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T L Burns

Publications and source records attributed to T L Burns.

At least 37 records · Page 2Linked to original sources
PubMed1996

Maternal alcohol use and risk of orofacial cleft birth defects.

Maternal alcohol use during pregnancy is a known cause of birth defects associated with the fetal alcohol syndrome, but its role in more common, isolated, craniofacial birth defects is not well understood. A population-based, case-control study of orofacial clefts was conducted in Iowa using births during 1987-1991. Cases were identified by the Iowa Birth Defects Registry and classified as having a cleft lip with or without cleft palate (CLP) or cleft palate only (CP) and whether the cleft was isolated or occurred with other birth defects. Controls were selected from normal Iowa births. Maternal alcohol use during pregnancy was classified according to self-reported drinks consumed per month. Results are based on 302 controls and the following numbers in each case group: 118 isolated CLP, 56 isolated CP, 51 CLP with multiple defects, and 62 CP with multiple defects. Compared to women who did not drink alcohol during pregnancy, the relative odds of isolated CLP rose with increasing level of maternal drinking as follows: 1-3 drinks per months, 1.5; 4-10 drinks per month, 3.1; more than 10 drinks per month, 4.7 (chi-square test for trend, P = 0.003). Adjustment for maternal smoking, vitamin use, education, and household income did not substantially alter these results. No significant association was found between alcohol use and isolated cleft palate or clefts in children with multiple birth defects. Alcohol use during pregnancy may be a cause of isolated cleft lip with or without cleft palate.

Adult↗
PubMed1996

Coronary risk factors measured in childhood and young adult life are associated with coronary artery calcification in young adults: the Muscatine Study.

OBJECTIVES: This study was designed to estimate the prevalence of coronary artery calcification in young adult men and women and to examine the association between the presence of coronary artery calcification and coronary risk factors measured in childhood and young adult life. BACKGROUND: Electron beam computed tomography is a sensitive, noninvasive method for detecting coronary artery calcification, a marker of the atherosclerotic process. Coronary artery calcification is associated with coronary risk factors in older adults. METHODS: Subjects (197 men, 187 women) had coronary risk factors measured in childhood (mean age 15 years) and twice during young adult life (mean ages 27 and 33 years). Each underwent an electron beam computed tomographic study at their second young adult examination. RESULTS: The prevalence of coronary artery calcification was 31% in men and 10% in women. Increased body size, increased blood pressure and decreased high density lipoprotein (HDL) cholesterol levels were the coronary risk factors that showed the strongest association with coronary artery calcification. Significant odds ratios for coronary artery calcification, using standardized risk factor measurements at a mean age of 33 years in men and women, respectively, were 6.4 and 13.6 for the highest decile of body mass index, 6.4 and 6.4 for the highest decile of systolic blood pressure and 4.3 and 4.7 for the lowest decile of HDL cholesterol. CONCLUSIONS: Coronary artery calcification is more prevalent in men in this young adult population. Coronary risk factors measured in children and young adults are associated with the early development of coronary artery calcification. Increased body mass index measured during childhood and young adult life and increased blood pressure and decreased HDL cholesterol levels measured during young adult life are associated with the presence of coronary artery calcification in young adults.

Adolescent↗
PubMed1996

Understanding logistic regression analysis through example.

Logistic regression is a valuable statistical tool that is often used in primary care research. When researchers explore the association between a possible risk factor and a disease, they attempt to control the effects of extraneous factors (confounders) that can obscure the true association. Using logistic regression, researchers can simultaneously control for the effects of multiple confounders. When investigators use logistic regression, they make subjective decisions about which factors to include in the analysis and in the final predictive model. Critical readers must understand basic concepts of logistic regression and potential problems with its use before they can accurately interpret study results. This article uses a familiar example to explain the principles of logistic regression to make it understandable to nonstatisticians.

Coffee↗
PubMed1995

Molecular analysis of nondisjunction in Down syndrome patients with and without atrioventricular septal defects.

BACKGROUND: Congenital heart disease is common in Down syndrome patients, with atrioventricular septal defects accounting for a majority of the abnormalities. The molecular mechanisms of meiotic nondisjunction resulting in Down syndrome were studied for associations with the presence of atrioventricular septal defects. METHODS AND RESULTS: Twenty highly polymorphic chromosome 21 microsatellite markers were used to genotype two groups of patients (group 1: Down syndrome with atrioventricular septal defects, n = 43; and group 2: Down syndrome without cardiac defects, n = 51) to determine (1) the parental origin of the extra chromosome, (2) the stage of meiotic nondisjunction resulting in the trisomy, (3) the presence or absence of disomic homozygosity or heterozygosity, and (4) the degree of recombination in the nondisjoined chromosomes. The parental origin of the nondisjoined chromosome was maternal in 86.2% of the families, with no significant differences between groups. The most centromeric marker was nonreduced, indicating a meiosis I nondisjunction in 76.5% of maternally derived trisomies, and reduced, indicating a meiosis II nondisjunction in 76.9% of paternally derived trisomies, with no significant differences between groups. There were no significant differences in the proportion of reduced markers at any locus between groups. The distribution of the number of crossovers was significantly different between groups (chi 2 = 14.12, P < .001), with less recombination observed in group 1. CONCLUSIONS: In Down syndrome patients, no association was found between the presence of an atrioventricular septal defect and the parent of origin, stage of meiotic nondisjunction, or disomic homozygosity or heterozygosity. A significant association was found between the presence of an atrioventricular septal defect and reduced frequency of recombination.

Case-Control Studies↗
PubMed1995

Predictors of left ventricular mass and resting blood pressure in children: the Muscatine Study.

The objective of this study was to determine predictors of left ventricular mass (LVM) and resting systolic blood pressure (SBP) in preteenage children. Subjects consisted of 124 children (7.9-12 yr) from Muscatine, Iowa. Methods consisted of echocardiographic examinations, random-zero SBP, hormone determination of serum androgens, physician's examination for Tanner stage, anthropometry, maximal bicycle ergometry, hand grip dynamometry, and a physical activity survey. Least square's regression analysis quantified the percentage of explained variability in LVM and resting SBP attributable to the predictor variables. All models were adjusted for body composition. In boys, 72% of the variability in LVM was explained by fat-free body mass (FFM), sum of skinfolds, and peak SBP. In girls, FFM and peak SBP explained 69% of the variability in LVM. Peak SBP was also a significant predictor of resting SBP in boys and girls. Study results indicated that physical fitness and physical activity are not significant predictors of LVM nor resting SBP; however, after adjusting for body composition, peak SBP was an independent predictor of LVM and resting SBP. This result suggests that peak SBP may aid in the prediction of subsequent hypertension and its complications such as left ventricular hypertrophy.

Blood Pressure↗
PubMed1994

Quantification of left ventricular function with an automated border detection system and comparison with radionuclide ventriculography.

Quantification of 2-dimensional echocardiograms with a recently developed automated border detection (ABD) system provides on-line estimation of left ventricular (LV) function. Previous studies showed that short-axis cavity area measurements with the ABD system approximate manually traced cavity areas obtained with conventional 2-dimensional echocardiography. Further clinical validation needs a comparison of LV function between the ABD system and established methods. Fractional area change and ejection fraction measured by the ABD system were compared with ejection fraction measured by radionuclide ventriculography. Echocardiographic measurements were obtained from LV short-axis views at the level of the papillary muscles. Calculation of ejection fraction by the ABD system was based on an algorithm using a modified ellipsoid model. Forty-six patients underwent echocardiography on the same day as radionuclide ventriculography. Patients were included in the study if > or = 75% of the endocardium was visualized with conventional 2-dimensional echocardiography. Twenty-seven of 46 patients (59%) had a technically adequate, conventional echocardiogram. Fractional area change with the ABD system was highly correlated with ejection fraction from radionuclide ventriculography (r = 0.92; SEE 8.4%). Ejection fraction determined by the ABD system and radionuclide ventriculography also showed a strong linear relation in the 23 patients without severe wall motion abnormality (r = 0.90; SEE 9.5%). It is concluded that LV function measurements by the ABD system and radionuclide ventriculography have a strong linear relation.

Adolescent↗
PubMed1994

Linkage analysis of autosomal dominant atrioventricular canal defects: exclusion of chromosome 21.

The association between trisomy 21 and a high incidence of atrioventricular canal defects (AVCDs) indicates that a locus on chromosome 21 is involved in this congenital heart defect. We have investigated whether a genetic locus on chromosome 21 is also involved in familial nonsyndromic AVCDs. Short tandem repeat polymorphisms (STRPs) from chromosome 21 were used for linkage analysis of a family having multiple members affected with AVCDs. In this family, the gene for AVCDs is transmitted as an autosomal dominant with incomplete penetrance. The affected family members are nonsyndromic and have normal karyotypes. Two-point and multipoint linkage analyses produced significantly negative LOD scores for all informative markers. A comparison of the overlapping exclusion distances obtained for each marker at LOD equal -2.0 with the 1000:1 consensus genetic map of the markers, excludes chromosome 21 as the genetic location for AVCDs in this family. The exclusion of chromosome 21 indicates that another gene, not located on chromosome 21, is involved in atrioventricular canal defect formation.

Chromosomes, Human, Pair 21↗
PubMed1994

Assessment of cardiac volumes and left ventricular mass by cine computed tomography before and after mitral balloon commissurotomy.

We used cine computed tomography (CT) to determine whether decreased mitral valve gradients and pulmonary artery pressures resulted in decreased right ventricular and atrial volumes after percutaneous mitral balloon commissurotomy (MBC). In patients treated for severe mitral stenosis, previous studies have shown that after the mitral valve gradient decreases, the left atrial volume is reduced and left ventricular stroke volume is increased. The effects of commissurotomy on right heart chamber sizes have been difficult to assess with angiography and echocardiography. Moreover, in follow-up studies performed after surgery, changes in cardiac chamber volumes occurring after the mitral valve gradient and pulmonary pressure are reduced are confounded by the effects of thoracotomy. Our group has previously demonstrated that cine CT can accurately measure both left and right cardiac chamber volumes. We studied 11 female patients before, immediately after, and at 1 year after MBC, and 9 female control subjects of comparable age. To assess cardiac chamber volumes, we used cine CT. To assess the effects of MBC, we used cardiac catheterization and Doppler echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1994

Prediction of change in mitral valve area after mitral balloon commissurotomy using cine computed tomography.

RATIONALE AND OBJECTIVES: Mitral balloon commissurotomy (MBC) can successfully increase the mitral valve area (MVA) in mitral stenosis, but the outcome is variable. In multicenter studies, qualitative echocardiographic scores obtained before MBC are only weakly predictive of the increase in MVA after MBC. METHODS: To evaluate whether the change in MVA after MBC can be predicted by evaluating mitral valve morphology using cine computed tomography (CT), we studied 12 women with mitral stenosis and 11 female control subjects. RESULTS: In the patients with mitral stenosis, MVA increased from 1.13 +/- 0.24 to 1.93 +/- 0.56 cm2 (P < .0001) after MBC. A standard echocardiographic score assessment of mitral valve morphology before MBC was not associated with the change in MVA after MBC in these patients (P > .20). However, the total mitral valve morphology score evaluated by cine computed tomography was strongly associated with the change in MVA after MBC (r = -.87; P < .0005). In addition, the individual morphologic characteristics of mitral valve mobility (P < .0025), leaflet thickness (P < .05), and subvalvular disease (P < .05) were significant predictors of the change in MVA after MBC. CONCLUSION: Cine computed tomography may be useful for predicting immediate increases in MVA in patients after MBC and may be helpful for preoperative assessment of these patients.

Catheterization↗
PubMed1994

Coronary risk factors in adolescents related to their knowledge of familial coronary heart disease and hypercholesterolemia: the Muscatine Study.

OBJECTIVE: To determine the utility of a school-based questionnaire, to identify adolescents with adverse coronary risk factor levels. DESIGN: In Muscatine, IA, students (9th through 12th grade) completed a questionnaire providing medical history information about first- and second-degree relatives. Anthropometric measures were obtained and blood pressure, lipid, lipoprotein, and apolipoprotein levels were determined. RESULTS: A history of parental coronary heart disease (CHD) was rare and a history of parental high cholesterol frequently was unknown; however, when known, a history of high cholesterol or early (30 to 55 years of age) or later (> 55 years of age) CHD (myocardial infarction, coronary bypass, or death from a heart attack) in grandfathers enriched the identification of adolescents with adverse coronary risk factors. Parental history of CHD was associated with an increased risk for high body mass index and low apolipoprotein A1 levels in their children. Grandfather history of early or later CHD was associated with an increased risk for low apolipoprotein A1 and high density lipoprotein cholesterol levels and high body mass index in their grandchildren. Students with positive grandfather histories of high cholesterol had higher total cholesterol, low density lipoprotein cholesterol, apolipoprotein B, and low density lipoprotein cholesterol to high density lipoprotein cholesterol ratios. Grandmother histories, because most were negative, did not help identify adolescents in this population with adverse coronary risk factors. CONCLUSIONS: A parental history of CHD as well as a grandfather history of high cholesterol or CHD enriches the identification of children with adverse coronary risk factor levels. The positive predictive values associated with using a school-based history obtained from adolescents, many with the aid of their parents, are small and many adolescents do not know their family history. It is essential that pediatricians inquire about parental and especially grandparental medical histories in accordance with the National Cholesterol Education Program guidelines to help identify children at highest familial risk. The importance of determining parental and grandparental histories of CHD or hypercholesterolemia should be emphasized to families who are uncertain of their histories to identify children and adolescents who require a physician's care. It is also important for pediatricians to remind their colleagues who care for patients with premature ischemic heart disease to refer their progeny for pediatric care so that their lipids and lipoproteins may be screened and counseling provided.

Adolescent↗
PubMed1993

Impact of transesophageal echocardiography on the anticoagulation management of patients admitted with focal cerebral ischemia.

Transesophageal echocardiography (TEE) improves the diagnostic accuracy of transthoracic echocardiography in the identification of potential cardiac sources of embolus. However, there are few studies of the impact of TEE on the medical management of patients with focal cerebral ischemia. The records of 52 consecutive, hospitalized patients undergoing both TEE and transthoracic echocardiography for suspected cardiac source of embolus were reviewed to determine the influence of TEE on the decision to anticoagulate patients. Of 52 patients, 39 had focal cerebral ischemia (transient ischemic attack, n = 9; acute cerebral infarction, n = 30). In 4 of these 39 patients (10%), the TEE results changed the management of anticoagulation. In 19 of 39 patients (49%), the TEE results helped confirm anticoagulation decisions, and in 16 (41%), the results had no effect on anticoagulation decisions, because of overriding clinical information. Ten of the latter 16 patients had TEE evidence for a possible source of an embolus, but were not anticoagulated; 5 of these were poor candidates for long-term anticoagulation, and the others had right-to-left shunting across a patent foramen ovale or an interatrial septal aneurysm. Clinical variables (atrial fibrillation, TEE findings and pre-TEE anticoagulation status) were considered as possible predictors of post-TEE anticoagulation status using logistic regression analysis; the strongest predictor of post-TEE anticoagulation status was pre-TEE anticoagulation status (p < 0.0005). Despite the selection of patients presumed to receive maximal benefit from TEE, this study suggests that TEE findings are not predictive of subsequent anticoagulation management. However, TEE is at least confirmatory of anticoagulation decisions in most cases.

Adult↗
PubMed1993

Genetic models of human obesity--family studies.

Childhood obesity is predictive of obesity as an adult, and individual differences in body weight relative to height (body mass index) in adults are important predictors of morbidity as well as mortality from atherosclerotic cardiovascular disease. The observation of strong familial correlations does not ensure that genes are involved in the determination of body mass index, because individuals in families share environments as well as genes. However, several recent studies have found evidence for both additive (polygene) and nonadditive (major gene) components. A question that results from these analyses is--what gene(s) has been inherited that carries an associated risk, most likely mediated by environmental exposures, for obesity? Studies to identify genetic loci linked to familial obesity should add to our understanding of the genetic factors involved in the determination of obesity and may lead to early identification of individuals and families at high risk for the chronic disorders that are associated with obesity.

Body Mass Index↗
PubMed1993

Relationship between diet composition and body fatness, with adjustment for resting energy expenditure and physical activity, in preadolescent children.

We examined the relationship between diet composition and body fatness in 48 children (25 girls, 23 boys) aged 9-11 y. Subjects were identified for two study groups, non-obese [triceps skinfold (TSF) thickness < 85th percentile] and obese (TSF thickness > or = 85th percentile). Measures for dietary intake, physical activity, resting energy expenditure (REE), and body composition were obtained by three 24-h dietary and activity recalls; indirect calorimetry; and anthropometrics, respectively. Percentage of body fat correlated positively with intakes of total (P < 0.0001), saturated (P < 0.01), monounsaturated (P < 0.0001), and polyunsaturated (P < 0.01) fatty acids, and negatively with carbohydrate intake (P < 0.001) and total energy intake adjusted for body weight (P < 0.001). After adjustment for study group, energy intake, REE, and physical activity, the associations remained for total, saturated, and monounsaturated fatty acid and carbohydrate intakes. These data suggest that diet composition, independent of total energy intake, REE, and physical activity may contribute to childhood obesity.

Adipose Tissue↗
PubMed1993

Rapid resolution of hyperkinesis after exercise. Two-dimensional echocardiographic studies in normal subjects.

Abnormal wall motion detected with exercise echocardiography identifies ischemic myocardium, while normal myocardium exhibits hyperkinetic motion. The normal, hyperkinetic response to exercise is transient and is predictive of an excellent prognosis. However, there are few data on the duration of the hyperkinesis after peak exercise. Our purpose was to determine the time course of wall thickening after exercise in eight normal subjects with two-dimensional echocardiography. Percentage of wall thickening increased from 53 +/- 24 percent at baseline to 82 +/- 24 percent at 0 to 2 min postexercise (p < 0.001 vs baseline) and then decreased to 64 +/- 27 percent at 2 to 4 min, and 54 +/- 20 percent at 5 to 7 min (both NS vs baseline). We conclude that (1) systolic wall thickening is maximal within the initial 2 min following peak exercise, and (2) accurate identification of hyperkinetic, normal myocardium with exercise echocardiography requires immediate postexercise imaging.

Adult↗
PubMed1993

Factors affecting left ventricular mass in childhood: the Muscatine Study.

OBJECTIVE: To examine the contribution of age, body size, and blood pressure to left ventricular mass (LVM) in childhood and develop a population-based reference of normative LVM data. METHODS: Age, sex, height, weight, and auscultatory systolic and diastolic blood pressures were measured and an echocardiogram was performed to estimate LVM in 904 normal children, aged 6 to 16 years, in Muscatine, IA. Pearson product-moment correlation coefficients were determined to describe the degree of linear association between LVM and age, body size, and blood pressure. Age-sex-, weight-sex-, and height-sex-specific Z scores were determined for LVM, age, weight, height, and blood pressure. Sex-specific LVM prediction equations were derived using weighted-least-squares regression analysis. RESULTS: A strong positive linear association of LVM with age, weight, height, Quetelet index, and systolic and diastolic blood pressure was demonstrated. Z scores for eight different LVM quintile patterns revealed that age, height, weight, and blood pressure each exert an independent influence on LVM in children. Sex-specific predicted M-mode LVM and upper limits of the 90% prediction intervals based on age and height are presented. CONCLUSION: Since age, height, weight, and blood pressure may each exert an independent influence on LVM in children, each factor must be considered when interpreting LVM in childhood. While age, sex, and height are unalterable, both weight and blood pressure can be modified. Thus the pathologic contribution of excess weight and blood pressure ought not be masked by statistical adjustments in reference values for LVM. Sex-specific values of LVM and the 90% and 95% prediction intervals of LVM that do not factor out the effects of obesity or blood pressure are presented. These provide the upper-limit reference values of LVM for the evaluation of children in whom increased LVM is suspected.

Adolescent↗