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W Mohl

Publications and source records attributed to W Mohl.

At least 19 recordsLinked to original sources
PubMed1996

Acute myocardial infarction, reperfusion injury, and intravenous magnesium therapy: basic concepts and clinical implications.

The concept of reperfusion-induced injury has aroused special interest during the past decade as thrombolysis and direct angioplasty were introduced for early restoration of coronary blood flow in patients with acute myocardial infarction. There is experimental and clinical evidence that oxygen-derived free radicals (oxyradical hypothesis), activation of the complement system (complement hypothesis), and disturbance in calcium homeostasis (calcium hypothesis), may account for the development of reperfusion injury. Data from numerous animal experiments and clinical trials suggest that magnesium, a physiologic calcium blocker, may be efficacious for reduction of reperfusion injury. Despite encouraging results from previous clinical trials that revealed beneficial effects of intravenous magnesium therapy with respect to mortality, left ventricular function, and infarct size, a recently published large-scale trial (ISIS-4) provided conflicting data and caused major controversy. Further clinical trials, well-designed and carefully conducted, should elucidate the beneficial effects of magnesium in acute myocardial infarction, especially in conjunction with new and aggressive reperfusion techniques.

Calcium Channel Blockers↗
PubMed1996

Perioperative myocardial injury with different modes of antegrade and retrograde cardioplegic delivery.

The effect of three cardioplegic protocols on perioperative myocardial injury was studied in 62 coronary artery bypass grafting (CABG) patients randomized into three groups with either antegrade or retrograde cold blood cardioplegia, or coronary sinus occlusion during antegrade supply. During the aortic cross-clamp time anterior and posterior septal temperatures were recorded, indicating the distribution of cardioplegic solution within the myocardium. Serum creatine kinase (CK), CK-isoenzyme MB and myoglobin as well as 12-lead electrocardiograms (ECG) were analyzed. Statistical analysis showed no effect of the cardioplegic protocol, whereas the patient's preoperative status, aortic cross-clamp time and intraoperative myocardial temperature had significant (P < 0.05) effects on immediate postoperative CK and CK-MB enzyme release. Creatine kinase-MB peak values were significantly increased in patients with major vessel disease and reduced left ventricular function (92 +/- 53 U/l versus 67 +/- 25 U/l). Both CK and CK-MB values were significantly higher in patients with aortic cross-clamp times of more than 1 h than in patients with shorter clamping times (661 +/- 188 and 78 +/- 40 U/l versus 500 +/- 200 and 57 +/- 24 U/l). Patients with 22 +/- 3 degrees C myocardial temperature before terminal cardioplegia had significantly elevated CK as compared to patients with temperatures of 15 +/- 2 degrees C (665 +/- 185 U/l versus 510 +/- 211 U/l). However, enzyme peak values had only poor predictive power for postoperative ECG changes, suggesting that enzyme peaks were not necessarily a sign of perioperative ischemia. Patients with major vessel disease and reduced myocardial function, with aortic cross-clamp time of more than 1 h and/or inadequate intraoperative myocardial cooling may be highly susceptible to global ischemia and operative procedures, and therefore show elevated peak enzyme levels shortly after surgery. In contrast, elevated myoglobin peaks within 1 h after aortic declamping were significantly correlated to perioperative signs of transient ischemia (P < 0.02).

Aged↗
PubMed1996

Closure of ruptured coronary sinus by a pericardial patch.

We report on a case of coronary sinus rupture that happened during placement of a cardioplegia balloon catheter and its subsequent repair. First, the defect was oversewn, however, not successfully. Under cardiopulmonary bypass and cardioplegic arrest, a pericardial patch was used to reconstruct the coronary sinus. Six months after the operation, blood drained during diastole into the right atrium but the flow was partially reversed during systole.

Adult↗
PubMed1995

Echocardiographic results after repair of incompetent bicuspid aortic valves.

INTRODUCTION: Valve-related complications and the necessity of anticoagulation after aortic valve replacement have led to new operative techniques for correction of aortic insufficiency (AI). Fourteen patients with bicuspid aortic valves and significant AI underwent valve repair. METHODS: Transthoracic echocardiography was performed preoperatively and 1 week postoperatively and in 10 patients who have come to follow-up so far. Operative procedures were triangular resection of one leaflet in all patients. Five patients had pericardial patch plasty in addition. RESULTS: Mean AI decreased significantly from grade 3.5 +/- 0.1 preoperatively to 0.5 +/- 0.1 postoperatively (p < 0.001). Postoperatively, 10 patients had no or trivial AI (0 to 0.5), and 2 patients had mild AI (1 to 1.5). Within the first week, 2 patients were reoperated on after echocardiography established significant AI. Ventricular dimensions decreased from preoperative to postoperative and were normal after 1 year. At follow-up, 7 patients show no change of AI; in 3 patients AI increased to moderate because of dilatation of the sinus of Valsalva or the sinotubular junction. CONCLUSIONS: Reconstruction of bicuspid aortic valves is feasible with good early results. Echocardiography shows that asymmetric sinuses may lead to early perioperative failures and postoperative dilatation of the proximal aorta to increasing AI. Operative techniques may have to consider the pathology of the proximal aorta.

Adolescent↗
PubMed1995

Transoesophageal echocardiographic follow-up of patients with surgically treated aortic aneurysms.

In the present study, biplane transoesophageal echocardiography (TEE) was scheduled as part of an aneurysm surveillance programme during routine ambulatory follow-up of 37 patients following aortic aneurysm surgery. Time from surgery ranged from 3-72 months. Twenty-two patients had had aortic dissection and 15 non-dissecting aneurysms. Nineteen patients received an interposition graft of the ascending aorta, 12 valved conduit and six an interposition graft of the descending thoracic aorta. TEE showed enlargement of the sinus of Valsalva > 45 mm in seven patients. Dilatation > 45 mm of one or more aortic segments was found in four patients. An intimal flap was present in all patients, with primary aortic dissection if the initial dissection extended beyond the replaced segment. This was the case in 17 of 22 patients with aortic dissection. One to four intimal tears were identified in 15 of these patients. In all patients with intimal tears, flow was detected by colour flow Doppler in the false lumen. Thrombus formation was nil or minimal in the false lumen in 12 patients. TEE significantly influenced further management in 14 of 37 patients (38%). More frequent follow-up was scheduled in eight patients. Aortic surgery was performed electively for the second or third time in six patients based on TEE findings. We conclude that after surgical repair of aortic aneurysm, the incidence of pathological findings by TEE is high. These may have significant influence on further patient management and emphasize the need for careful follow-up.

Adult↗
PubMed1994

Event-related desynchronization (ERD) during visual processing.

Event-related desynchronization (ERD) is the short-lasting attenuation or blocking of rhythms within the alpha (beta) band. ERD is found during but also before visual stimulation. Two different types of ERD can be differentiated: one short-lasting, localized to occipital areas and involving upper alpha components; the other longer lasting, more widespread, most prominent over parietal areas and maximal for lower alpha components. The former most likely reflects primary visual processing and feature extraction, the latter is more related to cognitive processing and mechanisms of attention.

Alpha Rhythm↗
PubMed1994

Sinus of Valsalva aneurysm: a late complication after repair of ascending aortic dissection.

Surgical advances and the introduction of new more rapid and accurate diagnostic techniques have led to significant improvement in the survival of patients with aortic aneurysms. However, considerable long-term morbidity and mortality remains a concern. In the present study we report on the occurrence of sinus of Valsalva (SV) aneurysm after repair of the ascending aorta for aortic dissection as a significant long-term complication. Since transesophageal echocardiography (TEE) became available it has been used for the follow-up of 33 hospital survivors after ascending aortic replacement for a mean of 27 +/- 20 months. Those patients who received a valved conduit were excluded from this analysis. The aortic valve was conserved in 22 patients: 17 had a dissecting aneurysm involving the ascending aorta and 4 patients non-dissecting aneurysms. A sinus of Valsalva diameter > 45 mm was considered an aneurysm and was found in a total of 7 patients (33%), 5 being patients with aortic dissection. The overall reoperation rate on account of SV aneurysms was 24%. We conclude that SV aneurysm is a significant long-term complication of patients after repair of the ascending aorta. In the light of these results we have changed our operative policy of repair to include resorcin glue as a reinforcing agent or to perform more extensive repair.

Aortic Dissection↗
PubMed1992

Prediction of the side of hand movements from single-trial multi-channel EEG data using neural networks.

Thirty channels of EEG data were recorded prior to voluntary right or left hand movements. Event-related desynchronization (ERD) was quantified in the 8-10 Hz and 10-12 Hz bands in single-trial data and used as training input for a neural network comprised of a learning vector quantizer (LVQ). After a training period, the network was able to predict the side of hand movement from single-trial EEG data recorded prior to movement onset.

Brain↗
PubMed1992

[Transesophageal echocardiography from the surgical viewpoint].

Following the development of new techniques in echocardiography and especially of Doppler color flow imaging, a new dimension of cardiac surgery has been brought about. The use of transesophageal probes facilitates routine surgery to be performed without interferences and, also, comparability between repeated ultrasonic measurements. Originally, echocardiography was mainly applied for quality control by comparing pre- and postoperative echocardiograms. Now it is equally important in perioperative strategy planning guiding the surgeon's decision throughout the operation as well as in cardiac emergencies. Using intraoperative echocardiography routinely in cardiac surgery establishes a more and more close cooperation between surgeons, cardiologists, and anesthesiologists. In order to evaluate the clinical relevance of echo findings, they have to be repeatedly correlated to surgical realities and to long term results of clinical outcome.

Adult↗
PubMed1992

Transesophageal echocardiography in the emergency surgical management of patients with aortic dissection.

The diagnostic accuracy and benefit of transesophageal echocardiography were investigated in 32 patients with suspected aortic dissection. Results of transesophageal echocardiography were compared with surgical assessment. The Stanford classification was used for differentiation of dissection type. Examination time was 5 to 15 minutes. Twenty-eight patients were correctly identified to have aortic dissection; four patients had nondissecting aneurysms of the ascending aorta. Both sensitivity and specificity for detection of aortic dissection were 100%. Type of dissection was misdiagnosed in one patient. Classification of dissection type was correct in 96%. The primary entry site was correctly identified in 25 patients (89%). Aortic regurgitation was found in 57% of patients. Pericardial effusion was detected in 21%, with tamponade in one patient. Myocardial infarction was suggested by transesophageal echocardiography in 7%, and 14% had significantly reduced left ventricular function. Eight patients underwent operation based on transesophageal echocardiography alone. Intraoperative transesophageal echocardiography, performed in 20 patients, verified retrograde flow in the true lumen after femoral cannulation. Transesophageal echocardiography documented postrepair persistence of the intimal flap in aortic segments that were not operated on in all patients. Secondary tears and flow in the false lumen were detected in 35% of patients. We conclude that transesophageal echocardiography allows expedient and accurate diagnosis and classification of aortic dissection, and we recommend it as the primary bedside diagnostic modality. It can especially identify patients requiring surgical intervention without further delay caused by other diagnostic procedures.

Adult↗
PubMed1992

Effects of coronary artery bypass grafting on global and regional myocardial function. An intraoperative echocardiographic assessment.

The immediate effect of coronary artery bypass grafting on global and regional myocardial function was studied by means of epicardial two-dimensional echocardiography during operations in 20 patients. Echocardiograms were recorded before cardiopulmonary bypass and 5 and 30 minutes after bypass. Global left ventricular function was expressed as percent short-axis area change and regional function as percent fractional area change. Segments were classified according to their baseline function as normal (percent fractional area change greater than 40%), moderately hypokinetic (percent fractional area change 21% to 40%), or severely dysfunctional (percent fractional area change less than 20%). Percent short-axis area change was significantly reduced immediately after cardiopulmonary bypass (from 42.0% +/- 4.6% to 34.9% +/- 3.0%, p less than 0.05) but had returned to baseline 30 minutes after bypass (42.6% +/- 4.0%). Similarly, function of normal and moderately hypokinetic segments decreased significantly immediately after cardiopulmonary bypass (normal segments: percent fractional area change 56% +/- 0.9% before bypass to 42.3% +/- 1.5% after bypass, p less than 0.0001; moderately hypokinetic segments: 31.0% +/- 0.9% to 25.1% +/- 1.4%, p less than 0.002). Both normal and moderately hypokinetic areas regained baseline function by 30 minutes after bypass (normal segments: 53.4% +/- 1.6%; moderately hypokinetic segments: 35.4% +/- 2.0%). In contrast, severely dysfunctional segments were found to be significantly improved immediately after bypass (14.7% +/- 0.9% before bypass to 27.7% +/- 2.1% after bypass, p less than 0.0001). This improvement was maintained 30 minutes after bypass (22.8% +/- 1.5%, p less than 0.001). We conclude that coronary revascularization exhibits an immediate beneficial effect on chronically underperfused myocardium having severely depressed baseline function. However, in normal and moderately hypokinetic areas, the depressant effects of global ischemia and reperfusion prevail in the immediate postbypass period, leading to a global depression of cardiac function.

Angina Pectoris↗
PubMed1991

Transesophageal echocardiographic evaluation in mechanically assisted circulation.

Transesophageal echocardiography (TEE) has assumed an increasing importance in cardiothoracic surgery, but its use in patients with mechanically assisted circulation is unclear. We performed TEE in 11 patients: total artificial heart (TAH) 2, right ventricular assist device (RVAD) 2, left ventricular assist device (LVAD) 6, biventricular assist device (BVAD) 1. TEE was helpful in three areas. (1) selection of the assist device (AD): evaluation of left and right ventricular function allows differentiation of left, right or biventricular failure. (2) management of patient and optimization of pump performance: in all patients, correct cannula position and pump flow could be identified. Right ventricular failure in the presence of LVAD was found to cause hemodynamic instability in 4 patients. In 1 patient with repeated RV dilation and hypotension despite RVAD, TEE allowed optimal pump settings to be determined. (3) weaning from AD: Recovery of ventricular function can be assessed prior to weaning and repeatedly monitored during weaning. TEE in TAH is limited to problems such as identification of atrial thrombus or inflow valve dysfunction. We conclude that TEE is useful in the setting of mechanically assisted circulation for AD selection, improvement of patient management, optimization of pump performance and during weaning from AD.

Assisted Circulation↗
PubMed1991

The relevance of coronary sinus interventions in cardiac surgery.

The concept of arterialization of the coronary venous system was first discussed almost 100 years ago. Subsequently, those attracted by this approach have chosen the coronary veins as an alternative route for interventional and surgical therapy. Modern techniques of coronary sinus interventions (CSI) have been suggested mainly for temporary support and protection of ischemic myocardium. Based on the dense meshwork structure of the venous vasculature, CSI may be effective even in the presence of serious coronary artery disease. Three major techniques have been suggested for different indications in cardiology and cardiac surgery: 1) ECG-synchronized retroperfusion of arterial blood, which is supposed to positively affect ischemic myocardium by phasic supply of oxygen to deprived areas mainly in cardiac emergencies, 2) retroinfusion of cardioplegia in the arrested heart, which is now a well-established clinical technique, and 3) intermittent coronary sinus occlusion during antegrade cardioplegic delivery in the arrested heart and in the early reperfusion period after surgical revascularization, or in cardiac emergencies. The beneficial effect of pressure-controlled intermittent coronary sinus occlusion is assumed to result from cyclic occlusion and release of the coronary sinus shifting venous blood to underperfused regions, thereby facilitating substrate delivery and subsequent washout of metabolites. Experimental studies and first clinical trials suggest that all methods of CSI are safe and feasible, and the ultimate goals of reduction of infarct size and preservation of jeopardized ischemic myocardium will be achieved.

Cardiac Catheterization↗
PubMed1991

Immediate effects of mammary artery revascularization versus saphenous vein on global and regional myocardial function: an intraoperative echocardiographic assessment.

The immediate effect of coronary artery bypass surgery on global and regional myocardial function using the internal mammary artery (IMA) versus saphenous vein (SV) was studied intraoperatively using transesophageal echocardiography (TEE). Thirty-two patients received an IMA and 10 patients only SV. Transesophageal echocardiography was recorded before thoracotomy, 5 minutes after the end of cardiopulmonary bypass (CPB) and after chest closure. Global and regional left ventricular function were expressed as a percent of the short axis area change (%SAAC) and a percent of the fractional area change (%FAC), respectively. Segments were classified according to their baseline function as normal, %FAC greater than 40%, or dysfunctional, %FAC less than 40%. Only normal segments were considered in this study. No significant change in %SAAC in either group was observed in this study. Internal mammary artery revascularized segments showed a significant decrease in %FAC from 57 +/- 1 before thoractomy to 53 +/- 2 5 minutes after CPB, whereas SV segments showed a significant improvement in %FAC from 56 +/- 1 to 61 +/- 1. Applying strict criteria derived from intraobserver and cycle-to-cycle variability, 17% of IMA segments had deteriorated by more than 36% whereas only 4% of SV segments showed such deterioration. Conversely, 17% of SV segments showed an increase in %FAC by more than 36% and only 3% of IMA segments improved similarily. The observed changes were of short duration and had largely resolved by chest closure.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

The role of the right parietal region in a movement time estimation task.

Thirteen right-handed male students performed a time estimation task by pressing a button with their left or right hand for an interval of either 0.5 or 1.3 s. Thirty channels of EEG were recorded, with the right ear as reference. After transforming the raw EEG data into local average reference data, the topography of event related desynchronization (ERD) of the rhythm within the 10-12 Hz frequency band was studied by computing ERD maps separately for accurate and inaccurate performance. Statistical comparison of ERD maps for accurate and inaccurate movement (Wilcoxon test) resulted in significant differences for the right parietal region prior to movement onset, with a larger ERD before accurate movement.

Adult↗
PubMed1990

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↗
PubMed1990

Event-related desynchronization, ERD-mapping and hemispheric differences for words and numbers.

Event-related desynchronization (ERD) is the amount of event-related decrease in alpha band power. In applying ERD as an index of cortical activation, the way in which attention and expectancy affect hemispheric differences for words and numbers was investigated. Subjects, 12 right-handed males, had to perform a semantic and a numerical classification task under two different counterbalanced expectancy conditions. Whereas under the high expectancy condition words and numbers were presented blockwise, they were presented randomly under the low expectancy condition. In the semantic task subjects had to indicate the category to which a word belonged; in the numerical task they had to judge whether a number was odd or even. Because 48 words and numbers were used in both expectancy conditions, each subject had to perform a total of 192 trials, practice trials not included. During each of the 192 trials, EEG-signals were recorded from 29 electrodes and analyzed in two frequency bands (6-10 Hz and 9-13 Hz). The data, which were also presented in the form of maps, were subjected to a 6-factorial ANOVA. The results reveal a complex pattern of interactions between the two frequency bands, expectancy conditions, stimulus types and the recording sites. The most important results concern the influence of expectancy. A consistent left hemispheric advantage could be observed under the high expectancy condition and in the lower alpha band only. This and other results seem to indicate that the lower alpha band is more sensitive to reflect expectancy and attentional processes.

Analysis of Variance↗