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Biomedical subjects

E Lakatos

Publications and source records attributed to E Lakatos.

35 records · Page 2Linked to original sources
PubMed1990

Management of cardiovascular disease risk factors in children. A national survey of primary care physicians.

A national survey of family physicians, general practitioners, and pediatricians revealed substantial physician differences in managing cardiovascular disease risk factors in children aged 2 to 18 years. Pediatricians tended to screen younger children but were more conservative in treatment. General practitioners tended to screen less and to initiate intervention in older children, but were more aggressive in therapy. While only 9% of surveyed physicians measured blood cholesterol levels routinely, 72% screened children with family histories of cardiovascular disease. The majority routinely measured blood pressure, but the ages of first measurements differed among physicians. Surprisingly, of those who had treated children with elevated blood pressure or blood cholesterol, 54% said that they had ever used antihypertensive and 12% used lipid-lowering drugs in children, including angiotensin converting enzyme inhibitors and clofibrate. Half the surveyed physicians felt prepared to provide dietary counseling, but only 14% felt successful with it. When asked what they considered were the major cardiovascular risk factors, less than one third of the physicians cited all three major factors: hypertension, hypercholesterolemia, and smoking.

Adolescent↗
PubMed1989

Surrogate endpoints in clinical trials: cardiovascular diseases.

A surrogate endpoint in a cardiovascular clinical trial is defined as endpoint measured in lieu of some other so-called 'true' endpoint. A surrogate is especially useful if it is easily measured and highly correlated with the true endpoint. Often the 'true' endpoint is one with clinical importance to the patient, for example, mortality or a major clinical outcome, while a surrogate is one biologically closer to the process of disease, for example, ejection fraction. Use of the surrogate can often lead to dramatic reductions in sample size and much shorter studies than use of the true endpoint. We discuss several problems common in trials with surrogate endpoints. Most important is the effect of missing data, especially in the face of informative censoring. Possible solutions are the assignment of scores or formal penalties to missing data.

Cardiovascular Diseases↗
PubMed1989

The Systolic Hypertension in the Elderly Program (SHEP): an intervention trial on isolated systolic hypertension. SHEP Cooperative Research Group.

The Systolic Hypertension in the Elderly Program (SHEP) is a randomized double-blind placebo-controlled trial to determine if antihypertensive treatment of isolated systolic hypertension (ISH) [systolic blood pressure (SBP) greater than or equal to 160 mmHg, diastolic blood pressure (DBP) less than 90 mmHg] reduces the 5 year incidence of fatal and nonfatal stroke. Between March 1, 1985 and January 15, 1988, 4736 persons (target 4800) with ISH, age 60 years and over, were enrolled. Potential participants met blood pressure (BP) and age criteria. Those on antihypertensive medication prior to enrollment without documented diastolic hypertension had their medication tapered and discontinued, and then met BP criteria (33% of cohort). Stepped-care therapy with chlorthalidone and atenolol (alternative, reserpine) or matching placebos was initiated as first and second steps. At baseline the trial population was 43.1% male, 56.9% female; 13.9% black, 86.1% non-black. Also, the mean age was 71.6 years; the mean SBP was 170.3 mmHg and the mean DBP was 76.6 mmHg; 59.8% had codeable resting electrocardiographic abnormalities. The trial is now in follow-up phase with scheduled termination in 1991.

Aged↗
PubMed1988

Sample sizes based on the log-rank statistic in complex clinical trials.

The log-rank test is frequently used to compare survival curves. While sample size estimation for comparison of binomial proportions has been adapted to typical clinical trial conditions such as noncompliance, lag time, and staggered entry, the estimation of sample size when the log-rank statistic is to be used has not been generalized to these types of clinical trial conditions. This paper presents a method of estimating sample sizes for the comparison of survival curves by the log-rank statistic in the presence of unrestricted rates of noncompliance, lag time, and so forth. The method applies to stratified trials in which the above conditions may vary across the different strata, and does not assume proportional hazards. Power and duration, as well as sample sizes, can be estimated. The method also produces estimates for binomial proportions and the Tarone-Ware class of statistics.

Clinical Trials as Topic↗
PubMed1987

A familial basis for the heterogeneity in coronary atherosclerotic disease.

Miniature swine fed a high-cholesterol, high-fat diet demonstrated heterogeneity in the extent of coronary artery disease. Plasma cholesterol or lipoprotein concentrations as well as other known risk factors accounted for little of this heterogeneity. However, the majority of the variability could be accounted for by the familial predisposition to develop cardiovascular disease in the individual animal kindreds. This study strongly suggests that the enhanced rate of development of coronary atherosclerotic disease during hypercholesterolemia is more critically modulated by previously unrecognized genetic actors than by absolute plasma cholesterol concentrations.

Animals↗
PubMed1987

Influence of cigarette smoking on lung function at baseline and at follow-up in 14 years: the Framingham Study.

Cross-sectional and prospective associations between lung function and potential determinants were examined in the Framingham Study. Personal characteristics of interest were body height and weight, hand grip strength, smoking habits, history of respiratory symptoms and disease, and hematocrit. Baseline pulmonary function was the most powerful indicator of future FEV1, and cigarette smoking was the most important correctable influence. In addition to baseline FEV1, FVC and smoking habits, the important predictors of future lung function were age, relative weight, respiratory symptoms and hematocrit. There was a higher follow-up FEV1 in those who quit smoking compared to those who continued even after adjustment for other associated variables. Relative weight and hematocrit were associated with FEV1 measured 14 years after baseline (directly for relative weight and inversely for hematocrit).

Adult↗
PubMed1987

Three year anatomic, functional and clinical follow-up after successful percutaneous transluminal coronary angioplasty.

Because the long-term anatomic effects of percutaneous transluminal coronary angioplasty are unknown, follow-up evaluations including coronary angiography, treadmill exercise testing and rest and bicycle exercise radionuclide angiography were performed in 46 patients 6.3 +/- 2.0 and 37.6 +/- 3.6 (mean +/- SD) months after they had undergone successful single lesion angioplasty. The severity of the coronary stenosis decreased significantly at each evaluation; the mean diameter stenosis was 66 +/- 13% before angioplasty, 30 +/- 13% immediately after and 26 +/- 16% and 19 +/- 13% at 6 months and 3 years, respectively. Exercise time increased from 9.8 +/- 4.4 minutes before angioplasty to 18.3 +/- 4.5 minutes immediately after the procedure and remained at that level at 6 months (20.3 +/- 4.6 minutes) and 3 years (18.2 +/- 4.5 minutes). Left ventricular ejection fraction during exercise decreased 4 +/- 6% compared with rest before angioplasty, but increased 7 +/- 7% immediately after angioplasty and this increase was maintained at 6 months (+/- 6 +/- 7%) and 3 years (+/- 4 +/- 6%). Before angioplasty, 1 patient was in Canadian Heart Association functional class 0, 15 were in class II, 24 in class III and 6 in class IV. Three years later, 25 were in class 0, 10 in class I, 7 in class II and 4 in class III. These results indicate that the short-term anatomic and functional success of coronary angioplasty is maintained for at least 3 years.

Adult↗
PubMed1986

Sample size determination in clinical trials with time-dependent rates of losses and noncompliance.

Sample size determination is an important part of planning for clinical trials. During the course of a typical clinical trial, people are lost because of competing risks, noncompliance, and the like. Event rates available to the trial designers usually do not take these losses into consideration so that adjustment of these rates is necessary for sample size calculation. This article presents a method of adjusting such rates in the presence of time-dependent rates of losses, noncompliance, and the like. Lag in the effectiveness of medication is also considered.

Clinical Trials as Topic↗
PubMed1986

Hypertension detection, treatment, and control in the United States: not as bad as it seems?

A 1982 report from the National Center for Health Statistics presents rates of awareness, treatment, and control among US adult hypertensives. These rates are age-adjusted by the direct method to permit comparisons among three surveys of US adults conducted over 20 years. The choice of a standard population for the age adjustment, however, results in a systematic decrease in the adjusted rates for awareness, treatment, and control. This decrease leads the casual reader of this often quoted report to conclude that awareness, treatment, and control of hypertension are worse than they actually are. An alternative choice for the standard population is suggested when the inference population is hypertensives rather than the general population.

Adult↗
PubMed1985

The association of LDL receptor activity, LDL cholesterol level, and clinical course in homozygous familial hypercholesterolemia.

Patients with homozygous familial hypercholesterolemia (FH), reveal a marked heterogeneity in plasma cholesterol levels, response to diet as well as drug treatment, and clinical course. Low-density lipoprotein (LDL) receptor activities were assessed by the rate of 14C-oleate cholesteryl ester biosynthesis in fibroblasts from 13 FH homozygotes in tissue culture. The receptor activity of the individual patients was highly correlated with initial pretreatment plasma cholesterol and LDL cholesterol levels (P less than .001, r = -0.89). In addition, the LDL receptor activity was positively correlated with the age of onset of angina based on the Cox model (P less than .035, likelihood ratio = 6.71). An association was also noted between LDL receptor activity and cholesterol reduction with drugs. These data provide direct evidence for the correlation between the heterogeneity of the LDL receptor and the expression of the clinical manifestations of homozygous FH. The determination of pretreatment plasma cholesterol level and LDL receptor activity in patients with homozygous FH provide useful parameters on which to base predictions of the clinical progression of cardiovascular disease. These parameters may also influence the selection of a program for diet and drug therapy. Patients with markedly elevated plasma cholesterol levels and very low LDL receptor activity should be considered to be candidates for multiple drug therapy, and portacaval shunt, and/or periodic plasma exchanges.

Adolescent↗
PubMed1985

Survival and functional results after valve replacement for aortic regurgitation from 1976 to 1983: impact of preoperative left ventricular function.

Recent studies suggest that preoperative left ventricular function may no longer be an important determinant of survival or functional results after operation for aortic regurgitation because of improved operative techniques. To assess the effect of left ventricular function on prognosis in the current surgical era, we performed echocardiographic and radionuclide angiographic studies in 80 consecutive patients undergoing valve replacement from 1976 to 1983. No patient had associated coronary artery disease. For all patients, 5 year survival was 83 +/- 5%, significantly better than the 62 +/- 9% 5 year survival in our patients operated on from 1972 to 1976. Preoperative resting left ventricular ejection fraction (p less than .001), fractional shortening (p less than .001), and end-systolic dimension (p less than .01) were the most significant predictors of survival (univariate life-table analysis). Five year survival was 63 +/- 12% in patients with subnormal ejection fraction (n = 50) compared with 96 +/- 3% in those with normal ejection fraction (n = 30). Patients with subnormal left ventricular ejection fraction and poor exercise tolerance or prolonged duration of left ventricular dysfunction (greater than 18 months) comprised the high-risk subgroup (5 year survival 52 +/- 11%). Patients in this subgroup also had persistent left ventricular dysfunction after operation, with greater left ventricular end-diastolic dimensions and reduced ejection fraction (both p less than .001) compared with patients with normal preoperative left ventricular ejection fraction or a brief duration of left ventricular dysfunction (less than 14 months). Cold hyperkalemic cardioplegia was used for myocardial preservation in 46 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1984

Exercise-induced ischemia in mildly symptomatic patients with coronary-artery disease and preserved left ventricular function. Identification of subgroups at risk of death during medical therapy.

To determine prospectively whether the severity of reversible left ventricular ischemia provides prognostic information in mildly symptomatic patients with coronary-artery disease and preserved left ventricular function at rest (ejection fraction greater than 40 per cent), we studied 117 patients by means of exercise electrocardiography and radionuclide angiography. No patient had stenosis of the left main coronary artery. Mortality during subsequent medical therapy was significantly associated (by univariate life-table analysis) with three-vessel coronary-artery disease and the magnitude of the ejection fraction during exercise. In patients with three-vessel disease who had both ST-segment depression of 1 mm or more and a decrease in ejection fraction during exercise, in association with an exercise tolerance of 120 W or less, the probability of survival at four years was only 71 +/- 11 per cent (S.E.). All deaths occurred in this subgroup. Thus, objective evidence of left ventricular ischemia during exercise and exercise capacity identify one subgroup of minimally symptomatic patients with three-vessel disease with an excellent prognosis and another subgroup at relatively high risk of dying during subsequent medical therapy.

Adult↗
PubMed1984

Importance of the lower respiratory tract in oxygen transfer. Exercise testing in patients with interstitial and destructive lung disease.

Evaluation of the gas exchange responses to steady state treadmill exercise of 176 patients with chronic disorders of the lower respiratory tract demonstrated that alveolar disease significantly affects O2 transfer with little effect on CO2 transfer. At exercise levels requiring oxygen delivery 2- to 3-fold above resting levels, patients with interstitial lung disease [idiopathic pulmonary fibrosis (IPF), sarcoidosis, histiocytosis-X (HX)] and "pure" destructive lung disease [alpha l-antitrypsin (alpha IAT) deficiency] demonstrated no ventilation or cardiac limitation, but all exhibited marked reductions in O2 transfer. Strikingly, although resting values of PaO2 were normal or mildly reduced, the average estimated PaO2 at a VO2 of 1 L/min was 47 mmHg in IPF, 65 mmHg in sarcoid, 54 mmHg in HX, and 41 mmHg in alpha IAT deficiency. Comparison of resting and exercise parameters revealed that: (1) exercise studies can uncover alveolar dysfunction in the presence of normal resting parameters, and (2) resting parameters cannot predict the magnitude of O2 related abnormalities induced by exercise. These observations suggest that exercise testing is a useful clinical tool in detecting alveolar disease and gauging the magnitude of abnormalities of O2 transfer.

Adult↗
PubMed1984

Risk of chronic obstructive pulmonary disease. Collaborative assessment of the validity of the Tecumseh index of risk.

Predictors of chronic obstructive pulmonary disease (COPD) have been identified in the prospective epidemiologic study of the population of Tecumseh, Michigan. Risk of developing COPD within 10 yr can be estimated from a profile that includes as risk factors age, sex, cigarette smoking habits, and forced expiratory volume in one second (FEV1). The index of risk placed 63% of male incidence cases and 64% of female incidence cases in the top 10% of the risk distribution and 81% of male and 86% of female COPD cases in the top 20% of the risk distribution for Tecumseh. The validity of the Tecumseh index of risk for other populations was determined in a collaborative investigation of data collected in longitudinal epidemiologic studies in Baltimore, Boston, Framingham, Louisiana, Staveley, and Tucson. The extent to which the risk model fitted these data sets was assessed by comparing predicted (or expected) onsets of COPD in each population with observations made in each study. The predictors of COPD identified in Tecumseh were shown to be the most important risk factors in the other populations as well. The goodness-of-fit of the index was satisfactory overall. In all populations, a high risk score was associated with an increased incidence of COPD, thus confirming the predictive ability of the risk index. The Tecumseh index of risk provides a practical method for developing a risk profile from answers to standard questions and simple tests of lung function. Risks are greatest for heavy cigarette smokers with reduced lung function, lower in smokers who stop smoking or reduce their cigarette consumption, and lowest of all in nonsmokers with above average lung function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Selective removal of sickle cells with the IBM 2997 continuous flow blood cell separator.

Partial red cell exchange transfusion is used to manage several complications of sickle cell anemia. Reports have stressed the safety, ease, and speed of red cell exchange procedures performed with blood cell separators, but little information exists concerning operating conditions for the most efficient removal of hemoglobin S (HbS) containing cells. We performed 13 red blood cell exchange transfusions with the IBM 2997 continuous flow blood cell separator on two previously transfused adult homozygous (SS) sickle cell patients. We used both a single stage and a dual stage disposable pathway and varied rotor speed, collection port, and collection interface independently. The patients' baseline percentage HbS ranged from 28 to 64% (mean = 46%); post exchange values ranged from 19.1 to 46% (mean = 32%). Thirty-three of 34 specimens collected from the white cell or platelet port showed a higher percentage of HbS in the collection line compared to simultaneous patient samples. Mean enrichment was 9.4% (range = -4.0 to 35.5%). There was an inverse relationship between the hemoglobin concentration and the percentage of HbS in the collected specimens (p = 0.001; N = 45). Differential separation of sickle cells should decrease the volume of blood required for partial red cell exchange of selected SS patients.

Anemia, Sickle Cell↗
PubMed1983

Detection in human serum by radioimmunoassay of histidyl-proline diketopiperazine, a metabolite of thyrotropin-releasing hormone.

Cyclo(His-Pro) is believed to be a metabolite of TRH. A specific antiserum directed against cyclo(His-Pro) was used to detect immunoreactive material in human serum. Gel filtration column chromatography was used to establish that cyclo(His-Pro)-like immunoreactivity was found not only in free form established to be identical to cyclo(His-Pro) by high pressure liquid chromatography analysis on reverse phase and cation exchange columns, but also in a fraction of about 100,000 mol wt. Free cyclo(His-Pro) was released by heating column fractions of 70,000 mol wt that were not immunoreactive before heating. A procedure for estimation of the content of free cyclo(His-Pro) in human serum was developed. Normal levels of cyclo(His-Pro) determined by this procedure were in the range of 11-33 pmol/ml. The level of cyclo(His-Pro) in sera of individuals with hypothyroidism, hyperthyroidism, or alcoholic cirrhosis was in the normal range, while patients with renal failure had approximately 3-fold elevated levels of the peptide. Analysis of human sera drawn at 3-h intervals over a 24-h period suggested a circadian rhythm of cyclo(His-Pro) levels.

Animals↗