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Biomedical subjects

D G Meyers

Publications and source records attributed to D G Meyers.

At least 19 recordsLinked to original sources
PubMed1997

Possible association of a reduction in cardiovascular events with blood donation.

BACKGROUND: The iron hypothesis suggests that females are protected from atherosclerosis by having lower iron stores than men, thus limiting oxidation of lipids. OBJECTIVE: To test the iron hypothesis by comparing cardiovascular event rates in whole blood donors compared with nondonors. DESIGN: Prospective cohort with telephone survey follow up. SETTING: The State of Nebraska, USA. PARTICIPANTS: A sample was selected from the Nebraska Diet Heart Survey (NDHS) restricting for age > or = 40 years and absence of clinically apparent vascular diseases at time of enrollment in to NDHS (1985-87). MAIN OUTCOME MEASURES: The occurrence of cardiovascular events (myocardial infarction, angina, stroke), procedures (angioplasty, bypass surgery, claudication, endarterectomy), nitroglycerin use, or death (all cause mortality), and level of blood donation. RESULTS: Participants were 655 blood donors and 3200 non-donors who differed in education, physical activity, diabetes, and frequency of antihypertensive treatment; 889 were lost to follow up. Sixty four donors and 567 non-donors reported cardiovascular events (crude odds ratio = 0.50, 95% confidence interval (CI) 0.38-0.66). The benefit of donation was confined to non-smoking males (adjusted odds ratio 0.67, 95% CI 0.45-0.99). Benefit was limited to current donors (the most recent three years). No additional benefit resulted from donating more than once or twice over three years. CONCLUSION: In support of the iron hypothesis, blood donation in non-smoking men in this cohort was associated with reduced risk of cardiovascular events. A randomised clinical trial is warranted to confirm these findings as the observed personal health benefit of donation has public policy ramifications.

Adolescent↗
PubMed1997

The usefulness of diagnostic tests on pericardial fluid.

STUDY OBJECTIVES: To determine the physical, chemical, and cellular characteristics of pericardial fluid in various disease states and to assess their diagnostic accuracies. SETTING: A metropolitan university hospital. DESIGN: Consecutive case series. PATIENTS: One hundred seventy-five hospital patients, aged 1 month to 87 years, who had undergone pericardiocentesis (n = 165) or control subjects who had undergone open heart surgery (n = 10) between 1984 and 1996. MEASUREMENTS: The appearance of pericardial fluid and results of chemistry tests, cell counts, cytologic studies, Gram's stain, and microbial cultures were obtained by chart review. The etiology of each pericardial fluid sample was determined using prospective diagnostic criteria. RESULTS: Exudates differed from transudates by higher leukocyte counts and ratios of fluid to serum lactate dehydrogenase levels. Fluid glucose levels were significantly less in exudates. Sensitivity for detecting exudates was high for specific gravity > 1.015 (90%), fluid total protein > 3.0 g/dL (97%), fluid to serum protein ratio > 0.5 (96%), fluid lactate dehydrogenase ratio > 0.6 (94%), and fluid to serum glucose ratio < 1.0 (85%). None of these indicators were specific. Fluid total protein and specific gravity were moderately correlated (r = 0.56). Fluid cytologic study had a sensitivity of 92% and specificity of 100% for malignant effusion. No other test was diagnostic for a specific etiology. Among infection-associated effusions, culture-positive fluid had more neutrophils, higher lactate dehydrogenase levels, and lower ratios of fluid to serum glucose than culture-negative (parainfective) fluid. CONCLUSIONS: Evaluation of pericardial fluid might be limited to cell count, glucose, protein, and lactate dehydrogenase determinations plus bacterial culture and cytology. While not used routinely, other tests that may be highly specific for particular diseases should be ordered only to confirm a high clinical suspicion.

Adolescent↗
PubMed1996

Safety of antioxidant vitamins.

As a result of the many scientific and popular press reports of the benefits of antioxidant vitamins (vitamin A, beta-carotene, vitamin E, and ascorbic acid), it is estimated that 40% of the US population is consuming vitamin supplements. The efficacy of these supplements is not yet proved, and some have questioned their safety. Approximately 10 to 15 cases of vitamin A toxic reactions are reported per year in the United States, usually at doses greater than 100,000 IU/d. No adverse effects have been reported for beta-carotene. The frequency of vitamin E toxic reactions is not well delineated, but case reports are few at dosages less than 3200 mg/d. Ascorbic acid toxic reactions are rare at dosages less than 4 g/d. Despite a lack of clinical trial data, it seems that antioxidant vitamins are safe, although prudence might dictate their avoidance by women of childbearing potential, persons with liver disease or renal dysfunction, and those taking certain medications or undergoing specific laboratory tests.

Antioxidants↗
PubMed1996

The iron hypothesis--does iron cause atherosclerosis?

Women experience only 30-50% of the coronary heart disease (CHD) incidence and mortality of age-matched men. Since oxidation of low-density lipoprotein (LDL) cholesterol is important in atherosclerosis, and oxidation is catalyzed by iron, it has been hypothesized that the lower iron stores of women reduce their risk of CHD through lessened lipid peroxide. The biochemistry of oxidation is well described in the literature and involves iron as a catalyst in the formation of powerful free radicals which subsequently modify LDL cholesterol. Chelating iron with desferrioxamine stops oxidation. Iron is present in atherosclerotic gruel and this gruel stimulates lipid peroxidation. Serum deficient in iron has minimal oxidative capacity which increases with iron repletion. At least seven epidemiologic studies have found a positive association between CHD and various indicators of body iron. Conversely 18 epidemiologic studies have found a negative or no association. While biochemically appealing, the iron hypothesis remains unproven.

Adult↗
PubMed1996

Prevalence and correlates of symptomatic peripheral atherosclerosis in individuals with coronary heart disease and cholesterol levels less than 240 mg/dL: baseline results from the Cholesterol and Recurrent Events (CARE) Study.

PURPOSE: To determine the prevalence and correlates of symptomatic peripheral atherosclerosis in individuals with a history of myocardial infarction (MI) and cholesterol levels lower than 240 mg/dL. MATERIALS AND METHODS: A cross-sectional analysis was conducted at baseline of 4159 participants in the Cholesterol and Recurrent Events (CARE) Study. Symptomatic diffuse atherosclerosis was defined as a history of MI plus lower extremity or cerebrovascular atherosclerosis or claudication by Rose questionnaire. RESULTS: The prevalence of symptomatic diffuse atherosclerosis was 12.9%; 353 participants (8.5%) had lower extremity disease and 219 (5.3%) had cerebrovascular disease. After controlling for other variables, diffuse atherosclerosis was associated with age (Odds Ratio [OR] = 1.44 per ten-year increase), systolic blood pressure (OR = 1.13 per 10 mm Hg increase), a history of multiple myocardial infarctions (OR = 1.76), diabetes (OR = 1.76), hypertension (OR = 1.38), reduced exercise performance (OR = 1.55), current smoking status (OR = 2.87), and lower alcohol intake (OR = 0.97 per drink per week). There was no association with race, gender, or lipid levels. CONCLUSIONS: The presence of clinically evident diffuse atherosclerosis is common and is associated with several modifiable risk factors. Early identification of these individuals could affect treatment and clinical outcomes.

Anticholesteremic Agents↗
PubMed1996

Do physicians' beliefs about coronary risk factors account for poor screening and treatment rates?

The authors hypothesized that the widely observed low rates of coronary risk factor screening and treatment among cardiologists could be due to lack of belief in the importance of risk factors. They performed an audit of 160 randomly selected medical records of patients with coronary artery disease and surveyed the attending physicians' ranking of importance of individual risk factors to determine the extent of risk factor screening and treatment done by these physicians. Screening and treatment rates for individual risk factors were highly variable but generally well below expected. There was no correlation among rank orders of screening rates, treatment rates, and physician-rated importance of each risk factor. These results suggest that lack of belief in risk factor importance does not explain failure of physicians to screen for and treat risk factors in coronary patients.

Adult↗
PubMed1995

Effect of vitamin C on plasma lipids.

OBJECTIVE: To review the effects of vitamin C (ascorbic acid) on plasma lipid concentrations, and to address the proposed mechanisms through which vitamin C may potentially alter lipid concentrations. DATA SOURCE: A MEDLINE search was performed to identify pertinent English-language literature including studies, abstracts, and review articles. Key search terms were vitamin C, ascorbic acid, lipoproteins, lipids, and atherosclerosis. STUDY SELECTION AND DATA EXTRACTION: Studies examining the relationships between vitamin C and plasma lipid concentrations including animal, observational, and clinical trials were selected. Because there were no large randomized, controlled clinical trials, data were extracted from all clinical trials, regardless of design. Review articles discussing the effects of vitamin C on plasma lipid concentrations and the atherosclerotic process also were included. Pertinent information, as judged by the authors, was extracted for discussion. DATA SYNTHESIS: Evidence suggests an inverse relationship between vitamin C intake and the development of atherosclerosis, although the effect has not yet been proven in clinical trials. It has been postulated that this effect might be mediated not only through the antioxidant properties of vitamin C, but also through a plasma lipid-modifying effect. Data from animal and observational trials suggest that high vitamin C concentrations may correlate negatively with concentrations of total cholesterol, triglycerides, and low-density lipoproteins and positively with high-density lipoproteins. Other studies, however, have not confirmed these findings. Similarly, results from clinical trials have been widely variable and inconclusive. CONCLUSIONS: Analysis of the literature suggests an association between vitamin C and plasma lipid concentrations and a potential role in slowing the development of atherosclerosis. Significant variations and inadequacies in trial design, however, prohibit definitive conclusions. On the basis of these preliminary data, it appears that there is justification for additional well-designed trials to further evaluate the relationship between vitamin C and plasma lipid concentrations.

Animals↗
PubMed1993

So much writing, so little science: a review of 37 years of literature on edetate sodium chelation therapy.

OBJECTIVE: To determine the safety and efficacy of edetate sodium (ethylenediamine tetraacetic acid; EDTA) chelation therapy for atherosclerosis. METHODS: Literature search using MEDLINE, encompassing 1966 through May 1993. Further references were obtained from articles and books, and from citations obtained from the American Academy of Medical Preventics. RESULTS: 16 case reports or case series, 2 longitudinal studies, and 3 clinical trials were reviewed, along with testimonials cited in 19 books. CONCLUSIONS: Little valid scientific evidence is available. Although the postulated mechanisms of action for EDTA are biologically plausible and EDTA appears to be safe, it has not been proven effective. Indeed, the best evidence shows it to be ineffective. Therefore, EDTA chelation therapy should not be used in clinical practice to treat atherosclerosis.

Arteriosclerosis↗
PubMed1993

Electrocardiographic changes in pericardial effusion.

OBJECTIVE: To investigate the association between ECG changes and the presence of pericardial effusion. BACKGROUND: The ECG changes associated with pericardial effusion described in textbooks are based only on small series of human cases and data from animals. These changes include low QRS voltage, electrical alternans, P wave changes, and T wave inversion. METHODS: All patients who had undergone 2 temporally separate echocardiographic and ECG examinations, with 1 echocardiographic examination indicating the presence and the other indicating the absence of pericardial effusion were identified (n = 46). These patients were age- and sex-matched to 46 patients without effusion (control subjects). Pericardial effusion was classified echocardiographically as small (n = 28), moderate (n = 13), and large (n = 5). The ECG variables were independently measured by two investigators blinded to effusion status. RESULTS: When 2 temporally separate ECGs for 46 patients were obtained in a repeated-measures fashion (1 obtained during the absence and the other during the presence of effusion; median time interval, 1.24 months), only the mean heart rate in patients with sinus rhythm (98 beats per minute increasing to 106 beats per minute) and the percentage of patients with QRS voltage of less than 0.5 mV (10 percent increasing to 22 percent) were associated with the development of effusion. A weak correlation (r = 0.296) was noted between QRS voltage and effusion size. Electrical alternans occurred only in one of the five patients with a large effusion but in no others. In addition, when the ECGs indicating effusion from the 46 patients were compared with the ECGs from their age- and sex-matched control subjects, differences in heart rate (106 beats per minute vs 80 beats per minute, respectively) and small changes in QRS voltage were associated with effusion status. No ECG variable was sensitive for the detection of pericardial effusion. CONCLUSIONS: In both repeated-measures and case-control comparisons, ECG findings are two few, subtle, insensitive, and nonspecific to be useful as indicators of the presence of pericardial effusion.

Adult↗
PubMed1992

Effect of exercise level on the diagnostic accuracy of thallium-201 SPECT scintigraphy.

The sensitivity of electrocardiographic ST analysis for detecting coronary artery disease is markedly decreased in patients unable to exercise vigorously. To determine the diagnostic accuracy of Thallium-201 SPECT scintigraphy at various exercise levels, we evaluated 179 patients without evidence of prior myocardial infarction or other confounding factors who performed symptom-limited exercise with Thallium-201 SPECT scintigraphy. Sensitivity decreased from 89% in those patients achieving greater than or equal to 85% of maximal heart rate to 63% in those achieving less than 65%. Like ST segment analysis, Thallium 201 SPECT scintigraphy has decreased diagnostic yield at low levels of exertion.

Aged↗
PubMed1991

Tissue plasminogen activator release and plasminogen activator inhibitor levels in coronary artery disease.

Unstable angina and Q wave myocardial infarction are associated with intraluminal coronary thrombosis, a process to which impaired fibrinolysis may contribute. The authors examined the extrinsic fibrinolytic system, including tissue plasminogen activator antigen, plasminogen activator inhibitor activity and antigen, and euglobulin clot lysis time before and after venous occlusion in 56 patients undergoing coronary angiography for chest pain syndromes and in 16 healthy controls. Fibrinolysis variables were similar (with greater than 95% confidence) in the patients with thrombus-associated coronary syndromes as compared with those with chest pain syndromes not due to coronary thrombosis. These fibrinolytic variables were also similar to those in patients without coronary artery disease and in healthy controls. Their data suggest that defective fibrinolysis is not involved, at least systemically, in the pathogenesis of thrombus-associated coronary artery syndromes.

Coronary Disease↗