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Biomedical subjects

J Nitsch

Publications and source records attributed to J Nitsch.

At least 55 records · Page 3Linked to original sources
PubMed1986

[Videodensitometric determination of relative blood regurgitation volume in aortic valve insufficiency].

A simple video densitometric method based on the indicator distribution principle in the region of interest permits the determination of the relative amount of regurgitation between the ascending aorta and the left ventricle in cases of aortic valve insufficiency. The experimental basis and early clinical measurements are described and are compared with the more conventional methods of cine angiography and radionuclide ventriculography.

Adult↗
PubMed1986

[Differential analysis of ventricular contraction using digital subtraction angiography].

One hundred and thirty-six patients with various cardiac abnormalities that had been diagnosed by standard methods, were examined by I-V DSA; images of the left and right ventricles during a representative cardiac cycle were submitted to amplitude and phase analysis, using a Fourier transformation. Temporal differentiation of ventricular function was derived from the best available right anterior oblique projection; the amplitude of cardiac movement of abnormal areas in the myocardium were obtained from a grey scale or colour coding at a fixed point. Comparison with a control group of 35 individuals showed the following pathological findings: hypokinetic segments (33 cases) showed delay, dyskinesias (20 cases) showed complete separation of maximal phases, frequently with a double peak in the phase histogram; disturbances of cardiac rhythm (14 cases) showed atypical localisation of initiation of contraction: in Wolfe-Parkinson-White syndrome this is basal-anterior, in left bundle branch block and VVI stimulation it is apical inferior; in hypertrophic obstructive cardiomyopathy (eight cases) it is postero-basal inferior with high, narrow peaks on the phase histogram. Differential phase analysis on I-V DSA enables one to define cardiac contraction in a simple manner.

Angiography↗
PubMed1986

[Results of fatty acid SPECT of the myocardium in coronary disease].

New developments in radiopharmacology of 123I-labeled metabolic tracers and single-photon emission computerized tomography (SPECT) allow now-a-days the assessment of parameters of cardiac energy metabolism in well-defined areas of the heart muscle. This article will present a brief outline of the basic pathophysiological principles used in the application of 123I-labeled phenyl fatty acids for the evaluation of CAD. First clinical results suggest an important application of cardiac fatty acid metabolic imaging to the detection, localisation and conceivable quantitation of myocardial ischemia, myocardial infarction and assessment of tissue viability. In addition to the diagnostic applications in CAD, cardiac fatty acid metabolic imaging may provide new perspectives to pathophysiological investigations of the coupling of local flow and substrate utilisation in vivo and the effect of therapeutic interventions.

Coronary Disease↗
PubMed1986

[Intravenous DSA of the heart: functional studies of the left ventricle in coronary heart disease at rest and following stress].

Intravenous digital subtraction angiography (i.v. DSA) of the heart is performed for demonstration of the morphologic and functional peculiarities of the left heart chamber, especially the ejection fraction and regional wall motion abnormalities. Employment of both geometric and video densitometric computation techniques resulted in a good correlation with direct ventriculography (r = 0.945), video densitometry, however, with a tendency to values up to 10% higher. Comparative DSA studies during rest and following exercise in 25 patients with coronary heart disease were suitable to discover pathologic strain reactions of the myocardium in 4 cases, typically depending on angiographic findings of the coronary arteries. In this way a simple method for better estimation of a deficit in coronary blood supply and its functional impact on myocardial performance may become useful.

Angina Pectoris↗
PubMed1985

[Functional disorders of chamber demand (VVI) and sequential AV (DDD) pacemakers caused by muscle potentials].

Muscle potentials as a cause of pacemaker malfunction are often unrecognized, because control examinations are usually performed without physical exercise. Two observations are cited to illustrate how malfunctioning of different modes of stimulation can be caused by interference from muscle potentials. In addition to the known suppression of impulse production, fixed-rate stimulation may occur. These observations indicate that pacemaker function should be tested also during physical activity. Any malfunction can almost always be stopped by re-programming amplifier sensitivity.

Action Potentials↗
PubMed1985

[Derivation and critical analysis of formulas for the calculation of the refractive power of intraocular lenses].

Using matrices, formulae are derived for calculating the refractive power of the ocular system and of intraocular lenses. These formulae take into account the finite extension of the lenses under consideration. They also contain only measurable quantities. Some sources of uncertainty in predicting the power of the IOLs are pointed out estimates of their orders of magnitude are given. By combining the new results with those obtained on the basis of regression analysis, the prediction of IOL power can be improved, especially for eyes with short axial length. In a critical comparison with formulae which are well known from the literature, a number of them were found to be incorrect. In conclusion, some suggestions are made for improving the prediction of lens power.

Humans↗
PubMed1985

[Localization of pre-excitation in the WPW syndrome by analysis of the ventricular contraction course].

Fourier phase analysis of gated radionuclide ventriculography (RNV) was applied in 23 patient for the identification of cardiac contraction patterns in WPW syndrome (controls with normal ventricular function and sinus rhythm, n = 30). The sequence and velocity of regional ventricular wall motion was determined and correlated to the results of electrophysiological studies. In 3/23 patients the contraction pattern was not different from controls. Indicating the preexcitation in 20/23 patients the earliest ventricular contraction was localized as follows: right atrial n = 5, paraseptal right n = 2, paraseptal left n = 6 and atrial left n = 7. In 15/16 patients nuclear data corresponded with electrophysiological endocardial mapping. Phase analysis of RNV provides a reliable non-invasive method for localization of preexcitation in WPW syndrome.

Electrocardiography↗
PubMed1984

[Course of contraction during physiological and ventricular pacemaker stimulation].

Phase imaging of gated radionuclide ventriculography was applied to the identification of cardiac activation patterns in patients with sinus rhythm (n = 14) or with ventricular (VVI)- (n = 28), atrial (AAI)- (n = 3) or AV-sequential (DDD)-pacing (n = 17). In patients with sinus rhythm, AAI- or DDD-pacing, analysis revealed homogeneous distribution of phase across both ventricles. In VVI-pacing a left bundle branch block configuration of the ventricular activation was found in 21 of 28 patients. In 7 of 28 patients phase distribution indicated a simultaneous activation of both ventricles (with or without delimitation of the apex of the right ventricle). This is of clinical importance because artificial spread of excitation and asynchronous contraction during VVI-pacing may be responsible for higher myocardial oxygen demand. Retrograde conduction in VVI-pacing was found in 9 of 28 patients. Phase analysis provides a reliable method for evaluation of pacing-induced activation patterns.

Adult↗
PubMed1984

[Control of anti-arrhythmia therapy with amiodarone. Value of the determination of blood levels].

An antiarrhythmic treatment was done in 56 patients with recurrent ventricular tachycardias using amiodarone. The dosage was 400 to 600 mg/d following a loading dosage of 1000 mg for 8 to 12 days. Amiodarone and desethylamiodarone concentration in serum (control group n = 33) and in erythrocyte haemolysate (control group n = 13) were determined in relapses of ventricular tachycardias (n = 7) and in pulmonary fibrosis as serious side effect (n = 3). It was shown that amiodarone levels rise continuously during loading treatment until the 8th to 12th day and that desethylamiodarone can be demonstrated after the 3rd day of treatment. The mean concentrations (+/- standard deviation) of amiodarone and desethylamiodarone were 2.21 +/- 0.89 microgram/ml and 1.3 +/- 0.74 microgram/ml in serum and 0.97 +/- 0.65 microgram/ml and 1.95 +/- 1.9 micrograms/ml in erythrocyte haemolysate. Amiodarone levels did not correlate with efficacy and with incidence of side effects. However, in pulmonary fibrosis high desethylamiodarone concentrations in serum (greater than 2.5 micrograms/ml) and in erythrocyte haemolysate (greater than 4 micrograms/ml) were found. Four out of 7 patients with recurrent ventricular tachycardia showed relatively low desethylamiodarone concentrations in serum (desethylamiodarone/amiodarone ratio less than 0.4). Thus control of amiodarone treatment can be enlarged by determination of desethylamiodarone levels as its concentrations correlate with relapses of ventricular tachycardias and serious side effects.

Adult↗
PubMed1984

Evaluation of left ventricular performance by radionuclide ventriculography in patients with atrioventricular versus ventricular demand pacemakers.

In 55 patients with coronary artery disease (n = 37), cardiomyopathy (n = 12), or myocarditis (n = 6) and programmable ventricular or dual-chamber atrioventricular (AV) demand pacemakers, left ventricular (LV) performance was studied by gated radionuclide ventriculography during pacing (60 or 70 to 120 bpm). Twenty-three patients were followed over 4 to 6 months. In 16 patients the findings in ventricular (VVI) and dual-chamber AV (DDD) pacing were compared. In all patients end-diastolic volume (EDV) decreased and cardiac output increased when the pacing rate was changed from 60 or 70 to 120 bpm. For instance, in the patient group with VVI pacemakers, EDV decreased by 7.53% +/- 3.5% (p less than 0.01) and cardiac output increased by 53.5% +/- 19.4% (p less than 0.01). The results were independent of the underlying heart disease. After 4 to 6 months, a reduction of both cardiac output and ejection fraction was found in 6 of the 23 patients. As compared to VVI pacing, a significantly higher cardiac output (2% to 16%) was derived from DDD pacing. The results indicate the dependence of LV performance on the pacing rate and the benefit of DDD pacing. Since gated radionuclide ventriculography provides the means to determine the effect of different pacing modes on LV performance, an optimal pacing mode may be found for each individual.

Adult↗
PubMed1983

Increase of mexiletine plasma levels due to delayed hepatic metabolism in patients with chronic liver disease.

The clinical relevance of changes in pharmacokinetics of oral mexiletine (600 mg daily dose) was studied in 82 patients with ventricular arrhythmias and impaired liver, renal or heart function (control group n = 51, patients with liver cirrhosis n = 9, with renal insufficiency n = 14, or heart failure n = 8). Increased plasma levels of mexiletine were found in patients with chronic liver disease (2.21 +/- 0.94 micrograms/ml, versus 0.63 +/- 0.22 micrograms/ml of controls, P less than 0.01). Plasma levels in patients with renal insufficiency or heart failure were not significantly different from the controls. The resulting elevated plasma levels in patients with liver cirrhosis emphasize the importance of hepatic metabolism in the elimination of mexiletine. Drug monitoring must be considered necessary in patients with impaired liver function.

Arrhythmias, Cardiac↗
PubMed1983

Treatment of recurrent sustained ventricular tachycardia with mexiletine and disopyramide. Control by programmed ventricular stimulation.

Oral antiarrhythmic treatment with mexiletine and disopyramide was evaluated in 34 patients with recurrent sustained ventricular tachycardias by programmed ventricular stimulation, except in a few instances where spontaneous attacks occurred under therapy. Coronary heart disease was present in 17 patients, cardiomyopathy in 11, myocarditis in five, and mitral valve prolapse in one. Complete suppression of ventricular tachycardia was observed in three of 30 patients under mexiletine and in one of 25 patients under disopyramide. Disopyramide slowed the rate of the ventricular tachycardia considerably, while mexiletine had no such influence. For a mean of 24 months, 19 patients were maintained on either substance. Complete suppression of ventricular tachycardia during programmed stimulation predicted freedom from recurrences. Ventricular tachycardias recurred less frequently and at a slower rate in the other patients, but 31% have died. This study shows that complete suppression of ventricular tachycardia by mexiletine or disopyramide can be achieved only in a minority of patients with previously drug-resistant tachycardias.

Adult↗
PubMed1983

[Effect of varied pacemaker stimulation on left ventricular volume data--studies with radionuclide ventriculography].

Left ventricular performance (parameters: EDV, ESV, EF, cardiac output) was studied by gated radionuclide ventriculography in 55 patients with ventricular or AV-sequential pacemakers. 23/55 patients were followed over 4-6 months. EDV and SV decreased significantly (p less than 0.01) and cardiac output increased (p less than 0.01) with changing pacing rate from 70-72 to 100/min. After 4-6 months a reduction of cardiac output was found in 15/23 patients. As compared to ventricular pacing, a significantly higher cardiac output was found during AV-sequential pacing. These nuclear data indicate the dependence of left ventricular performance on pacing mode. From non-invasive methods an individual adapted pacing mode can be derived.

Adult↗
PubMed1980

Comparison of myocardial potassium and thallium flux as studied by tracer methods.

Although myocardial scintigraphy with 201thallium is widely applied in humans, the behavior of thallium at the cellular level is still under discussion. We compared the transmembrane fluxes of potassium and thallium in the isolated papillary muscle of guinea pigs. A qualitative conformity exists between potassium and thallium fluxes with respect to heart rate and temperature. Quantative comparison revealed a decreased flux rate of thallium for efflux when compared with potassium. The time dependence of thallium influx indicates that thallium scintigraphy of the myocardium reflects mainly an extracellular distribution.

Animals↗