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Biomedical subjects

J Levenson

Publications and source records attributed to J Levenson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Predictive value of waist-to-hip ratio on cardiovascular risk events.

BACKGROUND: A central distribution of adipose tissue is frequently associated with cardiovascular disease (CVD) and its risk factors. METHODS: Clinical usefulness of waist-to-hip ratio (WHR) for predicting the risk of cardiovascular events, estimated with models based on data from the Framingham and Prospective Cardiovascular Münster (PROCAM) studies was evaluated. SUBJECTS: These were 552 men and 160 women, asymptomatic and at risk for CVD, aged 30-74 y, recruited from an ongoing risk factor screening program conducted at worksites. RESULTS: Abdominal fatness was a strong predictor of cardiovascular complications in subjects whose WHR was in the top quintile (> 0.98 for men and > 0.91 for women). The estimated percentage rate of coronary heart disease (CHD, P <0.01) and death (P < 0.01), myocardial infarction (P < 0.01), stroke (P < 0.01), total CVD (P < 0.001) and death (P < 0.01) increased with increasing quintile of WHR in men and women. In the highest WHR, the number of subjects exceeding a 15% risk of developing a coronary event over the next 10 y was more than two-fold greater (odds ratio (OR) 2.60 (confidence intervals (CI) 1.09-6.54) than in the lowest WHR quintiles. Similar six-year myocardial infarction (MI) risks at each quintile of WHR were observed in men in both Framingham and PROCAM models. In the overall population, CHD estimates increased with increasing quintiles of WHR with the Framingham model and an adapted model for estimating probabilities of disease in the French population of the Prevention Cardiovasculaire en Médecine du Travail (PCV-METRA) group. CONCLUSION: Abdominal deposition of fat assessed by WHR may be of strong clinical value for predicting high risk of cardiovascular events.

Adult↗
PubMed1999

Carotid wall inertial index increase is related to intima-media thickening in hypertensive patients.

OBJECTIVE: The aim of this study is to evaluate the relationship between carotid intima-media thickness (IMT) and arterial wall inertial behaviour. METHODS: The simultaneous and noninvasive assessment of the intima-media complex and arterial diameter waveform was performed using high-resolution ultrasonography. The common carotid artery of eleven normotensive subjects (NTA) and eleven mild-to-moderate essential hypertensive patients (HTA) were measured noninvasively using tonometry and an automatic densitometric analysis of B-mode images to obtain IMT and instantaneous pressure (P) and diameter (D) loops. A linear discrete time model was used to estimate the inertial index (K(M)) using a system modelling-identification approach. RESULTS: In NTA K(M) was 0.333+/-0.256 (mmHg x s2/mm) and IMT 0.643+/-0.061 (mm), whereas in HTA K(M) was 0.798+/-0.590 (P < 0.05) and IMT 0.760+/-0.034 (P < 0.025). When all data of K(M) versus IMT of NTA and HTA were pooled in a linear regression analysis, a correlation coefficient of r = 0.61 (P < 0.05) was obtained. CONCLUSION: Wall inertia increase was associated with a higher IMT, suggesting that the intima-media thickening might be partially related to vascular hypertrophy manifested as increase of inertial behaviour.

Adult↗
PubMed1999

Aging affects the ocular circadian pacemaker of Aplysia californica.

The eye of Aplysia has been used to explore various aspects of circadian rhythms. The authors discovered that age has profound effects on the circadian rhythm of nerve impulses from the eye. With age, there was a significant decrease in the amplitude of the rhythm. The decrease appeared to be continuous over the life span of the animal and was observed both in vitro and in vivo. The free-running period and phase angle of the rhythm steadily increased with age, indicating that the pacemaker itself was affected by age. Rates of transcription and translation were significantly increased with age, suggesting that age-associated alterations of the pacemaker may occur through changes in macromolecular synthesis. Interestingly, eyes from some older (> or = 10 months) animals had "cloudy" lenses (cataracts). Highly damped or arrhythmic rhythms always were seen in eyes with cloudy lenses. Morphology of eyes with cloudy lenses indicated severe retinal degeneration. No such degeneration was observed in eyes with clear lenses that were used in the analysis of the rhythm with age.

Action Potentials↗
PubMed1998

Evidence of carotid artery wall hypertrophy in homozygous homocystinuria.

BACKGROUND: We aimed to determine whether intima-media thickness (IMT) was increased in the carotid artery of subjects with homocystinuria to better understand the in vivo contribution of homocysteine to early atherogenesis. METHODS AND RESULTS: We investigated ultrasonographically the right common carotid artery in 14 subjects with homozygous homocystinuria aged 3 to 34 years (mean, 13 years) and in 15 of their heterozygous parents aged 32 to 47 years (mean, 41 years) by comparison with 2 control groups of 15 healthy subjects of the same age. Far-wall IMT and lumen diameter were measured with a computerized program, and the cross-sectional area of the intima-media complex (CSA-IMC) was calculated from IMT and diameter. Comparison with their respective controls, adjusted for body surface area or height, showed that homozygotes had greater IMT (P<0.001) and CSA-IMC (P<0.05) and smaller diameter (P<0.05), whereas heterozygotes had values similar to their controls. Multivariate analysis of the arterial parameters with age, body surface area (or height), and plasma total homocysteine in the homozygous and heterozygous groups combined showed that IMT was related to age (P<0.05) and homocysteine (P<0.01), diameter was related to body surface area (P<0.001) or height (P<0.05), and CSA-IMC was related to age (P<0.05), body surface area (P<0.05) (but not height), and homocysteine (P<0.05). CONCLUSIONS: Homozygous homocystinuria was associated with common carotid wall hypertrophy, whereas heterozygous disease was not. Such hypertrophy may reflect a smooth muscle proliferation induced by hyperhomocysteinemia and represent a promising target for testing vascular effects of therapeutic measures to lower homocysteine.

Adolescent↗
PubMed1998

Aortic stiffening does not predict coronary and extracoronary atherosclerosis in asymptomatic men at risk for cardiovascular disease.

Stiffness of aortic walls has been shown to be a marker of coronary and cerebrovascular diseases in patients with myocardial infarction or stroke. However, its value for predicting preclinical atherosclerosis has not been demonstrated. Therefore, this study tested the association of aortic wall stiffness and coronary and extracoronary atherosclerosis in the absence of clinical cardiovascular disease. In 190 asymptomatic men at cardiovascular risk, carotid-to-femoral pulse wave velocity (PWV) was measured mechanographically and the compliance of the aorta (C), as well as the intrinsic compliance (Ci), was deduced after correction for the effect of blood pressure. Also determined noninvasively were 1) the degree of coronary calcium deposit coded as grade 0, 1, 2, or 3 using ultrafast computed tomography; 2) the extent of extracoronary plaque detected by B-mode echography at three different sites (carotid, abdominal aorta, and femoral) coded as 0, 1, 2, or 3 diseased sites; and 3) the estimated Framingham coronary risk. The grade of coronary calcium was not associated with any aortic elastic parameter. The number of extracoronary diseased sites was not associated with PWV and C but correlated negatively with Ci before but not after age adjustment. The coronary risk correlated positively with PWV and negatively with C before but not after age adjustment and was not associated with Ci. In symptom-free subjects aortic stiffening does not predict the presence of coronary and extracoronary atheroma and therefore cannot be considered as a useful surrogate marker of early atherosclerosis.

Adult↗
PubMed1998

Utility of electrocardiogram for predicting increased left ventricular mass in asymptomatic men at risk for cardiovascular disease.

The objective of this study was to test the value of electrocardiogram for predicting left ventricular mass (LVM), assessed echographically in 136 asymptomatic men with at least one major cardiovascular risk factor. We measured the Sokolow-Lyon and Cornell voltages, as well as the ratio of Cornell voltage to QRS voltage in lead II. The prevalence of left ventricular hypertrophy (LVH), defined as LVM of > or = 125 g/m2, was 6%, whereas that of increased LVM, defined as LVM of > or = 99 g/m2, the 90th upper percentile of a control group, was 29%. Receiver operating characteristics curves showed that for predicting LVH at 80% specificity, the Cornell/QRS(II) voltage ratio had a sensitivity of 75%, whereas those of the Cornell and Sokolow-Lyon voltages were 50% and 12.5%, respectively. For predicting increased LVM at 80% specificity, the Cornell/QRS(II) voltage ratio had a sensitivity of 56%, whereas the sensitivities of the Cornell and Sokolow-Lyon voltages were 36% and 22%, respectively. We conclude that, in constrast with the Sokolow-Lyon voltage, the new dimensionless Cornell/QRS(II) voltage shows a sensitivity at a high specificity value at least as acceptable as that of the Cornell voltage for predicting borderline-high LVM in a population with a low prevalence of LVH.

Adult↗
PubMed1998

Early atherosclerosis in human hypertension.

The detection of preclinical atherosclerosis may contribute to better identifying hypertensive subjects at high risk of complications. Three alterations can be diagnosed noninvasively: calcification, thickening, and stiffening of the arterial wall. Their prevalence is increased in asymptomatic hypertensives and their presence may have important prognostic significance, especially with respect to coronary artery disease. They are also ideal targets to test the efficacy of hypertensive therapy on the arterial wall. Finally, the detection of early atherosclerosis may help to improve the clinical management of hypertensive patients.

Arteries↗
PubMed1998

Decreased regional blood flow in patients with acromegaly.

BACKGROUND AND AIMS: One-third of acromegalic patients have hypertension. Acromegaly is also associated with intrinsic cardiac abnormalities known collectively as a hyperkinetic heart syndrome, which is characterized by an increased cardiac index and decreased systemic vascular resistance. As a result, blood flow should be increased in the regional vascular beds of acromegalic patients. The aim of the study was to measure, using direct methods, blood flow and vascular resistance at the level of the brachial artery in acromegalic patients with a confirmed hyperkinetic heart syndrome. PATIENTS AND CONTROLS: Twelve patients with active acromegaly (five females, seven males; mean (+/- SD) age, 43 +/- 10 years) were studied. Twelve age- and sex-matched normal subjects served as controls. METHODS: Right heart catheterization was used to measure the cardiac index and stroke volume and to calculate systemic vascular resistance in the acromegalic patients. Brachial haemodynamics were evaluated with a two-dimensional pulsed Doppler system (double transducer probe and range-gated time system of reception). The mean diameter of the brachial artery and mean blood velocity were measured and used to calculate mean blood flow. Vascular resistance was calculated in the brachial artery as the mean arterial pressure/blood flow ratio. RESULTS: Age, body weight, height, body surface area and heart rate were similar in the acromegalic patients and controls, while mean arterial pressure was higher in patients. The cardiac index and stroke volume were increased in the acromegalic patients, at 4.08 +/- 0.47 (mean +/- SD) l/min/m2 body surface area and 116.7 +/- 19.4 ml, respectively, while systemic vascular resistance was low (12.5 +/- 2.1 U). Brachial artery diameter was similar in the patients and controls. Brachial artery mean blood velocity (P < 0.01) and mean blood flow (P < 0.05) were lower in the patients than in the controls (3.35 +/- 1.26 vs. 5.12 +/- 1.74 cm/s, and 16.4 +/- 9.4 vs. 25.6 +/- 11.6 ml/min/m2, respectively). The higher mean arterial pressure and lower mean blood flow resulted in higher forearm vascular resistance in the patients than in the controls (132 +/- 61 vs. 83.8 +/- 47 mmHg/ml/s/m2, respectively, P < 0.01). CONCLUSION: While cardiac output is increased and systemic vascular resistance is decreased in active acromegaly, direct measurement of brachial artery haemodynamics showed lower regional blood flow and increased local resistance relative to healthy controls. These results suggest a heterogeneous distribution of cardiac output in acromegaly.

Acromegaly↗
PubMed1998

Preclinical changes of extracoronary arterial structures as indicators of coronary atherosclerosis in men.

BACKGROUND: Carotid artery structure change was associated with coronary artery stenosis by angiography of subjects who were for the most part symptomatic. OBJECTIVE: To determine whether structural changes at multiple extracoronary sites were associated with noninvasively detected coronary calcium for 94 asymptomatic high-risk men. METHODS AND RESULTS: B-mode ultrasonography allowed us to detect plaque at three sites (carotid, femoral, and abdominal aorta) and to measure intima-medial thickness both in common carotid and in femoral arteries. Ultrafast computed tomography determined the presence and amount of coronary calcification. After adjustment for age, plaques at two or three sites were associated with extensive amounts of coronary calcium [odds ratio 4.94 (95% confidence interval 1.08-23)], but not with the presence of coronary calcium; increase in carotid intima-medial thickness was not associated with presence and extent of coronary calcium; and increase in femoral intima-medial thickness was associated with presence of coronary calcium [odds ratio 1.44 (95% confidence interval 1.03-2)] and extensive coronary calcium [odds ratio 1.50 (95% confidence interval 0.97-2.33)]. Adjustment for cardiovascular risk factors attenuated these associations. CONCLUSIONS: Femoral intima-medial thickness predicted presence of coronary calcium whereas femoral intima-medial thickness and overall multiple plaques predicted extensive coronary calcium. Because coronary calcium is a marker of atherosclerosis and a predictor of coronary events, B-mode ultrasonography could be of clinical value for stratifying coronary risk.

Adult↗
PubMed1998

Sex and topographic differences in associations between large-artery wall thickness and coronary risk profile in a French working cohort: the AXA Study.

Previous reports have investigated associations between carotid intima-media thickness (IMT) and cardiovascular risk factors. Our objective was to investigate this question in greater depth by measuring both femoral and carotid IMT in relation to sex and multifactorial coronary risk. We investigated carotid and femoral artery IMT by using ultrasonography in 326 men and 462 women, 17 to 65 years old. We also evaluated body mass index, blood pressure, blood lipids, glucose, smoking, and Framingham coronary risk. In both vessels, IMT was lower in women than in men. Significant relations between carotid and femoral IMT existed with age and most risk factors in both sexes. After adjustment for age, carotid IMT was related to risk factors in both sexes except for diastolic blood pressure, HDL cholesterol, and smoking in women, whereas femoral IMT was related to triglycerides and smoking in both sexes, systolic blood pressure and blood glucose in men, and total and HDL cholesterol in women. Significant unadjusted and age-adjusted relations of Framingham risk existed with carotid and femoral IMT in both sexes, but slopes of these relations were greater (1) before than after age adjustment, (2) in men than in women at both sites, except the femoral artery after age adjustment, and (3) at the carotid than at the femoral site in both sexes before age adjustment. Carotid IMT in men appears to be a more powerful predictor than it is in women and femoral IMT in both sexes in reflecting multifactorial coronary risk burden, but these differences are partly conditional on age.

Adolescent↗
PubMed1998

Carotid wall viscosity increase is related to intima-media thickening in hypertensive patients.

Increases in arterial wall viscosity and intima-media thickness (IMT) were found in hypertensive patients. Because smooth muscle cells are responsible for the viscous behavior of the arterial wall and they are involved in the process of thickening of the intima-media complex, this study evaluates the relationship between carotid thickness and wall viscosity. The simultaneous and noninvasive assessment of the intima-media complex and arterial diameter waveform was performed using high-resolution ultrasonography. This technique was contrasted against sonomicrometry in sheep, showing that the waveforms obtained by both methods were similar. The common carotid arteries of 11 normotensive subjects (NTA) and 11 patients with mild to moderate essential hypertension (HTA) were measured noninvasively by using tonometry and an automatic densitometric analysis of B-mode images to obtain IMT and instantaneous pressure and diameter loops. A viscoelastic model was used to derive the wall viscosity index (eta) using the hysteresis loop elimination criteria. In NTA, eta was 2.73+/-1.66 (mm Hg x s/mm) and IMT was 0.58+/-0.08 (mm), whereas in HTA, eta was 5.91+/-2.34 (P<.025) and IMT was 0.70+/-0.12 (P<.025), respectively. When all data of eta versus IMT of NTA and HTA were pooled in a linear regression analysis, a correlation coefficient of r=.71 (P<.05) was obtained. Partial correlation between eta and IMT holding constant pressure was r=.59 (P<.05). In conclusion, wall viscosity increase was associated with a higher IMT even maintaining blood pressure fixed, suggesting that the intima-media thickening might be related to smooth muscle alterations manifested as an increase in viscous behavior.

Algorithms↗
PubMed1998

Erythrocyte disaggregation shear stress, sialic acid, and cell aging in humans.

Erythrocyte aggregation, which plays an important role in the physiological behavior of blood fluidity, was found to be enhanced in hypertension and hypercholesterolemia. While the role of macromolecule bridging force has been widely described, cellular factors related to membrane sialic acid content, which might contribute to the negative charge of cell surface causing the repulsion of erythrocytes, have been less studied. Cell age-dependent changes in membrane sialic acid content (in micromoles per gram of integral membrane protein) were investigated in 24 normotensive and 24 hypertensive matched subjects, each divided into 2 identical subgroups according to a cutoff of 6.2 mmol/L serum cholesterol. A progressive and significant (P<0.001) decrease in membrane sialic acid content associated with an increase (P<0.001) of disaggregation shear rate threshold (laser reflectometry in the presence of dextran) were observed with increased erythrocyte density (erythrocytes fractionated by density using ultracentrifugation) in both normotensive and hypertensive groups regardless of the cholesterol level. However, disaggregation shear rate threshold was significantly higher and sialic acid content was lower (P<0.001) in both hypertensive and normotensive subjects with hypercholesterolemia compared with either normotensive or hypertensive subjects with low cholesterol, respectively. A high membrane sialic acid content variance, beginning in the younger erythrocytes, was due mainly to triglyceride and LDL cholesterol levels (R2=0.49 for low, R2=0.43 for middle, and R2=0.54 for high densities, ie, young, mean, and senescent erythrocytes, respectively). We conclude that an early decrease in erythrocyte sialic acid content may influence the rheological properties of blood by increasing the adhesive energy of erythrocyte aggregates.

Adult↗
PubMed1997

Coronary risk estimation and treatment of hypercholesterolemia.

BACKGROUND: Evidence-based treatment of hypercholesterolemia currently recommended for rationalizing drug prescription requires justification of treatment by randomized trials, such as the West of Scotland Coronary Prevention Study (WOSCOPS) or the Scandinavian Simvastatin Survival Study (4S), and evaluation of its benefit from the estimation of the coronary risk of each patient. METHODS AND RESULTS: The latest European guidelines and Sheffield tables apply these principles and justify the decision to treat hypercholesterolemia if the Framingham coronary multivariate risk estimate is high enough, ie, >20% risk of coronary event at 10 years in the former and >1.5% risk of coronary death per year in the latter. Nevertheless, the practice of these two recent guidelines results in discrepancies in the decision to treat, because coronary morbidity was considered in one but mortality was considered in the other, and the risk required for treating may be extrapolated from different trials (4S or WOSCOPS). CONCLUSIONS: Although the principle of targeting lipid-lowering treatment to high-risk subjects is unquestioned, further studies are needed to demonstrate that the Framingham risk profile is useful in selecting persons who are likely to benefit and to determine the place of newer risk factors and that of early noninvasive detection of atheroma in the risk estimation-based treatment.

Coronary Artery Disease↗
PubMed1997

Detection of preclinical atherosclerosis may optimize the management of hypertension.

Because of the limited ability of blood pressure elevation to predict risk, the mass drug treatment of hypertension above an arbitrary threshold may result in many subjects being overtreated. One potential way to overcome this problem is to noninvasively detect preclinical atherosclerosis. Hypertension has been shown to be associated with 1) increased intima-media thickness and more frequent plaques in extracoronary arteries, 2) more frequent calcifications in coronary arteries, 3) increased wall rigidity in the aorta and peripheral arteries, and 4) impaired endothelium dependent vasodilation and abnormal blood rheology, which are capable of promoting the conversion of atherosclerosis into atherothrombosis. The prognostic significance of these markers of preclinical atherosclerosis is supported by evidence of their association with numerous risk factors, and prevalence and incidence of cardiovascular damages. Preclinical arterial lesions also constitute ideal targets to test whether antihypertensive treatment can reverse or slow down arterial disease, and whether such a reversal produces better prevention than simply lowering blood pressure. Finally, the detection of atherosclerosis applied to large populations of mildly hypertensive subjects safely and at relatively low cost could help to better target the pharmacological treatment, given that a substantial proportion of subjects without evidence of preclinical disease may be suitable for nondrug treatment.

Arteriosclerosis↗
PubMed1997

Comparison of cardiovascular risk profile between male employees of two automotives companies in France and Sweden. The Coeur Project Group.

To determine whether or not the lower rate of coronary disease in France, in comparison with Sweden, might be explained by different cardiovascular risk profiles, a cross-sectional analysis (first step of a longitudinal study) of comparable samples of automotive workers was carried out in corporate occupational health clinics of Renault and Volvo. Traditional cardiovascular risk factors were evaluated and the Framingham coronary risk was estimated for 1000 randomly selected 45-50 years old Caucasian males from each company. Compared with the Frenchmen, the Swedish men consisted of more white collar workers and were slightly older. After adjustment for age and blue/white collar status, the Swedish men showed lower body mass indexes, waist to hip rations and heart rates, lower frequency of treatment of hypercholesterolemia and diabetes than the Frenchmen. The Swedish males also exhibited higher averages of blood cholesterol, low density lipoprotein (LDL) cholesterol and glucose, but lower frequencies of hypercholestrolemia and diabetes, and a higher frequency of family histories of cardiovascular disease. Blood pressure, hypertension prevalence, triglycerides level, and high density lipoprotein (HDL) did not differ between the groups. The average number of traditional risk factors was 1.1/person for the Frenchmen and 0.8/person for the Swedes. However, the coronary risk as estimated using the Framingham index was not different between the groups. This, together with the more frequent family history of cardiovascular disease in Swedish men, suggests a lower susceptibility to risk factors as a possible explanation for the lower cardiovascular disease prevalence reported in France, and/or the possibility that factors not measured were involved.

Age Factors↗
PubMed1997

In vivo angiotensin II receptor blockade and converting enzyme inhibition on canine aortic viscoelasticity.

The influence of the renin-angiotensin system (RAS) on the aortic wall mechanical properties under angiotensin I converting enzyme inhibition (enalaprilat, 0.3 mg/kg iv) or angiotensin II receptor (AT1) blockade (E-3174, 1 mg/kg iv) was examined in eight normotensive and eight renovascular hypertensive conscious dogs. Aortic diameter (D; sonomicrometry)-pressure (P; microtransducer) hysteresis loops during steady state and during rapid distal aortic occlusion allowed (after hysteresis elimination) calculation of the aortic wall viscosity index, the purely elastic P-D relationship, and derivation into compliance-pressure curves. At the early stage ofrenovascular hypertension when activation of RAS is more pronounced, aortic wall stiffness and wall viscosity were increased as compared with normotensive states. Blood pressure remained unchanged in normotensive animals and was reduced during hypertension after antihypertensive treatments. In hypertensive animals, enalaprilat and E-3174 decreased viscosity index and shifted the compliance-pressure curve upward with respect to pretreatment conditions. In normotensive dogs, whereas E-3174 did not change the compliance-pressure curve and viscosity index, enalaprilat increased compliance and reduced viscosity index. We concluded that in normotensive dogs converting enzyme inhibition modifies arterial viscoelastic parameters by angiotensin-independent mechanisms that contribute to the modulation of the buffering function of large arteries.

Angiotensin I↗