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Biomedical subjects

John R Crouse

Publications and source records attributed to John R Crouse.

17 recordsLinked to original sources
PubMed2006

Thematic review series: patient-oriented research. Imaging atherosclerosis: state of the art.

The ability to image obstructive arterial disease brought about a revolution in clinical cardiovascular care; the development of newer technologies that image arterial wall thicknesses, areas, volumes, and composition allows valid imaging of atherosclerosis for the first time. Development of noninvasive imaging of atherosclerosis has further led to a quantum shift in research in the field by enabling the study of asymptomatic populations and thus allowing investigators to focus on preclinical disease without the many biases associated with the study of symptomatic patients. These noninvasive investigations have broad implications for clinical care as well. Coronary angiography, computed tomographic (CT) imaging of coronary calcium, intravascular ultrasound, multidetector CT angiography, B mode ultrasound of the carotid arteries, and MRI of the carotid arteries all have unique strengths and weaknesses for imaging atherosclerosis. Certain of these techniques are extremely useful as outcome variables for clinical trials, and others are uniquely useful as predictors of the risk of cardiovascular disease. All are informative in one way or another with regard to the role of plaque remodeling and composition in disease causation. CT and MRI technology are advancing very rapidly, and research and clinical uses of these imaging modalities promise to further advance our understanding of atherosclerosis and its prevention.

Atherosclerosis↗
PubMed2005

Left ventricular concentric remodeling is associated with decreased global and regional systolic function: the Multi-Ethnic Study of Atherosclerosis.

BACKGROUND: The transition from compensatory concentric remodeling to myocardial failure is not completely understood in humans. To investigate determinants of incipient myocardial dysfunction, we examined the association between concentric remodeling and regional LV function in asymptomatic participants of the Multi-Ethnic Study of Atherosclerosis (MESA). METHODS AND RESULTS: Myocardial tagged MRI was performed. Regional myocardial function expressed as peak systolic midwall circumferential strain (Ecc) was analyzed in 441 consecutive studies by HARP (Harmonic Phase) tool. Peak Ecc was correlated with the extent of concentric remodeling determined by the ratio of left ventricular mass to end-diastolic volume (M/V ratio). In men, a gradual decline in peak global Ecc was seen with increasing M/V ratio (test for trend, P<0.001). Among women, however, Ecc tended to be lower only in the fifth compared with the first quintile of M/V ratio (P=0.1). The association of lower Ecc with increasing M/V ratio was regionally heterogeneous but was particularly prominent in the LAD region in men (test for trend, P<0.001) and in women (test for trend, P=0.02). In the right coronary and left circumflex artery territories, these associations were less marked in both genders. CONCLUSIONS: In this cross-sectional study of asymptomatic individuals, concentric left ventricular remodeling was related to decreased regional systolic function. The reduction in regional function, which was more pronounced in the left anterior descending coronary artery territory, may reflect the local transition from compensatory remodeling to myocardial dysfunction.

Atherosclerosis↗
PubMed2005

Coronary artery calcium outperforms carotid artery intima-media thickness as a noninvasive index of prevalent coronary artery stenosis.

OBJECTIVE: Increased carotid artery intima-media thickness (IMT) and increased coronary artery calcium (CAC) are noninvasive surrogate indices of prevalent coronary artery disease (CAD). We compared CAC to IMT for noninvasive detection of prevalent CAD in participants whose coronary status was identified by coronary angiography. METHODS AND RESULTS: Male and female CAD patients (> or =50% stenosis in one or more coronary artery, n=79) and controls (no lumen irregularities, n=93) were identified using coronary angiography. Mean maximum carotid IMT was quantified using B-mode ultrasound and total CAC was measured using ECG-gated helical computed tomography (HCT). Carotid IMT was approximately 20% higher in CAD cases compared with controls (P<0.001), whereas mean CAC was 1000% higher in CAD cases than controls (P<0.0001). In multivariable models adjusted for age and sex, IMT greater than the median (1.13 mm) was associated with 2-fold increase in likelihood of prevalent CAD compared with scores below that cut point (P=0.015). CAC scores that exceeded the median score of 92 were associated with 28-fold increase in likelihood of prevalent CAD (P<0.0001). Although associations of increased IMT with prevalent CAD were similar in males and females, CAC scores above the median in females were associated with 39-fold increase in odds of prevalent CAD, whereas males with elevated CAC had 19-fold risk of CAD. CONCLUSIONS: HCT-measured CAC compares favorably with carotid IMT measured by B-mode ultrasound as a noninvasive index of prevalent CAD.

Age Distribution↗
PubMed2005

Azithromycin for the secondary prevention of coronary events.

BACKGROUND: Epidemiologic, laboratory, animal, and clinical studies suggest that there is an association between Chlamydia pneumoniae infection and atherogenesis. We evaluated the efficacy of one year of azithromycin treatment for the secondary prevention of coronary events. METHODS: In this randomized, prospective trial, we assigned 4012 patients with documented stable coronary artery disease to receive either 600 mg of azithromycin or placebo weekly for one year. The participants were followed for a mean of 3.9 years at 28 clinical centers throughout the United States. RESULTS: The primary end point, a composite of death due to coronary heart disease, nonfatal myocardial infarction, coronary revascularization, or hospitalization for unstable angina, occurred in 446 of the participants who had been randomly assigned to receive azithromycin and 449 of those who had been randomly assigned to receive placebo. There was no significant risk reduction in the azithromycin group as compared with the placebo group with regard to the primary end point (risk reduction, 1 percent [95 percent confidence interval, -13 to 13 percent]). There were also no significant risk reductions with regard to any of the components of the primary end point, death from any cause, or stroke. The results did not differ when the participants were stratified according to sex, age, smoking status, presence or absence of diabetes mellitus, or C. pneumoniae serologic status at baseline. CONCLUSIONS: A one-year course of weekly azithromycin did not alter the risk of cardiac events among patients with stable coronary artery disease.

Aged↗
PubMed2005

Skin tissue cholesterol assay correlates with presence of coronary calcium.

BACKGROUND: Keratinocytes maintain cholesterol homoeostasis using LDL and HDL-scavenger receptor pathways implicated in atherosclerosis. We tested whether skin tissue cholesterol (SkTC) is associated with subclinical atherosclerosis, assessed using carotid intima-medial thickness (IMT) and coronary artery calcification (CAC). METHODS: Two hundred and twenty two subjects were recruited from the Baltimore site of the Multi-Ethnic Study of Atherosclerosis (MESA). Baseline MESA examination included fasting blood collection, IMT measurement by B-mode ultrasound and CAC determination by helical CT. SkTC was measured using the Cholesterol 1, 2, 3 kit (IMI Inc., Canada). RESULTS: SkTC was significantly higher if CAC was present in Caucasians (p = 0.04) but not African-Americans. SkTC was not significantly correlated with IMT in either group. Using multiple logistic regression adjusting for age, sex and serum lipids, a 1-standard deviation higher SkTC was associated with 187% higher odds of the presence of CAC in Caucasians (p < 0.01) but no significant difference in odds for African-Americans. In subjects in whom CAC was present, the extent of CAC was not related to the SkTC in multiple linear regressions. CONCLUSIONS: SkTC was associated with the presence of CAC independently of serum lipids/lipoproteins in Caucasians but not African-Americans. SkTC may provide a useful indicator of subclinical atherosclerosis in Caucasians.

Black or African American↗
PubMed2004

Racial differences in endothelial function in postmenopausal women.

OBJECTIVE: Racial differences in cardiovascular mortality among women remain largely unexplained. Preliminary data suggest that African American and Caucasian differences in endothelial function may parallel differential cardiovascular disease (CVD) risk in women. To further study differences in endothelial function between African American and Caucasian women, we analyzed measures of brachial artery flow-mediated dilation (FMD) in women enrolled in the Cardiovascular Health Study (CHS). METHODS AND RESULTS: Brachial artery FMD was measured in the fasting state using established ultrasound techniques in 1330 Caucasian and 297 African American female participants in CHS (mean age 78.4 +/- 4.4 years). General linear models were used to compare FMD between African American and Caucasian women after adjusting for baseline brachial diameter, hypertension, diabetes, smoking, cholesterol, systolic blood pressure, body mass index, waist/hip ratio, age, education, income level; use of angiotensin-converting enzyme inhibitors, beta-blockers, nitroglycerin, estrogens and lipid-lowering drugs; and presence of clinical or subclinical disease. Adjusted absolute change and percent change in brachial artery diameter was significantly reduced in African American women compared with Caucasian women (P <.0001 and P =.0002, respectively). Similar results were found when the women were stratified by history of CVD (- CVD, P =.02; + CVD, P =.001) and CVD or subclinical vascular disease (- disease, P =.01, + disease, P =.03). CONCLUSIONS: In this cohort, brachial artery FMD was lower in African American women compared to Caucasian women, and this difference persisted after adjustment by multivariable analysis. The increased CVD risk in African American women may be related to impaired endothelial function. It remains to be determined whether African American women may uniquely benefit by interventions designed to improve endothelial health.

Aged↗
PubMed2003

Estrogen plus progestin and the risk of coronary heart disease.

BACKGROUND: Recent randomized clinical trials have suggested that estrogen plus progestin does not confer cardiac protection and may increase the risk of coronary heart disease (CHD). In this report, we provide the final results with regard to estrogen plus progestin and CHD from the Women's Health Initiative (WHI). METHODS: The WHI included a randomized primary-prevention trial of estrogen plus progestin in 16,608 postmenopausal women who were 50 to 79 years of age at base line. Participants were randomly assigned to receive conjugated equine estrogens (0.625 mg per day) plus medroxyprogesterone acetate (2.5 mg per day) or placebo. The primary efficacy outcome of the trial was CHD (nonfatal myocardial infarction or death due to CHD). RESULTS: After a mean follow-up of 5.2 years (planned duration, 8.5 years), the data and safety monitoring board recommended terminating the estrogen-plus-progestin trial because the overall risks exceeded the benefits. Combined hormone therapy was associated with a hazard ratio for CHD of 1.24 (nominal 95 percent confidence interval, 1.00 to 1.54; 95 percent confidence interval after adjustment for sequential monitoring, 0.97 to 1.60). The elevation in risk was most apparent at one year (hazard ratio, 1.81 [95 percent confidence interval, 1.09 to 3.01]). Although higher base-line levels of low-density lipoprotein cholesterol were associated with an excess risk of CHD among women who received hormone therapy, higher base-line levels of C-reactive protein, other biomarkers, and other clinical characteristics did not significantly modify the treatment-related risk of CHD. CONCLUSIONS: Estrogen plus progestin does not confer cardiac protection and may increase the risk of CHD among generally healthy postmenopausal women, especially during the first year after the initiation of hormone use. This treatment should not be prescribed for the prevention of cardiovascular disease.

Aged↗
PubMed2003

Comparison of once-daily, niacin extended-release/lovastatin with standard doses of atorvastatin and simvastatin (the ADvicor Versus Other Cholesterol-Modulating Agents Trial Evaluation [ADVOCATE]).

This study compared the relative efficacy of a once-daily niacin extended-release (ER)/lovastatin fixed-dose combination with standard doses of atorvastatin or simvastatin, with a special emphasis on relative starting doses. Subjects (n = 315) with elevated low-density lipoprotein (LDL) cholesterol and decreased high-density lipoprotein (HDL) cholesterol blood levels (defined as LDL cholesterol blood levels > or =160 mg/dl without coronary artery disease, or > or =130 mg/dl if coronary artery disease was present, and HDL cholesterol <45 mg/dl in men and <50 mg/dl in women) were randomized to atorvastatin, simvastatin, or niacin ER/lovastatin for 16 weeks. The primary efficacy variables were the mean percent change in LDL cholesterol and HDL cholesterol levels from baseline. After 8 weeks, the starting dose niacin ER/lovastatin 1,000/40 mg and the 10-mg starting dose atorvastatin both lowered mean LDL cholesterol by 38%. After 12 weeks, niacin ER/lovastatin 1,000/40 mg lowered LDL cholesterol by 42% versus 34% with the 20-mg starting dose of simvastatin (p <0.001). Niacin ER/lovastatin increased HDL cholesterol significantly more than atorvastatin or simvastatin at all compared doses (p <0.001). Niacin ER/lovastatin also provided significant improvements in triglycerides, lipoprotein(a), apolipoprotein A-1, apolipoprotein B, and HDL subfractions. A total of 6% of study subjects receiving niacin ER/lovastatin withdrew because of flushing. No significant differences were seen among study groups in discontinuance due to elevated liver enzymes. No drug-induced myopathy was observed. Niacin ER/lovastatin was comparable to atorvastatin 10 mg and more effective than simvastatin 20 mg in reducing LDL cholesterol, was more effective in increasing HDL cholesterol than either atorvastatin or simvastatin, and provided greater global improvements in non-HDL cholesterol, triglycerides, and lipoprotein(a).

Adolescent↗
PubMed2003

Carotid arterial structure in patients with documented coronary artery disease and disease-free control subjects.

BACKGROUND: Although atherosclerosis often leads to lumen narrowing and symptomatic cardiovascular disease, it is now recognized that arteries have the potential to compensate by enlarging in response to atherosclerosis. We tested the hypotheses that carotid arterial interadventitial (IA) and lumen diameters were related to wall thickness and that carotid arterial diameters of individuals with coronary artery disease (CAD) differed from those of CAD-free controls. METHODS AND RESULTS: We measured lumen diameter, IA diameter, and intima-media thickness (IMT) using B-mode ultrasound in the common and internal carotid arteries of 141 CAD case patients and 139 disease-free control subjects. Common carotid IA diameter was greater in CAD cases than controls after adjustment for age, height, and sex (P<0.01). Common carotid lumen diameter was marginally larger in individuals with greater IMT (P=0.06) but was not associated with case status. Conversely, mean internal carotid IA and lumen diameters were smaller in CAD cases than controls in both univariable and multivariable models (both P<0.001), and lumina were smaller in individuals with greater IMT. Despite these cross-sectional differences in carotid artery dimensions, we were unable to detect any statistically significant interactive effects of CAD case status on the association of IMT with arterial dimensions. CONCLUSIONS: Internal carotid artery lumen and IA diameters are both smaller in CAD cases than controls. The association of increased IMT with arterial dimensions varies in a manner that is segment-specific for the common and internal carotid arteries.

Age Factors↗
PubMed2003

Effects of simvastatin, an HMG-CoA reductase inhibitor, in patients with hypertriglyceridemia.

BACKGROUND: Patients with elevated levels of serum triglycerides (TG) often have other associated lipid abnormalities (e.g., low levels of high-density lipoprotein cholesterol [HDL-C]) and are at increased risk of developing coronary heart disease. Although the therapeutic benefits of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) in hypercholesterolemic patients have been well established, less is known about the effects of statins in patient populations with hypertriglyceridemia. HYPOTHESIS: The purpose of this study was to evaluate the lipoprotein-altering efficacy of simvastatin in hypertriglyceridemic patients. METHODS: This was a multicenter, randomized, double-blind, placebo-controlled study. In all, 195 patients with fasting serum triglyceride levels between 300 and 900 mg/dl received once daily doses of placebo or simvastatin 20, 40, or 80 mg for 6 weeks. RESULTS: Compared with placebo, simvastatin treatment across all doses resulted in significant reductions (p < 0.05 - < 0.001) in serum levels of triglycerides (-20 to -31% decrease) and TG-rich lipoprotein particles. Significant (p < 0.001) reductions were also seen in low-density lipoprotein cholesterol (-25 to -35%) and non-HDL-C (-26 to -40%). Levels of HDL-C were increased (7-11%) in the simvastatin groups compared with placebo (p < 0.05 - < 0.001). CONCLUSION: The results of this study demonstrate the beneficial effects of simvastatin in patients with hypertriglyceridemia.

Adult↗
PubMed2002

Associations of extracranial carotid atherosclerosis progression with coronary status and risk factors in patients with and without coronary artery disease.

BACKGROUND: Intimal medial thickness of the extracranial carotid arteries (IMT) is related to coronary artery disease (CAD) and CAD risk factors. Few studies have explored the association of risk factors with progression of IMT, and none have evaluated their associations with IMT progression specifically in patients with and without CAD. METHODS AND RESULTS: We used coronary angiography to identify 280 patients equally divided between men and women and those with either > or =50% coronary artery stenosis or no CAD. Risk factors were measured at baseline and IMT was measured at baseline and yearly for 3 years in 241 of these individuals. Baseline risk factors and CAD status were related to IMT progression. IMT of patients with CAD progressed 3 times faster than that of patients with no CAD (mean+/-SEM, 33.7+/-7.4 versus 8.9+/-7.1 microm/year; P=0.02), and CAD status and high-density lipoprotein (HDL) cholesterol were independently associated with IMT progression. Male sex, increased waist to hip ratio, cigarette smoking, increased triglycerides, and decreased HDL cholesterol were associated with increased progression in CAD patients. CONCLUSIONS: Patients with CAD have more rapid progression of IMT than CAD-free controls, and risk factors are related to progression in them.

Carotid Artery Diseases↗