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W Mohl

Publications and source records attributed to W Mohl.

At least 55 records · Page 3Linked to original sources
PubMed1989

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↗
PubMed1989

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↗
PubMed1988

Two level entry concept for analog digital conversion package: usage as blackbox or toolkit.

Analog/Digital conversion of up to 16 channels can be set up and executed interactively with sampling rates individually adjusted for each channel. Additionally, asynchron and parallel digital I/0 is provided, including the possibility of triggering the beginning and the end of data acquisition on an external TTL signal. For non-experienced personnel the package can be run fully interactively with help-menus. Conversely, the experienced user can skip the menu level and directly access the A/D conversion card at the programmers' level in FORTRAN, BASIC or PASCAL. This two level approach considerably enhances the versatility of the package. Data structures in memory and on disk are the same for both levels. Thus, data acquired in menu mode can be compatibly accessed and evaluated from the menu--as well as the programmers' level. Furthermore, a concept is presented for a most efficient and convenient transfer of pre-processed data onto an IBM-mainframe for further analysis in SAS. This transfer scheme allows for continued transparency of the data files, should--for technical reasons or due to changes in the type of data acquired--changes or upgradings of the A/D conversion software become necessary. The package is available for IBM-XT/AT personal computers.

Analog-Digital Conversion↗
PubMed1988

Clinical evaluation of pressure-controlled intermittent coronary sinus occlusion: randomized trial during coronary artery surgery.

Pressure-controlled intermittent coronary sinus occlusion (PICSO) was evaluated in a randomized trial in 30 patients undergoing bypass surgery. PICSO was applied for one hour during early reperfusion. Myocardial function was determined from short-axis cross-sectional views of intraoperative two-dimensional echocardiography. Changes of sectional and segmental wall motion during extracorporeal circulation were analyzed. Although sectional wall motion did not change significantly, hypokinetic segments were preserved better in PICSO-treated patients than in controls (-1.3 +/- 2.4 versus -9.1 +/- 2.6 delta% fractional area change; p less than 0.04). Although not significant, the same trend was found for normal and severely hypokinetic segments. Cumulative enzyme release was related to coronary sinus occluded pressure (r = 0.94; p less than 0.006), indicating washout of metabolites during PICSO. Three months after operation, functional classification was similarly favorable in both groups. Long-term effects of PICSO cannot be predicted because PICSO was applied only during early reperfusion. We conclude that PICSO is a safe procedure and that its short-term beneficial effects on myocardial function suggest a preservation of myocardial viability.

Catheterization↗
PubMed1988

Computation of derived diagnostic quantities during intermittent coronary sinus occlusion in dogs.

The haemodynamic responses to pressure controlled intermittent coronary sinus occlusion (PICSO) were recorded intraoperatively in dogs. After analogue-digital conversion the data for coronary sinus pressure were submitted to numerical analysis for detection of systolic and diastolic envelopes and their subsequent fitting by a non-linear model. From the model variables derived quantities, such as plateau and rise times, were constructed so as to resemble the most important features of coronary sinus pressure rise during each occlusion-release cycle. The derived quantities were then monitored during all consecutive cycles throughout the entire experiment. In each dog the measurements were taken during normal coronary artery perfusion, left anterior descending coronary artery infarction, and reperfusion. The analysis comprise time course, stability, and physiological correlates of the derived quantities, on some of which a closed loop regulation may be based. Predicted plateaus (systolic and diastolic) and mean integrals (systolic and diastolic) were found to be stable quantities which, on subaveraging of about five successive estimates, yielded a 10% accuracy on the mean. By contrast, the rise times required subaveraging of about 15 cycles to achieve the same relative stability. It is concluded that, on subaveraging, derived quantities lend themselves for closed loop regulation input. Thus this quantitative assessment of numerical coronary sinus pressure analysis, as obtained from animal data, may lay the basis for future human application.

Animals↗
PubMed1988

Intermittent coronary sinus occlusion in humans: pressure dynamics and calculation of diagnostic quantities.

Pressure controlled intermittent coronary sinus occlusion (PISCO) was applied in 30 patients undergoing coronary artery bypass surgery. The occlusion and release times were manually adjusted according to visual control of the intraoperatively monitored coronary sinus pressure. In six patients the coronary sinus measurements were additionally digitised with a personal computer before postoperative mathematical analysis, which comprised automatic detection of systolic peaks, diastolic troughs, and the calculation of derived quantities. The purpose of the analysis was (a) to assess quantitatively human coronary sinus pressure dynamics, (b) to determine whether visual control and interpretation of coronary sinus pressure rise could be replaced by a mathematical model, and (c) to ascertain whether the occlusion and release cycle lengths were adequate. Numerical estimates for intraindividual and interindividual spread of calculated quantities were produced, the mathematically obtained results were related to a possible physiological interpretation, and the most efficient method of statistical analysis was ascertained. These results form the numerical basis for a closed loop adjustment of pressure controlled intermittent coronary sinus occlusion cycling.

Aged↗
PubMed1988

Topographic brain mapping of EEG before and after open-heart surgery.

The brain function of 60 patients undergoing open-heart surgery (36 patients receiving coronary artery bypass, 21 patients valve replacements, 3 both) was investigated before and 10 days after the operation utilizing topographic brain mapping of the electroencephalogram (EEG). The postoperative EEG changes were characterized by a slight delta-theta increase, an alpha decrease [especially in the fast alpha (10.5-13 Hz) band] and a beta increase in the relative power. The total power and the absolute power of the delta-theta, alpha and beta showed a decrease, the dominant frequency a significant slowing from 9.7 to 9.3 Hz. The centroid of alpha and beta activity decreased as well. These results are similar to findings obtained in patients with organic brain syndrome. The EEG changes were prominent over the left hemisphere, which may be of particular clinical relevance.

Adult↗
PubMed1987

Model of the haemodynamic reactions to intermittent coronary sinus occlusion.

Coronary sinus pressure data have been obtained from anaesthetized dogs during pressure controlled intermittent coronary sinus occlusion. It is the main aim of this paper to provide a mathematical procedure for modelling the typical time course of sinus pressure after temporary obstruction of the sinus. The model is produced by fitting a parameterized function to the systolic and diastolic pressures in order to represent mathematically the shape of the curves. The parameters characterize the rise in coronary sinus pressure following occlusion, and are used to calculate 'derived quantities' which mimic the physician's visual assessment of trace recordings and their clinical implications in certain forms of coronary sinus pressure reaction. This procedure should be thought of as a kind of pattern recognition which reflects the changing state of the myocardium. The mathematical results are shown to bear a close resemblance to the clinical effects of coronary sinus occlusion.

Animals↗
PubMed1987

Coronary sinus interventions: from concept to clinics.

For almost 100 years the coronary venous system has attracted researchers as an access route to deprived myocardium. Different concepts have been tried and numerous experimental studies have been performed to evaluate whether coronary sinus occlusion, retroinfusion, and retroperfusion of arterial blood via the coronary sinus represent an effective treatment of myocardial ischemia. The early successful studies of Drs. Gregg, Eckstein, Beck and others led to the application of the Beck II procedure, a permanent retroperfusion technique used in the early 1950s to revascularize patients with diffuse atherosclerosis. The coronary sinus route was also used to retroperfuse blood intraoperatively during opening of the heart to keep the heart beating. Excessive mortality and severe side effects, such as myocardial edema and hemorrhage, and an insufficiently advanced technology resulted in the temporary demise of the coronary sinus approaches. Recently, however, the need to improve myocardial protection, despite enormous advances in coronary bypass surgery and interventional cardiology, has resulted in renewed interest in the coronary sinus as an access route to deprived myocardium. Advances in technology such as percutaneous catheter techniques have improved access to the coronary venous system and allowed for a physiological adaptation of coronary sinus retroperfusion techniques. Today the three major coronary sinus techniques, i.e., sychronized retroperfusion (SRP), retroinfusion of cardioplegia during cardiac arrest and retroinfusion of pharmaceutical agents in the normal working heart, and pressure-controlled intermittent coronary sinus occlusion (PICSO) have been documented as providing superior protection of jeopardized myocardium in selected subsets of patients. All of these techniques currently are under clinical consideration; the retroinfusion of cardioplegia has already found wide clinical acceptance, SRP and PICSO have only recently been tested in first clinical trials. Due to a vast resurgence in interest, it is desirable to survey the results obtained with each of these techniques, to discuss the pathophysiology and mode of action of coronary sinus interventions, and to assign them a place in the perspective of conventional therapies. Furthermore, an attempt will be made to weigh individual coronary sinus techniques against each other, discuss in which clinical settings each of them may be most effective, and define issues facing current development.

Animals↗
PubMed1987

Retrograde cardioplegia via the coronary sinus.

The coronary sinus, collecting about 70% of the venous blood draining the myocardium lends itself particularly well to retrograde concepts of cardioplegia. It has been gaining wide acceptance as a safe means of access to the myocardium in the presence of atherosclerotic disease and as an important modality in providing a more homogeneous distribution of cardioplegic delivery. This article attempts to review all knowledge available on the pathophysiology of retroinfusion of cardioplegia as well as the state of the art of the technique involved. A new concept is being presented, which, in the form of antegrade delivery with postcapillary redistribution, this achieved either by pressure elevation of the venous effluent or pressure-controlled intermittent coronary sinus occlusion (PICSO), takes advantage of both antegrade and retrograde concepts. First experimental results suggest great potential for this combined approach in the effective delivery of cardioplegia.

Coronary Vessels↗
PubMed1986

Analysis of coronary-sinus-occlusion pressure by iterating the convolution integral.

Intermittent coronary sinus occlusion (ICSO) has been shown to reduce infarct size and to improve regional myocardial function. Since the efficiency of the procedure is closely related to proper intervals of occlusion and release of the coronary sinus, the reactions of coronary haemodynamics to this intervention have to be investigated. Coronary sinus pressure measurements obtained from anaesthetized dogs are analysed for three different conditions: normal coronary perfusion, experimentally induced infarction of the LAD performed according to a specific time pattern. The mathematical modelling of the coronary sinus pressure (CSP) reaction upon ICSO is accomplished by a convolution integral, incorporating a memory function g(x). With the aid of a numerical technique this function is evaluated to reproduce the measured data as closely as possible. Since g(x) describes the CSP response in a universal manner it can serve subsequently to predict reactions to different occlusion and release patterns not actually measured. This use of a mathematical model may provide economical paths for future investigations by avoiding prohibitively large numbers of animal studies. For different physiological states; normal perfusion, infarction and reperfusion; we obtained different memory functions. These differences in g(x) are then shown to be precisely related to known characteristics of the normal and diseased state of the myocardium. Understanding the link between cardiovascular physiology and its mathematical representation is seen as an important aid in the selection of therapeutic interventions.

Animals↗
PubMed1985

Effects of pressure-controlled intermittent coronary sinus occlusion on regional ischemic myocardial function.

Pressure-controlled intermittent coronary sinus occlusion has been reported to reduce infarct size in dogs with coronary artery occlusion, possibly because of increased ischemic zone perfusion and washout of toxic metabolites. The influence of this intervention on regional myocardial function was investigated in open and closed chest dogs. In six open chest dogs with severe stenosis of the left anterior descending coronary artery and subsequent total occlusion, a 10 minute application of intermittent coronary sinus occlusion increased ischemic myocardial segment shortening from 5.5 +/- 1.2 to 8.2 +/- 2.6% (NS) and from -0.1 +/- 2.1 to 2.3 +/- 1.2% (NS), respectively. In eight closed chest anesthetized dogs, intermittent coronary sinus occlusion was applied for 2.5 hours between 30 minutes and 3 hours of intravascular balloon occlusion of the proximal left anterior descending coronary artery. Standardized two-dimensional echocardiographic measurements of left ventricular function were performed to derive systolic sectional and segmental fractional area changes in five short-axis cross sections of the left ventricle. Fractional area change in all the severely ischemic segments (less than 5% systolic wall thickening) was -4.0 +/- 4.7% at 30 minutes after occlusion, and increased with subsequent 60 and 150 minutes of treatment to 13.1 +/- 3.3 and 7.0 +/- 3.3%, respectively (p less than 0.05). At the most extensively involved low papillary muscle level of the ventricle, regional ischemic fractional area change was increased by intermittent coronary sinus occlusion between 30 and 180 minutes of coronary occlusion from -0.4 +/- 0.1 to 14.4 +/- 4% (p less than 0.05), whereas a further deterioration was noted in untreated dogs with coronary occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Arteriovenous difference of the blood density in the coronary circulation.

The mechanical oscillator technique permits determining blood density continuously with high accuracy. Using this technique arteriovenous density gradients were recorded in the coronary vascular bed of anesthetized dogs. It was found that the coronary sinus blood has a higher density than arterial blood due to the loss of filtered fluid in the microcirculation. The amount of fluid loss corresponds to the lymph flow in the myocardium. Increase of venous pressure leads to an increase of the density gradient. Intermittent coronary sinus occlusion (ICSO) surprisingly leads to a reduction of the density gradient. Injection of osmotically hypertensive fluids influences the arteriovenous gradient by shifting extravascular fluid into the blood. The method permits the determination of filtration coefficients and to estimate the tissue volume available for fluid exchange.

Animals↗