Testosterone use and shorter electrocardiographic QT interval duration in men living with and without HIV.

OBJECTIVES: Testosterone usage (T-use) may alter risk factors for sudden cardiac death in men living with HIV (MLWH). Electrocardiographic QT interval prolongation, which could potentiate ventricular arrhythmias, has previously been associated with HIV infection and, separately, with low testosterone levels. We investigated whether T-use shortens the QT interval duration in MLWH and HIV-uninfected men. METHODS: We utilized data from the Multicenter AIDS Cohort Study, a prospective, longitudinal study of HIV infection among men who have sex with men. Multivariable linear regression analyses were used to evaluate associations between T-use and corrected QT interval (QTc) duration. RESULTS: Testosterone usage was more common in MLWH compared with HIV-uninfected men (19% vs. 9%). In a multivariable regression analysis, T-use was associated with a 5.7 ms shorter QT interval [95% confidence interval (CI): -9.5 to -1.9; P = 0.003). Furthermore, stronger associations were observed for prolonged duration of T-use and recent timing of T-use. CONCLUSIONS: This study is the first known analysis of T-use and QTc interval in MLWH. Overall, our data demonstrate that recent T-use is associated with a shorter QTc interval. Increased T-use duration above a threshold of ≥ 50% of visits in the preceding 5 years was associated with a shorter QTc interval while lesser T-use duration was not.

Associations between subcutaneous fat density and systemic inflammation differ by HIV serostatus and are independent of fat quantity.

OBJECTIVES: Adipose tissue (AT) density measurement may provide information about AT quality among people living with HIV. We assessed AT density and evaluated relationships between AT density and immunometabolic biomarker concentrations in men with HIV. DESIGN: Cross-sectional analysis of men enrolled in the Multicenter AIDS Cohort Study. METHODS: Abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) density (Hounsfield units, HU; less negative = more dense) were quantified from computed tomography (CT) scans. Multivariate linear regression models described relationships between abdominal AT density and circulating biomarker concentrations. RESULTS: HIV+ men had denser SAT (-95 vs -98 HU HIV-, P < 0.001), whereas VAT density was equivalent by HIV serostatus men (382 HIV-, 462 HIV+). Historical thymidine analog nucleoside reverse transcriptase inhibitor (tNRTI) use was associated with denser SAT but not VAT. In adjusted models, a 1 s.d. greater SAT or VAT density was associated with higher levels of adiponectin, leptin, HOMA-IR and triglyceride:HDL cholesterol ratio and lower hs-CRP concentrations in HIV- men. Conversely, in HIV+ men, each s.d. greater SAT density was not associated with metabolic parameter improvements and was significantly (P < 0.05) associated with higher systemic inflammation. Trends toward higher inflammatory biomarker concentrations per 1 s.d. greater VAT density were also observed among HIV+ men. CONCLUSIONS: Among men living with HIV, greater SAT density was associated with greater systemic inflammation independent of SAT area. AT density measurement provides additional insight into AT density beyond measurement of AT quantity alone, and may have implications for metabolic disease risk.

The metabolic syndrome and diabetes mellitus as predictors of thoracic aortic calcification as detected by non-contrast computed tomography in the Multi-Ethnic Study of Atherosclerosis.

AIMS: The metabolic syndrome (MetS) is a clustering of low levels of HDL cholesterol, hyperglycaemia, high waist circumference, hypertension and elevated triglycerides, and is associated with cardiovascular disease. Calcified atherosclerotic plaque in the thoracic aorta (TAC), measured by non-contrast cardiac computed tomography (CT) scans, is a marker for atherosclerosis and relates to mortality. We sought to evaluate the independent association of MetS and TAC on cardiac CT scans. METHODS: We examined the relation of the MetS, and each of its components, to the prevalence of TAC, measured from 2000 to 2002 in 6778 white, Chinese, African-American and Hispanic participants in the Multi-Ethnic Study of Atherosclerosis (MESA). RESULTS: Adjusting for age, gender, race, smoking, LDL cholesterol and lipid-lowering medications, relative risks and 95% confidence intervals (CI) for a TAC score > 0 were: 1.19 (95% CI 1.11 to 1.28) for participants with MetS, 1.34 (95% CI 1.21 to 1.49) for those with diabetes and MetS, and 1.33 (95% CI 1.11, 1.58) for those with diabetes and no MetS compared with participants who were free of the MetS and diabetes. Associations were found for most of the components of the MetS with TAC. CONCLUSIONS: We conclude that in adults without known heart disease, the MetS, most of its components and diabetes are associated with a higher prevalence of calcified atherosclerotic plaque in the thoracic arteries in a multi-ethnic population of men and women.

[Preliminary reports of noninvasive accurate method to measure pulmonary vascular capacity in normal volunteers].

OBJECTIVE: Because the traditional loop of breathing control and regulation effect on blood circulation, there was rare study of pulmonary vein capacity. We need a noninvasive and accurate pulmonary vascular capacity measurement and analysis method. METHODS: Twelve normal volunteers were performed a total lung CT scan, image data analysis processing by computer software, the whole lungs from the apex to the base of lung with 40-50 layers by hand-cut, the connection between adjacent layers automatically by a computer simulation, the full pulmonary vascular (≥ 0.6 mm) were treated by high-accuracy three-dimensional imaging technology after removing the interference, and then calculate the whole lung and pulmonary vascular. RESULTS: The whole lung of the 12 normal volunteers from the apex to the base of lung CT scan image layers was 530 ± 98 (range, 431-841). The total capacity of lung and pulmonary vascular blood was 3705 ± 857 (range, 2398-5383) ml, and the total volume of the pulmonary vascular blood was 125 ± 32 (range, 94-201) ml. The pulmonary vein vascular blood volume was 63 ± 16 (range, 47-100) ml. CONCLUSION: The method of measuring the three-dimensional imaging of pulmonary vascular capacity by analyzing lung CT scan data is available and accurate.

[Normal reference values and predict equations of heart function].

OBJECTIVE: For heart functional parameters, we commonly used normal range. The reference values and predict formulas of heart functional parameters and their relationships with individual characteristics are still lack. METHODS: Left ventricular (LV) volumes (end-diastolic volume and end-systolic volume), stroke volume (SV), ejection fraction (EF) and cardiac output (CO) were measured by cardiac CT angiography (CAT) in 1 200 healthy Caucasian volunteers, men 807 and women 393, and age 20-90yr. The results are analyzed by high-accuracy three-dimensional imaging technology, and then measured the dynamic changes of the volumes of each atriam and ventricule during their contractions and relaxations. The gender, age, height and weight were analyzed by multiple linear regression to predict LV functional parameters. RESULTS: Except the LVEF was lower in man than in women (P < 0.001), all other LV functional parameters of EDV, ESV, SV, FE and CO were higher in man (P < 0.001). Multiple linear regression indicated that age, gender, height and weight are all independent factors of EDV, ESV and SV (P < 0.001). CO could be significantly predicted by age, gender and weight (P < 0.001), but not height (P > 0.05). The predict equation for CO (L x min(-1)) = 6.963+0.446 (Male) -0.037 x age (yr) +0.013 x weight (kg). CONCLUSION: Age, gender, height and weight are predictors of heart functions. The reference values and predict equations are important for noninvasive and accurate evaluation of cardiovascular disease and individualized treatment.

[The correlation of the stroke volume with pulmonary venous volume and left atrial volume].

OBJECTIVE: The same person's pulmonary venous blood volume, left atrial volume and stroke volume were measured by lung CT scans and cardiac CT angiography (CTA). Then their relationships were analyzed in order to investigate the mechanism of breathing control. METHODS: As we described before, full pulmonary vascular (-0.6mm) volume was accurately calculated by three-dimensional imaging technology from lung CT scan; left atrial volume and stroke volume of left ventricle were calculated from the CTA data. Then the relationships among them were analyzed for estimation of the lung-artery time. RESULTS: The total volume of lung and pulmonary vascular blood was 3486 ± 783 (2156-4418) ml, and the pulmonary vascular blood volume was 141 ± 20 (105-163) ml. The estimated pulmonary venous volume was 71 ± 10 (52-81) ml. Left atrial volume at the end diastolic was 97 ± 39 (53-165) ml, Stroke volume of left ventricle was 86 ± 16 (60-106) ml. Pulmonary venous volume and the left atrial volume were double of stroke volume(1.7-2.4). CONCLUSION: The estimated lung-artery time was three heart beat.

Lessons learned from the design and implementation of myocardial infarction adjudication tailored for HIV clinical cohorts.

We developed, implemented, and evaluated a myocardial infarction (MI) adjudication protocol for cohort research of human immunodeficiency virus. Potential events were identified through the centralized Centers for AIDS Research Network of Integrated Clinical Systems data repository using MI diagnoses and/or cardiac enzyme laboratory results (1995-2012). Sites assembled de-identified packets, including physician notes and results from electrocardiograms, procedures, and laboratory tests. Information pertaining to the specific antiretroviral medications used was redacted for blinded review. Two experts reviewed each packet, and a third review was conducted if discrepancies occurred. Reviewers categorized probable/definite MIs as primary or secondary and identified secondary causes of MIs. The positive predictive value and sensitivity for each identification/ascertainment method were calculated. Of the 1,119 potential events that were adjudicated, 294 (26%) were definite/probable MIs. Almost as many secondary (48%) as primary (52%) MIs occurred, often as the result of sepsis or cocaine use. Of the patients with adjudicated definite/probable MIs, 78% had elevated troponin concentrations (positive predictive value = 57%, 95% confidence interval: 52, 62); however, only 44% had clinical diagnoses of MI (positive predictive value = 45%, 95% confidence interval: 39, 51). We found that central adjudication is crucial and that clinical diagnoses alone are insufficient for ascertainment of MI. Over half of the events ultimately determined to be MIs were not identified by clinical diagnoses. Adjudication protocols used in traditional cardiovascular disease cohorts facilitate cross-cohort comparisons but do not address issues such as identifying secondary MIs that may be common in persons with human immunodeficiency virus.

Adipokines and body fat composition in South Asians: results of the Metabolic Syndrome and Atherosclerosis in South Asians Living in America (MASALA) study.

OBJECTIVE: To investigate whether leptin and adiponectin are associated with body fat composition in a South Asian population independent of metabolic variables. DESIGN: Cross-sectional study. SUBJECTS: 150 South Asian men and women, between the ages of 45-79 years, in the San Francisco Bay Area without pre-existing clinical cardiovascular disease. MEASUREMENTS: Blood samples were obtained to measure glucose metabolism variables, lipid profiles and adipokines. Total body fat was determined using dual-energy X-ray absorptiometry. Abdominal computed tomography was used to measure subcutaneous, visceral and hepatic fat. RESULTS: Average body mass index (BMI) was overweight at 26.1±4.6 kg m(-2) and did not differ by sex. However, women had significantly more total body fat (P<0.001) and subcutaneous fat (P<0.001) than men, whereas men had significantly more visceral fat (P<0.001) and hepatic fat (P=0.04) than women. Women had significantly higher levels of adiponectin (P<0.01) and leptin (P<0.01). In sex-stratified analyses, leptin was strongly associated with all-body composition measures in women (P<0.05) as well as in men (P<0.05 except for hepatic fat), whereas there was an insignificant trend towards an inverse association between adiponectin and body composition in both women and men, which was significant in combined bivariate analyses. In multivariate analyses, leptin was strongly associated with all measures of adiposity, including BMI (P<0.001), total body fat (P<0.001), visceral fat (P<0.001) and hepatic fat (P=0.01). However, adiponectin's inverse association with adiposity was significantly attenuated by high-density lipoprotein (HDL), triglycerides and insulin resistance. The association between adipokines and diabetes was markedly attenuated after adjusting for body composition. CONCLUSION: Despite only modestly elevated BMI, South Asians have elevated levels of total and regional adiposity. Leptin is strongly associated with adiposity, whereas adiponectin's association with adiposity is attenuated by metabolic variables in South Asians. Adipokines in association with adiposity have an important role in the development of diabetes.

Impact of phosphate binder type on coronary artery calcification in hemodialysis patients.

AIMS: In individuals with chronic kidney disease (CKD), including those undergoing maintenance hemodialysis (MHD), coronary artery calcification (CAC) is common. We hypothesized that, in MHD patients, intake of the calcium-free phosphate binder sevelamer is associated with lower CAC compared to calcium-based phosphate binders (CBPB). MATERIAL AND METHODS: This is a cross-sectional study of MHD patients, who underwent computerized tomography to assess coronary artery calcium scores (CACS). Patients were stratified into two mutually exclusive groups based on taking only a CBPB vs. sevelamer. Logistic regression was used to calculate adjusted odds ratio (OR) of CACS > or = 400, CACS 100 < or =; CACS < 400, 10 < or =; CACS < 100 vs. CACS < 10. RESULTS: 117 MHD patients were either on a CBPB alone (n = 60) or sevelamer alone (n = 57). Despite increased prevalence of DM in the sevelamer group (58%) as compared to the CBPB group (35%), CACS was significantly lower with sevelamer use (283 + or - 83 vs. 494 + or - 94, p = 0.02). The OR of significant CACS > or =; 400 vs. CAC < 10 was 4.35 (95% confidence interval: 1.5 - 9.9, p = 0.008) for CBPB compared with sevelamer, after controlling for case-mix, cholesterol-lowering medication, DM, and inflammatory markers. CONCLUSION: In our cohort, significant CAC was significantly more prevalent among MHD patients taking CBPB as compared to sevelamer monotherapy.

Prevalence and correlates of diabetes in South asian indians in the United States: findings from the metabolic syndrome and atherosclerosis in South asians living in america study and the multi-ethnic study of atherosclerosis.

BACKGROUND: Individuals from South Asia have high diabetes prevalence despite low body weight. We compared the prevalence of diabetes among South Asian Indians with other U.S. ethnic groups and explored correlates of diabetes. METHODS: This was a cross-sectional study of 150 South Asian Indians (ages 45-79) in California, using similar methods to the Multi-Ethnic Study of Atherosclerosis (MESA). Type 2 diabetes was classified by fasting plasma glucose (FPG) >or=126 mg/dL, 2-h postchallenge glucose >or=200 mg/dL, or use of hypoglycemic medication. RESULTS: A total of 29% of Asian Indians had diabetes, 37% had prediabetes, and 34% had normal glucose tolerance. After full adjustment for covariates, Indians still had significantly higher odds of diabetes compared to whites and Latinos, but not significantly different from African Americans and Chinese Americans in MESA: Indians [odds ratio (OR), 1.0], whites [OR, 0.29; 95% confidence interval (CI), 0.17-0.49], Latinos (OR, 0.59; CI, 0.34-1.00) African Americans (OR, 0.77; CI 0.45-1.32), Chinese Americans (OR, 0.78, CI, 0.45-1.32). Variables associated with prediabetes or diabetes among Indians included hypertension, fatty liver, visceral adiposity, microalbuminuria, carotid intima media thickness, and stronger traditional Indian beliefs. CONCLUSIONS: Indian immigrants may be more likely to have diabetes than other U.S. ethnic groups, and cultural factors may play a role, suggesting that this is a promising area of research.

Using basic science to design a clinical trial: baseline characteristics of women enrolled in the Kronos Early Estrogen Prevention Study (KEEPS).

Observational and epidemiological studies suggest that menopausal hormone therapy (MHT) reduces cardiovascular disease (CVD) risk. However, results from prospective trials showed neutral or adverse effects most likely due to differences in participant demographics, such as age, timing of initiation of treatment, and preexisting cardiovascular disease, which reflected in part the lack of basic science information on mechanisms of action of hormones on the vasculature at the time clinical trials were designed. The Kronos Early Estrogen Replacement Study (KEEPS) is a prospective, randomized, controlled trial designed, using findings from basic science studies, to test the hypothesis that MHT when initiated early in menopause reduces progression of atherosclerosis. KEEPS participants are younger, healthier, and within 3 years of menopause thus matching more closely demographics of women in prior observational and epidemiological studies than women in the Women's Health Initiative hormone trials. KEEPS will provide information relevant to the critical timing hypothesis for MHT use in reducing risk for CVD.

Measurement of coronary artery calcification by electron beam computerized tomography in persons with chronic spinal cord injury: evidence for increased atherosclerotic burden.

BACKGROUND/OBJECTIVE: Individuals with spinal cord injury (SCI) have been reported to have an increased prevalence of premature cardiovascular disease. Whether the increased risk of disease is owing to clustering of traditional cardiac risk factor or is over and above that predicted by risk factors was addressed. METHODS: Ninety-one persons with chronic SCI were studied for subclinical atherosclerosis. Cardiac risk factors and coronary artery calcium (CAC) was compared to matched non-SCI controls. The 273 controls were 3:1 matched for age, gender, ethnicity and risk factors and were drawn from a national database of over 30,000 asymptomatic persons undergoing coronary scanning. RESULTS: Seventy-six men and 15 women were studied. Average age was 49.7+/-12 years. Duration of injury was 19.7+/-10 years. The ethnicity of the study cohort included 36% Caucasian, 49% Latino, 10% African American, and 5% other. The mean calcium score of the SCI group was significantly greater than the control group (75+/-218 versus 28+/-104, P<0.001). The prevalence of any CAC score was greater in the SCI population than the control population (51 versus 39%, P<0.05), as was CAC score >100 (16 versus 7%, P<0.01). Women with SCI had a significantly lower CAC score than men (mean score: 12 versus 86, P<0.01). CONCLUSION: Patients with SCI were shown to have greater atherosclerotic burden than able-bodied controls. Of note, and unexplained, this finding is beyond that explained by the clustering of traditional risk factors. On the basis of these findings, increased attention should be directed toward the prevention of coronary heart disease in those with SCI.

Survival predictability of time-varying indicators of bone disease in maintenance hemodialysis patients.

Although renal osteodystrophy and vitamin D analogs may be related to survival in maintenance hemodialysis (MHD) patients, most studies have examined associations between baseline values and survival without accounting for variations in clinical and laboratory measures over time. We examined associations between survival and quarterly laboratory values and administered paricalcitol in a 2-year (July 2001-June 2003) cohort of 58,058 MHD patients from all DaVita dialysis clinics in USA using both time-dependent Cox models with repeated measures and fixed-covariate Cox models with only baseline values. Whereas hypercalcemia and hyperphosphatemia were robust predictors of higher death risk in all models, the association between serum calcium and mortality was different in time-varying models. Changes in baseline calcium and phosphorus values beyond the Kidney Disease Outcome Quality Initiative recommended targets were associated with increased mortality. Associations between high serum parathyroid hormone and increased death risk were masked by case-mix characteristics of MHD patients. Time-varying serum alkaline phosphatase had an incremental association with mortality. Administration of any dose of paricalcitol was associated with improved survival in time-varying models. Controlling for nutritional markers may introduce overadjustment bias owing to their strong collinearity with osteodystrophy surrogates. Whereas both time-dependent and fixed-covariate Cox models result in similar associations between osteodystrophy indicators and survival, subtle but potentially clinically relevant differences between the two models exist, probably because fixed models do not account for variations of osteodystrophy indices and changes in medication dose over time.

Optimal ECG trigger point in electron-beam CT studies: three methods for minimizing motion artifacts.

RATIONALE AND OBJECTIVES: The authors hypothesized that electrocardiographic triggering near end systole could minimize motion artifacts in electron-beam computed tomography (CT) of the coronary artery. MATERIALS AND METHODS: The study included 2,660 patients who underwent coronary artery calcium scanning with electron-beam CT. Trigger times were as follows: end of T wave, 120 to 25 msec before end of T wave, 25-50 msec after end of T wave, 40%, 45%, 50%, 55%, 60%, 70%, 75%, 80%, 90%, and 100% of R-R interval. The authors divided each group into seven subgroups according to heart rate. The percentages of cases with motion artifact in the right coronary artery were computed. Optimal trigger times were defined for each group, as well as for scan acquisitions of 250 and 200 msec. RESULTS: The optimal trigger times were as follows for heart rates of less than 50, 51-60, 61-70, 71-80, 81-90, 91-100, and more than 100 beats per minute, respectively: for 100-msec scans, 359 (27% of the R-R interval), 228 (31%), 314 (34%), 304 (38%), 289 (41%), 283 (45%), and 274 msec (48%) after the R wave; for 250-msec scans, 840 (63%), 654 (60%), 240 (26%), 224 (28%), 219 (31%), 208 (33%), and 200 msec (35%) after the R wave; and for 200-msec scans, 722 (65%), 687 (63%), 249 (27%), 248 (31%), 244 (35%), 233 (37%), and 223 msec (39%) after the R wave. CONCLUSION: The use of these new electrocardiographic triggers before end systole yielded the lowest percentage of motion artifacts (<3% across all heart rates), much lower than for conventional triggers (51% of cases with motion artifact for 80% trigger, P < .001).

Effects of window and threshold levels on the accuracy of three-dimensional rendering techniques in coronary artery electron-beam CT angiography.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the effect of window level and gray-scale threshold on the demonstration of coronary artery lumina at three-dimensional electron-beam computed tomographic (CT) angiography. MATERIALS AND METHODS: Forty-four coronary artery branches in postmortem pigs were evaluated with electron-beam CT angiography, and the findings were compared with those from conventional angiography. Images from electron-beam CT angiography were reconstructed with maximal intensity projection (MIP), multiplanar reformation (MPR), and shaded-surface display (SSD). Four categories of window level and gray-scale threshold were evaluated. RESULTS: Three-dimensional electron-beam CT angiography accurately depicted the luminal diameters of the coronary arteries compared with conventional angiography (r = 0.83-0.90, P < .0001). The length of lumina visualized at electron-beam CT angiography was significantly shorter than that visualized with conventional angiography (P < .001). The use of MPR enabled visualization of longer segments of coronary arteries than did the use of MIP or SSD (P < .05). The higher the window level and gray-scale threshold used, the smaller the coronary luminal diameters measured (P < .05). The most accurate window level and gray-scale threshold (82.6 HU +/- 29.8 and 89.5 HU +/- 29.7, respectively) were found to correspond to the attenuation of the lumina (275.8 HU +/- 58.8). Results of simple linear regression showed a strong correlation between luminal attenuation and window level (r = 0.89, P < .0001) or gray-scale threshold (r = 0.95, P < .0001). CONCLUSION: Electron-beam CT angiography shows promise in the visualization of coronary artery lumina. For accurate display of lumina, a proper window level and gray-scale threshold for three-dimensional rendering techniques should be determined and used on the basis of the attenuation of the target vessel.

Effect of electrocardiogram triggering on reproducibility of coronary artery calcium scoring.

PURPOSE: To test the hypothesis that computed tomographic (CT) scanning during early rather than middle diastole can significantly reduce the interscan variability of coronary artery calcium (CAC) scores. MATERIALS AND METHODS: Five hundred thirty-eight patients were initially enrolled; 282 of them were found to have CAC at electron-beam CT and underwent repeat scanning to measure interscan variability with different electrocardiogram (ECG) triggers. Eight patients were excluded owing to respiratory motion; thus, 274 asymptomatic patients were examined. Patients were randomly assigned to different ECG trigger interval groups: 40% (group 1), 50% (group 2), 60% (group 3), and 80% (group 4). Patients in whom more than one-third of sections had greater than 10% ECG trigger variability were classified in the untriggered group (group 5). Interscan variation was compared among all five groups. RESULTS: Interscan variabilities in CAC groups 1-5 were 11.5%, 15.3%, 20.3%, 17.4%, and 33.1%, respectively, for total calcium area, and 15.0%, 23.3%, 25.6%, 24.0%, and 42.4%, respectively, for total calcium score. CAC score variability was reduced by 34%; and calcium area variability, by 38% in group 1, as compared with the reduced variabilities in group 4 (P <.01 for both measures). Breath holding was adequate in 812 cases, and ECG triggering was correct in 790 of cases. CONCLUSION: Study results strongly support the use of an ECG trigger of 40% rather than 80% of the R-R interval in electron-beam CT calcium studies.

Improved reproducibility of coronary artery calcium scoring by electron beam tomography with a new electrocardiographic trigger method.

RATIONALE AND OBJECTIVES: To improve the interscan reproducibility with electron beam tomography (EBT) by choosing an optimal electrocardiographic (ECG) trigger time. METHODS: Two hundred fourteen asymptomatic subjects found to have coronary artery calcium (CAC) on EBT were rescanned immediately to measure the interscan variability. Subjects were randomized to one of two different ECG trigger interval groups: the new trigger method (group 1) and the 80% R-R interval trigger method (group 2). The new trigger method was derived from a previous study of motion in the coronary arteries. In group 1 (new trigger method), the ECG trigger was programmed for a certain time (in ms) after the R wave, based on the resting heart rate. The triggers for group 1 were 360 (heart rate <50 beats per minute [bpm]), 340 (51--60 bpm), 314 (61--70 bpm), 300 (71--80 bpm), 290 (81--90 bpm), 280 (91--100 bpm), and 270 ms (>100 bpm). The interscan variation (CAC area and Agatston score) was compared between the two groups. RESULTS: The interscan variability was significantly reduced using the new trigger method for both CAC area and score compared with the 80% trigger method. The individual lesion variation was also significantly reduced by the new trigger method compared with the 80% trigger method. Area measure had a significantly lower variability compared with the Agatston score. CONCLUSIONS: These results strongly support the use of this new ECG trigger that relies on a rate-adjusted millisecond delay after the R wave instead of the more commonly used 80% R-R interval in EBT calcium studies.

Coronary artery stenoses: a phantom study using contrast enhanced three-dimensional electron beam tomography.

This paper evaluated the accuracy of electron beam tomographic angiography (EBA) with conventional coronary arteriography (CCA) using four graded artificial stenoses in a postmortem swine coronary phantom model. The sensitivity, specificity, and accuracy of EBA for diagnosing significant stenosis (> or =50% stenosis) were 94.3%, 96.7%, and 95.8%, respectively. The diagnostic accuracy of EBA had no significant difference with CCA (chi(2)=0.0162; P>.05). EBA three-dimensional (3D) procedures had high interobserver reproducibility (k=.92-.95, P>.05). Maximum intensity projection (MIP) was the most sensitive and curved planar reformation (CPR) was the most accurate 3D procedure for quantitatively identifying coronary stenosis. EBA yields promising results concerning the visualization of coronary artery stenosis with high accuracy for stenoses >50%.