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H Mächler

Publications and source records attributed to H Mächler.

At least 19 recordsLinked to original sources

Influence of bileaflet prosthetic mitral valve orientation on left ventricular flow--an experimental in vivo magnetic resonance imaging study.

OBJECTIVE: Orientation-related bileaflet mechanical valve flow and velocity studies in the downstream area are limited in mitral valve replacement studies. METHODS: In five sheep, ventricular blood flow was visualized prior to the implantation of a mitral Edwards Mira Bileaflet Mechanical Valve Model 9600. The implant orientation was either anatomic, with a 45 degrees rotation, or anti-anatomic, with a 90 degrees rotation. Sheep were positioned within an 1.5T field strength MR scanner (Magnetom Sonata; Siemens) to assess time-dependent three-dimensional blood flow velocities displayed as color-encoded vectors. RESULTS: The preoperative ventricular velocity profiles presented negligible individual variances. Streamlines passed homogeneously without any spatial differences into the left ventricle. Starting from the anatomical position, the areas with inhomogeneous and accelerated local blood velocities increased in comparison to the preoperative status. Rotating the prosthesis until it was in a 45 degrees position caused a significant increase in turbulence immediately downstream; fluids stagnated longer at the apex. In the anti-anatomic orientation, mean velocities decreased. In all three positions, but less so in the anatomical position, the flow pattern of the blood helix at the apex was disturbed. The intraventricular flow patterns between prostheses in the three orientations were, however, not significant when compared to the differences between physiologic intraventricular flow and any of the postoperative measurements. CONCLUSIONS: To achieve optimal hemodynamics, rotation of the mitral valve has to be considered carefully, as has long been known from aortic valve replacement studies. To this end, a method for qualitative assessment of left ventricular blood flow patterns was developed.

Animals↗

Effects of K+ channel openers on I K(ATP) of human atrial myocytes at physiological temperatures.

The aim of this study was to investigate the effects of the potassium channel openers (PCOs) cromakalim and pinacidil on the ATP-dependent potassium current I(K)(ATP) in human atrial myocytes. Cells were isolated from the right atrial appendage obtained during cardiac surgery. Membrane currents were studied with the patch-clamp technique in the whole-cell recording mode at 36 degrees -37 degrees C. Under physiological conditions (4.3 mmol/l ATP in the pipette solution, ATPi) I(K)(ATP) did not contribute to basal electrical activity. When ATPi was omitted from the pipette solution I(K)(ATP) activated with a time lag of 4.92+/-0.92 min (n=6) and was completely inhibited by glibenclamide. Using 4.3 mmol/l ATPi I(K)(ATP) at +30 mV was increased by 2.04+/-0.51, 7.24+/-1.65 and 13.22+/-3.71 pA/pF (n=7) with 10, 30 and 100 micromol/l cromakalim, respectively, and by 3.24+/-0.98 (n=6), 4.07+/-0.48 (n=10) and 3.46+/-1.23 pA/pF (n=6) with 10, 30 and 100 micromol/l pinacidil, respectively. Control current density was 5.39+/-0.47 pA/pF (n=39). Using 1 mmol/l ATPi I(K)(ATP) showed a more pronounced activation (4.81+/-3.28, n=6; 9.78+/-2.60, n=7; and 15.1+/-4.18 pA/pF, n=6; with 10, 30 and 100 micromol/l pinacidil, respectively). I(K)(ATP) activated by both compounds could be effectively inhibited by glibenclamide. Repetitive exposure to pinacidil (30 micromol/l at 4.3 mmol/l ATPi) caused a potentiation of I(K)(ATP). Current density at +30 mV was increased by 87% during the first and by 401% during the second pinacidil application (n=5). The data presented in this paper provide new information about electrophysiological characteristics of human atrial I(K)(ATP) and its modulation by the PCOs cromakalim and pinacidil and suggest species-dependent differences.

Adenosine Triphosphate↗

Left ventricular architecture after valve replacement due to critical aortic stenosis: an approach to dis-/qualify the myth of valve prosthesis-patient mismatch?

OBJECTIVES: Left ventricular hypertrophy in patients with critical aortic stenosis (AS) is an adaptive process that compensates for high intracavitary pressure and reduces systolic wall stress followed by an increase in myocardial masses. In the present prospective clinical trial, we investigated long-term compensatory changes in left ventricular geometry and function after aortic valve replacement using mechanical bileaflet prostheses with the main emphasis on the small-sized aortic annulus and valve prosthesis-patient mismatch. METHODS: A total of 58 patients with critical AS were assigned to the following groups according to the predictive value of prosthetic valve area index (VAI): group EXMIS: 29 patients (VAI < or =0.99), expected mismatch; group NOMIS: 29 patients (VAI < or =0.99), no mismatch. At controls T(0) (before operation/operation (OP), T(1) and T(2) (4 and 20 months after OP) the left ventricular geometry was recorded by means of Imatron electron beam tomography and the transprosthetic velocities were measured by echocardiography. RESULTS: Statistical analysis showed a consistent reduction in the absolute (P=0.04) and indexed (P=0.04) left ventricular myocardial mass for both cohorts; furthermore, there was a significant difference between EXMIS and NOMIS patients concerning the factors, time and mass reduction (P=0.005), because of distinct baselines. A logistic regression report revealed preoperative cardiac output, absolute left ventricular myocardial mass, perfusion, body surface area and the native valve orifice area as predicting coefficients and factors for a minimum mass reduction of 25%. We explain a mathematical formula that turned out to be the most sensitive for correctly classified factors. CONCLUSIONS: The left ventricular geometry and transprosthetic velocities resulted in the same postoperative recovery for both EXMIS and NOMIS patients. The presented data showed that valve prosthesis-patient mismatch had no influence in several stepwise logistic regression models. We conclude that modern mechanical bileaflet prostheses allow both acceptable hemodynamics and recovery of left ventricular hypertrophy, even in small aortic annuli.

Aged↗

Workplace conditions predict the risk of premature death and functional dependence after retirement--results of a gerontological follow-up study in Germany.

Between 1983 and 1985, 595 employees who were entering retirement in East Germany were given a medical examination and asked to assess their workplace conditions. Ten years later, we examined whether occupational predictors were associated with death and functional dependence among the study participants and assessed how the surviving pensioners coped with activities and instrumental activities of daily living. We assigned the occupational factors reported between 1983 and 1985 to two scales: demands and resources. Multiple logistic regression analyses were carried out to examine the association of occupational and medical predictors with the outcome variables death and functional dependence. Workplace resources but not demands were significantly associated with a reduced chance of death in women, independent of medical diagnoses. For men neither of these associations were verified. Concerning functional dependence individual items such as 'control over work content' (for both sexes) significantly reduced the risk of developing ADL-dependence. The associations remained stable after medical diagnoses were additionally taken into consideration. The results of our study highlight the influence of occupational factors beyond working life and support the importance of starting geriatric health promotion before retirement age.

Activities of Daily Living↗

The influence of medical information on the perioperative course of stress in cardiac surgery patients.

UNLABELLED: Cardiac surgery correlates with increased perioperative stress and anxiety. We tested whether preoperative extensive oral information in combination with more personal attention by the surgeon is associated with any effect on patients' perioperative stress, anxiety, and well-being. Sixty patients awaiting open heart surgery were divided into two groups. Group I consisted of 30 patients who received routine medical information through an informative pamphlet. In Group II (n = 30 patients), additional, extensive oral medical information and more personal attention by the surgeon was provided before surgery. Salivary cortisol, plasma cortisol, state anxiety, and patients' well-being were measured perioperatively. Extensive preoperative oral information in combination with more personal attention by the physician did not have any significant influence on the perioperative psychoendocrinologic course of stress. During transport to the operating room, salivary cortisol increased significantly (P < 0.001) in both groups (ranges are 95% confidence intervals) (Group I, 23.2 nmol/L [17.1-31.5]; Group II, 14.6 nmol/L [9.9-21.3]) versus the first day in the hospital (Group I, 8.4 nmol/L [6.2-11.4]; Group II, 6.7 nmol/L [5.3-8.6]). After the induction of anesthesia, plasma cortisol decreased significantly (P < 0.001) in both groups (Group I, 170.1 nmol/L [143.6-201.4]; Group II, 172.0 nmol/L [142.2-208.1]) versus preoperative levels. After surgery, well-being decreased (P = 0.003) in all patients, and patients' state anxiety was reduced (P = 0.001) after surgery. Our data demonstrate a lack of effect of extensive oral medical information that was presented as part of clinical routine on the perioperative psychoendocrinologic course of stress. High levels of stress during transport to the operating room were detected. IMPLICATIONS: The quantity of stress during transport to the operating room and the perioperative psychoendocrinologic course of stress in combination with two different methods of preoperative medical information are described in 60 consecutive patients awaiting cardiac surgery.

Aged↗

[Forensic aspects of a trainee in robotic surgery of the heart].

The grounds for liability with robotic surgery include damage to patients, causality, illegality and guilt. The patient must receive very comprehensive information on the treatment under consideration, his/her risk and what will be done in the case of technical failure. The surgeon operating the robotic device is obliged to provide normal conscientious care and state-of-the-art treatment. In addition, there is possible neglect of supervisory duties vis-à-vis other hospital personnel to be considered. A special problem is posed by a forensic physician who lacks experience in robotic surgery. There should be a surgeon at the operating table who is at least equally skilled as the surgeon operating the monitor. Robotic surgery must ultimately be at least as effective as conventional surgery, if not better. It must, however, be borne in mind that in cases involving this new technology, it is that patient who is the pioneer.

Education, Medical, Graduate↗

[Does health status improve after re-assumption of ABM employment?].

UNLABELLED: Due to structural problems of the East German economy the level of unemployment will probably remain high for the next ten years. Thus, thousands of health-employment-schemes are established to reduce negative social and financial consequences of unemployment for those groups that are most affected. In this study the effects of temporary re-employment on health within the bounds of a job-creating measure are examined. By questionnaire employees of two firms in Magdeburg that exclusively occupies former unemployed men and women were asked about their subjective health status and changes in health status since re-employment. 217 employees filled the questionnaire (response rate: 50%; mean age: 45 years, mean duration of former unemployment: 18 months). About one half of the employees (48%) report positive effects on health after re-employment. This percentage is highest in the age group 50 years and older. The frequency of health impairments remained unchanged for half of the workers, the rest mainly stated fewer impairments. Poor working conditions or physical overtaxing decreases the positive effects of re-employment. Employees who had a positive attitude towards their work report on positive effects on health and other aspects of life more than average. CONCLUSIONS: Negative consequences of unemployment on physical and psychological health are well understood. On the other hand, our study demonstrates positive effects on health and a reduction of health impairments by temporary job-creating measures. This is influenced by the working conditions and the social environment of the employees. Further investigation are needed for detailed medical evaluation of job-creating schemes.

Adult↗

[Lead stability in long-term follow-up of bipolar leads].

From 1990 to 1999, 2,853 ventricular and 1,084 atrial bipolar leads of various manufacturers (Medtronic, Biotronik, Vitatron, Ela, Pacesetter and Stöckert) were implanted during first implantations of pacemakers at the University of Graz, Dept. of Cardiac Surgery. Surgical complications with the need of reintervention were analyzed during a follow up period of up to 10 years. The overall lead-related complication rate for ventricular bipolar leads was 6.5% (187 of 2,853) and 5.3% (58 of 1,084) for atrial bipolar leads. Early complications within the first month were higher in the atrium (5.3% versus 2.2% in the ventricle), primarily due to dislocation, late complications were higher in the ventricle (4.3% versus 2% in the atrium) due to insulation problems and lead fracture. Insulation material had a marked influence with a higher failure rate in some leads with polyurethane insulation compared with silicone. Therefore we recommend a close follow-up of bipolar polyurethane leads by measurement of chronic impedance in order to assess insulation problems as early as possible.

Austria↗

Repolarizing currents in ventricular myocytes from young patients with tetralogy of Fallot.

OBJECTIVE: It was the aim of our study to describe repolarizing currents in ventricular myocytes isolated from children with tetralogy of Fallot. This is the first report on outward currents in ventricular myocytes from children. METHODS: Ventricular myocytes were isolated from tissue samples of the outflow tract of the right ventricle which were obtained during corrective surgery of tetralogy of Fallot. Action potentials and whole-cell currents were recorded with the patch clamp technique at a temperature of 36-37 degrees C. RESULTS: The mean resting potential was -71.7 +/- 1.92 mV, action potential amplitude was 110 +/- 2.96 mV and action potential duration at 90% repolarization was 794 +/- 99.5 ms (n = 12). In four out of 12 myocytes early afterdepolarizations (EADs) were observed. Upon hyperpolarization Ba(2+)-sensitive inward currents similar to the inward rectifier current (IKl) could be observed. The current density at -120 mV was -22.8 +/- 2.47 pA/pF (n = 14). A transient outward current (Itol) could be recorded in all myocytes studied, the current density varied from 0.3 to 8.6 pA/pF with a mean of 3.77 +/- 0.47 pA/pF at +40 mV (n = 38). Recovery of Itol from inactivation was fast (70% recovery within 100 ms), rate-dependent reduction amounted to 38.2% at 4 Hz. A delayed rectifier current was seen in only two out of 38 myocytes (rapid component IKr). CONCLUSIONS: The electrophysiological characteristics of right ventricular myocytes isolated from children with tetralogy of Fallot resemble in most cases subendocardial myocytes from adults. The most prominent difference is a fast recovery from inactivation as well as a small rate dependent reduction of Itol. The observed EADs may have clinical implications.

Action Potentials↗

The sulphonylurea glibenclamide inhibits voltage dependent potassium currents in human atrial and ventricular myocytes.

1 It was the aim of our study to investigate the effects of the sulphonylurea glibenclamide on voltage dependent potassium currents in human atrial myocytes. 2 The drug blocked a fraction of the quasi steady state current (ramp response) which was activated positive to -20 mV, was sensitive to 4-aminopyridine (500 microM) and was different from the ATP dependent potassium current IK(ATP). 3 Glibenclamide dose dependently inhibited both, the peak as well as the late current elicited by step depolarization positive to -20 mV. The IC50 for reduction in charge area of total outward current was 76 microM. 4 The double-exponential inactivation time-course of the total outward current was accelerated in the presence of glibenclamide with a tau(fast) of 12.7+/-1.5 ms and a tau(slow) of 213+/-25 ms in control and 5.8+/-1.9 ms (P<0.001) and 101+/-20 ms (P<0.05) under glibenclamide (100 microM). 5 Our data suggest, that both repolarizing currents in human atrial myocytes, the transient outward current (Ito1) and the ultrarapid delayed rectifier current (IKur) were inhibited by glibenclamide. 6 In human ventricular myocytes glibenclamide inhibited Ito1 without affecting the late current. 7 Our data suggest that glibenclamide inhibits human voltage dependent cardiac potassium currents at concentrations above 10 microM.

Adenosine Triphosphate↗

The influence of different strategies on clinical outcome in patients undergoing total cavopulmonary connection.

BACKGROUND: We report on results of a prospective clinical trial designed to demonstrate the influence of various strategies in "Total Cavopulmonary Connection" (TCPC) for palliative therapy of patients with "single ventricle" physiology. METHODS: From 1989 to 1997, a total of 47 patients (mean age 4.8 +/- 3.6 years) underwent definitive TCPC at our unit. 31 patients (66%) underwent one-stage TCPC, in 16 patients (34%) we performed a two-stage modified Fontan operation; 21 patients had central fenestration (4 mm). Inhalative NO therapy in the immediate postoperative period was adopted in 1993. RESULTS: Overall 5-year survival was 76.4%, after two-stage TCPC 87.5%, and 81.3% in patients undergoing fenestrated procedures. Two of three patients survived perioperative Fontan take-down. We lost 11 patients (nine early and two late deaths): three patients died primarily because of neurologic dysfunction and eight patients because of cardiac failures. Under perioperative NO therapy there was no early death. After a mean follow-up of 35.9 +/- 23.3 months, 76% of all patients were in NYHA I and 21 % in NYHA I-II. 89.7% had sinus rhythm. 42% of our patients suffered from temporary pleuropericardial effusions. CONCLUSIONS: Definitive palliation with TCPC achieves acceptable clinical results. Two-stage repair, fenestration, and postoperative inhalative NO therapy - each have a positive influence on early and long-term survival.

Administration, Inhalation↗

Invasive ductal carcinoma of the male breast expanding from pacemaker pocket decubitus.

After twenty-five years of therapy with different unifocal pacemaking systems, an 84-year old male patient developed a nonseptic pacemaker decubitus. A rare incidental finding of invasive ductal carcinoma of the right mammary gland was surgically treated by a generous excision of the tumor and by consecutive modified radical mastectomy. According to published literature, the association of invasive ductal carcinoma arising from a pacemaker pocket decubitus and followed by curative treatment has not been previously reported. We do conclude that pacemaker generators in close relationship to the mammary gland should be considered with suspicion.

Aged↗

Estimation of outward currents in isolated human atrial myocytes using inactivation time course analysis.

The aim was to investigate outward currents in single, isolated, human, atrial myocytes and to determine the relative contribution of individual current components to the total outward current. Currents were recorded using the whole-cell patch-clamp technique at 36-37 degreesC. Individual outward current components were estimated from recordings of total outward current using a mathematical procedure based on the inactivation time course of the respective currents. This method allows estimation of outward currents without the use of drugs or conditioning voltage-clamp protocols to suppress individual current components. A rapidly activating and partially inactivating total outward current was recorded when myocytes were voltage clamped at potentials positive to -20 mV (peak current density 24. 0+/-0.97 pA/pF at +40 mV; n=107 cells, 33 patients). This total outward current comprised three overlapping currents: a rapidly inactivating, transient, outward current (Ito1) a slowly and partially inactivating current (ultrarapid delayed rectifier, IKur) and a third current component which most probably reflects a non selective cation current (not characterized). The average current densities at +40 mV were 8.92+/-0.44 pA/pF for Ito1 and 15.1+/-0.72 pA/pF for IKur (n=107 cells). Recovery from inactivation was bi-exponential for both currents and was faster for Ito1. A slowly activating delayed rectifier current (IK) was not found. The current densities of peak Ito1 and IKur varied strongly between individual myocytes, even in those from the same patient. The ratio IKur/Ito1 was 0.5-6.9 with a mean of 1.98+/-0.11 (n=107 cells), suggesting that IKur is the main repolarizing current. The amplitudes of the total outward current, Ito1 and IKur, and the ratio of the latter two were independent of patient age (16-87 years).

Adolescent↗

L-type calcium current in human ventricular myocytes at a physiological temperature from children with tetralogy of Fallot.

OBJECTIVE: The aim was to investigate the electrophysiological properties of the L-type calcium current (ICa,L) in ventricular myocytes at a physiological temperature (36-37 degrees C) isolated from children undergoing surgical repair of tetralogy of Fallot. METHODS: ICa,L was recorded with the patch-clamp technique in the single electrode whose-cell mode at a physiological calcium concentration (1.8 mmol/l) at 36-37 degrees C. RESULTS: Under these conditions, maximum current density averaged -5.80 +/- 0.45 pA/pF. ICa,L showed a bell-shaped current-voltage relationship: the current activated at -37.7 +/- 1.36 mV, peaked at +9.41 +/- 1.60 mV and reversed at +57.7 +/- 2.12 mV (n = 17). At +10 mV, time to peak of ICa,L was 5.23 +/- 0.46 ms. Membrane potentials for half-maximal steady-state activation and inactivation of ICa,L were -6.02 and -20.4 mV, respectively, the slope factors were 7.16 mV for steady-state activation and 6.49 mV for steady-state inactivation. ICa,L did not completely inactivate and showed a big window current between -45 and +40 mV. The inactivation of ICa,L showed a biexponential time course with a fast time constant ranging from 9.11 to 12.9 ms and a slow time constant ranging from 60.9 to 220 ms between -30 and +30 mV. Only the slow time constant showed a pronounced voltage dependency. The recovery from inactivation of ICa,L was biphasic with a fast time constant of 60.7 ms and a slow time constant of 619 ms. beta-Adrenergic stimulation with isoprenaline (1 mumol/l) increased the ICa,L density from -5.71 +/- 1.55 to -13.8 +/- 1.96 pA/pF (142%; P < 0.05) at +10 mV. CONCLUSIONS: The present study demonstrates that most of the electrophysiological properties of ICa,L in ventricular myocytes isolated from children with tetralogy of Fallot resemble those of adult ventricular cells. The existence of a big calcium window current could be involved in the occurrence of early afterdepolarizations which could lead to the high incidence of arrhythmias after surgical repair of tetralogy of Fallot.

Adrenergic beta-Agonists↗

Effects of the class III antiarrhythmic drug ambasilide on outward currents in human atrial myocytes.

We have studied the inhibitory influence of the class III antiarrhythmic drug ambasilide (LU 47110) on the transient outward current Ito1 and the sustained current Iso following inactivation of Ito1, in human atrial myocytes. The two currents are separated by a mathematical procedure based on the amplitudes and time constants of the biexponential inactivation of the total outward current. The frequency dependence, the recovery from inactivation and the kinetics of activation and inactivation are described. Ambasilide reversibly and concentration dependently inhibited Ito1, Iso and the sodium current INa. Concentration required for half maximal inhibition (IC50) for the effects on Ito1 and Iso were 23.3 mumol/l and 45.7 mumol/l respectively, concentrations shown by others to be effective in terminating and preventing fibrillation in a dog atrial arrhythmia model. Ambasilide not only reduced the amplitude of Ito1 and Iso but also accelerated the time course of inactivation from 14.22 to 6.69 ms and from 202.3 to 87.9 ms respectively. The amplitude of Ito1 showed only a small dependence on stimulation frequency characteristic for human atrial myocytes, whereas Iso was reduced significantly at higher stimulation frequencies. Ambasilide did not change these relationships (0.1-4 Hz) and therefore did not show the reverse use-dependence known from other class III antiarrhythmic agents and which is an important property for a prospective antiarrhythmic drug. The lack of an effect of ambasilide on both steady-state activation and inactivation of Ito1, and the time constant of recovery from inactivation, suggests that ambasilide acts by changing conductance rather than by influencing the gating mechanism. The described characteristics make ambasilide an interesting substance in the group of class III antiarrhythmic drugs.

Aged↗

Concomitant procedures in the small versus standard aortic root.

BACKGROUND AND AIMS OF THE STUDY: Aortic valve replacement (AVR) in the small aortic root (SAR) has always been a severe challenge with an uncertain surgical outcome. The purpose of this study was to assess the surgical and clinical performance of 19 mm and 21 mm CarboMedics valves (CPHV) based on a review of valve-related morbidity and mortality over a period of six years. METHODS: A total of 361 patients undergoing aortic valve replacement (AVR) with the CPHV between January 1989 and August 1995 was subdivided and studied. (i) Group A patients (n = 137) received 19 mm or 21 mm prostheses; subgroup AI (n = 85) underwent isolated AVR and subgroup AII (n = 52) underwent AVR with associated cardiac procedures. (ii) Group B patients (n = 224) were given 23 mm or larger prostheses; subgroup BI (n = 147) underwent isolated AVR and subgroup BII (n = 77) underwent AVR with concomitant cardiac procedures. RESULTS: Hospital mortality was group A 7.3% versus group B 4.9%. Cumulative survival after six years was 83.7% in AI and 76.9% in AII versus 72.1% in BI and 77.4% in BII. There were no significant statistical differences between the subgroups concerning cardiac mortality. Thromboembolic events occurred with a linearized rate of 1.41%/pty in group A versus 1.03%/pty in group B, the incidence of anticoagulant-related major hemorrhage was 1.41%/pty in group A versus 1.20%/pty in group B and that of periprosthetic leakage 1.69%/pty in group A versus 1.89%/pty in group B. CONCLUSION: Our results demonstrate that this bileaflet prosthesis is highly efficient in patients with small aortic roots undergoing AVR with or without associated procedures.

Adolescent↗

[Indications and outcome of simultaneous operation of carotid stenoses and stenosing coronary arteriosclerosis].

Between 1986 and September 1995 100 patients with carotid artery stenosis and coronary artery disease underwent combined carotid endarterectomy and CABG. The indications for carotid endarterctomy were transient neurological events in 38 patients and in 62 cases high-grade asymptomatic carotid artery stenosis. The surgical procedures were always performed by a vascular and a cardiac surgical team. In all cases carotid endarterectomy was performed prior to CABG, 3 patients died during the in-hospital-postoperative period: 2 patients died on the first day after surgery because of cardiac failure, 1 on the 18th day because of pneumonia. 2 patients had postoperative transient neurological events. The results are similar to those of isolated single procedures. Thus combined surgery for severe carotid and coronary artery disease can be performed with low mortality and morbidity.

Aged↗