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Biomedical subjects

W Heimisch

Publications and source records attributed to W Heimisch.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effect of the 'specific bradycardic agent' alinidine on the function of ischemic myocardium.

In patients with coronary artery disease, the reduction of heart rate (HR) by beta-blockers can further impair myocardial function by reducing the contractility and coronary perfusion. This is possibly not the case for "specific bradycardic agents" like alinidine (ALI). The effect of ALI on ischemic myocardium, therefore, was studied in anesthetized open-chest dogs measuring left ventricular end-diastolic pressure (LVedP), dP/dt, aortic pressure (AoP) by catheter tip manometers, coronary blood flow (Q) electromagnetically, end-diastolic length (edL) and systolic shortening (sdL in %edL) of ischemic (RISC) and non-ischemic (NISC) wall segments by sonomicrometry. Group A (n = 11): Left coronary artery constriction to reduce Q (-53%) and poststenotic sdL (-54%), then i.v. injection of ALI (0.25 + 0.25 + 0.5 + 1.0 mg/kg), thereafter atrial pacing at HR before ALI. Group B (n = 9): Installation of an aorto-coronary bypass, pump-perfused at 50% of free flow, infusion of ALI into the bypass. The results showed that ALI iv dose-dependently reduced HR from 135/min to 90/min, LVedP rose from 8.6 to 10.0 mmHg and NISC-edL from 14.1 to 14.6 mm indicating increased ventricular filling. Non-ischemic systolic shortening did not change. Ischemic systolic shortening was improved from 9.2% to 17.5%, which was not due to an increase in RISC-edL (14.8 versus 14.7 mm), enhanced RISC-Q (13 versus 12 ml/min), reduced AoP (86 versus 84 mmHg) or change in inotropy (dP/dtmax: 2290 versus 2240 mmhg/s), but the increase in RISC-sdl correlated closely (r greater than 0.85) to the reduction in HR (oxygen-demand).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Relation between epicardial electrograms and signal-averaged electrocardiograms after acute myocardial infarction in dogs.

Signal-averaged electrocardiograms allow the non-invasive detection of late potentials which represent locally delayed conduction in the myocardium. To validate this method, it is necessary to compare the signal-averaged data with electrograms recorded directly from the heart. However, the studies performed to date involve only a consecutive collection of the invasively and non-invasively obtained data. To obtain a more direct comparison, we examined this relation at operation by simultaneous epicardial and signal-averaged measurements. Acute infarction in animals was chosen, because the ischemic area is a zone of delayed conduction whose presence can be verified in a signal-averaged electrocardiogram. For this purpose, the left anterior descending artery, proximal of large septal and diagonal branches, was tied off in nine mongrel dogs after thoracotomy. Before infarction, a signal-averaged electrocardiogram was recorded from the body surface. At the same time, epicardial electrograms were performed using bipolar electrodes both from the supply area of the left anterior descending artery and from that of the circumflex artery. Five minutes after coronary ligation, both the epicardial measurements and the signal-averaged electrocardiogram were repeated on the open thorax. Before occlusion of the left anterior descending artery, narrow activation complexes occurred in general in the epicardial electrograms and no late potentials were recorded in any dog by the signal-averaged electrocardiogram. Five minutes after coronary ligation, fractionated and prolonged electrograms occurred in the epicardial recordings from the ischemic zone, while the activation complexes in the uninfarcted supply area of the circumflex artery remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Preservation versus severance of the subvalvular apparatus in mitral valve replacement: an experimental study.

Preservation of the subvalvular apparatus in mitral valve replacement has been suggested to improve postoperative left ventricular performance. As it is difficult to quantify the change in left ventricular performance clinically, an experimental model was devised to demonstrate the contribution of the subvalvular apparatus to left ventricular function. In eight dogs mitral valve replacement (St. Jude prostheses) was performed, preserving the subvalvular apparatus by plicating the leaflets with the prosthesis on the mitral annulus. Left ventricular function was assessed during volume loading with blood before and after cutting the chordae tendineae by means of electrocautery applied via flexible wires slung around the chordae and exteriorized through the left ventricular wall. Left ventricular internal diameters were measured by sonomicrometry. End-diastolic volume (LVedV) and stroke volume were determined by dye dilution and left ventricular pressure (LVP) by cathter tip manometer. The results showed that after cutting the chordae the heart rate did not differ from the pre-cut values at any LVedP. The peak left ventricular pressure was only significantly reduced at an LVedP of 5 mmHg and minor axis diameters were only increased at an LVedP of 9-12 mmHg. Significant changes were observed, however, in LV dP/dtmax (= maximum rise of LVP) (-15%), major axis end-diastolic diameter (+10%) and systolic shortening (-40%), end-diastolic volume (+18%) and ejection fraction (-16%) at any LVedP, and stroke volume (-24%) at any LVedV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effect of urapidil on the performance of ischaemic myocardium in anaesthetized dogs.

The effect of urapidil on the ischaemic myocardium was studied in eight anaesthetized dogs. Stenosis of the left descending coronary artery reduced blood flow and systolic contraction of the post-stenotic myocardium by about 50%; the end-diastolic length of the post-stenotic myocardium and the end-diastolic pressure increased, while aortic pressure slightly decreased. Subsequent administration of urapidil (0.25 + 0.25 + 0.5 + 1.0 mg/kg intravenously) did not affect the systolic shortening and end-diastolic length of the myocardium supplied by the left circumflux coronary artery, while the stroke volume and the systolic shortening of the ischaemic myocardium increased. The latter was correlated with a decrease in the heart rate (r = -0.92), but not with the reduction in aortic pressure. Urapidil by itself does not impair the performance of the ischaemic myocardium, but might be beneficial in decreasing the heart rate or suppressing reflex tachycardia during reduction of the afterload.

Adrenergic alpha-Antagonists↗
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↗
PubMed1984

[Isolated aortic isthmus stenosis: operation indications and results].

The goal of surgical correction of isolated coarctation of the aorta is normalization of the blood pressure. To assess the optimal age for the intervention with respect to operative morbidity and mortality, residual stenosis and recoarctation rate as well as the postoperative persistence of arterial hypertension without recoarctation, the pre- and postoperative findings of 237 patients (age at surgery: range one week to 17 years) were analyzed. The blood pressure, which was above the 95th percentile of age-matched normal values preoperatively in 93%, showed a clear decrease postoperatively in all age groups. On surgical correction, however, performed as of six years of age, there was a continuously increasing rate of persistent arterial hypertension without recoarctation which ranged from about 10% in those undergoing surgery between the ages of six and eight years to 31% in patients operated at ages between 13 and 17 years. In consideration of the operative results only with respect to the response of the resting blood pressure, insight is enabled only into one aspect of the prognosis, since the latter is equally dependent on the postoperative systemic arterial resistance. The systemic arterial resistance is already slightly elevated at three to five years of age, significantly increased as of six years of age, and at surgery after the age of six, shows a further increasing tendency. Accordingly, patients with postoperative normal or borderline-elevated blood pressure and apparently adequate surgical results, may be at risk of subsequent development of hypertension due to persistence of increased resistance, in particular, if surgery is performed after the age of five years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

[The cardiac hazard of tocolysis and antagonising possibilities. I. The haemodynamic situation of the patient during tocolysis/Protection of the myocardium by means of cardioselective beta-blockade. Experimental results (author's transl)].

7 mongrel dogs underwent general anaesthesia and thoracotomy. For the assessment of the haemodynamic situation the following parameters were measured: Left ventricular and aortic pressure, coronary flow, oxygen-saturation in the coronary sinus, pulmonal arterial pressure, central venous pressure, heart rate. From these measurements cardiac output volume and myocardial oxygen consumption could be calculated. Using an ultrasound transit-time method regional myocardial function could be assessed. After the establishment of these measurements Fenoterol has been given in an increasing dosage up to the upper therapeutical range. Then additionally the cardioselective beta-antagonist Metoprolol was administered stepwise up to a total dose of 1.2 mg/kg body weight. The measurements proved evidence, that a relatively small dose of 0,2-0,4 mg Metoprolol/kg body weight is sufficient to compensate the haemodynamic situation impaired by Fenoterol, esp. the rise in myocardial oxygen consumption.

Animals↗
PubMed1982

[The cardiac hazard of tocolysis and antagonizing possibilities. II. Communication: protection of the myocardium by means of substitution of magnesium].

In a comparative study the value of the substitution of magnesium for the evaluation of cardiac side-effects of tocolysis has been assessed with regard to haemodynamic as well as to metabolic and morphologic alterations. Haemodynamic studies at the thoracotomized dog using the technique described in the first publication showed significantly less severe haemodynamic alterations in a group with normal magnesium blood levels than in the second group with reduced magnesium blood levels. Significant differences could be found at systolic blood pressure, cardiac output, velocity and acceleration of pressure rising, total peripherial resistance, myocardial contraction status and myocardial oxygen consumption. Likewise, a beneficial tendency could be found at the parameters: heart rate, Bretschneiders index of inotropy, pulmonal arterial pressure and coronary reserve. During chronic experiments at the rat, the addition of magnesiumaspartate led to a significantly improved preservation of high-energy phosphates in the myocardium with a concomitant reduction of lactic acid output. Also the increase of body weight was significantly higher when substituting magnesium. Microscopic examination showed no irritations of myocardial structure within the magnesium-substituted group, whereas lymphocytic infiltrations and a slight fibrosis of the endocardium could be seen at the animals having received only Fenoterol. Together, these findings lead to the conclusion, that the substitution of magnesium can act prophylactically against cardiac alterations, induced by Fenoterol. Consequently, magnesium deficiency, which frequently accompanies pregnancy, should be balanced before starting a tocolytic therapy.

Animals↗
PubMed1982

[Effect of the combination of the beta-1-blocker metoprolol with the tocolytic fenoterol on uteroplacental hemodynamics and fetal cardiovascular sensitivity with particular consideration of intrauterine fetal malnutrition. Results of animal experiments].

7 merino sheep in an advanced state of pregnancy received oxytocin for labour induction under the conditions of control, monotherapy with the beta 2-adrenergic tocolytic fenoterol, combination of the latter with the beta 1-blocking substance metoprolol (Beloc). Likewise, the effect of labour induction was investigated when putting an artificial stenosis around the a. uterina during simultaneous application of fenoterol alone and combined with metoprolol. The following parameters were measured: aortic pressure and heart rate both in dam and fetus, maternal left ventricular pressure rising velocity, intrauterine pressure, uterine blood flow, uterine vascular resistance and regional myometrial contraction patterns by means of an ultrasonic transit time method. Measurement of maternal cardiovascular parameters once more showed, that maternal cardiovascular derangements could excellently be antagonised by metoprolol. Intrauterine pressure measurements as well as regional myometrial contraction patterns proved evidence, that there is no counteraction between the beta 2-mimetic substance and the beta 1-blocking agent concerning the tocolytic effect. When artificially stenosing the a. uterina, a rise in uterine contraction status could be observed; this hypoxic augmentation of myometrial tone could almost completely be reverted when combining fenoterol and metoprolol. Finally, no difference could be observed in the reaction of fetal cardiovascular parameters to reduced uterine blood flow before and after application of the beta 1-blocking substance metoprolol.

Animals↗
PubMed1981

[Hyperoncotic hemodilution in the ewe asa model of therapy in EPH gestosis (author's transl)].

Hyperoncotic hemodilution is proposed as a new therapeutic procedure in EPH-gestosis for improvement of uterine blood flow. By infusion of human albumin solutions in acute experiments on pregnant Merino sheep the effects of altered maternofetal colloid osmotic pressure gradients were investigated. The proposed hemodilution treatment improved uterine blood flow without a theoretically apprehended and undesired fetal hemoconcentration. An absolute indication for hypervolemic EPH-gestosis is suggested in accordance with modern knowledge of the pathophysiology of microcirculation. Isovolemic hemodilution is proposed to be of potential value in cases of EPH-gestosis with normovolemia, hypertension, intrauterine fetal growth retardation or other symptoms of placental insufficiency, at least as a subject to further studies.

Amniotic Fluid↗
PubMed1980

Hyperoncotic hemodilution with human albumin (20%) as a new therapeutic procedure in EPH-gestosis.

Improvement of uteroplacental blood supply in EPH-gestosis by infusion of human albumin solution is proposed. This procedure may be hazardous for the fetus by shifting the maternofetal colloid osmotic pressure gradient. In acute experiments on pregnant Merino ewes, the circulatory, biochemical and oncotic effects of hypervolemic and isovolemic, hyperoncotic hemodilution on mother and fetus were investigated. Both procedures showed the advantage of albumin as a physiological and effective plasma expander and significantly improved uteroplacental blood flow without an undesired action of fetal hemoconcentration. A catalogue of indications for hemodilution in EPH-gestosis is introduced.

Animals↗
PubMed1978

[Heart rhythm during esophago-gastro-duodenoscopy].

The ECGs of 157 patients were registered continuously during the oesophago-gastro-duodenoscopy with a R-R intervall monitoring system. The behavior of frequencies and cardiac arrhythms of 53 patients with and 104 patients without heart diseases is reported. 32 patients were premedicated with 0,5 mg Atropin intravenously, 121 patients received intramuscular premedication. The influence of the vegetative nervous system is discussed in view of the heart actions during the diagnostic procedure. A clinically relevant danger for the heart and circulatory system caused by oesophago-gastro-duodenoscopy was not observed.

Arrhythmias, Cardiac↗
PubMed1978

Acute effects of aortocoronary bypass surgery on left ventricular function and regional myocardial mechanics: a clinical study.

The acute effects of myocardial revascularization on overall left ventricular performance and on myocardial segmental wall motion were assessed intraoperatively in 22 patients who had unstable (11 patients) or stable angina pectoris (11 patients). Segmental contraction patterns were evaluated using an ultrasonic transit-time method. In 9 patients with unstable angina pectoris, notable improvement in segmental wall motion was observed as the short-term response to coronary bypass grafting. Hypokinetic patterns were rendered normal after revascularization. Despite marked changes in segmental myocardial function, overall left ventricular performance was not altered notably. In contrast, reperfusion did not lead to acute effects on either segmental wall motion or total left ventricular function in patients with stable angina pectoris. The results indicate that aortocoronary bypass grafting may improve segmental wall motion in patients with unstable angina.

Adult↗
PubMed1978

[External interference of cardiac pacemakers (author's transl)].

The pacemaker patient is faced with potential origins of interference to the pacemaker function in his daily life, at his working place and during medical-therapeutic interventions. Technical faults in the electronic circuit induced by external sources can be neglected. Malfunctions of synchronized cardiac pacemakers may occur in the presence of electrical signals similar to the intracardiac ECG (e.g. nerve stimulators) or by the influence of high energy electrical field (e.g. pulsed electromagnetic fields). Technical improvements like metalshielding of the unit, electronic filtering components and automatic conversion to fixed rate stimulation increase the reliability to a high degree.

Activities of Daily Living↗
PubMed1978

[Current status of pacemaker technology (author's transl)].

Since the first cardiac pacemaker was implanted twenty years ago, advances rendered have provided patients with increased reliability and therapeutic efficiency as well as subsequent incrementation in their life expectancy. Technological developments have yielded improvement in the main components such as electrode, the energy source and the electronic circuitry. A variety of leads are available to effect pacing requirements at ventricular and, in part, atrial levels. The introduction of lithium energy sources has prolonged the useful life of pacemakers to more than 8 years. Consumption of current has been reduced by decreasing electrode surface area, shortening of pulse duration and employment of hybrid circuits. Microprocessing of the electronic components have enabled reduced size of pulse generators while providing increased reliability and capabilities for additional functions. Amelioration of electrophysiologic disturbances has been specifically approached through increasing use of atrial and bifocal pacemakers, external programmability and overdrive pacing.

Cardiac Pacing, Artificial↗
PubMed1977

[The effect of nitrates on the function of intact and ischemic myocardium (author's transl)].

The effects of Sodium Nitroprusside (NPN), of Isosorbidedinitrate (ISDN), and of a combined therapy with NPN and the intraaortic balloon pump (IABP) on left ventricular function and on local contraction patterns of normal and ischemic myocardial regions were studied. In acute experiments on 16 dogs the anterior descending branch of the left coronary artery was stenosed to produce a hypokinesia or dyskinesia of the anterior wall of the left ventricle. Regional myocardial function was assessed using the ultrasound transit time method. When the LV filling pressure was initially norman (LVedP 5.7 +/- 0.6mmHg) nitrate infusion (120 microgram/minn NPN: 800 microgram/min ISDN) resulted in an aggravation of the ischemic dysfunction. Conversely, with high initial filling pressure (LVedP 15.4 +/- 1.3MMHg) regional myocardial function in the ischemic area returned to normal under therapy. Additional application of the IABP further improved regional myocardial mechanics. It is concluded, that reduction of coronary perfusion pressure due to nitrate therapy becomes critical when coronary reserve is depleted. Compensation is however possible if ventricular wall stress can be reduced and thus the oxygen consumption and the extravascular component of coronary resistance are decreased. Only when the initial filling pressure is high these conditions are met.

Animals↗