Search PubMed⌕ Search

Biomedical subjects

F Schwarz

Publications and source records attributed to F Schwarz.

278 records · Page 16Linked to original sources
PubMedDate not supplied

Pacing-induced myocardial ischemia in spite of nitroglycerin. Correlations regarding the extent of coronary artery disease.

In 10 patients without and 20 patients with various degrees of angiographically proven CAD 93 pacing runs were studied. Changes of PAm, of ECG, and of anginal pain serving as parameters of myocardial ischemia were correlated to the rate-pressure-product. In patients without CAD no correlations could be ascertained. In each patient with CAD determination of ischemia was achieved reproducibly. Ischemia threshold is represented by a sharp increase of PAm. Ischemia threshold seems a parameter to be preferred as compared to pain threshold. The extent of CAD (angiographically estimated) correlates well with the pacing test especially when collaterals are taken into account. After NG no substantial improvement of ischemia can be detected: Ischemia threshold before and after NG was reached at same rate pressure in each case. We conclude the atrial pacing test to be an excellent test for the provocation of myocardial ischemia. The test is also useful for estimation of the extent of CAD.

Adolescent↗
PubMedDate not supplied

Tolerance to ischemia of hypertrophied human hearts during valve replacement.

This study evaluates the tolerance to ischemia during induced cardiac arrest in patients undergoing aortic valve replacement. In all patients cardiac standstill was of 45 minutes duration. Biopsies for electron microscopic study were taken from the left ventricle before induction of arrest, at the end of the ischemic period and 20 minutes after coronary perfusion had been reestablished. Structural ischemic damage was more pronounced in patients with severe hypertrophy and structural reconstitution was delayed. Degenerative changes of the myocardial cells, although observed frequency, apparently did not influence the tolerance to ischemia. It is concluded from this study that patients with severe hypertrophy represent a high-risk group in cardiac surgery because of their reduced tolerance to induced myocardial ischemia during cardiopulmonary bypass.

Adult↗
PubMedDate not supplied

End-systolic pressure-volume and end-systolic stress-volume relationships in patients with aortic stenosis and with normal valvular function.

In order to study the effect of left ventricular hypertrophy on the endsystolic pressure-volume relationship, three left ventricular angiograms were performed in ten patients with normal valvular function but with varying left ventricular function (group 1) after 0.15 mg/kg propranolol and 1 mg atropine: at rest, after isosorbide-dinitrate at a decreased afterload and after methoxamine at an enhanced afterload. In eight patients with aortic stenosis (group 2) two left ventricular angiograms were performed: at rest and after isosorbide-dinitrate. Heart rate was kept constant by atrial pacing. Left ventricular mass in group 1 was 89 g/m2 and in group 2 180 g/m2. In group 1 the slope k of the end-systolic pressure-volume relation was related to the ejection fraction (EF) at rest: k = 0.024 . e0.072 EF; r = 0.93. In group 2 this relation was shifted to the left (P less than 0.001): k = 0.135 . e0.057 EF; r = 0.81. The relations, however, between the slope k of the end-systolic stress-volume relation and the ejection fraction were close together in group 1 and in group 2 and crossed at an ejection fraction of 67%. It is concluded: 1. In patients with aortic stenosis the end-systolic pressure-volume relation is steeper than in patients without valvular dysfunction at a given ejection fraction, so the relation between the slope k and the ejection fraction is shifted to the left. 2. The end-systolic stress-volume relationship is not altered in patients with aortic stenosis and seems to be advantageous for the evaluation of left ventricles with substantial hypertrophy due to pressure load.

Adult↗
PubMedDate not supplied

Quantitative ultrastructure of the myocardium in chronic aortic valve disease.

Light and electron microscopic morphometry was carried out in tissue samples which were obtained from the left ventricular free wall in 29 patients with chronic aortic valve disease during open-heart surgery. 6 patients had aortic stenosis, 9 had aortic insufficiency and 14 had a mixed aortic valve lesion. Hemodynamics were studied before operation. Patients with mixed aortic valve disease had a higher left ventricular mass, a lower ejection fraction and mean circumferential fiber shortening rate than patients with aortic stenosis. Peak systolic wall stress was comparable between groups. The intracellular content of contractile material was lower and the sarcoplasmic volume was higher in mixed aortic valve disease than in aortic stenosis. Mitochondrial volume and interstitial fibrosis were not different between groups. Patients with aortic insufficiency showed no significant difference of parameters as compared to both other groups. We conclude that an intracellular deficiency of myofibrils causes lack of contractility in advanced hypertrophy due to mixed aortic valve disease.

Aortic Valve Insufficiency↗
PubMedDate not supplied

Acquired antibiotic resistance in lactic acid bacteria from food.

Acquired antibiotic resistance, i.e. resistance genes located on conjugative or mobilizable plasmids and transposons can be found in species living in habitats (e.g. human and animal intestines) which are regularly challenged with antibiotics. Most data are available for enterococci and enteric lactobacilli. Raw material from animals (milk and meat) which are inadvertantly contaminated with fecal matters during production will carry antibiotic resistant lactic acid bacteria into the final fermented products such as raw milk cheeses and raw sausages. The discovered conjugative genetic elements of LAB isolated from animals and food are very similar to elements studied previously in pathogenic streptococci and enterococci, e.g. theta-type replicating plasmids of the pAMbeta1, pIP501-family, and transposons of the Tn916-type. Observed resistance genes include known genes like tetM, ermAM, cat, sat and vanA. A composite 29,871 bp resistance plasmid detected in Lactococcus lactis subsp. lactis isolated from a raw milk soft cheese contains tetS previously described in Listeria monocytogenes, cat and str from Staphylococcus aureus. Three out of five IS elements on the plasmid are almost or completely identical to IS1216 present in the vanA resistance transposon Tn1546. These data support the view that in antibiotic challenged habitats lactic acid bacteria like other bacteria participate in the communication systems which transfer resistance traits over species and genus borders. The prevalence of such bacteria with acquired resistances like enterococci is high in animals (and humans) which are regularly treated with antibiotics. The transfer of antibiotic resistant bacteria from animals into fermented and other food can be avoided if the raw substrate milk or meat is pasteurized or heat treated. Antibiotic resistance traits as selectable markers in genetic modification of lactic acid bacteria for different purposes are presently being replaced, e.g. by metabolic traits to generate food-grade vectors.

Animals↗
PubMedDate not supplied

Tolerance to ischemia in the human heart.

The tolerance to ischemic cardiac arrest during open-heart surgery depends on the degree of hypertrophy and on the functional impairment of the heart. The angiographically determined muscle mass is a good indicator of the susceptibility of the myocardium to ischemic injury and of its ability to quickly restore myocardial structure upon reperfusion. Tissue from extremely hypertrophied hearts exhibited numerous degenerative alterations.

Adult↗