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Biomedical subjects

Shunichi Homma

Publications and source records attributed to Shunichi Homma.

At least 37 records · Page 2Linked to original sources
PubMed2005

Electrocardiographic left atrial abnormalities and risk of ischemic stroke.

BACKGROUND AND PURPOSE: We evaluated the association between electrocardiographic left atrial abnormality (ECG-LAA) and ischemic stroke, especially whether ECG-LAA provides additional prognostic information to that provided by echocardiography. METHODS: A population-based, case-control study included 146 patients with first ischemic stroke and 195 age-, gender-, and race/ethnicity-matched community control subjects. ECG-LAA was defined as either P-wave duration >120 ms or P-terminal force in precordial lead V1 (PTFV1) >40 ms.mm. RESULTS: PTFV1 >40 ms.mm was associated with ischemic stroke after adjustment for other stroke risk factors (odds ratio [OR], 2.32; 95% CI, 1.29 to 4.18). The association remained significant after adding echocardiographic left atrial diameter to the model (OR, 2.31; 95% CI, 1.28 to 4.17). PTFV1 was independently associated with stroke in patients in the upper half of echocardiographically determined left ventricular mass (adjusted OR, 4.5; 95% CI, 2.20 to 9.15) but not in those in the lower half (OR, 0.58; 95% CI, 0.20 to 1.65; P=0.0008). CONCLUSIONS: ECG-LAA can supplement 2D echocardiography in assessing the risk of ischemic stroke, especially in subjects with increased left ventricular mass.

Aged↗
PubMed2005

Relation of plasma glucose and endothelial function in a population-based multiethnic sample of subjects without diabetes mellitus.

To determine whether endothelial dysfunction precedes the clinical diagnosis of diabetes mellitus, we investigated the relation of endothelial flow-mediated dilation (FMD) with fasting plasma glucose among a multiethnic population-based cohort of 579 nondiabetic subjects without previous myocardial infarction or stroke enrolled in the Northern Manhattan Study (age 66 +/- 9 years; 41% men, 16% white, 15% black, and 68% Hispanic). Impaired fasting glucose or prediabetic status, defined as a fasting glucose level of 100 to 125 mg/dl, was present in 95 subjects (16%). Endothelial function was determined using FMD during reactive hyperemia. Multiple linear regression analyses were used to assess the relation between plasma glucose and endothelial function after adjustment for potential confounders. FMD was significantly lower (4.9 +/- 3.8% vs 6.1 +/- 3.7%, p = 0.003) in those with impaired fasting glucose than in subjects with normal fasting glucose. Prediabetic status was significantly associated with impaired FMD (odds ratio 1.9, 95% confidence interval 1.1 to 3.1, p = 0.02). After adjustment for age, gender, body mass index, and hypertensive status, a higher fasting glucose was significantly associated with a lower FMD (beta = -0.024 +/- 0.012, p = 0.04) in a continuous linear relation. Thus, for each 10-mg/dl increase in plasma glucose, a 0.24% decrease occurred in FMD. Impaired FMD was present among prediabetics. An elevated fasting plasma glucose level is associated with impaired endothelial function among nondiabetics. These results further support the role of hyperglycemia in the pathogenesis of vascular dysfunction at different stages of diabetes development and the role of impaired fasting glucose as a risk factor for macrovascular disease.

Black or African American↗
PubMed2005

Usefulness of arterial compliance in the thigh in predicting exercise capacity in individuals without coronary heart disease.

This study examined the relation between arterial compliance of the lower extremities and aerobic capacity in patients with a broad spectrum of cardiovascular risk but without overt coronary heart disease (CHD). Local arterial compliance was noninvasively measured in the thigh and calf in 104 men and 99 women using air plethysmography. Subjects also underwent maximal exercise treadmill testing as a measure of aerobic capacity. In univariate analysis, age (r = -0.49, p <0.001), systolic blood pressure at rest (r = -0.27, p <0.001), pulse pressure (r = -0.39, p <0.001), total cholesterol (r = -0.25, p <0.001), triglycerides (r = -0.025, p <0.001), non-high-density lipoprotein cholesterol (r = -0.23, p <0.001), high-sensitivity C-reactive protein (r = -0.21, p = 0.002), and low-density lipoprotein cholesterol (r = -0.15, p = 0.03) all demonstrated a significant inverse association with treadmill time. Thigh and calf compliance demonstrated a significant positive association with treadmill time (r = 0.48, p <0.001; r = 0.46, p <0.001). In multivariate analysis, thigh compliance (p = 0.003), age (p <0.001), gender (p = 0.005), and triglycerides (p = 0.017) were independent predictors of treadmill time. In conclusion, thigh compliance measured with a simple-to-use, fully automated device independently predicts aerobic fitness in patients with a wide range of cardiovascular risk but without CHD.

Arteries↗
PubMed2005

Ankle-brachial index and subclinical cardiac and carotid disease: the multi-ethnic study of atherosclerosis.

The authors studied associations between ankle-brachial index (ABI) and subclinical atherosclerosis in the Multi-Ethnic Study of Atherosclerosis. Participants included 3,458 women (average age = 62.6 years) and 3,112 men (average age = 62.8 years) who were free of clinically evident cardiovascular disease. Measurements included ABI, carotid artery intima-media thickness, and coronary artery calcium assessed with computed tomography. Five ABI categories were defined: <0.90 (definite peripheral arterial disease (PAD)), 0.90-0.99 (borderline ABI), 1.00-1.09 (low-normal ABI), 1.10-1.29 (normal ABI), and > or =1.30 (high ABI). Compared with that in men with normal ABI, significantly higher internal carotid artery intima-media thickness was observed in men with definite PAD (1.58 vs. 1.09; p < 0.001), borderline ABI (1.33 vs. 1.09; p < 0.001), and low-normal ABI (1.18 vs. 1.09; p < 0.001) after adjustment for confounders. Fully adjusted odds ratios for a coronary artery calcium score greater than 20 decreased across progressively higher ABI categories in both women (2.85 (definite PAD), 1.27 (borderline ABI), 1.11 (low-normal ABI), 1.00 (normal ABI; referent), and 0.78 (high ABI); p for trend = 0.0002) and men (3.26 (definite PAD), 1.72 (borderline ABI), 1.14 (low-normal ABI), 1.00 (normal ABI; referent), and 1.43 (high ABI); p for trend = 0.0002). These findings indicate excess coronary and carotid atherosclerosis at ABI values below 1.10 (men) and 1.00 (women) and may imply increased risk of cardiovascular events in persons with borderline and low-normal ABI.

Aged↗
PubMed2005

Comparison of the relation of triglyceride-rich lipoproteins and muscular artery compliance in healthy women versus healthy men.

To determine whether structural features or concentrations of plasma lipoproteins are predictive of arterial compliance in healthy women versus healthy men, cohorts of 111 men and 112 women with a wide range of 10-year risks for coronary artery disease were selected using assessments based on the Framingham Heart Study. Age ranges were restricted to 35 to 69 years for men and 45 to 79 years for women. Lipid-lowering drugs or any evidence of vascular disease was cause for exclusion. Fasting lipoprotein analysis and arterial compliance measurements in thigh and calf were completed in all patients. Plasma triglyceride levels were the most powerful predictor of compliance in women. Weaker but significant relations were observed between plasma non-high-density lipoprotein cholesterol, apolipoprotein-B, and apolipoprotein-CIII. In contrast, the only significant predictor of compliance in men was body weight. Thus, the major lipid predictors of arterial stiffness in women are concentrations of triglyceride-rich lipoproteins. These results are consistent with previous findings that triglyceride measurements are more strongly related to clinical vascular events in women than in men.

Adult↗
PubMed2005

Leukocyte count is associated with reduced endothelial reactivity.

BACKGROUND: Leukocyte count has been associated with cardiovascular and cerebrovascular disease in several studies. We hypothesized that white blood cell count is associated with endothelial reactivity. METHODS AND RESULTS: Leukocyte count was measured in a sample of stroke-free community participants undergoing brachial artery testing for endothelial reactivity. Flow-mediated dilation (FMD) during reactive hyperemia was assessed in each subject using high-resolution B-mode ultrasound. Multivariate linear regression was used to calculate the effect of leukocyte count on endothelial reactivity after adjusting for potential confounding factors. Mean age of the 868 participants was 66.7+/-8.8 years; 57% were women. Mean leukocyte count was (6.1+/-1.8)x10(9)/L. Each unit increase in leukocyte count was associated with a mean 0.18% decrease in FMD (p = 0.01). After adjusting for other atherosclerosis risk factors, including age, sex, hypertension, diabetes, hyperlipidemia, and smoking, the relationship persisted (mean decrease in FMD per unit leukocyte count = 0.17%, p = 0.02). There was a linear decrease in FMD by quartile of leukocyte count (p = 0.0014). The effect of leukocyte count on FMD was greater for women, those under age 70, and non-diabetics. CONCLUSIONS: Relative elevations in leukocyte count are associated with a reduction in brachial artery endothelial reactivity. These findings are consistent with current hypotheses regarding the inflammatory or infectious etiology of risk of atherosclerosis and stroke, but also suggest interactions with demographic and other risk factors.

Aged↗
PubMed2005

Peroxisome proliferator-activated receptor agonists modulate heart function in transgenic mice with lipotoxic cardiomyopathy.

hLpL(GPI) transgenic mice that overexpress human lipoprotein lipase (hLpL) with a glycosylphosphatidylinositol anchor on cardiomyocytes develop lipotoxic cardiomyopathy associated with increased cardiac uptake of plasma lipids. We hypothesized that peroxisome proliferator-activated receptor (PPAR)alpha, PPARgamma, or a PPARalpha/gamma agonist would alter cardiac function by modulating lipid uptake by the heart. hLpL(GPI) mice were administered rosiglitazone (10 mg/kg/day), fenofibrate (100 mg/kg/day), or DRF2655, an alkoxy propanoic acid analog (10 mg/kg/day), for 16 days. Rosiglitazone reduced plasma triglyceride (TG) from 107.63 +/- 6.98 to 77.61 +/- 3.98 mg/dl, whereas fenofibrate had no effect. DRF2655 reduced TG to 33.17 +/- 4.12 mg/dl. Rosiglitazone and DRF2655 decreased heart TG and total cholesterol; fenofibrate had no effect. Molecular markers for cardiac dysfunction, atrial natriuretic factor, brain natriuretic peptide, and tumor necrosis factor-alpha were decreased with rosiglitazone and increased with fenofibrate. Echocardiographic measurements showed reduced fractional shortening and increased left ventricular systolic dimension with fenofibrate. No changes in these parameters were observed with rosiglitazone or DRF2655 treatment. Muscle-specific carnitine palmitoyltransferase-1 and fatty acid transporter protein-1 gene expression were increased with fenofibrate and DRF2655 treatment; no change in expression of these genes was noted with rosiglitazone treatment. Rosiglitazone and DRF2655 reduced TG uptake by the heart, and fenofibrate treatment increased fatty acid uptake. Thus, in a lipotoxic cardiomyopathy mouse model, a PPARgamma agonist reduced cardiac lipid and markers of cardiomyopathy, whereas an agonist of PPARalpha did not improve cardiac lipids and worsened heart function. These changes were paralleled by alterations in heart lipid uptake. Overall, PPAR activators exhibit differential effects in this model of lipotoxic dilated cardiomyopathy.

Animals↗
PubMed2005

Parameterization of left ventricular wall motion for detection of regional ischemia.

While qualitative wall motion analysis has proven valuable in clinical cardiology practice, quantitative analyses remain too time-consuming for routine clinical use. Our long-term goal is therefore to develop automated methods for quantitative wall motion analysis. In this paper, we utilize a finite element model of the regionally ischemic canine left ventricle to demonstrate a new approach based on parameterization of the left ventricular endocardial surface in prolate spheroidal coordinates. The parameterization provided a substantial data reduction and enabled simple definition, calculation, and display of three-dimensional fractional shortening (3DFS), a quantitative measure of wall motion analogous to the fractional shortening measure used in 2D analysis. The endocardial surface area displaying akinesis or dyskinesis by 3DFS corresponded closely to simulated ischemic region size and 3DFS identified appropriate wall motion abnormalities during experimental coronary occlusion in a canine pilot study. 3DFS therefore appears to be a reasonable candidate for clinical tests to determine its utility in identifying and quantifying acute regional ischemia in patients. By linking state of the art finite element models to the clinically relevant framework of wall motion analysis, the methods presented here will facilitate formulation, in silico prescreening, and clinical testing of additional candidate measures of wall motion.

Animals↗
PubMed2005

Stroke as a complication of congenital heart disease.

Patent foramen ovale is a common finding in the general population. It is associated with an increased risk of stroke, but it may not have a significant effect on recurrent stroke risk in medically treated patients. Recently, many questions have arisen with respect to best treatment for preventing recurrent stroke. Some data from a clinical trial of anticoagulation compared with antiplatelet therapy support antiplatelet treatment for secondary prevention. There are not enough data currently to support surgical or percutaneous closure of patent foramen ovale for stroke prevention.

Anticoagulants↗
PubMed2005

Additional impact of electrocardiographic over echocardiographic diagnosis of left ventricular hypertrophy for predicting the risk of ischemic stroke.

BACKGROUND: Patients with left ventricular hypertrophy (LVH) have an increased risk of ischemic stroke. Although echocardiography is commonly used for the diagnosis of LVH, there is little information about the potential role of electrocardiography in providing additional prognostic information. The purpose of this study is to determine if electrocardiographically derived criteria for LVH provide additional prognostic value over echocardiography for predicting ischemic stroke in a multiethnic population. METHODS: A population-based, case-control study was conducted in 177 patients who had had a first ischemic stroke and in 246 control patients matched for age, gender, and race or ethnicity. Left ventricular mass was measured by using 2-dimensional transthoracic echocardiography. Logistic regression analysis was performed to assess the risk of stroke associated with the presence of LVH diagnosed by electrocardiography (defined by 4 established criteria) after adjustment for the presence of other stroke risk factors and for echocardiographically determined LVH. RESULTS: After adjustment for the presence of other established stroke risk factors, ECG-LVH was associated with ischemic stroke, using Sokolow-Lyon (odds ratio [OR] 2.12, 95% CI 1.05-4.30), Cornell voltage (OR 2.06, 95% CI, 1.26-3.35), and Cornell product criteria (OR 2.12, 95% CI, 1.13-3.97). Cornell voltage criterion (men, >2.8 mV; women, >2.0 mV) was associated with ischemic stroke even after adjustment for echocardiographically determined LVH (OR 1.73, 95% CI, 1.04-2.88). The combination of echo-LVH and a positive Cornell voltage criterion was associated with a 3.5-fold increase in stroke risk. CONCLUSIONS: Our study indicates that the presence of ECG-LVH is associated with an increased risk of ischemic stroke after adjustment for other stroke risk factors. For Cornell voltage criteria, this relationship persisted even after adjustment for echocardiographic LVH. Electrocardiographic results can provide independent information for left ventricular myocardial changes and should be considered together with echocardiographic results to fully assess the risk of ischemic stroke.

Aged↗
PubMed2005

In vitro ablation of cardiac valves using high-intensity focused ultrasound.

The purpose of this study was to evaluate the possibility of using high-intensity focused ultrasound (US), or HIFU, to create lesions in cardiac valves in vitro. Calf mitral valves and aortic valves were examined. Focused US energy was applied with an operating frequency of 4.67 MHz at a nominal acoustic power of 58 W for 0.2, 0.3 and 0.4 s at 4-s intervals. Mitral valve perforation was achieved with 20.8 +/- 3.7 exposures of 0.2 s, 15.4 +/- 2.1 exposures of 0.3 s or 11.2 +/- 2.3 exposures of 0.4 s. Aortic valve perforation was achieved with 13.3 +/- 2.4 exposures of 0.2 s, 10.3 +/- 2.2 exposures of 0.3 s or 8.4 +/- 1.8 exposures of 0.4 s. The mean diameter of the perforated area was 1.09 +/- 0.11 mm. The lesions were slightly discolored and coagulation of tissue around the perforation was observed. HIFU was successful in perforating cardiac valves. With further refinement, HIFU may prove useful for valvulotomy or valvuloplasty.

Animals↗
PubMed2005

Segmentation of real-time three-dimensional ultrasound for quantification of ventricular function: a clinical study on right and left ventricles.

Among screening modalities, echocardiography is the fastest, least expensive and least invasive method for imaging the heart. A new generation of three-dimensional (3-D) ultrasound (US) technology has been developed with real-time 3-D (RT3-D) matrix phased-array transducers. These transducers allow interactive 3-D visualization of cardiac anatomy and fast ventricular volume estimation without tomographic interpolation as required with earlier 3-D US acquisition systems. However, real-time acquisition speed is performed at the cost of decreasing spatial resolution, leading to echocardiographic data with poor definition of anatomical structures and high levels of speckle noise. The poor quality of the US signal has limited the acceptance of RT3-D US technology in clinical practice, despite the wealth of information acquired by this system, far greater than with any other existing echocardiography screening modality. We present, in this work, a clinical study for segmentation of right and left ventricular volumes using RT3-D US. A preprocessing of the volumetric data sets was performed using spatiotemporal brushlet denoising, as presented in previous articles Two deformable-model segmentation methods were implemented in 2-D using a parametric formulation and in 3-D using an implicit formulation with a level set implementation for extraction of endocardial surfaces on denoised RT3-D US data. A complete and rigorous validation of the segmentation methods was carried out for quantification of left and right ventricular volumes and ejection fraction, including comparison of measurements with cardiac magnetic resonance imaging as the reference. Results for volume and ejection fraction measurements report good performance of quantification of cardiac function on RT3-D data compared with magnetic resonance imaging with better performance of semiautomatic segmentation methods than with manual tracing on the US data.

Adolescent↗
PubMed2004

Comparison of suppression of the circulating and vascular renin-angiotensin system by enalapril versus trandolapril in chronic heart failure.

Experimental studies suggest that angiotensin-converting enzyme (ACE) inhibitors with high tissue affinity confer a greater degree of vascular renin-angiotensin system suppression than those with low tissue affinity despite similar suppression of the circulating renin-angiotensin system. To test this hypothesis in a clinical setting, we randomized subjects with chronic heart failure to receive the low tissue affinity ACE inhibitor enalapril or the high tissue affinity ACE inhibitor trandolapril, and assessed the degree of circulating and vascular renin-angiotensin system suppression. Vascular renin-angiotensin system suppression was determined by measuring the pressor response to intravenous injections of angiotensin I. Circulating renin-angiotensin system suppression was determined by measuring plasma angiotensin II. Vascular and circulating renin-angiotensin system suppression, endothelial function (flow-mediated vasodilation), and maximal exercise capacity (peak oxygen uptake) were assessed after a 4-week run-in period on open-label enalapril 40 mg/day and after 8 weeks of randomized double-blind treatment with enalapril 40 mg/day or trandolapril 4 mg/day. Twenty-six men and 4 women (mean age 52 +/- 11 years; mean left ventricular ejection fraction 25 +/- 9%; New York Heart Association class II [n = 16] and III [n = 14]) were studied. After a 2-month randomized treatment period, vascular renin-angiotensin system suppression, circulating renin-angiotensin system suppression, endothelial function, and exercise capacity did not differ between subjects treated with enalapril and those treated with trandolapril. Despite substantial differences in the tissue affinity of enalapril and trandolapril, the degree of vascular renin-angiotensin system suppression achieved with these agents did not differ in subjects with chronic heart failure during long-term therapy.

Angiotensin II↗
PubMed2004

Age as a determinant of adverse events in medically treated cryptogenic stroke patients with patent foramen ovale.

BACKGROUND AND PURPOSE: Patent foramen ovale (PFO) is associated with cryptogenic stroke. There is no study that assessed the effect of age on adverse event rates in cryptogenic stroke patients with PFO. The purpose of this retrospective analysis from PFO in Cryptogenic Stroke Study (PICSS) database was to assess the effect of age on the risk of adverse events in medically treated cryptogenic stroke patients with PFO. METHODS: 250 cryptogenic stroke patients from PICSS were followed-up for 24 months, with death and recurrent ischemic stroke as primary endpoints. Hazard ratios were calculated for determination of relative risk in cryptogenic stroke patients with and without PFO in 3 age groups (younger than 55, 55 to 64, and 65 years or older). RESULTS: Among the 2 younger age groups, the presence of PFO did not significantly affect the risk of adverse events (P=0.15; hazard ratio=0.21; 95% CI, 0.02 to 1.78; 2-year event rates, 2.0% versus 9.3%; and P=0.70; hazard ratio=0.72; 95% CI, 0.14 to 3.73; 2-year event rates, 10.0% versus 13.9%). However, in those aged 65 years or older, the risk of adverse events was significantly higher in the patients with PFO (P=0.01; hazard ratio=3.21; 95% CI, 1.33 to 7.75; 2-year event rates 37.9% versus 14.5%). CONCLUSIONS: In this exploratory analysis, the presence of PFO in the younger cryptogenic stroke patients did not increase the risk of adverse events. However, in the older patients, PFO significantly increased the risk of adverse events.

Adult↗
PubMed2004

Black tea increases coronary flow velocity reserve in healthy male subjects.

Epidemiologic studies suggest that tea consumption decreases the risk for cardiovascular events. However, there has been no clinical report examining the effects of tea consumption on coronary circulation. The purpose of this study was to evaluate the effects of black tea on coronary flow velocity reserve (CFVR) using transthoracic Doppler echocardiography (TTDE). This was a double-blind crossover study of 10 healthy male volunteers conducted to compare the effects of black tea and caffeine on coronary circulation. The coronary flow velocity of the left anterior descending coronary artery was measured at baseline and at hyperemia during adenosine triphosphate infusion by TTDE to determine CFVR. The CFVR ratio was defined as the ratio of CFVR after beverage consumption to CFVR before beverage consumption. All data were divided into 2 groups according to beverage type: group T (black tea) and group C (caffeine). Two-way analysis of variance showed a significant group effect and interaction in CFVR before and after beverage consumption (p = 0.001). CFVR significantly increased after tea consumption in group T (4.5 +/- 0.9 vs 5.2 +/- 0.9, p <0.0001). The CFVR ratio of group T was larger than that of group C (1.18 +/- 0.07 vs 1.04 +/- 0.08, p = 0.002). Acute black tea consumption improves coronary vessel function, as determined by CFVR.

Adult↗
PubMed2004

High lipoprotein(a) levels and small apolipoprotein(a) sizes are associated with endothelial dysfunction in a multiethnic cohort.

OBJECTIVES: This study sought to determine the effect of lipoprotein(a), or Lp(a), levels and apolipoprotein(a), or apo(a), sizes on endothelial function and to explore ethnic differences in their effects. BACKGROUND: Although high levels of Lp(a) have been shown to confer increased cardiovascular risk in Caucasians, its significance in non-Caucasian populations is uncertain. The pathogenic role of the apo(a) component of Lp(a) is also unclear. METHODS: The relationship of Lp(a) levels and apo(a) sizes to endothelial function was examined in a multiethnic cohort of 89 healthy subjects (age 42 +/- 9 years; 50 men, 39 women) free of other cardiac risk factors. Endothelium-dependent, flow-mediated dilation (FMD) and endothelium-independent, nitrate-induced dilation (NTG) were assessed by ultrasound imaging of the brachial artery. RESULTS: Plasma Lp(a) levels were lowest in Caucasians (18.3 +/- 21.1 mg/dl, n = 40); intermediate in Hispanics (30.2 +/- 30.5 mg/dl, n = 21); and highest in African Americans (68.8 +/- 46.0 mg/dl, n = 28). Lipoprotein(a) levels were found to correlate inversely to FMD (r = -0.33, p < 0.005) but not to NTG (r = 0.06, p = 0.60). This association remained significant after adjusting for gender (p = 0.002). In addition, subjects with small apo(a) size of <or=22 kringle 4 repeats had significantly lower FMD than those with large apo(a) (2.23 +/- 2.37% vs. 6.26 +/- 4.29%, p < 0.0001), irrespective of Lp(a) levels. CONCLUSIONS: These findings support an independent role of Lp(a) in atherogenesis, an effect that is particularly evident in African Americans. The proatherogenic property of Lp(a) can be attributed in part to its apo(a) component.

Adult↗