patients with CRF. These findings may have important implications for understanding mechanisms underlying the link between CRF and cardiovascular disease.

A possible relationship of nocturnal blood pressure variability with coronary artery disease in diabetic nephropathy

Evidence suggests a relationship between short-term blood pressure (BP) variability and cardiovascular target-organ damage. Although a blunted nocturnal decrease in BP and reduced heart rate variability have been shown to be associated with cardiovascular morbidity in diabetic patients, little information is available on short-term BP variability. In this study, short-term BP variability was assessed in 36 subjects with type 2 diabetes and overt nephropathy who underwent ambulatory BP monitoring, and the factors that correlated with short-term BP variability were examined. The incidence of coronary artery disease (CAD) was significantly greater in the patients with increased 24-h systolic BP variability (67% versus 11%; p < 0.0005), while that of cerebrovascular disease was not significantly affected (61% versus 50%). Multiple stepwise regression analysis revealed that serum cholesterol (cholesterol) and plasma norepinephrine (p-NE) were significant and independent contributors to nighttime systolic BP variability (partial R2 = 0.490, p < 0.001; partial R2 = 0.470, p < 0.001) and demonstrated that body mass index and p-NE were primary determinants of nighttime diastolic BP variability (partial R2 = 0.539, p < 0.0005; partial R2 = 0.304, p < 0.05). Diabetic nephropathy patients with CAD had significantly increased daytime systolic (17.8 mmHg versus 13.1 mmHg, p < 0.0005), nighttime systolic (17.4 mmHg versus 10.5 mmHg, p < 0.0001), and nighttime diastolic (10.4 mmHg versus 7.2 mmHg, p < 0.05) BP variability. Furthermore, logistic regression analysis demonstrated that nighttime systolic BP variability was an independent risk factor for CAD (odds ratio 3.13 [95% CI 1.02-9.61]; p < 0.05). The increase in nighttime BP variability is associated with a proportional sympathetic activation in diabetic nephropathy. Elevated short-term BP variability combined with relative sympathetic prevalence during the night might represent an important risk factor for cardiovascular events in the diabetic population.

Beta blockers in the management of chronic kidney disease

The sympathetic nervous system modulates renal function through its receptors namely beta1 (cardiac output and renin release), alpha1 (systemic and renovascular constriction), and beta2 renovascular dilation. Sympathetic overactivity is commonly seen in chronic kidney disease (CKD) and is an important contributor to increasing the risk of cardiovascular events as well as increasing renal disease progression. Recent evaluations of drug use in people with CKD shows a remarkably low percentage of patients receiving beta-blockers, especially in more advanced stage CKD when cardiovascular risk is higher. This is in large part due to tolerability of these agents. Moreover, water-soluble beta-blockers such as atenolol and metoprolol are dialyzable and require supplementation to avoid exacerbation of arrhythmias following dialysis. Newer vasodilating beta-blockers have better tolerability and different effects on renal hemodynamics as well as metabolic variables. These effects are related to the relative alpha1-blocking effect of agents such as carvedilol and labetolol, with carvedilol having relatively greater alpha-blocking effects. Few studies evaluate beta-blockers on cardiovascular risk in CKD patients. Studies with carvedilol demonstrate attenuated increases in albuminuria as well as reduction in cardiovascular events in CKD patients with hypertension. This paper reviews the animal and clinical trial data that evaluate beta-blockers in CKD highlighting the vasodilating beta-blockers. It is apparent that greater use of this drug class for blood pressure control would further enhance reduction of risk of heart failure, the most common cause of death in the first year of starting dialysis.

Sympathetic nerve activity in renal transplant patients before and after withdrawal of cyclosporine

BACKGROUND

It has been suggested that the increase in blood pressure observed in transplant patients treated with cyclosporine is mediated by cyclosporine-induced sympathoexcitation. However, the chronic effects of cyclosporine on sympathetic outflow in renal transplant patients have not been investigated. Therefore we studied sympathetic nerve activity and blood pressure before and 6 months after the withdrawal of cyclosporine in renal transplant patients.

METHODS

Twenty-four renal transplant patients with histologically confirmed chronic allograft nephropathy (age 48 +/- 3 years, 60 +/- 10 months after transplantation) were included in the prospective study and randomly assigned to either withdrawal (n = 12) or continuation (n = 12) of cyclosporine. Both groups received mycophenolate mofetil and prednisolone as additional immunosuppressants. At entry and 6 months later blood pressure, muscle sympathetic nerve activity (MSNA), and plasma norepinephrine were measured. To assess the potential influence of the diseased native kidneys, three renal transplant patients who had their native kidneys removed were studied before and after cyclosporine withdrawal.

RESULTS

Mean arterial pressure decreased significantly in the cyclosporine-withdrawal group (95 +/- 4 versus 105 +/- 4 mmHg 6 versus 0 months, P < 0.05) but not in the cyclosporine-continuation group (103 +/- 3 versus 105 +/- 4 mmHg, NS). However, plasma norepinephrine and MSNA did not change significantly in either group (MSNA 43 +/- 4 versus 44 +/- 3 and 38 +/- 5 versus 39 +/- 4 bursts/min in the cyclosporine-withdrawal and cyclosporine-continuation groups, NS). Graft function remained stable in both groups and in transplant patients who had their native kidneys removed MSNA did not decrease after cyclosporine withdrawal.

CONCLUSION

The withdrawal of cyclosporine in renal transplant patients, receiving relatively low doses of cyclosporine, resulted in a substantial decrease in blood pressure. However, MSNA and norepinephrine did not change. This suggests that cyclosporine treatment does not cause chronic sympathetic activation that could explain the cyclosporine-induced blood pressure elevation in renal transplant patients.

Increased arterial vascular tone during the night in patients with essential hypertension

The time-dependent incidence of cardiovascular events points to an important role of chronobiology for arterial properties. To evaluate arterial properties in patients with essential hypertension, we assessed arterial vascular tone during sleep at night in patients with essential hypertension and normotensive control subjects. Vascular tone was continuously quantified by the reflective index obtained by non-invasive digital photoplethysmography and an algorithm for continuous, investigator-independent, automatic analysis of digital volume pulse. During the first half of the night, the reflective index was significantly higher in 31 patients with essential hypertension compared to 30 normotensive control subjects (30.0+/-0.2 vs 28.8+/-0.2; P=0.001). In patients with essential hypertension, the reflective index significantly increased from 30.0+/-0.2 in the first half (from 2301 to 0230) to 30.7+/-0.2 in the second half (from 0231 to 0600) of the night (n=31; P=0.027). In normotensive control subjects the reflective index also significantly increased from 28.8+/-0.2 in the first half of the night to 30.2+/-0.2 in the second half of the night (n=30; P=0.001). An increase of the reflective index tone indicated systemic vasoconstriction as confirmed by cold pressure tests and a significant correlation between arterial vascular tone and sympathetic nerve activity measured by microneurography from the peroneal nerve. Photoplethysmographic determination of arterial vascular tone demonstrated a significant increase of systemic arterial vascular tone in patients with essential hypertension during the first half of the night compared to normotensive control subjects.

Left ventricular mass and heart sympathetic activity after renal transplantation in children and young adults

Recent studies considered that an increase in sympathetic activity (SA) may be responsible for left ventricular hypertrophy (LVH). Before and after renal transplantation (RT), we evaluated changes on left ventricular mass (LVM) and SA in 40 end-stage renal disease patients between 8 and 35 years old. Hypertension (95.0% vs. 71.0%; p=0.005), use of combined antihypertensive drugs (57.5% vs. 30.0%; p=0.01), and LVH (77.5% vs. 52.5%; p=0.01) significantly decreased after RT whereas low-to-high frequency ratio (LF/HF), which represents SA, increased (3.1 vs. 5.3; p=0.0001). However, LVM regressors (with decrease on LVM index more than 20%) showed a trend of lower change on LF/HF ratio (1.6 vs. 2.4; p= 0.09) than nonregressors. Living-donor graft, baseline LVM, use of antihypertensive drugs, lower change on LF/HF ratio, and lower systolic blood pressure levels were associated with LVM regression in the simple correlation analysis. However, in the logistic regression analysis, only baseline LVM and donor type remained in the model (R(2)=0.35; p=0.0003). Thus, LVH decreased after RT and was related to baseline LVM and living-donor type. However, it is possible that the higher persistence of LVH after RT could be explained at least in part by increase in heart sympathetic activity and use of immunosuppressors.

Impaired Muscle Oxygen Metabolism in Uremic Children: Improved After Renal Transplantation

BACKGROUND

The purpose of this study is to clarify skeletal muscle oxidative metabolism in children with end-stage renal disease (ESRD) before and after renal transplantation.

METHODS

We examined muscle oxygenation and metabolism by using noninvasive near-infrared spectroscopy in 10 patients (age, 12.4 +/- 3.1 years) 1 week before and 4 weeks after renal transplantation and in 10 controls (age, 12.8 +/- 2.6 years) during submaximal hand-grip exercise using the flexor digitorum superficialis muscle. We used 2 indicators to evaluate muscle metabolism. The rate of initial decrease in hemoglobin/myoglobin deoxygenation during arterial occlusion after exercise relative to the value at rest (S2/S1) was used as an indicator of mitochondrial oxygen consumption, whereas recovery time (TR) after exercise was used as an indicator of oxygen delivery to the muscle and aerobic capacity.

RESULTS

S2/S1 and TR after exercise were significantly lower in patients before renal transplantation compared with the control group (P < 0.05). S2/S1 and TR after exercise improved significantly after renal transplantation (P < 0.01, P < 0.05) and were not significantly different from those of controls.

CONCLUSION

Oxidative metabolism in skeletal muscle during exercise is impaired in children with ESRD and recovers after renal transplantation.

Nonhypotensive dose of β-adrenergic blocker ameliorates capillary deficits in the hearts of rats with moderate renal failure

Renal failure causes sympathetic overactivity and inadequate capillary growth in response to cardiomyocyte hypertrophy in experimental renal failure, as well as in uremic patients. In nonuremic animals, sympathetic overactivity was shown to suppress capillary growth. The purpose of this study was to examine whether blockade with alpha- and beta-adrenoblockers ameliorates the capillary deficit that was documented in the hearts of rats with moderate renal failure. Male Sprague-Dawley rats, 3 days after surgical ablation [subtotal nephrectomy (SNX)] or sham operation (sham), were treated with phenoxybenzamine, metoprolol, or a combination of both: After 12 weeks, the hearts were investigated using morphometric and stereologic techniques. The length density of myocardial capillaries was lower (p<0.05) in untreated SNX than in sham (2,786+/-372 vs 3,397+/-602 mm/mm3); the decrease was abrogated by metoprolol (3,305+/-624 mm/mm3), but not by phenoxybenzamin (2,628+/-480 mm/mm3). The intercapillary distance increased (p<0.05) in SNX (20.5+/-1.5 microm) and tended to be lower after metoprolol treatment (19.0+/-1.9 microm). The media area of intramyocardial arterioles was significantly higher in untreated SNX (1,158+/-1,343 vs 686+/-771 microm2 in sham). Metoprolol in nonhypotensive doses prevents the capillary deficit in the hearts of rats with moderate renal failure and presents an argument for an important role of sympathetic overactivity in the genesis of the capillary deficit in moderate chronic renal insufficiency.

‘Takotsubo’ Cardiomyopathy in a Maintenance Hemodialysis Patient

An 84-year-old woman undergoing maintenance hemodialysis presented with chest discomfort lasting several days and electrocardiographic abnormalities. She had stopped smoking 2 weeks earlier and was experiencing irritability. Upon admission, electrocardiography showed ST-segment elevation in leads I, II, aVF, and V2-6 and an abnormal Q wave in leads II, III, and aVF. Ultrasound cardiography showed left ventricular anteroapical akinesia and basal hyperkinesia. The chest discomfort disappeared without specific therapy. During hospital days 1-5, the ST-segment elevation gradually improved. Giant negative T waves then developed. The left ventricular asynergy resolved by day 8. Radionuclide imaging with iodine-123-beta-methyl-p-iodophenyl pentadecanoic acid, but not with technetium-99 m-sestamibi, showed an apical defect. Elective coronary angiography showed no stenosis. 'Takotsubo' cardiomyopathy was diagnosed. After discharge, the patient continued regular dialysis without cardiac symptoms. We concluded that endogenously activated sympathetic nerve action in hemodialysis patients, especially those under emotional or physical stress, might be a causative factor for Takotsubo cardiomyopathy.

Chronic kidney disease in patients with non-ST-segment elevation acute coronary syndromes

PURPOSE

Chronic kidney disease has been linked to high mortality rates in patients with ST-segment elevation myocardial infarction but has not been well described for patients with non-ST-segment elevation acute coronary syndromes. We examined the treatment and outcomes of patients with both non-ST-segment elevation acute coronary syndromes and moderate to severe chronic kidney disease.

SUBJECTS AND METHODS

We evaluated 45343 patients with non-ST-segment elevation acute coronary syndromes enrolled in the CRUSADE Quality Improvement Initiative and compared treatments and outcomes in patients with and without moderate to severe chronic kidney disease.

RESULTS

Patients presenting with moderate to severe chronic kidney disease (n = 6560) were older, more often diabetic, and more likely to present with signs of congestive heart failure. Adherence to Class IA/IB guidelines recommendations was lower in patients with moderate to severe chronic kidney disease, who were significantly less likely to be treated with medications, undergo invasive cardiac procedures, and be given discharge counseling. Moderate to severe chronic kidney disease was associated with a 50% increased risk of mortality and a 70% increased likelihood of transfusion. Despite having a higher risk of adverse outcomes, patients with moderate to severe chronic kidney disease were treated less aggressively than patients with normal renal function.

CONCLUSIONS

These findings suggest that, in patients with moderate to severe chronic kidney disease, safety concerns about adverse outcomes and the absence of trial data for this population may limit the use of guidelines-recommended therapies and interventions for non-ST-segment elevation acute coronary syndromes. The decreased use of discharge counseling in patients with moderate to severe chronic kidney disease and non-ST-segment elevation acute coronary syndromes may represent therapeutic nihilism.

Pathogenesis of hypertension in renal failure: role of the sympathetic nervous system and renal afferents

1. The kidney receives a dense innervation of sympathetic and sensory fibres and can be both a target of sympathetic activity and a source of signals that drive sympathetic tone. In the normal state, interactions between the kidney and sympathetic nervous system (SNS) serve to maintain blood pressure and glomerular filtration rate within tightly controlled levels. In renal failure, a defect in renal sodium excretory function leads to an abnormal pressure natriuresis relationship and activation of the renin-angiotensin-aldosterone system, contributing to the development of hypertension and progression of kidney disease. 2. Evidence now strongly indicates a role for the SNS in the pathogenesis of hypertension in renal failure. Hypertension occurs commonly and early in renal disease and is paralleled by increases in SNS activity, as indicated by increased muscle sympathetic nerve activity and circulating catecholamines. This appears to be driven by the diseased kidneys, because nephrectomy or denervation has been shown to correct blood pressure and SNS activity in human and animal studies. 3. Afferent signals from the kidney, detected by chemoreceptors and mechanoreceptors, feed directly into central nuclei of the SNS, including the hypothalamus and circumventricular organs, in addition to the stimulus provided by circulating and brain-derived angiotensin II. Therefore, the pathogenesis of hypertension in renal failure is complex and arises from the interaction of haemodynamic and neuroendocrine factors. 4. Increased SNS activity has significant implications with regard to increased risk of cardiovascular disease and is an important consideration in the treatment of renal failure.

Proven Strategies to Reduce Cardiovascular Mortality in Hemodialysis Patients

BACKGROUND

In hemodialysis patients, left ventricular hypertrophy (LVH) correlates with mortality. The reason for LVH in uremics is multifactorial. The primary objective of our study was to investigate the effects of a multi-interventional treatment strategy on LVH.

METHODS

In 230 ambulatory patients, including patients with coronary artery disease, diabetes, diastolic and systolic dysfunction, we continued optimized cardiac therapy (beta-blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers) with full anemia correction by intravenous epoetin-beta. The dose of epoetin-beta for maintaining target hemoglobin (Hb) was 68 +/- 23 IU/kg/week. Serial echocardiograms were recorded every 3-6 months. The mean observation period was 4.8 +/- 1.2 years.

RESULTS

Mean Hb at baseline was 11.2 +/- 2.0 versus 14.1 +/- 1.4 g/dl (p < 0.001) at study end. There was a significant reduction in left ventricular mass index (LVMI: 159 +/- 50.4 vs. 130.2 +/- 42.7 g/m(2); p < 0.001). In a subgroup of 2/3 of the patients, LVMI returned to normal (169 +/- 33 vs. 114 +/- 14 g/m2; p < 0.001).

CONCLUSION

Baseline LVMI (p < 0.001), Hb increase (p < 0.03), and triple cardiac therapy (p < 0.03) were significant and independent prognostic factors for a reduction in LVMI. The annual cardiovascular mortality was 5%. Even anemia correction from 12 to 14 g/dl results in further (p < 0.001) regression of LVMI.

Cause and Consequences of Sympathetic Hyperactivity in Chronic Kidney Disease

Patients with chronic kidney disease and patients undergoing hemodialysis treatment show a sustained overactivity of the sympathetic nervous system, which originates from signals arising in the failing kidneys and traveling via afferent renal nerves to cardiovascular centers in the brainstem. Additional important factors are increased levels of angiotensin II and asymmetrical dimethylarginine. The sympathetic overactivity contributes to hypertension and cardiovascular morbidity and mortality in that patient population. Sympathetic overactivity can be reduced by adrenergic receptor blockers, centrally acting sympathicolytic drugs such as moxonidine and rilmenidine, angiotensin-converting enzyme inhibition, and angiotensin II type 1 receptor antagonists. Daily short hemodialysis and long nocturnal hemodialysis may reduce the elevated sympathetic activity, possibly because of an increased clearance of asymmetrical dimethylarginine, an endogenous nitric oxide synthase inhibitor. Prospective trials examining the potential impact of both beta-blockers and centrally acting sympatholytic drugs on cardiovascular mortality in chronic kidney disease and hemodialysis patients are very much needed.

Impaired gastric motility and its relationship to gastrointestinal symptoms in patients with chronic renal failure

BACKGROUND

Gastrointestinal (GI) symptoms are common in patients with chronic renal failure (CRF), but the pathogenesis of these symptoms is unclear. Gastric motor function in CRF patients remains controversial, and the correlation between GI symptoms and gastric motility is also unclear. The aim of this study was to elucidate the relationship between gastric motility and GI symptoms in patients with CRF.

METHODS

Gastric motility was evaluated with cutaneously recorded electrogastrographs (EGGs) and gastric emptying of a solid meal, using 13C-octanoic acid breath testing, in 21 patients with predialysis endstage CRF and in 21 matched healthy controls. GI symptom severity was quantified in all patients.

RESULTS

The CRF patients had a significantly lower incidence of normogastria postprandially and a lower power ratio than did healthy controls on the EGGs, with the CRF patients showing delayed gastric emptying. Three patients with normal gastric motility had no GI symptoms, and ten patients with both abnormal EGG and delayed gastric emptying had significantly higher GI symptom scores than the patients without abnormalities.

CONCLUSIONS

The patients with CRF showed gastric hypomotility, including impaired gastric myoelectrical activity and delayed gastric emptying. Gastric hypomotility appears to be an important factor in the generation of GI symptoms in patients with CRF.

Assessment of coronary artery disease in hemodialysis patients with delayed systolic blood pressure response after exercise testing

BACKGROUND

We evaluated usefulness of the postexercise systolic blood pressure (SBP) response for detecting coronary artery disease (CAD) in hemodialysis patients.

METHODS

A treadmill exercise testing was done, and the SBP response was measured in 44 hemodialysis patients (30 men, 14 women; age 41 to 81 years). The postexercise SBP response was defined as the ratio of SBP after 3 minutes of recovery to SBP at peak exercise.

RESULTS

The SBP ratio of the 25 subjects with coronary artery stenosis (1.01+/- 0.13) was significantly greater (p<0.01) than 19 subjects without coronary artery stenosis (0.83+/- 0.10). An SBP ratio greater than 0.92 identified CAD with higher sensitivity, specificity, and accuracy than did the conventional ST-segment depression criterion (76 vs. 56%, 90 vs. 53%, and 82 vs. 55%, respectively).

CONCLUSION

Determination of the SBP ratio is a clinically useful, noninvasive method for accurately detecting CAD in hemodialysis patients.

Effects of optimized heart failure therapy and anemia correction with epoetin beta on left ventricular mass in hemodialysis patients

BACKGROUND

In chronic hemodialysis (HD) patients, the presence and degree of left ventricular hypertrophy (LVH) correlates with mortality. Previous studies have shown that interventions, such as anemia correction or treatment of hypertension and/or chronic heart failure (CHF), can result in moderate regression of LVH. The primary objective of our study was to investigate the effects of a multi-interventional treatment strategy on LVH in HD patients.

METHODS AND RESULTS

In a series of 202 consecutive HD patients, we combined optimized CHF therapy, including beta-blockers (BB), ACE inhibitors and angiotensin receptor blockers (ARBs), to target doses with full anemia correction by epoetin beta (hemoglobin (Hb) target males 14.5 g/dl, females 13.5 g/dl). Serial echocardiograms were recorded every 3-6 months. Mean follow-up was 3.4 +/- 1.2 years. Mean Hb at baseline was 11.4 +/- 1.4 vs. 14.6 +/- 1.6 g/dl (p < 0.001) at study end. There was a significant reduction in left ventricular mass index (LVMI, 159 +/- 65 vs. 132 +/- 46 g/m2 (p < 0.001)), an improvement in left ventricular ejection fraction (LVEF, 60 +/- 15 vs. 66 +/- 12% (p < 0.01)) and in NYHA class (2.8 +/- 0.76 vs. 1.96 +/- 0.76 (p < 0.01)) from baseline to follow-up in the overall study population. In a subgroup of 70 patients, LVMI returned to normal (169 +/- 33 vs. 114 +/- 14 g/m2 (p < 0.001)) after 1.4 +/- 1 years.

CONCLUSIONS

Our study shows that optimized CHF therapy, in combination with anemia correction to normal Hb targets, results in a significant reduction of LVH, an increase in LVEF and an improvement in NYHA class. Moreover, in contrast to previous studies, our data also demonstrate that complete regression and prevention of LVH in HD patients is possible.

Effects of Peripheral Chemoreceptors Deactivation on Sympathetic Activity in Heart Transplant Recipients

Heart transplantation initially normalizes sympathetic hyperactivity directed at the muscle circulation. However, sympathetic activity increases with time after transplantation and the exact mechanisms responsible for sympathetic control in heart transplant recipients remain unclear. We examined the effects of peripheral chemoreflex deactivation caused by breathing 100% oxygen on muscle sympathetic nerve activity (expressed as number of burst per minute and mean burst amplitude), heart rate, and mean blood pressure in 13 heart transplant recipients, 13 patients with essential hypertension, and 10 controls. Heart transplant recipients disclosed the highest sympathetic activity, whereas it did not differ between controls and patients with essential hypertension (51+/-16 versus 37+/-14 versus 39+/-12 burst/min, respectively; P<0.05). Breathing 100% oxygen, in comparison with 21% oxygen, reduced sympathetic activity (-4+/-4 versus -1+/-2 burst/min, P<0.01; 85+/-9 versus 101+/-8% of amplitude at baseline, P<0.001) and mean blood pressure (-4+/-5 versus +3+/-6 mm Hg; P<0.05) in heart transplant recipients, decreased sympathetic activity (-4+/-4 versus 0+/-3 burst/min, P<0.05; 90+/-16 versus 101+/-9% of amplitude at baseline, P<0.05) in patients with essential hypertension, but did not reduce sympathetic activity (2+/-4 versus 3+/-3 burst/min, P=NS; 95+/-11 versus 95+/-13% of amplitude at baseline, P=NS) in control subjects. The sympathetic response to hyperoxia was more marked in heart transplant recipients than in controls (85+/-9 versus 95+/-11% of baseline amplitude; P<0.05). The decrease in sympathetic activity was most evident in patients with the longest time after heart transplantation (r=-0.75, P<0.01). In conclusion, tonic chemoreflex activation increases resting muscle sympathetic nerve activity and favors blood pressure elevation after heart transplantation.

Renalase is a novel, soluble monoamine oxidase that regulates cardiac function and blood pressure

The kidney not only regulates fluid and electrolyte balance but also functions as an endocrine organ. For instance, it is the major source of circulating erythropoietin and renin. Despite currently available therapies, there is a marked increase in cardiovascular morbidity and mortality among patients suffering from end-stage renal disease. We hypothesized that the current understanding of the endocrine function of the kidney was incomplete and that the organ might secrete additional proteins with important biological roles. Here we report the identification of a novel flavin adenine dinucleotide-dependent amine oxidase (renalase) that is secreted into the blood by the kidney and metabolizes catecholamines in vitro (renalase metabolizes dopamine most efficiently, followed by epinephrine, and then norepinephrine). In humans, renalase gene expression is highest in the kidney but is also detectable in the heart, skeletal muscle, and the small intestine. The plasma concentration of renalase is markedly reduced in patients with end-stage renal disease, as compared with healthy subjects. Renalase infusion in rats caused a decrease in cardiac contractility, heart rate, and blood pressure and prevented a compensatory increase in peripheral vascular tone. These results identify renalase as what we believe to be a novel amine oxidase that is secreted by the kidney, circulates in blood, and modulates cardiac function and systemic blood pressure.

Central autonomic innervation of the kidney. What can we learn from a transneuronal tracing study in an animal model?

PURPOSE

Renal sympathetic innervation is involved in the maintenance of fluid homeostasis, modulation of renal secretion from juxtaglomerular cells, sodium resorption from renal tubular cells and renal hemodynamics. The understanding of central innervation and neuronal connections is important for studying the consequences of renal disease and surgical interventions compromising renal nerves.

MATERIALS AND METHODS

A total of 38 individual adult male Sprague-Dawley rats were used for retrograde transneuronal mapping of the spinal cord and brain stem after pseudorabies virus (PRV) injection into the left kidney in 30 and control experiments in 8. After a survival time of 72, 96 or 120 hours the animals were sacrificed. Exploration of the abdominal and pelvic visceral organs was done, and the brain and spinal cord were harvested via dorsal laminectomy. After cutting on a freezing microtome the tissue was immunostained for PRV.

RESULTS

After kidney injection inspection of the abdominal and pelvic cavity revealed an enlarged bladder with hemic urine. The urine was sterile and the bladder wall showed signs of neurogenic inflammation. Other organs were not affected. PRV positive cells were primarily found within the ipsilateral nucleus intermediolateralis of thoracic spinal cord segments T6 to T13. At the supraspinal level PRV positive cells were found within certain regions, namely the nuclei raphes, rostral ventromedial and ventrolateral medulla, A5 noradrenergic cell region, locus coeruleus and nucleus paraventricularis of the hypothalamus.

CONCLUSIONS

This investigation demonstrates the anatomical basis for broad central sympathetic innervation of the kidney. The neurogenic inflammation within the spinal cord inherent to the PRV tracing method causes an inflammatory reaction within the bladder. This can be due to increased sympathetic nerve activity, followed by peripheral, neurogenically mediated inflammation.

Sympathetic hyperactivity in chronic kidney disease: pathogenesis, clinical relevance, and treatment

Cardiovascular morbidity and mortality importantly influence live expectancy of patients with chronic renal disease (CKD). Traditional risk factors are usually present, but several other factors have recently been identified. There is now evidence that CKD is often characterized by an activated sympathetic nervous system. This may contribute to the pathogenesis of renal hypertension, but it may also adversely affect prognosis independently of its effect on blood pressure. The purpose of this review is to summarize available knowledge on the role of the sympathetic nervous system in the pathogenesis of renal hypertension, its clinical relevance, and the consequences of this knowledge for the choice of treatment.

Volume-independent mechanisms of hypertension in hemodialysis patients: clinical implications

The renin-angiotensin and sympathetic nervous systems are often activated in hemodialysis (HD) patients; the pathogenesis of this condition is discussed. Medications aimed at reducing renin and sympathetic activity may improve the cardiovascular prognosis, independent of its effect on blood pressure. This knowledge has important implications for the choice of treatment in HD patients.

Sympathetic nerve activity is inappropriately increased in chronic renal disease

The hypothesis that in hypertensive patients with renal parenchymal disease sympathetic activity is "inappropriately" elevated and that this overactivity is a feature of renal disease and not of a reduced number of nephrons per se is addressed. Fifty seven patients with renal disease (various causes, no diabetes, all on antihypertensive medication) were studied, age range 18 to 62, creatinine clearance 10 to 114 ml/min per 1.73 m(2). Antihypertensives were stopped, but diuretics were allowed, to prevent overhydration. Matched control subjects were also studied. The effect of changes in fluid status was examined in seven patients while on and after stopping diuretics and in eight control subjects while on low- and high-sodium diet. Seven kidney donors were studied before and after unilateral nephrectomy. Sympathetic activity was quantified as muscle sympathetic nerve activity (MSNA) in the peroneal nerve. Mean arterial pressure, MSNA, and plasma renin activity were higher in patients than in control subjects, respectively (115 +/- 12 and 88 +/- 11 mmHg, 31 +/- 15 and 18 +/- 10 bursts/min, and 500 [20 to 6940] and 220 [40 to 980] fmol/L per s; P < 0.01 for all items). Extracellular fluid volume (bromide distribution) did not differ. Seven patients were studied again after stopping diuretics. MSNA decreased from 34 +/- 18 to 19 +/- 18 bursts/min (P < 0.01). Eight healthy subjects were studied during low- and high-sodium diet. MSNA was 26 +/- 12 and 13 +/- 7 bursts/min (P < 0.01). The curves relating extracellular fluid volume to MSNA were parallel in the two groups but shifted to a higher level of MSNA in the patients. In the kidney donors, creatinine clearance reduced by 25%, but MSNA was identical before and after donation. It is concluded that in hypertensive patients with renal parenchymal disease, sympathetic activity is inappropriately high for the volume status and that reduction of nephron number in itself does not influence sympathetic activity.

Renal function and long term mortality after unstable angina/non-ST segment elevation myocardial infarction treated very early and predominantly with percutaneous coronary intervention

OBJECTIVES

To quantify the impact of baseline renal function on in-hospital and long term mortality in patients with unstable angina/non-ST elevation acute myocardial infarction (UA/NSTEMI) treated with a very early invasive strategy.

DESIGN

Prospective cohort study of 1400 consecutive patients with UA/NSTEMI undergoing coronary angiography and subsequent coronary stenting of the culprit lesion as the primary revascularisation strategy within 24 hours of admission. Patients were stratified according to calculated glomerular filtration rate (GFR) on admission.

RESULTS

In-hospital mortality was 0% among patients with a GFR > or = 130 ml/min/1.73 m2, 0.4% with a GFR of 90-129 ml/min/1.73 m2, 2.6% with a GFR of 60-89 ml/min/1.73m2, and 5.1% with a GFR of < 60 ml/min/1.73 m2. Cumulative three year survival rates were 92.6%, 95.5%, 91.9%, and 76.8%, respectively. Patients with a GFR of < 60 ml/min/1.73 m2 were four times more likely to die in hospital (hazard ratio (HR) 4.0, 95% confidence interval (CI) 1.8 to 9.1; p = 0.001) and four times more likely to die during long term follow up (HR 4.0, 95% CI 2.5 to 6.4; p < 0.001). After adjusting for potential confounders, a GFR of < 60 ml/min/1.73 m2 remained a strong independent predictor of long term mortality (HR 2.6, 95% CI 1.5 to 4.5; p = 0.001).

CONCLUSIONS

Baseline renal function is a strong independent predictor of in-hospital and long term mortality after UA/NSTEMI treated with very early revascularisation.

Modulation of gene expression by moxonidine in rats with chronic renal failure

BACKGROUND

Sympathetic overactivity is a hallmark of chronic renal failure. In a previous experimental study, the sympatholytic drug moxonidine (MOX) had beneficial effects on progression of chronic renal failure. The present study investigates whether moxonidine influences the expression of genes associated with adaptive changes in kidneys of subtotally nephrectomized rats.

METHODS

RNA was isolated from remnant kidneys of sham-operated, subtotally nephrectomized (SNX) and moxonidine-treated SNX (SNX-M) rats 12 weeks after operation. Genes that might play a role in renal adaptation processes after subtotal nephrectomy were selected and their expression was analysed by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

After subtotal nephrectomy, there was an increase in gene expression of cysteine protease cathepsin (H + L), ATP receptor subtypes P2Y(2) and P2Y(6), cell cycle regulator p21 and transforming growth factor-beta1 (TGF-beta1), and a decrease of the metalloprotease aminopeptidase-M (APM), membrane transporter megalin, ageing-related klotho, type I TGF-beta receptor, mitochondrial cytochrome oxidase-1, kallikrein, leucine zipper-1, matrix-degrading metalloprotease meprin, the organic anion transporter and the P2 receptor subtypes P2Y(1) and P2Y(4). In SNX-M rats, mRNA levels of APM, megalin, klotho, TGF-beta1, type I TGF-beta receptor, p21, P2Y(1) and P2Y(2) were shifted back towards control levels.

CONCLUSIONS

Several genes showing altered expression levels after subtotal nephrectomy were identified in remnant kidneys. These genes might act as candidates to promote disease progression. The sympatholytic drug moxonidine, at a concentration devoid of blood pressure effects, regulates the renal expression of some of these genes back towards control levels. To what extent sympathetic neurotransmitters directly alter expression of these genes in cultured renal cells currently is under investigation.

Abnormal cardiac function in children after renal transplantation

BACKGROUND

Cardiac hypertrophy frequently is found in children with a renal transplant. In adults with a transplant, left ventricular (LV) mass (LVM) is associated with cardiac dysfunction. However, in children with a transplant, the relationship between LVM and LV function has not been evaluated.

METHODS

Twenty-nine children who underwent transplantation and 33 controls had echocardiographic evaluations during rest and peak exercise. LV contractility was determined based on the relation between heart rate-corrected velocity of circumferential fiber shortening and end-systolic wall stress. Contractile reserve was assessed by the difference between contractility at rest and peak exercise. Early diastole was assessed using indices of LV relaxation derived from transmitral and tissue Doppler and reported as maximal early (E wave) and late (A wave) wave ratio (E-A ratio) and septal mitral annular velocities (Em). Late diastole was determined using an index of LV compliance (E-Em ratio).

RESULTS

Compared with controls, children with a transplant had a significantly greater LVM index (P < 0.001) and high prevalence of LV hypertrophy (LVH; 55%). Transplant recipients had increased LV contractility (P < 0.001). Contractile reserve was similar to that of controls. Patients with a transplant had a lower E-A ratio and Em (P < 0.01 for both variables) and higher E-Em ratio (P < 0.001) than controls. In children with a transplant, LVM index was a significant independent predictor for both abnormal LV relaxation (Em; P = 0.03) and abnormal LV compliance (E-Em ratio; P = 0.02).

CONCLUSION

Results show impaired cardiac structure and diastolic function in pediatric renal allograft recipients. This suggests that LVH may be a risk factor for diastolic dysfunction in these children.

Progression of renal disease: new insights into risk factors and pathomechanisms

PURPOSE OF REVIEW

Progression of renal failure, irrespective of the primary cause, is characterized by modification of renal structure, which culminates in terminal renal insufficiency. Interfering with progression continues to be a major challenge and is at the forefront of renal research. This review focuses on recent progress in the understanding of the mechanisms of progression and efforts to interfere with this process.

RECENT FINDINGS

In addition to the long-known risk factors (hypertension and inadequate activation of the renin-angiotensin system), several novel risk factors and pathomechanisms, such as obesity, hyperglycemia, smoking, and several hormones, have recently been identified and investigated. Furthermore, the specific and blood pressure-independent pathogenetic roles of the sympathetic nervous system and the endothelin system in progression have been further clarified. Finally, novel animal models and techniques for studying specific aspects of progression have been developed and introduced.

SUMMARY

Recently, considerable progress has been made concerning novel risk factors, understanding the underlying pathomechanisms, and interfering with the course of progression of renal diseases. Such improved insights will undoubtedly lead to new strategies in the future.

Acute arterio-venous fistula occlusion decreases sympathetic activity and improves baroreflex control in kidney transplanted patients

BACKGROUND

The acute bradycardia induced by the occlusion of an arteriovenous fistula (AVF), known as the Nicoladoni-Branham sign, is considerably larger than that which occurs during carotid sinus massage. This suggests increased arterial baroreflex sensitivity during acute AVF occlusion. Moreover, the influence of acute AVF occlusion on muscle sympathetic nerve traffic (MSNA, by microneurography) is unknown. We therefore assessed the effects of acute AVF occlusion on baroreflex sensitivity and on MSNA in patients with stable functional kidney grafts and patent AVF.

METHODS

We measured blood pressure (BP), MSNA (n = 11), heart rate (HR), cardiac output (CO) and arterial baroreflex sensitivity (n = 18) at baseline and during acute, 30-s pneumatic AVF occlusions in 23 renal transplanted recipients.

RESULTS

During the first 5 s of the AVF occlusion, mean BP increased from 98+/-4 to 112+/-4 mmHg (P<0.0001) while MSNA decreased to 28+/-5% of baseline values (P<0.0001) and HR decreased from 71+/-3 to 61+/-3 b.p.m. (P<0.0001). The largest increases in BP were accompanied by the most marked decreases in MSNA (r = -0.79, P = 0.003) and HR (r = -0.49; P = 0.01) during the first 5 s of the AVF occlusion. During AVF occlusion baseline CO of 6.9+/-0.3 decreased to 5.6+/-0.3 l/min (P<0.0001) while baroreflex sensitivity increased from 10+/-1 to 17+/-2 ms/mm Hg (P<0.001).

CONCLUSIONS

Arterial baroreceptor activation and increased arterial baroreflex sensitivity decrease heart rate during AVF occlusion. In addition, our study is the first to demonstrate that arterial baroreflex activation decreases sympathetic nerve traffic during the Nicoladoni-Branham sign.

Causes and consequences of increased sympathetic activity in renal disease

Much evidence indicates increased sympathetic nervous activity (SNA) in renal disease. Renal ischemia is probably a primary event leading to increased SNA. Increased SNA often occurs in association with hypertension. However, the deleterious effect of increased SNA on the diseased kidney is not only caused by hypertension. Another characteristic of renal disease is unbalanced nitric oxide (NO) and angiotensin (Ang) activity. Increased SNA in renal disease may be sustained because a state of NO-Ang II unbalance is also present in the hypothalamus. Very few studies have directly compared the efficacy of adrenergic blockade with other renoprotective measures. Third-generation beta-blockers seem to have more protective effects than traditional beta-blockers, possibly via stimulation of NO release. Although it has been extensively documented that muscle SNA is increased in chronic renal failure, data on renal SNA and cardiac SNA are not available for these patients before end-stage renal disease. It is also unknown whether additional treatment with third-generation beta-blockers can delay the progression of renal injury and prevent cardiac injury in chronic renal failure more efficiently than conventional treatment with angiotensin-converting enzyme inhibitors only.

Review of clinical outcomes in nocturnal haemodialysis patients after renal transplantation

BACKGROUND

Nocturnal haemodialysis (NHD) is a novel form of haemodialysis therapy that is associated with improved blood pressure control when compared to conventional haemodialysis (CHD). Current studies suggest that NHD lowers blood pressure through a decrease in peripheral resistance. The graft and blood pressure outcomes of NHD patients who undergo renal transplantation are unknown.

METHODS

We reviewed the renal allograft and blood pressure outcomes of 15 NHD patients who underwent renal transplantation. An age and vintage matched cohort of 29 CHD patients was used as controls.

RESULTS

The rate of delayed graft function (DGF) tended to be higher in the NHD group compared to the CHD group (64 vs 41%, P = 0.15), however the 1-year graft function (53+/-6 vs 59+/-5 ml/min, P = 0.426) and graft survival (92 vs 95%, P = 0.751) were similar. Intra-operatively, NHD patients had lower minimum systolic (92+/-5 vs 109+/-4, P = 0.03) and diastolic (48+/-3 vs 64+/-2, P = 0.02) blood pressures in comparison to the CHD cohort. Pathologically, acute tubular necrosis accounted for 100% of DGF in the NHD group in contrast to 75% in the CHD population (P = 0.01). Pre-transplant mean systolic BP (sBP) was significantly lower in the NHD group compared to the CHD group (113+/-6 vs 145+/-10 mmHg, P<0.001). At 12 months post-transplant, mean sBP increased from baseline in the NHD group ( triangle up sBP 22+/-7 mmHg, P = 0.009) while in the CHD group mean sBP fell (Delta sBP -14+/-5 mmHg, P = 0.014). Mean arterial and diastolic BP exhibited similar changes. These trends persisted after 24 months of post-transplant follow-up.

CONCLUSIONS

One-year graft outcomes and blood pressures are similar for NHD and CHD patients who undergo renal transplantation. Unlike CHD patients, NHD patients experienced a significant fall in their intra-operative blood pressures, which likely contributed towards the delayed graft function in this cohort of patients. Further prospective studies are needed to examine the underlying differences in haemodynamics and long-term graft survival between the two renal replacement modalities.

[Sympathetic overactivity and the kidney]

Hypertension is present in the majority of patients with chronic renal failure and constitutes a major risk factor for the very high cardiovascular morbidity and mortality in this patient population. Furthermore hypertension is known to be a substantial progression factor in renal disease. In the past, it had been presumed that hypertension in chronic renal failure is due to enhanced sodium retention, chronic hypervolemia and increased activity of the renin-angiotensin-aldosterone-system. Recent studies now provide evidence that sympathetic overactivity plays an additional important role and also promotes progression of renal failure. The treatment goal in renal patients is to delay or even prevent progression of renal failure and to reduce the cardiovascular risk. Recent studies have investigated the respective impact of sympatholytic drugs, e.g. inhibitors of the renin-angiotensin-aldosterone-system, beta-blockers or I1-Imidazolin-receptor-agonists in fulfilling these aims. The present report will review experimental and clinical studies on the role of sympathetic overactivity in hypertension and chronic renal failure and possible new therapeutic options.

Timing of cardiac contraction in humans mapped by high-temporal-resolution MRI tagging: early onset and late peak of shortening in lateral wall

Mechanical asynchrony is an important parameter in predicting the response to cardiac resynchronization therapy, but detailed knowledge of cardiac contraction timing in healthy persons is scarce. In this work, timing of cardiac contraction was mapped in 17 healthy subjects with high-temporal-resolution (14 ms) MRI myocardial tagging and strain analysis. Both the onset time of circumferential shortening (T(onset)) in early systole and the time of peak circumferential shortening (T(peak)) at end systole were determined. The onset of shortening width (time needed for 20-90% of the left ventricle to start shortening) was small (35 +/- 9 ms). A distinct spatial pattern for T(onset) was found, with earliest onset in the lateral wall and latest onset in the septum (P = 0.001). Compared with T(onset), T(peak) had a larger width (121 +/- 22 ms) and an opposite spatial pattern, with peak shortening occurring earlier in the septum than in the lateral wall (P < 0.001). Postsystolic shortening (T(peak) later than aortic valve closure; P < 0.05) was observed in 13 of the 30 cardiac segments, mainly in the lateral and basal segments. Shortening in these segments continued 58 +/- 14 ms after aortic valve closure, during which circumferential shortening increased from 16.9 +/- 1.2% to 20.0 +/- 1.5%. Maps of the timing of contraction in normal subjects may serve as a reference in detecting mechanical asynchrony due to intraventricular conduction defects or ischemia.

Short-Term Blood Pressure, Noradrenergic, and Vascular Effects of Nocturnal Home Hemodialysis

Long-term nocturnal hemodialysis, which uses longer and more frequent sessions than conventional hemodialysis, lowers clinic blood pressure and left ventricular mass. We tested the hypotheses that short-term nocturnal hemodialysis would (1) reduce ambulatory blood pressure; (2) cause peripheral vasodilation; (3) lower plasma norepinephrine concentration; and (4) improve the arterial response to reactive hyperemia (a marker of endothelium-dependent vasodilation). We studied 18 consecutive patients (age, 41±2; [mean±SEM]) before and 1 and 2 months after conversion from conventional (three 4-hour sessions per week) to nocturnal (six 8-hour sessions per week) hemodialysis. As the dialysis dose per session (Kt/V) increased from 1.24±0.06 to 2.04±0.08 after 2 months ( P =0.02), symptomatic hypotension developed and most antihypertensive medications were withdrawn. Nocturnal hemodialysis nonetheless lowered 24-hour mean arterial pressure (from 102±3 to 90±2 mm Hg after 2 months; P =0.01), total peripheral resistance (from 1967±235 to 1499±191 dyne · s · cm −5 ; P <0.01) and plasma norepinephrine (from 2.66±0.4 to 1.96±0.2 nmol; P =0.04). Endothelium-dependent vasodilation could not be elicited during conventional hemodialysis (−2.7±1.8%) but was restored (+8.0±1.0%; P =0.001) after 2 months of nocturnal hemodialysis. The brachial artery response to nitroglycerin also improved (from 6.9±2.8 to 15.7±1.6%; P <0.05). Nocturnal hemodialysis had no effect on weight or on stroke volume. Rapid reversal of these markers of adverse cardiovascular events with more intense hemodialysis may translate into improved outcome in this high-risk group of patients.

Moxonidine treatment of hypertensive patients with advanced renal failure

OBJECTIVES

To compare safety and tolerability of moxonidine versus nitrendipine in hypertensive patients with renal failure. A secondary endpoint was to test whether the sympatholytic drug moxonidine slows decline of renal function when added to standard therapy with an angiotensin-converting enzyme inhibitor or AT(1) receptor antagonist plus loop diuretic.

DESIGN

This prospective, randomized, double-blind, multicenter study recruited 177 patients with advanced renal failure receiving antihypertensive standard therapy at outpatient clinics in Germany and Hungary. Following a 2 week run-in, patients were randomized to 24 weeks of add-on treatment with 0.3 mg/day moxonidine or 20 mg/day nitrendipine.

RESULTS

The incidence of pre-defined specific adverse events was 42% in the moxonidine (37/89 patients) and 46% in the nitrendipine group (38/82 patients) in intention-to-treat analysis. Intensity and multiplicity were comparable. The dropout rate due to adverse events was 12.4% in the moxonidine and 9.8% in the nitrendipine group. Creatinine clearance according to Cockcroft and Gault decreased by 0.5 +/- 4.3 ml/min (mean +/- standard deviation) in the moxonidine group and 2.3 +/- 4.0 ml/min in the nitrendipine group. Serum creatinine increased by 12.7 +/- 49.2 micromol/l in the moxonidine group and by 43.4 +/- 71.3 micromol/l in the nitrendipine group. These differences were statistically significant (P < 0.05).

CONCLUSION

Add-on treatment with 0.3 mg/day moxonidine in hypertensive patients with renal failure is well tolerated and not inferior to 20 mg/day nitrendipine with respect to the incidence of specific adverse events. The idea of a sympatholytic drug to be renoprotective is appealing but needs further evaluation.

Dialysis filter type determines the acute effect of haemodialysis on endothelial function and oxidative stress

BACKGROUND

Endothelial function of large arteries is impaired in chronic haemodialysis patients and oxidative stress due to the dialysis procedure has been suggested as a causal factor. However, it is not clear whether different types of dialysis membranes affect endothelial function differently. Therefore we determined endothelium-dependent, flow-mediated dilatation (FMD) of the brachial artery as well as markers of oxidative stress immediately before and after haemodialysis (HD) with either a cellulosic cuprophane or a synthetic polysulphone dialyser in a blinded, randomized, cross-over study.

METHODS

Twelve haemodialysis patients (age 55+/-3 years, time on dialysis 20+/-2 months, mean fluid change -1782+/-21 ml, systolic/diastolic blood pressure 139/75 mmHg) were included. Using a multi-gate-pulsed Doppler system (echo-tracking device) brachial artery FMD and nitroglycerine-induced, endothelium-independent vasodilatation (NMD) were measured. Patients were randomized to HD with either a polysulphone or a cuprophane membrane and were crossed over to the other filter. Investigators were blinded to the type of membrane used. Serum concentrations of oxidized LDL (oxLDL) and alpha-tocopherol as markers of oxidative stress were measured before and after each dialysis session.

RESULTS

Data are given as mean+/-SEM. Treatment with polysulphone filter HD did not significantly affect FMD (baseline 9.3+/-2.0% vs after HD 9.6+/-1.8%). After dialysis with a cuprophane membrane FMD decreased from 9.4+/-2.1 to 7.4+/-1.8% (P<0.05). NMD was not significantly affected by HD irrespective of the membrane material used. Serum levels of oxLDL were not changed by either treatment; however, alpha-tocopherol concentrations fell significantly after dialysis with the cuprophane filter (baseline 18.0+/-2.3 after HD 16.6+/-1.3 micro g/ml, P<0.05), while alpha-tocopherol levels remained unchanged when the polysulphone membrane was used.

CONCLUSIONS

The type of dialysis filter membrane determines the acute effect of haemodialysis on arterial endothelial function. Differences in biocompatibility and oxidative stress may account for the observed differential effects, since the decrease of FMD after dialysis with a cellulosic cuprophane membrane-but not with a synthetic polysulphone membrane-was associated with a reduction in serum vitamin E.