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Biomedical subjects

R Prineas

Publications and source records attributed to R Prineas.

31 records · Page 2Linked to original sources
PubMed1985

Cardiovascular responses in type A children during a cognitive challenge.

The few studies which have examined stress-induced cardiovascular reactivity among Type A children have had equivocal results. In the present study, 41 extreme Type A and 46 extreme Type B children were monitored for heart rate and blood pressure during a challenging cognitive task under clear or ambiguous performance standards. Significant heart-rate and blood-pressure responses were observed, but no effects could be attributed to the behavior pattern or performance standards. Type A's were more self-involved, generally attributing their performance to effort. Under ambiguous performance standards, they perceived themselves more negatively and attributed performance to luck and task difficulty. These results do not support the exaggerated cardiovascular response hypothesis but do suggest that Type A children look toward external cues in the evaluation of both themselves and their performance, particularly when the external standards for performance are ambiguous.

Achievement↗
PubMed1982

Electrocardiographic measures of left ventricular hypertrophy in children across the distribution of blood pressure: the Muscatine study.

We sought to test the effectiveness of the ECG as a measure of increased left ventricular wall mass in children with high blood pressure. One hundred eighty-one children, ages 9-18 years, were selected from the lowest, middle and highest quintile of systolic blood pressure from the Muscatine Study, based upon two biennial school screenings. After correction for age, sex, height, weight and skinfold thickness, children with the highest blood pressure had increased echocardiographic left ventricular wall mass (p less than 0.02). Voltage measurements of maximum R and S waves in the standard and precordial leads were measured by computer. We correlated blood pressure and echocardiographic measurements of the interventricular septum, left ventricular posterior wall and left ventricular wall mass to electrocardiographic combinations used to predict left ventricular hypertrophy in both children and adults. The electrocardiographic correlations ranged from -0.01 to + 0.17. Poor correlations were found between electrocardiographic measures and blood pressure, left ventricular wall thickness or left ventricular wall mass. Skinfold thickness and weight had negative correlations, suggesting a damping effect upon measured voltage. We conclude that the echocardiogram is a more sensitive measurement of increased left ventricular mass than the ECG in children with elevated blood pressure.

Adolescent↗
PubMed1979

Ventricular premature contractions: a randomized non-drug intervention trial in normal men.

The influence of a 6-week intervention on factors thought to be related to ectopic cardiac rhythms was tested in normal men with frequent ventricular premature contractions (VPCs), using a randomized, controlled and partial crossover design. The VPC intervention trial experimental regimen included total abstinence from caffeine and smoking, reduction of alcohol intake, and a physical conditioning program. Effects were studied in detail among 81 healthy men with persistent VPCs. VPCs were measured during standard states of rest, dynamic and isometric exercise and other stresses, and 24-hour ambulatory monitoring. Adherence to the treatment was excellent. The experimental group achieved more than 80% of activities asked of them, and little "contamination" occurred in the control group. VPCs were analyzed according to VPC/min, VPC/man and VPC/total number of heart beats. Moderate changes in VPC rates occurred in both experimental and control groups but no significant group differences were found at rest or during any induction test. This 6-week, multiple-factor "hygienic" intervention program had no significant influence on the frequency or occurrence of VPCs in apparently normal men with persistent and frequent VPCs. Because the mechanisms and the significance of VPCs are different in patients with ischemic heart disease, our approach and methods may be useful for similar trials among cardiac patients of adjunct or non-drug therapy for ectopic rhythms.

Adult↗
PubMed1978

Changing electrocardiographic recording technology and diagnostic accuracy of myocardial infarction criteria. Improved standards for evaluation of ECG measurement precision.

An analytical study was performed to estimate the magnitude of the visual Q wave duration bias produced by pressurized ink round stylus electrocardiographic (ECG) recorders. With a paper speed of 25 mm/sec and the ECG tracing width of 0.25 mm, the visually measured Q waves are on the average 8 msec too short. The corresponding error with the older type flat stylus recorder is less than 2 msec. Considerable differences can thus be anticipated in the frequency of observed ECG abnormalities in studies which use different types of electrocardiographs. The effect of the visual Q wave duration measurement bias on the diagnostic ECG classification was investigated in a group of 237 patients with old myocardial infarction and 299 subjects with no clinical evidence of infarction. An 8 msec measurement bias toward too short Q wave duration was observed to result in a potential loss of diagnostic accuracy of about 25% in some ECG coding categories. As a corrective procedure, it is recommended that the baseline width produced by a round recording stylus of uniform thickness irrespective of the vertical deflection velocity should be less.

Diagnosis, Computer-Assisted↗
PubMed1978

Ventricular premature beats. Reliability in various measurement methods at rest and during exercise.

The yield and reproducibility of various methods of ventricular premature beat (VPB) detection are examined in otherwise healthy middle-aged men first found to have VPB in a 2-min lead I ECG rhythm strip. With a combination of an isometric and treadmill exercise test, VPB were repeatedly detected in 83%. Test-retest reliability in classifying the subjects by frequency of VPB was 67%. The reliability of detecting complex VPB was 47% for multiform VPB, 35% for pairs of VPB, 17% for runs and 36% for VPB showing the R-on-T phenomenon. These data suggest that simple and complex VPB detected by the described methods among normal men are poorly reproducible in the individual. Taking the VPB reproducibility for the group as a whole, the proportion of subjects having different frequency or kinds of ectopic beats is reasonably stable for the different test occasions.

Adult↗
PubMed1976

Epidemiology and prevention of ventricular ectopic rhythms.

Current work of the Laboratory of Physiological Hygiene is reviewed on the epidemiology and prevention of ectopic ventricular rhythms (VPB). The evidence suggests that uniform simple VPB at rest, or exercise-induced, are prognostically important only in those having clinically manifest coronary disease. A simple rhythm strip is an effective first screen method for detecting individuals having rather frequent VPB, and frequency of VPB is correlated with complex ectopic rhythms. A multifaceted stress induction test induces VPB and does it consistently. Hygienic intervention, in which cardiac stimulants are removed and conditioning exercises given, is being tested as VPB suppressive therapy.

Adult↗
PubMedDate not supplied

Effect of alendronate on risk of fracture in women with low bone density but without vertebral fractures: results from the Fracture Intervention Trial.

CONTEXT: Alendronate sodium reduces fracture risk in postmenopausal women who have vertebral fractures, but its effects on fracture risk have not been studied for women without vertebral fractures. OBJECTIVE: To test the hypothesis that 4 years of alendronate would decrease the risk of clinical and vertebral fractures in women who have low bone mineral density (BMD) but no vertebral fractures. DESIGN: Randomized, blinded, placebo-controlled trial. SETTING: Eleven community-based clinical research centers. SUBJECTS: Women aged 54 to 81 years with a femoral neck BMD of 0.68 g/cm2 or less (Hologic Inc, Waltham, Mass) but no vertebral fracture; 4432 were randomized to alendronate or placebo and 4272 (96%) completed outcome measurements at the final visit (an average of 4.2 years later). INTERVENTION: All participants reporting calcium intakes of 1000 mg/d or less received a supplement containing 500 mg of calcium and 250 IU of cholecalciferol. Subjects were randomly assigned to either placebo or 5 mg/d of alendronate sodium for 2 years followed by 10 mg/d for the remainder of the trial. MAIN OUTCOME MEASURES: Clinical fractures confirmed by x-ray reports, new vertebral deformities detected by morphometric measurements on radiographs, and BMD measured by dual x-ray absorptiometry. RESULTS: Alendronate increased BMD at all sites studied (P<.001) and reduced clinical fractures from 312 in the placebo group to 272 in the intervention group, but not significantly so (14% reduction; relative hazard [RH], 0.86; 95% confidence interval [CI], 0.73-1.01). Alendronate reduced clinical fractures by 36% in women with baseline osteoporosis at the femoral neck (>2.5 SDs below the normal young adult mean; RH, 0.64; 95% CI, 0.50-0.82; treatment-control difference, 6.5%; number needed to treat [NNT], 15), but there was no significant reduction among those with higher BMD (RH, 1.08; 95% CI, 0.87-1.35). Alendronate decreased the risk of radiographic vertebral fractures by 44% overall (relative risk, 0.56; 95% CI, 0.39-0.80; treatment-control difference, 1.7%; NNT, 60). Alendronate did not increase the risk of gastrointestinal or other adverse effects. CONCLUSIONS: In women with low BMD but without vertebral fractures, 4 years of alendronate safely increased BMD and decreased the risk of first vertebral deformity. Alendronate significantly reduced the risk of clinical fractures among women with osteoporosis but not among women with higher BMD.

Absorptiometry, Photon↗
PubMedDate not supplied

Epidemiology of congestive heart failure in three ethnic groups.

Congestive heart failure (CHF) is a leading cause of morbidity, disability, and mortality in old age, but little is known about the epidemiology of this condition in free-living minority populations. To determine the prevalence of CHF and associated risk factors in a multiethnic community, a population sample of 2759 elderly (i.e., 65 years of age and older) African American (AA), Hispanic-Cuban (HC), and white non-Hispanic (WNH) men and women from Miami-Dade County, Florida, were examined. There were 153 (5.6%) cases of self-reported CHF in the sample. The unadjusted prevalence rate of CHF was virtually identical among elderly AA (4.8%) and WNH (4.9%) but was significantly (p=0.04) lower than the rate among HC (6.8%). Sex- and ethnic-specific analyses showed that the highest prevalence rate of CHF was among HC women (8.2%). A multiple logistic analysis was used to calculate the odds ratio (OR) and 95% confidence interval (CI) of CHF in relation to age, sex, ethnicity, medical history, and smoking and alcohol drinking habits. Age (65-74 vs. 75-84; OR 1.7; CI 1.2-2.4; p=0.01), HC ethnic group (OR 1.5; CI 1.0-2.4; p=0.05), history of hypertension (OR 1.5; CI 1.1-2.1; p=0.02), history of myocardial infarction (OR 2.3; CI 1.5-3.5; p=0.0001), and history of diabetes mellitus (OR 1.9; CI 1.3-2.8; p=0.001) were directly, significantly, and independently associated with the prevalence of self-reported CHF. The findings here confirm those of prior studies in elderly white US residents, which indicate that heart attack, hypertension, and diabetes mellitus are major risk factors for CHF. The results also show that elderly AA and WNH have similar CHF prevalence rates. The higher CHF prevalence in elderly HC women found in this study requires further investigation. (c)2001 by CHF, Inc.

Journal Article↗