[AIDS. Response to the letter by P. Kammerlander et al. on the subject of our article: HIV epidemic: the end of a special law?].
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Acquired Immunodeficiency Syndrome↗
Biomedical subjects
W Schreiner
Publications and source records attributed to W Schreiner.
The determinants of elevated total plasma cholesterol levels in cardiac transplant recipients administered low dose cyclosporine for immunosuppression.
Elevated total plasma cholesterol level is a frequent finding after cardiac transplantation. To identify risk factors for the development of hypercholesterolemic states, we applied multivariate statistics in a logistic and linear manner. Six-month posttransplantation levels of total plasma cholesterol in 57 adult heart recipients were available for analysis. Maintenance immunosuppression was carried out with either cyclosporine and azathioprine or both agents plus low-dose steroids. Total plasma cholesterol levels were dichotomized for the logistic analysis (1) by the age- and sex-matched 75th and 90th percentiles of a reference population according to National Institutes of Health treatment guidelines and (2) by the cut point 250 mg/dl. Twelve potential risk factors were evaluated as covariates: recipient age, body weight after 6 months, body weight gain over 6 months, body mass index after 6 months, body mass index gain over 6 months, current cyclosporine dosage, trough level of cyclosporine in whole blood according to high-performance liquid chromatography after 6 months, cumulative cyclosporine dosage over 6 months, serum bilirubin, type of original cardiac disease, maintenance steroids, and steroid bolus treatment. Multivariate logistic regression yielded the type of original cardiac disease as a significant predictor of posttransplantation hypercholesterolemia exceeding the 90th percentile (p = 0.019) and of hypercholesterolemia exceeding 250 mg/dl (p = 0.032). Maintenance steroids were identified as a second significant cofactor (p = 0.069) for total plasma cholesterol levels exceeding 250 mg/dl. Multiple linear regression again revealed the type of original cardiac disease and maintenance steroids as significant predictors by p values of 0.005 and 0.013, respectively. Patients with coronary artery disease as the original cardiac pathology and low-dose maintenance steroids had the greatest risk for the development of elevated total plasma cholesterol levels after cardiac transplantation. However, the overall predictive quality of the linear model was limited (multiple r value 0.43), which indicates that other variables besides the tested ones attributed to elevated total plasma cholesterol levels. These results confirm the adverse role of maintenance steroids on posttransplantation hypercholesterolemia and demonstrate the type of original cardiac disease as the most important risk factor. They suggest that abnormalities of lipoprotein metabolism and dietary factors continue to affect total plasma cholesterol levels after cardiac transplantation.
Adult↗
[The HIV epidemic: the end of special status].
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AIDS Serodiagnosis↗
Computerized acquisition and evaluation of whole blood aggregometry data.
A special-purpose software package has been developed to acquire and analyze analog signals from a whole blood aggregometer. Up to four independent blood samples can be analyzed simultaneously or with arbitrary delays in time. The user menu ensures proper calibration prior to each measurement and provides a real-time graphic display of the signals. From analog/digital converted data, several "derived diagnostic quantities" are calculated. They are constructed with the aim to mimic the process of visual inspection of aggregometry curves and thus place the intuitive diagnostics of blood platelet function on a quantitative basis.
Computer Graphics↗
A beat-by-beat analysis of electrocardiograms from cardiac transplant recipients.
A software system is described for producing a beat-by-beat analysis of the electrocardiograms from patients after heart transplantation. Pacemaker spikes are automatically detected and eliminated from the signals. R waves are located by a robust and accurate two-step algorithm. Based on the variable length of single heart beats, the Fourier coefficients of three orthogonal surface leads and of two intracardiac leads are calculated beat-by-beat. Power spectra are then obtained by combining contributions from the variable fundamental frequency and its multiples (harmonics) into fixed frequency classes of 1 Hz width and averaging over 60-120 cardiac cycles. Additionally, averaged beat-by-beat power spectra are calculated for windowed QRS complexes and T waves. As by-products, single beat quantities, such as R-R and R-T intervals, averaged signals for all leads, and the orientational autocorrelation function of the electrical vector of the heart, are obtained. Following beat-by-beat evaluation, mean values and standard deviations are obtained for all quantities.
Algorithms↗
The influence of sample age on collagen-induced platelet aggregation in whole blood.
Whole blood electrical aggregometry (WBEA) has become an accepted method to gain quick information on platelet disorders. Compared to the optical method WBEA is closer to physiology and less complicated, but on the other hand more difficult to standardize. Different approaches have been attempted in the past to improve the reliability and practicability of this technique. The influence of sample age has not been defined so far. In a first step a mathematical modelling program was established, which is able to characterize the aggregation curves obtained after collagen stimulation. In a mathematical analysis various characteristics of the curve function were calculated and their sensitivity for aging investigated. Regression was performed for each characteristic, and correction factors defined. Our results indicate, that whole blood specimen for collagen induced aggregation can be used without correction factor up to 30 minutes. Data obtained with an age exceeding half an hour have to be corrected following a quadratic regression.
Blood Preservation↗
[The problem of the effectiveness of condoms against HIV infection].
In several countries the condom is recommended as the most important protection against HIV infection, although there is no proof that the condom is effective against sexually transmitted diseases (STD). Prior to the HIV epidemic the condom was used to prevent pregnancy and to decrease the risk of STD. To prevent a deadly infection such as that with HIV, safe ways of protection are mandatory. Recent studies on HIV prevention show the assumption that condoms provide reliable protection against HIV to be a dangerous illusion. In carefully planned studies the residual risk was 13% and 27% and more respectively.
Adult↗
Simulation of coronary circulation with special regard to the venous bed and coronary sinus occlusion.
The vascular beds of the left circumflex and the left anterior descending coronary arteries are modelled by means of coupled differential equations that consider an arterial, a capillary and a venous section. In a stepwise procedure, experimental data from normal coronary perfusion and coronary sinus occlusion are used to assess the model parameters. For venous distensibility, a non-linear form of pressure-volume relationship proved vital to reproduce the characteristics of the rise in venous pressure after the onset of coronary sinus occlusion. Numerical integration was carried out for normal perfusion and for coronary sinus occlusion, yielding time courses of flows, volumes and pressures within large coronary arteries, capillaries and coronary veins. Coronary sinus occlusion reduces total mean flow by 18% and divides intramyocardial flow between the capillaries and the veins into a forward component of 3.03 mls-1 and a backward component of -1.54 mls-1. This result represents a prediction for a haemodynamic quantity which is therapeutically important but inaccessible to measurement. Varying degrees of systolic myocardial squeezing are studied to display the impact of myocardial contractility and vessel collapse on the mean values and phasic components of intra-myocardial flows.
Blood Pressure↗
The role of intramyocardial pressure during coronary sinus interventions: a computer model study.
A model consisting of an arterial, a capillary, and a venous compartment was developed to reproduce experimentally determined hemodynamic results of the arterial and venous sides of the coronary circulation. From the model, intramyocardial flow between capillaries and veins, which is inaccessable to measurement, was then estimated. Results are given for normal perfusion and coronary sinus occlusion conditions. For both conditions, intramyocardial pressure was varied within the model in order to study its impact on intramyocardial flow. For low and moderate intramyocardial pressures under coronary sinus occlusion, retrograde flow from veins to capillaries was seen to increase with increasing intramyocardial pressure. However, for very high values of intramyocardial pressure, which are close to left ventricular pressure, retrograde flow declined.
Computer Simulation↗
[Analysis of the ECG in diagnosis of graft rejection following heart transplantation].
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Electrocardiography↗
Diagnosis of perioperative myocardial infarction by considering relationship of postoperative electrocardiogram changes and enzyme increases after coronary bypass operation.
We report the results of enzyme determinations in sera from 88 patients, 65 of whom showed inconspicuous reconvalescence, 14 who had myocardial infarction within 24 h (MI 1) after bypass surgery, and nine with myocardial infarction between 24 and 48 h postoperatively (MI 2). We wanted to determine whether the consequent measurement of activities of total creatine kinase (CK), CK isoenzyme MB (CK-MB), lactate dehydrogenase, alpha-hydroxybutyrate dehydrogenase, and aspartate aminotransferase, conducted as a part of routine laboratory diagnostics, provided meaningful information for diagnosing infarcts besides that obtained from the electrocardiogram. The postoperative mean values of the enzyme activities in blood were significantly different among the three groups; however, only a combined evaluation of CK and CK-MB by means of a discriminant analysis allowed the prediction of MI (sensitivity: MI 1 = 98.5%, MI 2 = 95.4%; specificity: MI 1 = 71.4%, MI 2 = 81.8%). CK greater than 600 U/L or CK-MB greater than 45 U/L supports the diagnosis of acute MI.
Adult↗
[The extra-anatomic bypass in the therapy of aortoiliacal occlusive disease].
The extra-anatomic bypass procedure is a well accepted alternative to direct aortoiliac reconstruction in high-risk patients or in cases of local inoperability. Between 1980 and 1987 74 patients (54 men, 20 women; mean age = 71 years, 43 to 90) underwent a total of 78 extra-anatomic reconstructions: 23 axillounifemoral, 15 axillobifemoral, 34 femoro-femoral cross-over, 4 axillo-popliteal and 2 femoro-popliteal cross-over bypasses. The operations were performed for severe claudication in 16, rest pain in 27 and gangrene in 26 patients; acute ischaemia was the indication in 6 and acute aortic aneurysms in 2 cases; in 1 patient there was an infected bifurcation graft. At a median follow-up time of 11 months the secondary patency rates for axillofemoral and femoro-femoral cross-over bypasses are predicted to be 75%, 71% and 62% after 1, 3 and 5 years, respectively (Kaplan-Meier estimate); on exclusion of vein and composite grafts, the patency rate increases to 79%, 75% and 65%, respectively. Femoro-femoral cross-over grafts seem to produce better results than axillounifemoral grafts (86% versus 77% at 3 years; logrank p greater than 0.05). The patency of the superficial femoral artery providing good run-off conditions, an appropriate technique for performing the anastomoses and adequate choice of graft material appear to improve the results.
Adult↗
Thromboxane A2 generation by human umbilical endothelial cells.
Human umbilical endothelial cells were examined for their ability to release thromboxane A2 (TXA2) and prostacyclin (PGI2). We could show that the basal, unstimulated release of the two eicosanoids was inversely related to the cell density. At a density of 100,000 cells/cm2 TXA2 release was 0.062 +/- 0.28 fg/cell/h and PGI2 release was 0.184 +/- 0.051 fg/cell/h, whereas at a cell density of 20,000 cells/cm2 the cells released 1.075 +/- 0.055 fg TXA2/cell/h and 1.653 +/- 0.09 fg PGI2/cell/h. In stimulation experiments ATP and ADP significantly (p less than 0.001) increased the TXA2 and the PGI2 release. ANF caused a slow but still significant (p less than 0.001) enhancement of TXA2 release. Thrombin and ionophore A23187 caused the strongest stimulatory response, resulting in a significantly (p less than 0.001) increased release of both eicosanoids.
Data Interpretation, Statistical↗
[Breast-preserving treatment of breast carcinoma].
Based on our 14-year experience with breast-preserving treatment of breast cancer, we recommend limited surgical intervention for the removal of a small mammary carcinoma under the proviso that adequate radiotherapy is available and that the patient can be thoroughly followed up. We are convinced that the good cosmetic result and especially the excellent psychological reaction are particularly important in order that women lose their fear of an ablative operation. Only then, by performing an operation which is not excessive at the earliest possible time can the prognosis of this type of carcinoma, which is increasing be improved.
Breast Neoplasms↗
Software interface between SAS and the GDDM interactive chart utility.
Data from temporary or permanent SAS-data-sets on disk are transferred to the GDDM Interactive Chart Utility (ICU). Within the ICU these data can be displayed graphically, including all features of modification, supported by the ICU. The transfer is accomplished by a user written SAS procedure, which transforms the data from SAS internal format to the structure required to call the ICU from a PL/1 program. The interface provides interactive menu driven graphics from SAS-data-sets without the need to use SAS control language. The implementation refers to the CMS operating system.
Computer Graphics↗
Computation of diagnostic data from coronary sinus pressure: a comparison between two possible models.
We have evaluated two mathematical models to describe the increase in coronary sinus pressure (CSP) following pressure controlled intermittent coronary sinus occlusion (PICSO). The models are evaluated and compared on the basis of human and canine data. Both models were fitted by non-linear least squares algorithms. Next, derived quantities, such as plateau, rise-time and mean integral of the coronary sinus pressure were calculated from the model parameters. Corresponding quantities for the two models were compared with regard to mean values, rate of successful calculation and specific features characterizing the human or canine case. One model was found to be superior for investigational purposes. The other model was found to be more stable in critical situations and is therefore suggested for usage in closed loop regulation of PICSO. Physiologically, the differences in mean values of the derived quantities between the two models were found to be negligible. The formal statistical significance of the differences is but a consequence of the large number of PICSO cycles analysed.
Algorithms↗
Coronary sinus pressure and arterial flow during intermittent coronary sinus occlusion.
The relationship between coronary artery flow and coronary venous pressure during intermittent coronary sinus occlusion was studied in dogs at normal perfusion, left anterior descending artery occlusion, and reperfusion. Coronary sinus occlusion and release phases were varied systematically. The periodicity of the data and the assumption of a linear relationship between pressure and flow suggested Fourier analysis as a methodological approach. To show the systematic slow oscillations of coronary venous pressure and arterial flow induced by intermittent occlusion of the coronary sinus, the data were smoothed by superimposing consecutive cycles of identical occlusion-release timing and filtering the higher frequencies. A small number of Fourier components, corresponding to the time scale of the respective occlusion-release cycle, was sufficient to study the long wavelength behavior. The effect of arbitrarily varying the occlusion-to-release ratio at a given total cycle length was investigated in hypothetical pressure and flow curves based on interpolation of experimental Fourier coefficients. By means of a transfer function relating pressure and flow in the frequency domain, it was possible to predict the arterial flow curve using coronary venous pressure measurements only. Because at zero frequency the pressure-flow relationship cannot be assumed to be linear, the mean value of flow could not be obtained in this way. However, the deviation of flow from the mean, i.e., the shape of the flow curve, was reproduced satisfactorily.
Animals↗
Hemodynamic effects of mexiletine and disopyramide after cardioplegic arrest.
To study the hemodynamic side effects of mexiletine and disopyramide when administered before cardioplegic arrest 15 dogs underwent sham cardiac surgery with a 90-min period of aortic cross-clamping. 5 dogs served as control, 5 were given 8 mg/kg/day mexiletine and another five 11 mg/kg/day disopyramide for 1 week before surgery. On the day of surgery a continuous infusion was started. After reperfusion treated animals exceeded their preischemic blood pressure and regained their preoperative cardiac output. Compared to control animals left ventricular work was higher in the treated animals after reperfusion. The two tested type I antiarrhythmics tend to add to myocardial protection when given before cardioplegic arrest and do not exhibit negative inotropic side effects.
Animals↗