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Biomedical subjects

A Covic

Publications and source records attributed to A Covic.

At least 19 recordsLinked to original sources
PubMed2003

Successful renal transplantation decreases aortic stiffness and increases vascular reactivity in dialysis patients.

BACKGROUND: Patients with end-stage renal disease on dialysis have among the highest cardiovascular event rates documented. Abnormal nitric oxide (NO)-dependent endothelial reactivity and increased arterial stiffness are commonly described in hemodialysis (HD) patients. Measures of aortic stiffness--aortic pulse wave velocity (PWV) and augmentation index (AGI)--have been shown to be powerful predictors of survival on hemodialysis. It is not known how these parameters interfere with successful renal transplantation. METHODS: PWV and aortic AGI (difference between the first and second systolic peak on the aortic pressure waveform divided by the pulse wave height) were determined from contour analysis of arterial waveforms recorded by applanation tonometry using a SphygmoCor device in 41 HD patients (20 men; age, 41.8 years) and in a control group of 20 patients with essential hypertension (HTA) (10 men; age, 43.6 years). Twenty of the HD patients (10 men; age, 39.7 years) received live-related renal transplants (RTx) and were restudied (3 months after RTx, normal serum creatinine). NO-dependent and NO-independent vascular reactivity were assessed by changes in AGI after challenges with inhaled salbutamol (SAL) and sublingual nitroglycerin (NTG), respectively. RESULTS: AGI values were significantly lower in RTx patients compared with subjects on hemodialysis (15.9 +/- 13.9% vs. 27.9 +/- 11.9%, P<0.05), but similar to essential HTA controls (16.5 +/- 17%). Serial AGI measurements showed that successful renal transplantation is associated with a decrease in AGI in all cases, from a mean of 25.1 +/- 7.8% while on dialysis to 15.9 +/- 7.0% 3 months after transplantation (P<0.0001). The responsiveness to both endothelium-dependent stimuli (inhaled SAL) and endothelium-independent stimuli (sublingual NTG) was greater in transplant patients than in hemodialysis patients (SAL-induced decrease in AGI -82.3 +/- 65.7% vs. 45 +/- 72.3%, P<0.01; and NTG-induced decrease in AGI 197 +/- 108 vs. -129.0 +/- 215.5%, P<0.01). PWV values in dialysis patients (7.19 +/- 1.88 m/sec) were significantly higher than those measured in essential HTA patients (6.34 +/- 1.32 m/sec, P<0.05) with normal renal function (despite similar blood pressure levels). PWV after RTx was 6.59 +/- 1.62 m/sec, significantly different from pretransplantation (dialysis) values (P<0.05 for comparison) but similar to the control group of essential HTA patients. CONCLUSIONS: Renal transplantation is associated with marked improvements in vascular structure and function to a profile comparable to essential HTA patients.

Adult↗
PubMed2002

New markers and therapies for coronary artery disease in renal patients.

Coronary artery disease is very frequent in dialysis patients, and influences their survival while on dialysis and even after renal transplantation. There are problems with screening tools in that they have reduced sensitivity and specificity in the uraemic individual. There is a real need for additional and complementary markers of coronary disease in these patients. We discuss some novel ideas for screening and for intervention in this most challenging clinical setting.

Biomarkers↗
PubMed2001

Coronary artery disease in uremia: Etiology, diagnosis, and therapy.

Cardiovascular disease is a major challenge to nephrologists, whether we deal with patients with pre-end-stage renal failure, on dialysis or after successful renal transplantation. It is the most common cause for death in patients with a functional allograft, and prevents many dialysis patients from being engrafted. Coronary artery disease is a diagnostic and therapeutic challenge, as it differs in some respects from that seen in non-uremic cohorts, and lacks much of the evidence-base on which therapeutic intervention rests. This review examines the experimental and clinical literature on cardiovascular disease in uremia, focusing on coronary artery disease. We focus on the incidence, presenting syndromes, screening tools, and interventions in the context of acute and chronic coronary syndromes. Recent evidence comparing coronary angioplasty, coronary artery stenting, and bypass surgery in subjects with renal failure is also reviewed. Coronary artery disease is more prevalent in uremia, more difficult to diagnose and less rewarding to treat compared to non-uremic subjects. Many more randomized trials are needed. In the absence of information from such trials, we advocate aggressive control of conventional and novel cardiovascular risk factors, and early intervention for symptomatic coronary disease.

Arteriosclerosis↗
PubMed2001

Coronary artery disease in patients with renal failure.

Cardiovascular disease is prevalent in patients with advanced renal failure or on dialysis treatment, and after renal transplantation. The risk factors for the cardiovascular problems are a mixture of conventional and novel ones. Inflammation and oxidation may be especially important in the acceleration of atherosclerosis in chronic renal failure. This article discusses these factors and gathers together the evidence for cardiovascular intervention and treatment in a group of patients whose overall mortality is high.

Acute Kidney Injury↗
PubMed2000

Reduced blood pressure diurnal variability as a risk factor for progressive left ventricular dilatation in hemodialysis patients.

Cardiovascular mortality places a considerable burden on chronic renal replacement therapy programs. Left ventricular hypertrophy (LVH) increases the risk for cardiovascular mortality. Risk factors for LVH in the dialysis population are numerous and include arterial distensibility, hypertension, anemia, arteriovenous fistula, and hyperparathyroidism. An important factor to consider in the diagnosis and evaluation of hypertension in this clinical setting is blood pressure (BP) level variation, only accessible using ambulatory BP monitoring (ABPM). In uremic patients, a relative elevation of BP during sleep periods leading to an increased 24-hour BP load is frequently described. Whether this additional BP burden is pathophysiologically significant has not been resolved. This study is designed to examine the effect on echocardiographically derived measurements of the left ventricle in 60 stable chronic hemodialysis patients of abnormal (reduced) diurnal BP variability, measuring ambulatory BP on three occasions and performing echocardiography twice over a 12-month period. First, we found that most dialysis patients (76%) had consistent diurnal BP rhythms over a 12-month period, and second, those patients with persistently reduced diurnal BP rhythm tended to develop a dilated left ventricle and left atrium in the absence of other known and/or relevant risk factors (persistently increased sleep BP group; n = 36; LV end-diastolic diameter, 38.2 +/- 2.5 mm/m(2) versus persistently normal sleep BP group; n = 10; LV end-diastolic diameter, 30.6 +/- 3. 3 mm/m(2); P < 0.05). These results suggest that persistent abnormal BP variability is a risk factor for a dilated heart on dialysis, independent of the BP level.

Adult↗
PubMed2000

Analysis of the effect of hemodialysis on peripheral and central arterial pressure waveforms.

BACKGROUND: Arterial stiffening is very pronounced in renal patients. Carotid artery stiffening is a powerful predictor of future cardiovascular mortality, and measures of arterial compliance correlate much better with left ventricular mass (LVM) in dialysis patients than does brachial artery blood pressure (BP). The aim of our study was to describe the influence of a hemodialysis (HD) session on arterial cushioning function and to correlate the potential different types of behavior with echocardiographic derived parameters. METHODS: Radial artery pressure waveforms were measured and recorded noninvasively by applanation tonometry in 51 healthy patients on regular three times weekly HD. The data were then converted into aortic pressure waveforms using a regression equation (SphymoCortrade mark apparatus). Measurements were done pre- and post-HD in order to ascertain the effect of a single HD session on arterial hemodynamics. The augmentation index (AGI; the difference between early and late pressure peaks divided by the pulse pressure amplitude) was used as an index for vascular compliance. Reproducibility was assessed in 20 young healthy subjects by determining the aortic pulse wave augmentation index twice from radial artery BP measurements one minute apart. Intraobserver error was 2.4%. For 10 dialysis patients similarly studied, the intraobserver error was 1.6%. RESULTS: AGI was correlated with subjects' height (r = -0.37, P = 0.009), weight (r = -0.41, P = 0.002), and BP levels: radial systolic BP (r = 0.33, P = 0.018), radial diastolic BP (r = 0.29, P = 0.036), and central systolic BP (r = 0.51, P < 0.001). Comparing the pre- with the post-HD AGI values, four patterns of evolution became apparent: (1) The AGI was negative before the HD session and became even more negative afterward (N = 3 out of 51). (2) The AGI was positive before the HD session but became negative after dialysis (N = 19 out of 51). (3) The AGI was positive before the HD session and, although diminished afterward, remained positive (N = 23 out of 51). (4) The AGI was positive before the HD session and increased afterward (N = 6 out of 51). We also found that in some patients, AGI remained at lower than predialysis levels for at least 24 hours. Significant relationships between echocardiographic parameters and pulse wave contour (PWC) variables included pre-HD AGI and LVM (r = 0.47, P < 0. 001). There was better correlation between LVM and derived predialysis aortic systolic BP (r = 0.56, P < 0.001) than measured brachial (peripheral) systolic BP (r = 0.35, P = 0.04). Patients whose waveform remained abnormal (AGI remained positive) after HD had a more dilated LV (LV-EDD = 52.07 +/- 3.48 mm) than did those patients for whom HD restored "normal" arterial hemodynamics (LV-EDD 46.86 +/- 4.06 mm, P < 0.05). CONCLUSIONS: A standard HD session profoundly affected aortic BP waveform characteristics, with a reduction in wave reflection in 88% of patients. However, restoration by HD of a normal aortic waveform was unusual. Patients whose waveform remained abnormal after HD had larger more dilated LV chambers than did those patients for whom HD restored "normal" arterial hemodynamics.

Adult↗
PubMed2000

Inaccuracy of clinical phenotyping parameters for hypertensive nephrosclerosis.

BACKGROUND: Multiple studies suggest that hypertension-induced end-stage renal disease (ESRD) is heritable. Identification of nephropathy susceptibility genes absolutely requires accurate phenotyping, but the clinical hypertensive nephrosclerosis (HN) phenotype is poorly characterized. We hypothesized that many patients with HN as the indicated cause of ESRD on the Health Care Financing Administration (HCFA) 2728 form, fail to satisfy stringent HN phenotyping criteria. METHODS: Since renal biopsy documentation of HN is uncommon, clinical parameters for HN phenotype were applied: family history of hypertension, left ventricular hypertrophy, proteinuria <0.5 g/day, and hypertension preceding renal dysfunction (Schlessinger et al., 1994) or urine protein:creatinine (prot:creat) ratio <2.0 and no evidence of other renal diseases (AASK Trial Group, 1997). RESULTS: ESRD patients (n=607, 73% African American, 25% Caucasian) were enrolled in a study to identify HN susceptibility genes. HN was the most common cause of ESRD according to HCFA 2728 forms (37% prevalence). Phenotyping of randomly selected patients with HN from the total cohort revealed that 4/100 subjects satisfied the Schlessinger criteria, and 28/91 African Americans met AASK criteria for HN. From these figures, the adjusted prevalence of HN was only 1.5-13.5%. Of patients that could not be phenotyped for HN, 14 were misdiagnosed, 14 had urine prot:creat >2.0, and insufficient data were available in the remainder. Four patients underwent renal biopsy, but histology from only one was consistent with HN. If the HN phenotype definitions are revised to exclude 'hypertension preceding renal dysfunction', or proteinuria limits, then 44/100 and 39/91 patients respectively satisfy clinical phenotyping parameters for HN. CONCLUSIONS: (i) We provide the strongest evidence to date that HN is less frequent in an ESRD population than commonly assumed if strict clinical criteria are used; many patients clinically diagnosed with HN may have undetected, treatable renal disease from other causes; (ii) relaxing HN phenotype criteria may erroneously include patients with glomerular diseases and secondary hypertension; (iii) reliance on HCFA 2728 diagnoses will confound identification of HN susceptibility genes; (iv) to attain adequate statistical power for genotype analysis, rigorous HN phenotyping will require screening an extremely large number of patients, which can be reasonably accomplished only in a multi-centre trial design.

Black People↗
PubMed1999

Hepatitis virus infection in haemodialysis patients from Moldavia.

BACKGROUND: Although the epidemiology of hepatitis B (HBV) and C (HCV) now seems well established for Western European countries, in Central and Eastern Europe < 50% of all dialysis centres routinely test for hepatitis C antibodies since testing is not available or is not applied to all patients. This study describes the prevalence, risk factors and clinical significance of HBV and HCV infection for the haemodialysis population of the North Eastern region of Romania, Moldavia. METHODS: The presence of HBV antigens was determined with an ELISA kit (Wellcome, Abbot) and HCV antibodies with the ELISA-3 Ortho-HCV, third generation test. The following individual data were collected: gender, age, duration of dialysis, rural/urban domicile, actual and previous HBV status, actual HCV status, known acute, clinically evident hepatitis episodes in the last 3 years, monthly alanine aminotransferase (ALAT) and aspartate aminotransferase (ASAT) levels, complete biochemical hepatic assessment at the time of the study, transfusions for the past 3 years and family history. RESULTS: HBV and HCV prevalences were 17% (stable over the last 3 years) and 75%, respectively; co-infection was seen in 10% of the subjects. Hospitalization (nosocomial infection) for HBV, blood transfusions and duration on dialysis for HCV, emerged as the main risk factors for hepatitis infection. Socio-economic conditions appear to be equally important for HCV infection, since the prevalence was significantly higher among patients from rural, underdeveloped areas than urban areas (80.8 vs 60.3%), and infection was already present in a large proportion of patients (47%) before starting dialysis, without being related to previous disease duration or blood transfusions. HBV and/or HCV was not associated with a worse clinical or biochemical profile at the time of the study. However, infected patients had significantly more previous cytolytic episodes, with higher, transient increases in ALAT and ASAT levels. CONCLUSIONS: HCV infection is endemic among dialysis centres in Moldavia. Apart from previously well-known risk factors for hepatitis infection, our study demonstrates the negative impact of socio-economic underdevelopment. Simple measures such as enforced general asepsia rules, careful disinfection and equipment sterilization, routine testing of patients from economically disadvantaged areas and monthly, serial determination of hepatic enzymes should be the common practice in dialysis centres in Romania.

Adult↗
PubMed1999

Long-hours home haemodialysis--the best renal replacement therapy method?

Two hundred and eighty-six patients (190 males and 96 females) with end-stage renal failure (ESRD) started haemodialysis (HD) at Withington Hospital between 1 January 1968 and 31 December 1986. Of these, 152 (53.1%) were successfully transplanted, while 134 had only HD or one transplant lasting < 3 months (i.e. total HD interruption < 3 months). For the whole group, the probabilities of being alive on long-hours home HD at 10 and 20 years were 58.7% and 33.2%, respectively. Mean gross mortality 1968-1986 was 6.5 +/- 3.2% per year. The main causes of death were cardiovascular (36.6%), infection-related (19.2%) and malignancy (9.6%). Males and younger cohorts had a significantly (p < 0.05) higher probability of being alive on long-hours home HD than did females and older cohorts. Eighty-two patients (29% of the total group) survived more than 10 years, of whom 54 were still alive at 1 January 1996: 44 continuing on HD while the other ten had been successfully transplanted. In these 54 patients, mean 24-h ambulatory blood pressure recorded at the date of the study was 117.6/68.9 mmHg; mean BP for the last 5 years on HD was 136.4/81.2 mmHg. Only four (7.4%) were regularly taking antihypertensive medication. Left ventricular hypertrophy (LVH) (by ECG) was present in 64.8% of the 54 patients; its prevalence by echocardiography (LVM index > 130 g/m2 for men and > 110 g/m2 for women) was 77.5%. Only 10 (18.5%) had symptoms or clinical signs of ischaemic heart disease and/or peripheral vascular disease. None had cardiac failure symptoms NYHA class 3-4. Our data show a low incidence of all-cause and cardiovascular mortality, confirming those from the Tassin unit in France, and make a medical case for extended haemodialysis treatment hours.

Adolescent↗
PubMed1998

Urea kinetic modelling--are any of the 'bedside' Kt/V formulae reliable enough?

BACKGROUND: Longevity on dialysis is determined by many factors. One of these has increasingly been seen to be 'dialysis dose'. There are several methods for calculating dialysis dose. We wanted prospectively to test 'gold-standard' UKM-Kt/V with various shortcut bedside formulae, to see whether reliance on the latter approach was likely to lead to errors in over- or underprescribing dialysis regimens. METHODS: Ten bedside formulae for the calculation of Kt/V (urea) were compared with UKM Kt/V values, in a month-long study involving 507 dialysis sessions in 50 patients in a single-centre in-patient haemodialysis unit. RESULTS: For patients with UKM Kt/V<0.8 (median 0.69, n=140), simplified formulae had a difference (delta) of 0.094-0.396 from the calculated UKM resulting in an inter-method variability ranging from 13 to 57%. The least difference was seen with the Calzavara formula (P=NS), maximum difference with the Barth formulae (P<0.05). No statistically significant differences were seen when comparing Daugirdas 1 and 2 and Keshaviah formulae with UKM, for patients with UKM Kt/V<0.8. For patients with UKM Kt/V in the range 0.8-1.4 (median 1.06, n=285) the extreme recorded values from simplified formulae were 0.012 (least different) and 0.245 (most different) from the UKM mean, with an inter-method variability ranging between 1.1% (Basile method) to 23.1% (Calzavara). No statistically significant difference were seen when comparing Daugirdas 1 and 2, Keshaviah, and Lowrie formulae with UKM, for patients with UKM Kt/V 0.8-1.4. For patients with the highest UKM Kt/V values (>1.4; median 1.58, n=72), all simplified formulae gave Kt/V values lower than UKM Kt/V: the minimum difference was 0.070 using Jindal (P=NS, intermethod variability of 4.4%), while the maximum was seen when using Calzavara (P<0.05; difference = 0.69; intermethod variability of 43.7%). There was also no statistically significant difference for Basile and Kerr methods. For the group as a whole the biggest difference from UKM mean values was obtained using Barth's and Calzavara's formulae (delta of 0.171 and 0.140 respectively (P<0.05)). CONCLUSIONS: The best correlations were seen with the Daugirdas 2 formula (r2=0.953). Also, comparing grouped formulae containing ln(Co/Ct) terms with those incorporating the (Co-Ct)/Co ratio (i.e. the urea reduction) there was a better correlation for all formulae employing the logarithmic transformation (r2=0.951-0.953 cf. r2=0.939-0.940). Nevertheless no bedside formula had the accuracy of UKM-Kt/V.

Adult↗
PubMed1998

Rifampicin-induced acute renal failure: a series of 60 patients.

BACKGROUND: Since 1971, 55 case-reports of rifampicin-induced ARF have been published, but systematic data on this condition are not available, in view of the disparate nature of the observations. METHODS: We retrospectively assessed prevalence, clinical and biochemical features, and prognostic factors of 60 consecutive cases (41 males/19 females, age 22-68 years), who were admitted to the Iasi Dialysis Centre from 1987 to 1995 for acute renal failure (ARF) following re-treatment with rifampicin. RESULTS: The clinical appearance consisted mainly of gastrointestinal and 'flu-like' symptoms and clinical signs of intravascular haemolysis (the latter in 17% of cases). Frequent laboratory findings were anaemia (96% of cases), leukocytosis (63%), and thrombocytopenia (50%). Severe anaemia was associated with marked haemolysis (25% cases), thrombocytopenia, longer anuria, and slower rate of renal function recovery. Signs of hepatic injury were found in 25% of patients, but it did not seem to affect the outcome of renal function. Prognostic factors in post-rifampicin ARF proved to be the following: the duration of the anuric phase (correlated with the number of dialysis sessions and with the rate of decrease of azotaemia) and the severity of the immunological abnormalities and inflammatory syndrome (haemolysis, leukocytosis, hypergammaglobulinaemia). Post-rifampicin ARF accounted for 16.6% of all ARF cases hospitalized in our Centre during the studied period. Its clinical course was favourable; the mortality rate was only 1.6% (1 case), compared to a 20% general mortality rate among all ARF patients. Full recovery of renal function was achieved in 40% and 96% of patients, 30 and 90 days respectively from onset. CONCLUSIONS: ARF after treatment with rifampicin is not an uncommon condition, especially when tuberculosis prevalence is high, but renal prognosis is usually favourable. Thrombocytopenia, immune haemolytic anaemia, and intravascular haemolysis are frequent complications which are associated with a more severe renal injury.

Acute Kidney Injury↗
PubMed1997

Vascular calcification in long-term haemodialysis patients in a single unit: a retrospective analysis.

Vascular calcification (VC), which is described in the elderly and in diabetics, is frequently seen in uraemia. It is usually regarded as having little significance. We studied the roentgenological appearance of VC in a homogeneous group of 38 long-hours haemodialysis patients whose longevity on dialysis allowed sustained (10-25 years) follow-up, including annual skeletal surveys and thrice-yearly clinical examinations and biochemical profiles. We compiled a dossier of clinical and laboratory parameters from the start of dialysis to the present day. We were able to analyze the natural history of VC and to determine which clinical parameters were linked with progression. We found that VC became steadily more prevalent-at dialysis onset present in 39% of the patients, but in 92% after an average dialysis duration of 16 years, with a mean onset 9.7 years after starting dialysis. As well as becoming more prevalent, the calcification became progressively more severe in most patients. There were two patterns of VC: axial (aorta and iliac and femoral arteries), seen alone in 32% of the patients, and peripheral (digital arteries), seen alone in 3% of patients. Most patients (65%) had evidence of both types. Calcification was scored for site and severity. Patient age (r = 0.57, p < 0.001), systolic blood pressure (r = 0.54, p < 0.001), hyperparathyroidism (reduced progression after parathyroidectomy), plasma phosphate (r = 0.34, p = 0.042), and vitamin D concentrations (r = 0.53, p < 0.001) were the principal determinants of severity and rate of progression of VC in this population. There was a weak negative association between progression and serum ferritin (r = -0.33, p = 0.046). The reduced vessel compliance that results from VC is likely to be cardiovascularly deleterious. In severe cases, tissue perfusion or vascular access for haemodialysis can be compromised. VC and accelerated cardiovascular mortality are common to uraemia, diabetes, and systolic hypertension in the elderly. Better understanding of these pathological processes may permit intervention and possibly lead to a reduction in cardiovascular mortality.

Calcinosis↗
PubMed1996

Echocardiographic findings in long-term, long-hour hemodialysis patients.

This article describes the echocardiographic structural and functional findings in a cohort of 30 patients on ten or more years of uninterrupted long-hour (24 hours per week dialysis schedule) hemodialysis (mean duration 187.7 months, range 120 to 299 months). Cardiac structural analysis was remarkable for the prevalence of LVH (76%), very rarely asymmetric (3%). Hemoglobin and (log) plasma renin activity were determinants of the LV wall thickness ratio (r = -0.57 and 0.54, p = 0.003 and 0.044 respectively). Markers of systolic contractile function were frequently normal (100% MVCFS; 85% FSI). Diastolic ventricular compliance was abnormal in 59% of patients. Blood pressure history appeared important in determining LVH, but office/ABPM measures of BP were not. Patients after parathyroidectomy (PTx) had a smaller LVPWTN (8.68 mm/m2 without PTx cf 7.01 mm/m2 after PTx, p = 0.036). Left ventricular cavity size was rarely enlarged (10%), with hemoglobin (r = -0.47, p = 0.012) and PTH (r = -0.65, p < 0.001) the major determinants of EDDN. Left atrial diameter was increased in 77% of patients. Cardiac valvular calcification was seen in 50% of patients. Our findings show that despite good BP control without recourse to antihypertensive drugs, LVH with good LV systolic function is very common in these long-survivors.

Aortic Valve↗