Biomedical subjects

Shenghan Lai

Publications and source records attributed to Shenghan Lai.

At least 19 recordsLinked to original sources

PubMed2006

Intraclass correlation coefficients and bootstrap methods of hierarchical binary outcomes.

Intraclass correlation coefficients are designed to assess consistency or conformity between two or more quantitative measurements. When multistage cluster sampling is implemented, no methods are readily available to estimate intraclass correlations of binomial-distributed outcomes within a cluster. Because statistical distribution of the intraclass correlation coefficients could be complicated or unspecified, we propose using a bootstrap method to estimate the standard error and confidence interval within the framework of a multilevel generalized linear model. We compared the results derived from a parametric bootstrap method with those from a non-parametric bootstrap method and found that the non-parametric method is more robust. For non-parametric bootstrap sampling, we showed that the effectiveness of sampling on the highest level is greater than that on lower levels; to illustrate the effectiveness, we analyse survey data in China and do simulation studies.

Biometry↗

PubMed2006

Impact of inversion of the CD4/CD8 ratio on the natural history of HIV-1 infection.

BACKGROUND: HIV-1 infection is characterized by an inverted CD4/CD8 T-cell ratio, but the distribution of inversions over time after seroconversion and whether delay of inversion is associated with a favorable prognosis are not known. METHODS: T-cell counts and clinical outcomes among men in the Multicenter AIDS Cohort Study who had incident HIV-1 infection before December 31, 1995 were analyzed by Kaplan-Meier and Cox proportional hazards methods. Results were also analyzed by time-dependent multivariate methods to adjust for CD4 lymphocyte counts, viral loads, age, race, and polymorphisms in host chemokine receptor genes (CCR5-Delta32 and CCR2-64I). RESULTS: Among 424 cases whose date of seroconversion was known to within +/-4.5 months, 317, 52, and 55 inverted their CD4/CD8 ratio within less than 1, 1 to 2, and more than 2 years of seroconversion, respectively. Longer time to inversion was significantly associated with longer time to AIDS, even after adjusting for CD4 lymphocyte count and viral load at the first seropositive visit and over the first 3 seropositive visits. Of the 6 seroconverters who had more than 500 CD4 lymphocytes 10 years after seroconversion without receiving highly active antiretroviral therapy, 5 took more than 2 years to invert their CD4/CD8 ratio. CONCLUSIONS: Time from HIV-1 seroconversion to inversion of the CD4/CD8 ratio independently predicted time to AIDS. Early measurements of the CD4/CD8 ratio until inversion occurs may identify people likely to become long-term nonprogressors or slow progressors, thus facilitating detailed studies of the mechanism of HIV-1 disease progression.

Adult↗

PubMed2006

Lower myocardial perfusion reserve is associated with decreased regional left ventricular function in asymptomatic participants of the multi-ethnic study of atherosclerosis.

BACKGROUND: Myocardial ischemia is an important determinant of regional left ventricular systolic function. Myocardial blood flow reserve may be impaired by cardiovascular disease before alterations of myocardial perfusion at rest become manifest. Nevertheless, the relation between flow reserve and regional myocardial function has not been studied in individuals without a history of clinical heart disease. METHODS AND RESULTS: Seventy-four participants (66+/-9 years, mean+/-SD) of the Multi-Ethnic Study of Atherosclerosis (MESA) underwent myocardial magnetic resonance tagging and contrast-enhanced perfusion studies. Regional myocardial function was evaluated as peak systolic circumferential strain (Ecc) in the three main coronary territories (left anterior descending [LAD], left circumflex, and right coronary artery [RCA]). Myocardial blood flow at rest and during adenosine-induced hyperemia was quantified by contrast-enhanced magnetic resonance imaging, to study the relation between regional flow and function after multivariable adjustment for age, gender, body mass index, left ventricular mass, and traditional risk factors. Lower regional myocardial blood flow during hyperemia was associated with reduced regional left ventricular function expressed as lower Ecc in the RCA (P<0.01) and left circumflex regions (P<0.05) measured in the subendocardium, mid-wall, and subepicardium. In contrast, no significant association was seen in the LAD territory (P=0.16). In addition, segmental function in LAD and RCA regions was reduced when individuals in the lowest 10th percentile for regional myocardial flow reserve were compared with the other participants. Absolute decreases in mid-wall Ecc LAD and RCA and global Ecc were 3.0%, 3.4%, and 2.8%, respectively (P<0.05 for all regions). CONCLUSIONS: Lower myocardial flow reserve is related to reduced regional function in asymptomatic individuals.

Aged↗

PubMed2006

Effect of long-term cocaine use on regional left ventricular function as determined by magnetic resonance imaging.

This study examined left ventricular (LV) regional midwall circumferential strain by cardiac tagged magnetic resonance imaging in 32 long-term cocaine users and 14 nonusers. Most of the LV segmentations in the cocaine users had less average circumferential strain in the systolic and diastolic phases. The average diastolic strain in 5 ventricular segmentations was significantly less in the cocaine users (p<0.05). In conclusion, long-term cocaine use may be associated with regional LV dysfunction, especially diastolic dysfunction.

Adult↗

PubMed2006

Hypertension and smoking are associated with reduced regional left ventricular function in asymptomatic: individuals the Multi-Ethnic Study of Atherosclerosis.

OBJECTIVES: This study sought to test the hypothesis that reduced regional left ventricular (LV) function is associated with traditional risk factors including hypertension, hypercholesterolemia, and smoking in asymptomatic individuals. BACKGROUND: Coronary artery disease is the main etiology of congestive heart failure in the U.S. and Europe. However, the relationship between risk factors for coronary artery disease and decreased myocardial function has not been studied systematically in asymptomatic individuals. METHODS: The Multi-Ethnic Study of Atherosclerosis (MESA) is a cohort study designed to investigate the nature of atherosclerosis in asymptomatic individuals. A total of 1,184 participants (45 to 84 years old) underwent tagged cardiac magnetic resonance imaging. Regional LV function was quantified by analyzing peak systolic circumferential strain (Ecc) in regions corresponding to the left anterior descending (LAD), circumflex (LCX), and right coronary (RCA) territories. The association between risk factors and strains was studied using multiple linear regression. RESULTS: Higher diastolic blood pressure (DBP) was associated with lower Ecc (p < or = 0.002). The Ecc's in the LAD territory of participants with DBP <80, 80 to 84, 85 to 89, and > or =90 mm Hg were -15.6%, -14.8%, -14.2%, and -13.7%, respectively (p < 0.001). Similar results were documented in other territories and after multivariable analysis. Smokers had lower Ecc in the LAD and RCA regions compared with nonsmokers. Furthermore, dose response relationship between cigarette consumption measured in pack-years and regional LV dysfunction by Ecc was noted (p < or = 0.01 in LAD and RCA territories). Finally, combined diastolic hypertension and smoking was associated with a greater reduction of regional LV function. CONCLUSIONS: Higher diastolic blood pressure and smoking are associated with decreased regional LV function in asymptomatic individuals.

Aged↗

PubMed2006

Characterization of radiofrequency ablation lesions with gadolinium-enhanced cardiovascular magnetic resonance imaging.

OBJECTIVES: This study was designed to evaluate the characteristics of gadolinium-enhanced imaging of radiofrequency ablations. BACKGROUND: Gadolinium-enhanced magnetic resonance imaging (MRI) has been used successfully to evaluate tissue necrosis after myocardial infarction. In electrophysiology, radiofrequency energy is used to create a targeted myocardial necrosis for the treatment of various arrhythmias. METHODS: Using a power-controlled, cooled-tip 7-F catheter system, radiofrequency lesions (10 to 40 W for 30 s) were created on the epicardium of the right ventricle in eight mongrel dogs. After injection of 0.225 mmol/kg gadolinium, T1-weighted fast gradient echo images were obtained during a follow-up of 10 h using an intrathoracic high-resolution coil. Radiofrequency ablations were analyzed on the MR images and compared with gross anatomy and histopathology. RESULTS: Four distinct phases of signal enhancement were observed. After gadolinium injection, radiofrequency lesions were delineated clearly as contrast-free areas of low signal intensity (contrast-to-noise ratio [CNR] = -21.1 +/- 19.8). Signal enhancement in the lesion periphery started 4.0 +/- 1.8 min after injection and progressively extended toward the lesion center at a rate of 0.02 mm/min. Full delayed enhancement was observed after 98 +/- 21 min (CNR = +17.8 +/- 9.0). During the follow-up period, CNR started to decrease, but the lesions were detectable for as long as 10 h of follow-up. During the first three phases of enhancement, MRI correlated well with the pathological findings (r = 0.88, r = 0.88, and r = 0.86 [p < 0.001], respectively). CONCLUSIONS: Radiofrequency ablation can be evaluated accurately by using gadolinium-enhanced MRI, which may allow the noninvasive assessment of procedural success. The dissimilar wash-in and wash-out kinetics compared with myocardial infarction suggest a different pathophysiological process with complete loss of microvasculature.

Animals↗

PubMed2006

Integrated electroanatomic mapping with three-dimensional computed tomographic images for real-time guided ablations.

BACKGROUND: New ablation strategies for atrial fibrillation or nonidiopathic ventricular tachycardia are increasingly based on anatomic consideration and require the placement of ablation lesions at the correct anatomic locations. This study sought to evaluate the accuracy of the first clinically available image integration system for catheter ablation on 3-dimensional (3D) computed tomography (CT) images in real time. METHODS AND RESULTS: After midline sternotomy, 2.3-mm CT fiducial markers were attached to the epicardial surface of each cardiac chamber in 9 mongrel dogs. Detailed 3D cardiac anatomy was reconstructed from contrast-enhanced, high-resolution CT images and registered to the electroanatomic maps of each cardiac chamber. To assess accuracy, targeted ablations were performed at each of the fiducial markers guided only by the reconstructed 3D images. At autopsy, the position error was 1.9+/-0.9 mm for the right atrium, 2.7+/-1.2 mm for the right ventricle, 1.8+/-1.0 mm for the left atrium, and 2.3+/-1.1 mm for the left ventricle. To evaluate the system's guidance of more complex clinical ablation strategies, ablations of the cavotricuspid isthmus (n=4), fossa ovalis (n=4), and pulmonary veins (n=6) were performed, which resulted in position errors of 1.8+/-1.5, 2.2+/-1.3, and 2.1+/-1.2 mm, respectively. Retrospective analysis revealed that a combination of landmark registration and the target chamber surface registration resulted in <3 mm accuracy in all 4 cardiac chambers. CONCLUSIONS: Image integration with high-resolution 3D CT allows accurate placement of anatomically guided ablation lesions and can facilitate complex ablation strategies. This may provide significant advantages for anatomically based procedures such as ablation of atrial fibrillation and nonidiopathic ventricular tachycardia.

Animals↗

PubMed2006

Regional diastolic dysfunction in individuals with left ventricular hypertrophy measured by tagged magnetic resonance imaging--the Multi-Ethnic Study of Atherosclerosis (MESA).

BACKGROUND: Impairment of global diastolic function is considered to be the mechanism of congestive heart failure in individuals with preserved systolic left ventricular (LV) function. Left ventricular hypertrophy (LVH) is known to be a risk factor for congestive heart failure with preserved systolic function, and this process may begin as a regional process. We investigated whether regional LV diastolic function measured by magnetic resonance tagging is altered in asymptomatic participants of the MESA with LVH and preserved systolic LV function. METHODS: Regional systolic and diastolic strain rates were calculated from strain data in 218 participants of the MESA study. Circumferential strain was calculated from the midwall layer of the septum, anterior, lateral, and inferior walls at mid-LV level. Global LV function measures were studied by magnetic resonance imaging in 4291 MESA participants. Left ventricular hypertrophy for men and women was defined from the MESA population using previously established Framingham criteria. RESULTS: Global systolic function was slightly less in the LVH (ejection fraction = 0.66 +/- 0.10) versus the non-LVH group (ejection fraction = 0.69 +/- 0.07, P < .001). Stepwise regression analyses showed a direct relationship between regional diastolic dysfunction and increasing LV mass. Regional systolic strain and strain rate measures from participants with LVH were not significantly different from those without LVH. However, regional diastolic strain rate was significantly reduced in participants with LVH (1.5 +/- 1.1 s(-1)) compared with the non-LVH group (2.2 +/- 1.1 s(-1), P < .001) regardless of age or sex. CONCLUSIONS: Left ventricular hypertrophy is associated with regional diastolic dysfunction in individuals without evidence of clinical cardiovascular disease and preserved systolic function. Magnetic resonance imaging tagging provides detailed quantification of regional diastolic function noninvasively.

Aged↗

PubMed2006

HIV prevalence among injection drug users in rural Guangxi China.

AIMS: To determine the HIV-1 seroprevalence, risk behaviors and demographic characteristics associated with HIV-1 infection among injection drug users (IDU) in rural Guangxi, China. DESIGN AND SETTING: Between July and November 2002, 702 IDU were screened for HIV-1 antibody through community outreach in rural Guangxi, China for enrollment in an HIV sero-incidence study. PARTICIPANTS: A total of 702 active high-risk IDU were screened. High-risk injection was defined as anyone who reported injecting drugs at least three times per week in the last month or injected drugs with shared equipment on at least three occasions in the last 3 months. MEASUREMENTS: HIV-1 antibody testing with confirmation by Western blot was performed on all subjects. Demographic and risk assessment survey data were collected at screening from everyone whose baseline HIV antibody status was known. FINDINGS: HIV-1 antibody prevalence among 702 IDU at baseline was 25% with a median age of 26.7 years (18.2-43.2). Based on a multivariate logistic regression model using risk factors identified in univariate analyses, the following risk factors were associated significantly with an increase in risk for HIV seropositivity: age > 26 years (OR 1.50; 95% CI 1.04, 2.17), sharing of rinse water (OR = 1.24; 95% CI 1.09, 1.40), not having sex in the last 6 months (OR = 1.62; 95% CI 1.08, 2.43). CONCLUSIONS: HIV infection among IDU in Guangxi, one of China's major HIV epidemic regions, is high and the infection occurs predominantly among older IDU males who share rinse water.

Adolescent↗

PubMed2006

Cardiovascular function in multi-ethnic study of atherosclerosis: normal values by age, sex, and ethnicity.

OBJECTIVE: MRI provides accurate and high-resolution measurements of cardiac anatomy and function. The purpose of this study was to describe the imaging protocol and normal values of left ventricular (LV) function and mass in the Multi-Ethnic Study of Atherosclerosis (MESA). SUBJECTS AND METHODS: Eight hundred participants (400 men, 400 women) in four age strata (45-54, 55-64, 65-74, 75-84 years) were chosen at random. Participants with the following known cardiovascular risk factors were excluded: current smoker, systolic blood pressure > 140 mm Hg, diastolic blood pressure > 90 mm Hg, fasting glucose > 110 mg/dL, total cholesterol > 240 mg/dL, and high-density lipoprotein (HDL) cholesterol < 40 mg/dL. Cardiac MR images were analyzed using MASS software (version 4.2). Mean values, SDs, and correlation coefficients in relationship to patient age were calculated. RESULTS: There were significant differences in LV volumes and mass between men and women. LV volumes were inversely associated with age (p < 0.05) for both sexes except for the LV end-systolic volume index. For men, LV mass was inversely associated with age (slope = -0.72 g/year, p = 0.0021), but LV mass index was not associated with age (slope = -0.179 g/m2/year, p = 0.075). For women, LV mass (slope = -0.15 g/year, p = 0.30) and LV mass index (slope = 0.0044 g/m2/year, p = 0.95) were not associated with age. LV mass was the largest in the African-American group (men, 181.6 +/- 35.8 [SD] g; women, 128.8 +/- 28.1 g) and was smallest in the Asian-American group (men, 129.1 +/- 20.0 g; women, 89.4 +/- 13.3 g). CONCLUSION: The normal LV differs in volume and mass between sexes and among certain ethnic groups. When indexed by body surface area, LV mass was independent of age for both sexes. Studies that assess cardiovascular risk factors in relationship to cardiac function and structure need to account for these normal variations in the population.

Black or African American↗

PubMed2006

Coronary CT angiography with 64-MDCT: assessment of vessel visibility.

OBJECTIVE: The objective of our study was to evaluate the image quality of 64-MDCT for coronary angiography. SUBJECTS AND METHODS: Fifty consecutive CT coronary angiograms obtained on a 64-MDCT scanner were independently reviewed by two reviewers. Segments were scored as showing no motion (score of 1), minimal motion (2), moderate motion (3), respiratory motion (4), or vessel blurring (5). Opacification was graded as good (score of 1) or limited (2). Segments < 2 mm were graded as well seen; or as poorly seen or not seen. The scores for motion artifact, opacification, and visibility were combined for overall vessel assessment. Segments with a motion score of 1 or 2 that had good opacification and were well seen were judged to be assessable. RESULTS: A total of 714 segments were analyzed in 50 patients. Seven hundred segments were assessed in all patients (segments 1-3, 11-20, 4, or 27), and a ramus intermedius segment was evaluated in 14 patients. Combining the scores for both reviewers, the average motion score was 1 for 619 segments (86.7%), the average motion score for all segments in an individual patient was 1.14 (range, 1-3.35), and the average opacification score for all segments in a patient was 1.02 (range, 1-1.38). A total of 374 segments were less than 2 mm in diameter. Combining the scores for both reviewers, an average of 36 segments (5.0% of 714) could not be identified by the reviewers, 319.5 segments (85.4%) were well seen, and 18.5 segments (4.9%) were poorly seen. Overall, an average of 637 segments (89.2%) were judged assessable by the reviewers. On a per-patient basis, 10 or more vessel segments were judged assessable in 47 patients (94%). CONCLUSION: On 64-MDCT, 89% of coronary artery segments are assessable. Ten or more vessel segments are assessable in 94% of patients.

Adolescent↗

PubMed2005

Coronary artery atherosclerosis is related to reduced regional left ventricular function in individuals without history of clinical cardiovascular disease: the Multiethnic Study of Atherosclerosis.

OBJECTIVE: We investigated whether regional coronary calcium score by computed tomography is related to regional left ventricular systolic function measured by MRI tagging in participants of the Multiethnic Study of Atherosclerosis. METHODS AND RESULTS: The Multiethnic Study of Atherosclerosis is a prospective observational study of men and women without a history of previous heart disease from 4 ethnic groups. Calcium scores were measured separately for the left anterior descendent (LAD), left circumflex (LCX), and right (RCA) coronary arteries. Left ventricular strain and strain rate were determined by tagged MRI in the corresponding vascular territories of the coronary vessels in 509 participants. Greater coronary calcification in the LAD, LCX, and right RCA coronary arteries were related to worse function in their respective perfusion. Anterior wall strain rate was -1.37+/-0.41 when LAD calcium was zero versus -1.17+/-0.24 1/s in the highest quartile of calcium score (P<0.001). Similar relationships were evident in the LCX and RCA regions. Participants with 1- and 2-vessel coronary artery calcium had better myocardial function in the remote area compared with the territory supplied by the diseased artery. CONCLUSIONS: High-local calcium score is related to regional dysfunction in the corresponding coronary territory among individuals without a history of previous heart disease. These results indicate a link between atherosclerosis and subclinical regional left ventricular dysfunction.

Black or African American↗

PubMed2005

Age, gender and metabolic syndrome-related coronary heart disease in U.S. adults.

BACKGROUND: Metabolic syndrome (MetS), a clustering of several prominent risk factors for atherosclerosis, is common among U.S. populations. The contribution of MetS to the prevalence of coronary heart disease (CHD) in different age-gender groups is currently unknown. METHODS: MetS was defined according to the definition of the National Cholesterol Education Program Adult Treatment Panel III. CHD was defined as having had a diagnosed heart attack in self-reported medical history. Data from the Third National Health and Nutrition Examination Survey (NHANES III) were used to evaluate the MetS-associated CHD prevalences in different age-gender subpopulations, which include 35- to 54-year-old women, 55- to 74-year-old women, 35- to 54-year-old men, and 55- to 74-year-old men. RESULTS: The prevalences of MetS in these 4 age-gender subpopulations are 21%, 24%, 39%, and 38%, respectively. The odds ratios (and the 95% confidence intervals) of MetS to increased CHD in each subpopulations are 1.05 (0.40-2.79), 1.95 (1.19-3.20), 2.22 (1.03-4.81), and 1.96 (1.41-2.70), respectively. CONCLUSIONS: MetS-associated CHD prevalence in women aged 35-54 years is almost the same as in the control, whereas in women aged 55-74 and in men aged 35-54 or 55-74, this prevalence is about 2-fold that of the control. Endogenous estrogen may play a role in suppressing the pro-atherosclerotic effects of MetS-related risk factors, but further studies are needed for a more certain conclusion.

Adult↗

PubMed2005

Hepatitis C virus infection in former commercial plasma/blood donors in rural Shanxi Province, China: the China Integrated Programs for Research on AIDS.

BACKGROUND: Unsafe practices during illegal plasma donation in the late 1980s and early 1990s spread bloodborne infections in central China. METHODS: A cross-sectional survey of a random sample of 538 adult residents of 12 villages in rural Shanxi Province, where there had been an illegal commercial plasma-collection center, was conducted in 2003. Structured questionnaires were administered, and blood samples were tested for hepatitis C virus (HCV) antibodies. RESULTS: HCV seroprevalence rates were 8.2% in all subjects, 27.7% in former commercial plasma/blood donors, and 2.6% in nondonors. Selling blood or plasma was the strongest independent predictor of HCV seropositivity (odds ratio [OR], 14.4 [95% confidence interval {CI}, 7.1-31.6]). A history of blood transfusion was also independently associated with HCV seropositivity (OR, 8.3 [95% CI, 2.1-32.0]). Plasma donors had a higher risk of being HCV seropositive than did whole-blood donors (OR, 7.6 [95% CI, 2.9-20.9]), and female donors had a lower risk than did male donors (OR, 0.32 [95% CI, 0.12-0.80]). The strength of the association between selling blood and HCV seropositivity was weaker when plasma donors were excluded (OR, 8.0 vs. 14.4). CONCLUSIONS: Unsafe practices during illegal plasma donation led to a high risk of HCV seropositivity for donors during the 1980s and 1990s. Failure to screen for HCV increased the risk of seropositivity for transfusion recipients during this same period. China has taken steps to halt illegal plasma collection and to improve blood-banking methods. However, there will be an ongoing challenge to care for patients with HCV infection, even as its incidence decreases.

Adult↗

PubMed2005

HIV-related wasting in HIV-infected drug users in the era of highly active antiretroviral therapy.

BACKGROUND: A decrease in the rate of human immunodeficiency virus (HIV) infection-related wasting has been reported in the era of highly active antiretroviral therapy (HAART). We investigated this concern in a hard-to-reach population of HIV-infected drug users in Miami, Florida. METHODS: After informed consent was obtained, 119 HIV-infected drug users were administered questionnaires involving demographic, medical history, and food-security information. Blood samples were drawn for immunological and viral studies. HIV-related wasting over a period of > or =6 months was defined as a body mass index of <18.5 kg/m2, unintentional weight loss of > or =10% over 6 months, or a weight of <90% of the ideal body weight. RESULTS: The prevalence of HIV-related wasting was 17.6%. A significantly higher proportion of those who experienced wasting (81%) reported that there were periods during the previous month when they went for > or =1 day without eating (i.e., food insecurity), compared with those who did not experience wasting (57%). Although a greater percentage of patients who experienced wasting were receiving HAART, their HIV RNA levels were more than twice as high (mean+/-standard deviation [SD], 166,689+/-238,002 copies/mL; median log HIV RNA level +/- SD, 10.2+/-2.7 log10 copies/mL) as those for the group that did not experience wasting (mean+/-SD, 72,156 +/- 149,080; median log HIV RNA level+/-SD, 9.2+/-2.3 log10 copies/mL). Participants who experienced wasting were more likely to be heavy alcohol drinkers and users of cocaine. In multivariate analysis that included age, sex, food security, alcohol use, cocaine use, viral load, and receipt of antiretroviral therapy, the only significant predictors of wasting were > or =1 day without eating during the previous month (odds ratio [OR], 1.96; 95% confidence interval [CI], 1.18-3.26; P=.01) and viral load (OR, 1.64; 95% CI, 1.00-2.69; P=.05). CONCLUSIONS: HIV-related wasting continues to be common among HIV-infected drug users, even among HAART recipients. Food insecurity and viral load were the only independent predictors of wasting. The social and economic conditions affecting the lifestyle of HIV-infected drug users constitute a challenge for prevention and treatment of wasting.

Anti-HIV Agents↗

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

Coinfection with HIV and hepatitis C virus among injection drug users in southern China.

BACKGROUND: We sought to examine coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) among injection drug users (IDUs) in Guangxi, China. METHODS: A longitudinal cohort of IDUs (547 subjects) was established to study risk factors for bloodborne infections. At each visit, participants completed questionnaires defining demographic characteristics, patterns of drug use, and sexual behaviors. Blood samples were collected and analyzed for the presence and genotype of HIV and HCV. RESULTS: Coinfection with HIV and HCV was found in 17.6% of the IDUs. HCV was present in 95.1% of HIV-positive and 70.4% of HIV-negative heroin users. The prevalence of HIV in HCV-positive and HCV-negative heroin users was 23.4% and 3.6%, respectively. Multivariate logistic regression analysis revealed that sexual activity during the past 6 months and duration of injection drug use were significantly associated with coinfection with HIV and HCV. The main circulating HCV genotypes included 6a (38%), 3b (37%), and 1a (19%), whereas genotypes 6e (4%), 3a (2%), and 1b (1%) were present in only a few IDUs. Multiple HCV genotypes were present at each study site and did not segregate by HIV status or subtype. CONCLUSIONS: HCV is highly prevalent in IDUs throughout southern China. In Guangxi, HIV infections are the result of parenteral and sexual transmission, and, therefore, all IDUs are at high risk of coinfection with HIV and HCV. Molecular tracking of HCV may be a more sensitive predictor of the future spread of the HIV-1 epidemic than is HIV subtyping. This study emphasizes that, without implementation of injection prevention and primary substance abuse programs in China, the extent and effect of coinfection with HIV and HCV will only increase.

Adult↗

PubMed2005

Reproducibility of 3D free-breathing magnetic resonance coronary vessel wall imaging.

AIMS: Although the coronary artery vessel wall can be imaged non-invasively using magnetic resonance imaging (MRI), the in vivo reproducibility of wall thickness measures has not been previously investigated. Using a refined magnetization preparation scheme, we sought to assess the reproducibility of three-dimensional (3D) free-breathing black-blood coronary MRI in vivo. METHODS AND RESULTS: MRI vessel wall scans parallel to the right coronary artery (RCA) were obtained in 18 healthy individuals (age range 25-43, six women), with no known history of coronary artery disease, using a 3D dual-inversion navigator-gated black-blood spiral imaging sequence. Vessel wall scans were repeated 1 month later in eight subjects. The visible vessel wall segment and the wall thickness were quantitatively assessed using a semi-automatic tool and the intra-observer, inter-observer, and inter-scan reproducibilities were determined. The average imaged length of the RCA vessel wall was 44.5+/-7 mm. The average wall thickness was 1.6+/-0.2 mm. There was a highly significant intra-observer (r=0.97), inter-observer (r=0.94), and inter-scan (r=0.90) correlation for wall thickness (all P<0.001). There was also a significant agreement for intra-observer, inter-observer, and inter-scan measurements on Bland-Altman analysis. The intra-class correlation coefficients for intra-observer (r=0.97), inter-observer (r=0.92), and inter-scan (r=0.86) analyses were also excellent. CONCLUSION: The use of black-blood free-breathing 3D MRI in conjunction with semi-automated analysis software allows for reproducible measurements of right coronary arterial vessel-wall thickness. This technique may be well-suited for non-invasive longitudinal studies of coronary atherosclerosis.

Adult↗