Microalbuminuria predicts cardiovascular events and renal insufficiency in patients with essential hypertension

Left ventricular mass assessed by electrocardiography and albumin excretion rate as a continuum in untreated essential hypertension

OBJECTIVE

To study an association between albumin excretion rate and left ventricular mass (LVM) determined by electrocardiogram (ECG)-based criteria, and with respect to ambulatory blood pressure, in patients with newly diagnosed and never-treated essential hypertension.

METHODS

We measured 24 h ambulatory blood pressure, albumin excretion rate and LVM in 74 patients with newly diagnosed (within the past year) and never-treated essential hypertension, who were admitted to the hypertension clinic (Ulleval University Hospital). Albumin excretion rate was evaluated by determination of the albumin:creatinine ratio in the first-voided morning urine sample. LVM was assessed by ECG using Cornell voltage-QRS duration product and Sokolow- Lyon criteria.

RESULTS

Albumin excretion rate was significantly related to ambulatory blood pressure. There was a weak but significant negative correlation between the decrease in diastolic blood pressure during the night and the rate of excretion of albumin. The patients classified as dippers had a significantly lower albumin excretion rate compared with the non-dippers (1.36+/-0.83 compared with 1.68+/-0.87 mg/mmol; P = 0.03). LVM was found to be significantly related to ambulatory blood pressure. A weak relationship was observed between albumin excretion rate and LVM as evaluated by Cornell criterion (r = 0.23, P = 0.045). When only normoalbuminuric patients were included (i.e. four patients with microalbuminuria were excluded), the relationship was stronger (r = 0.36, P = 0.002).

CONCLUSIONS

The present findings show a continuous relationship between albumin excretion rate, LVM and ambulatory blood pressure in newly diagnosed patients with essential hypertension, and suggest the occurrence of early effects on target organs (kidneys and heart). These associations were observed using easily applicable methods such as ECG monitoring and determination of the albumin:creatinine ratio in morning urine samples.

Frequency and determinants of microalbuminuria in mild hypertension: a primary-care-based study

OBJECTIVE

To evaluate the frequency of microalbuminuria and its relationship with several risk factors and left ventricular mass in a population of mildly hypertensive subjects attended in a primary-care setting.

DESIGN

Cross-sectional study.

SETTING

Eight primary-care centres.

PATIENTS

Two hundred and twenty-three non-diabetic patients recently diagnosed with mild hypertension were included in the study. None of them had clinical evidence of target-organ damage or had received prior antihypertensive treatment.

INTERVENTIONS

Subjects included in the study underwent clinical interview, measurement of blood pressure (BP) on three visits, blood analysis, measurement of albumin by immunonephelometry in three overnight urine collections, 24 h BP monitoring and M-mode and Doppler echocardiography.

MAIN OUTCOME MEASURES

Tobacco habit, clinic BP, body mass index, serum lipids and uric acid, glycaemia, urinary albumin excretion (UAE), ambulatory BP and left ventricular mass index.

RESULTS

The frequency of microalbuminuria was 7.2%. Microalbuminuric patients were more likely to be men and to be characterized by higher ambulatory BP, body mass index and uric acid levels. Regression analysis demonstrated that male sex and 24 h systolic BP were determinants of UAE. Patients with white-coat hypertension showed lower UAE than did subjects with sustained hypertension. Although a certain relationship between UAE and left ventricular mass index was found, these variables were not significantly correlated.

CONCLUSIONS

A low proportion of mildly hypertensive patients attended in a primary care setting are microalbuminuric. In this population, UAE is an expression of BP values over 24 h and correlates with several risk factors.

Microalbuminuria is associated with abnormal thoracic aortic mechanics in essential hypertension

In a population of 162 patients with currently untreated essential hypertension, those with microalbuminuria (n = 75) had significantly impaired elastic properties of the proximal ascending thoracic aorta compared with their normoalbuminuric counterparts (n = 87), whereas urinary albumin excretion was a significant predictor of aortic mechanics in the entire population. Impaired aortic mechanics in microalbuminuric hypertensives were not fully accounted for by clustering of classic risk factors for atherosclerosis, and constitute a finding that may entail additional long-term cardiovascular risk in this subgroup of patients.

Proteinuria as a risk factor for cardiovascular disease and mortality in older people: a prospective study

BACKGROUND

The prognostic significance of proteinuria in older people is not well defined. We examined the associations between proteinuria and incident coronary heart disease, cardiovascular mortality, and all-cause mortality in older people.

SUBJECTS AND METHODS

Casual dipstick proteinuria was determined in 1,045 men (mean [+/- SD] age 68 +/- 7 years) and 1,541 women (mean age 69 +/- 7 years) attending the 15th biennial examination of the Framingham Heart Study. Participants were divided by grade of proteinuria: none (85.3%), trace (10.2%), and greater-than-trace (4.5%). Cox proportional hazards analyses were used to determine the relations of baseline proteinuria to the specified outcomes, adjusting for other risk factors, including serum creatinine level.

RESULTS

During 17 years of follow-up, there were 455 coronary heart disease events, 412 cardiovascular disease deaths, and 1,214 deaths. In men, baseline proteinuria was associated with all-cause mortality (hazards ratio [HR] = 1.3, 95% confidence interval [CI] 1.0 to 1.7 for trace proteinuria; HR = 1.3, 95% CI 1.0 to 1.8 for greater-than-trace proteinuria; P for trend = 0.02). In women, trace proteinuria was associated with cardiovascular disease death (HR = 1. 6, 95% CI 1.1 to 2.4), and all-cause mortality (HR = 1.4, 95% CI 1.1 to 1.7).

CONCLUSION

Proteinuria is a significant, although relatively weak, risk factor for all-cause mortality in men and women, and for cardiovascular disease mortality in women.

Clinical value of microalbuminuria in hypertension

Microalbuminuria (MA) is a well recognized marker of cardiovascular complications in hypertension, but whether MA can predict adverse outcome in this clinical condition is still a subject for debate. The fact that in hypertensive cohorts those patients who showed an increase in albumin excretion rate also manifested an increased incidence of morbid events indicates that the presence of MA in hypertension may carry an increased cardiovascular risk. However, the prognostic significance of MA remains controversial because no results of prospective studies performed in hypertensive subjects without diabetes mellitus are available. Several factors can affect the prevalence of MA in hypertension, including severity of the disease, selection procedures, concomitant risk factors, degree of obesity, age, and sex distribution. This accounts for the large differences in the prevalence of MA that can be found in the literature, with prevalence rates going from a low of 4.7% to a high of 40%. There is still conflict over whether MA in hypertension is due to increased intraglomerular pressure or to glomerular damage. The data from the literature suggest that in subjects with mild hypertension the main determinant of albumin excretion rate is the haemodynamic load. In subjects with more severe hypertension and hypertensive complications, the augmented urinary albumin leak is probably the consequence of a systemic microvascular disturbance which involves the glomeruli. In this respect, the insulin resistance state often associated to high blood pressure appears as one of the main pathogenetic factors. Whether management of hypertensive populations may be improved by monitoring of albumin excretion rate and whether antihypertensive drugs which are more effective in decreasing urinary albumin can be more beneficial in patients with MA remains to be determined.

Proteinuria: its clinical importance and role in progressive renal disease

In patients with essential hypertension and in those with diabetes mellitus, the presence of increased amounts of urinary protein or albumin has been shown to be an important and independent risk for an increased incidence of cardiovascular morbidity and mortality. A constellation of cardiovascular risk factors has been described in these individuals, as well as evidence for diffuse endothelial cell dysfunction, which suggests these individuals are particularly susceptible to the development of extensive vascular disease. Recent studies have also suggested that proteinuria is not only a marker for renal disease but it also predicts those patients at greatest risk for the development of chronic and progressive renal insufficiency. This effect of proteinuria was evident in patients in whom urinary protein excretion rates exceeded 1 g/24 hours, but probably is true even in patients with smaller amounts of proteinuria. This effect of proteinuria on progression of renal disease is independent of other risk factors such as level of renal function, blood pressure, and dyslipidemia. Recent clinical studies have demonstrated that modification of proteinuria by the use of angiotensin-converting enzyme (ACE) inhibitors independent of reductions in systemic blood pressure results in slowing of the rate of loss of renal function and even stabilization of renal function over longer periods of treatment. In patients with renal disease, the totality of evidence suggests that multiple pharmacological and dietary modifications will be necessary to achieve the optimal slowing of the progression of renal disease. In addition, strategies will be required to reduce risks involved in the development of cardiovascular disease to ensure optimal patient survival. The similarity of risk factors involved in cardio-renal disease progression should allow us to achieve this goal with our current therapeutic armamentarium.

Arterial hypertension, microalbuminuria, and risk of ischemic heart disease

Albumin excretion in urine is positively correlated with the presence of ischemic heart disease and atherosclerotic risk factors. We studied prospectively whether a slight increase of urinary albumin excretion, ie, microalbuminuria, adds to the increased risk of ischemic heart disease among hypertensive subjects. In 1983 and 1984, blood pressure, urinary albumin/creatinine concentration ratio, plasma total and HDL cholesterol levels, body mass index, and smoking status were obtained in a population-based sample of 2085 subjects, aged 30 to 60 years, who were free from ischemic heart disease, diabetes mellitus, and renal or urinary tract disease. Untreated arterial hypertension or borderline hypertension was present in 204 subjects, who were followed until 1993 by the National Hospital and Death Certificate Registers with respect to development of ischemic heart disease. During 1978 person-years, 18 (9%) of the hypertensive subjects developed ischemic heart disease. Microalbuminuria, defined as a urinary albumin/creatinine ratio above the upper decile (1.07 mg/mmol), was the strongest predictor of ischemic heart disease, with an unadjusted relative risk of 4.2 (95% CI 1.5 to 11.9, P=0.006) and a relative risk of 3.5 (95% CI 1.0 to 12.1, P=0.05) when adjusted for all other atherosclerotic risk factors, including age and gender. In conclusion, microalbuminuria confers a 4-fold increased risk of ischemic heart disease among hypertensive or borderline hypertensive subjects. Urinary albumin excretion should be measured regularly in a hypertension clinic, and a rigorous control of blood pressure and of other atherosclerotic risk factors is recommended in hypertensive patients with microalbuminuria.

Microalbuminuria and pulse pressure in hypertensive and atherosclerotic men

To identify the biological covariates of microalbuminuria (albuminuria >/=15 microg/min) in nondiabetic subjects, brachial blood pressure, echocardiographic left ventricular mass, and other cardiovascular and metabolic parameters were evaluated in 211 untreated males (38 normal controls, 109 uncomplicated stage 1 to 3 essential hypertensives, and 64 patients with clinically stable atherosclerotic peripheral vascular disease either with [n=44] or without [n=20] essential hypertension) with normal cardiac and renal function. Compared with normoalbuminuric subjects, microalbuminuric subjects (n=67) were characterized by higher systolic blood pressure, comparable diastolic blood pressure, and, therefore, wider pulse pressure. Greater prevalence of hypertension, peripheral vascular disease, left ventricular hypertrophy, and reduced HDL cholesterol values further distinguished microalbuminuric from normoalbuminuric subjects in univariate comparisons. The risk of microalbuminuria increased by ascending pulse pressure quintiles in age-corrected logistic regression models, in which pulse pressure was more predictive than systolic pressure and was independent of mean pressure. When microalbuminuric status was regressed against a series of dichotomous (vascular and active smoker status) and continuous (age, pulse and mean pressure, left ventricular mass index, and HDL and LDL cholesterol) variables, only pulse pressure, left ventricular mass index, and smoking status were independent predictors. The association of increased albuminuria with wider pulse pressure, a correlate of the pulsatile hemodynamic load and conduit vessel stiffness as well as an important cardiovascular risk factor, may explain why microalbuminuria predicts cardiovascular events in nondiabetic subjects. The independence from concomitant vascular disease also suggests that wider pulse pressure, rather than representing a simple marker for atherosclerotic disease, influences albuminuria directly.

Influence of the I/D polymorphism of the angiotensin-converting enzyme gene on the outcome of microalbuminuria in essential hypertension

The objective of the present study was to analyze the influence of the I/D polymorphism of the ACE gene on the outcome of microalbuminuria in essential hypertensive patients who were receiving antihypertensive treatment. One hundred thirty-six essential hypertensive patients who were <50 years old and had never previously received treatment with antihypertensive drugs were included in the study. During a 3-year period, patients received nonpharmacological treatment consisting of moderate salt restriction and a low-calorie diet they were obese, with or without a regimen of antihypertensive drugs based on beta-blockers or ACE inhibitors. Hydrochlorothiazide was added when necessary to maintain the blood pressure goal of <135/85 mm Hg. At the beginning of the study and at yearly intervals, systolic and diastolic blood pressures (SBP and DBP, respectively), 24-hour urinary albumin excretion (UAE), renal function, and biochemical profile measurements were made. The insertion/deletion (I/D) polymorphism of the ACE gene was determined through the use of polymerase chain reaction. The variables used in the statistical analysis were the measurements at the start of the study and the increase or decrease detected during the follow-up, estimated as individual specific regression line slope values. At baseline, no differences in blood pressure or UAE values were observed among genotypes. Likewise, the genotype or allele frequency was not significantly different between normoalbuminurics and microalbuminurics. After the 3 treatment years, significant reductions in SBP, DBP, and UAE were found (SBP 151.6+/-17.3 reduced to 137.2+/-14.3 mm Hg, P<0.001; DBP 96.6+/-8.9 reduced to 84.5+/-9.8 mm Hg, P<0.001; UAE 36.7+/-71.5 reduced to 28.3+/-78.6 mg/24 h, P<0. 05). The slopes of these parameters over time did not differ significantly among genotypes. The slope of SBP was the main factor related to the slope of logUAE (P<0.003). A significant positive correlation coefficient between the SBP and logUAE slopes was observed for the DD patients (r=0.57, P<0.0001) but was absent in patients carrying the I allele (II r=-0.03, P=NS; I/D r=0.01, P=NS). Follow-up studies should be used to achieve a better understanding of the impact of candidate gene polymorphisms on the development of hypertension-induced organ damage. Assessment of the I/D polymorphism of the ACE gene may identify subjects who require a greatly lowered blood pressure to prevent organ damage and to reduce hypertension-associated complications and death.

Microalbuminuria in essential hypertension: significance, pathophysiology, and therapeutic implications

Some patients with essential hypertension manifest greater than normal urinary albumin excretion (UAE). The significance of this association, which is the object of this review, is not well established. Hypertensive patients with microalbuminuria manifest greater levels of blood pressure, particularly at night, and higher serum levels of cholesterol, triglycerides, and uric acid than patients with normal UAE. Levels of high-density lipoprotein cholesterol, on the other hand, were lower in patients with microalbuminuria than in those with normal UAE. Patients with microalbuminuria manifested greater incidence of insulin resistance and thicker carotid arteries than patients with normal UAE. After a follow-up of 7 years, we observed that 12 cardiovascular events occurred among 54 (21.3%) patients with microalbuminuria and only two such events among 87 patients with normal UAE (P < 0.0002). Stepwise logistic regression analysis showed that UAE, cholesterol level, and diastolic blood pressure were independent predictors of the cardiovascular outcome. Rate of creatinine clearance from patients with microalbuminuria decreased more than that from those with normal UAE. In conclusion, these studies suggest that hypertensive individuals with microalbuminuria manifest a variety of biochemical and hormonal derangements with pathogenic potential, which results in hypertensive patients having a greater incidence of cardiovascular events and a greater decline in renal function than patients with normal UAE.

High plasma renin activity is combined with elevated urinary albumin excretion in essential hypertensive patients

BACKGROUND

Several studies suggest that the hyperactivity of the circulating renin-angiotensin system might favor the progression of renal disease in essential hypertension. To elucidate this aspect, we investigated the relationship between plasma renin activity (PRA) and the urinary albumin excretion rate (UAER), an early marker of hypertension-related renal changes, in human essential hypertension.

METHODS

Ninety nonobese, nondiabetic, nonhyperlipidemic patients with mild-to-moderate essential hypertension (67 males, 23 females; mean age 51.4 +/- 6.2 years) were divided into low renin (LR), normal renin (NR), and high renin (HR) subgroups according to individual PRA while they were on a constant NaCl intake (120 mmol NaCl/day). The UAER was assessed during the same NaCl intake.

RESULTS

Data showed significantly higher UAER (31.3 +/- 12.9 microg/min) in HR (N = 30) than NR (N = 30, 22.7 +/- 14.4 microg/min, P < 0.02) and LR patients (N = 30, 21.7 +/- 10.8 microg/min, P < 0. 01).

CONCLUSIONS

Our study demonstrates that the UAER is elevated in HR essential hypertensive patients, suggesting that high PRA accelerates the onset of early renal changes in human essential hypertension.

Microalbuminuria and transcapillary albumin leakage in essential hypertension

Microalbuminuria (an increased urinary albumin excretion that is not detectable by the usual dipstick methods for macroproteinuria) predicts cardiovascular events in essential hypertensive patients. A possible reason for this behavior is that albumin leaks through exaggeratedly permeant glomeruli exposed to the damaging impact of subclinical atherogenesis. To evaluate this possibility, the transcapillary escape rate of albumin (TER(alb), the 1-hour decline rate of intravenous (125)I-albumin), a parameter that estimates the integrity of systemic capillary permeability, albuminuria, blood pressure, echocardiographic left ventricular mass, lipids, and body mass index were measured in 73 uncomplicated, glucose-tolerant men with essential hypertension and normal renal function; 53 were normoalbuminuric, and 20 were microalbuminuric. Twenty-one normotensive age-matched male subjects were the controls. TER(alb) was higher in hypertensives, a behavior explained in part by a positive correlation with blood pressure values, although body mass index, lipids, and left ventricular mass showed no association. Transcapillary albumin leakage values did not differ between normoalbuminuric and microalbuminuric patients and were unrelated to albuminuria. Blood pressure, particularly systolic, and cardiac mass were higher in microalbuminuric patients in whom albuminuria correlated with both cardiovascular variables and indicated the influence of the hemodynamic load on urinary albumin levels. Thus, TER(alb), a parameter influenced by the permeability surface area product for macromolecules and the filtration power across the vascular wall, is altered in essential hypertensives. However, this abnormality is dissociated from the amount of albuminuria, which is contrary to the hypothesis that a higher albumin excretion reflects a greater degree of systemic microvascular damage in essential hypertension.

Risk factors for nephropathy in type 2 diabetes mellitus

The main risk factors for diabetic nephropathy are hypertension, hyperlipidemia, and hyperglycemia. Nephropathy heralds the downhill course of arteriosclerosis. Early and intensive blood pressure and glucose control will attenuate the course of nephropathy and significantly reduce cardiovascular events and stroke.

Microalbuminuria in essential hypertension

Urinary excretion of albumin exceeds normal values in 10 to 25% of patients with essential hypertension. The level of albuminuria is highly correlated with arterial pressure, and more closely with ambulatory arterial pressure. The interaction between albuminuria and arterial pressure is enhanced by overweight, smoking, protein intake, insulin resistance, lipid abnormalities, and possibly genotypes of the components of the renin-angiotensin system. The renal mechanisms of microalbuminuria are not well elucidated. Notably, an increase in filtration fraction suggestive of intraglomerular hypertension was observed in patients with hyperfiltration. Microalbuminuria may be a marker of diffuse vascular abnormalities predisposing to cardiovascular disease and/or hypertensive renal disease heralding future renal failure, but its predictive value needs to be tested in more long-term follow-up studies. Antihypertensive treatment has a varied influence on albuminuria; angiotensin-converting enzyme inhibitors may correct this abnormality (at least partially) better than other agents.