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Biomedical subjects

M Ritter

Publications and source records attributed to M Ritter.

At least 199 records · Page 11Linked to original sources
PubMed1988

Left ventricular systolic series elastic properties in aortic stenosis before and after valve replacement.

In seven patients with aortic valve disease the time course of an auxotonic beat was compared with that of an isovolumetric beat produced by aortic cross clamping during open heart surgery. The rate of systolic stress rise (dS/dt; g.cm-2) of the isovolumetric beat at peak meridional wall stress (Sp; g.cm-2) of the auxotonic beat was determined by tipmanometry and simultaneous sonomicrometry and was found to be 87% of maximum dS/dt. In the second part of the study the stiffness index (k) was calculated in patients undergoing cardiac catheterisation according to: k = 0.87.(max.dS/dt)/Sp.Vcf, where Vcf = normalised midwall circumferential fibre shortening velocity (circ.s-1). In 22 patients, 10 controls and 12 patients with aortic stenosis before (pre) and after (post) valve replacement the systolic stiffness index k (circ-1) was determined using tipmanometry and frame by frame angiocardiography. Muscle fibre diameter and interstitial fibrosis were assessed from left ventricular endomyocardial biopsies. The systolic stiffness index k was 15 circ-1 in controls, 14 in preoperative patients with aortic stenosis and 12 (p less than 0.01 v controls) in postoperative patients. There was a significant correlation between k and muscle fibre diameter (r = 0.55; p less than 0.01) but not between k and interstitial fibrosis or ejection fraction. We conclude that systolic stiffness index k is normal despite marked left ventricular hypertrophy in preoperative patients with aortic stenosis. Following successful valve replacement systolic stiffness index decreased and was significantly lower than in controls. Series elasticity appears to be determined by structures related to the muscle cell rather than to interstitial fibrosis.

Aortic Valve Stenosis↗
PubMed1988

Left ventricular systolic function in aortic stenosis.

In aortic valve stenosis, concentric hypertrophy develops which is characterized by a reduced end-diastolic radius-to-wall thickness ratio (r/h) with an essentially normal cavity shape. As long as the product of (r/h) and LV systolic pressure remains constant, hypertrophy is appropriate. An increase in the product, which represents an increase in wall stress signals inadequate LV hypertrophy. Although at first glance, massive LV hypertrophy appears favourable for the maintenance of a normal LV ejection fraction in aortic stenosis, data from 23 studies of the literature have shown an inverse relationship between ejection fraction and LV angiographic mass m-2 (r = -0.59). Both a degree of hypertrophy inadequate to keep systolic wall stress within normal limits and a reduction of LV contractility may explain the depression of ejection fraction when LV angiographic mass is sizeably increased. Conversely, a normal ejection fraction in aortic stenosis may not be indicative of normal systolic myocardial function under all circumstances. In the presence of mildly reduced contractility, a normal ejection fraction may be maintained by the use of preload reserve. Assessment of myocardial structure from LV endomyocardial biopsies revealed no differences in muscle fibre diameter, interstitial fibrosis and volume fraction of myofibrils between patients with aortic stenosis having a normal and those with a depressed ejection fraction. Preoperative ejection fraction is a poor predictor of postoperative survival, whereas markedly increased preoperative angiographic mass and end-systolic volume have been reported to predict an unsatisfactory postoperative outcome characterized by either death or poor LV function.

Aortic Valve↗
PubMed1988

Diastolic properties of the normal left ventricle during supine exercise.

Diastolic function in response to dynamic exercise was studied by biplane left ventriculography and by measuring left ventricular pressure with a high fidelity micromanometer tipped catheter at rest and during supine bicycle exercise in nine normal subjects. During exercise there was a fall in end systolic volume, in the time constant of left ventricular isovolumic pressure decay, and in the lowest diastolic pressure. Stroke volume, peak filling rate, mean passive filling rate, and the volume at the lowest diastolic pressure increased. There was an increase in the number of time constants that had elapsed before the lowest diastolic pressure was reached and the slope of the pressure-volume curves during passive filling (delta P/delta V) increased without changes in end diastolic pressure and volume. These results show that during exercise elastic recoil is enhanced and left ventricular relaxation is faster and more complete. Both phenomena reduce the lowest diastolic filling pressure. The observed increase in chamber stiffness from rest to exercise is probably related to increased resistance of the left ventricular wall caused by higher passive filling rates. The enhanced early diastolic pressure decay during exercise allows stroke volume to increase despite an increase in diastolic viscoelastic resistance and chamber stiffness.

Adult↗
PubMed1988

Frequency analysis of cytotoxic T lymphocyte precursors--possible relevance to HLA-matched unrelated donor bone marrow transplantation.

HLA-matched unrelated donor (MUD) bone marrow transplants and transplants between HLA mismatched family members are associated with an increased incidence and severity of graft-versus-host disease (GVHD) in comparison with HLA-identical sibling transplants. A limiting dilution analysis system was set up to measure the frequency of alloreactive cytotoxic T lymphocyte precursors (CTL-p) in normal individuals and in potential donor/patient pairs selected for bone marrow transplantation. The donor/recipient pairs were divided into four groups depending on their degree of HLA disparity. A distinct range of CTL-p frequencies was obtained for each group and these showed a hierarchy of response related to the degree of HLA disparity between donors and recipients in that particular group. This assay system may be of value in selecting potential matched unrelated and mismatched family donor/patient pairs for those at lower risk of GVHD.

Analysis of Variance↗
PubMed1987

Ectopic expression of Thy-1 in the kidneys of transgenic mice induces functional and proliferative abnormalities.

Hybrid human--mouse Thy-1.1 genes were injected into pronuclei of Thy-1.2 mice to produce transgenic animals. A hybrid gene composed of the 5' part of the mouse Thy-1.1 gene combined with the 3' human untranslated regions was expressed abnormally in the kidney podocytes, which resulted in severe protein-uria and subsequent death in several founder mice. A hybrid Thy-1 gene composed of the human coding region with the 5' and 3' flanking regions of the mouse gene was expressed abnormally in a different part of the kidney (the tubular epithelia), which resulted in a proliferative kidney disorder. In addition, a neoplasm was found in the brain of one of these mice. These results show that the Thy-1 protein can play an important role in the activation, proliferation, and differentiation of many different cell types.

Animals↗
PubMed1987

Is there coronary vasoconstriction after intracoronary beta-adrenergic blockade in patients with coronary artery disease.

Vasomotility of normal and stenosed coronary arteries was studied at rest and during supine bicycle exercise in 10 patients with classical exercise-induced angina pectoris receiving 1 mg intracoronary propranolol before the exercise test (propranolol group). Normal and stenotic coronary lumen areas were determined from biplane coronary arteriograms using a computer-assisted system. Measurements were performed at rest, after 1 mg intracoronary propranolol, during supine exercise (89 W for 3.4 minutes) and 5 minutes after 1.6 mg sublingual nitroglycerin administered at the end of the exercise test. The results were compared with previously obtained data on the effect of dynamic exercise on coronary lumen area in 12 patients receiving no medication (control group) and in 6 patients receiving 0.1 mg intracoronary nitroglycerin before the exercise test (nitroglycerin group). In the control group, coronary stenosis area decreased during exercise to 71% of levels at rest (p less than 0.001) whereas normal coronary lumen area increased to 123% of control (p less than 0.01). In the propranolol group both normal (113%, p less than 0.05 versus rest) and stenotic coronary lumen area (122%, p less than 0.05 versus rest) increased during exercise. A similar increase in both normal and stenotic areas was observed during exercise after pretreatment with 0.1 mg intracoronary nitroglycerin (123%, p less than 0.01 and 114%, p = NS versus rest). Sublingual administration of 1.6 mg nitroglycerin at the end of exercise increased coronary stenosis area to 145% (p less than 0.01 versus rest) in the propranolol group and to 115% in the control group (p = NS versus rest). It is concluded that intracoronary administration of propranolol does not potentiate coronary vasoconstriction of the epicardial vessels at rest and during exercise. In contrast, intracoronary propranolol prevents exercise-induced stenosis narrowing either because of reduced myocardial oxygen demand with a lower coronary blood flow resulting in a smaller transstenotic pressure gradient and, thus, a smaller flow-induced fall in stenosis distending pressure; or because of "local" beta-receptor blockade with unopposed distal arteriolar alpha-receptor tone, resulting in a higher poststenotic pressure and, thus, in a greater stenosis distending pressure; or because of a local anesthetic effect of propranolol with a decrease in calcium influx to the coronary smooth musculature.

Adult↗
PubMed1987

[Dynamics of cardiac output in patients with hypertrophic obstructive cardiomyopathy].

To characterise the duration of aortic flow velocity waveforms in hypertrophic obstructive cardiomyopathy (HOCM) the dynamics of aortic flow were investigated in 10 normals and 11 patients with hypertrophic obstructive cardiomyopathy performing 16-gated Doppler 2D-echocardiography of the ascending aorta. 16 flow velocities were recorded along the Doppler beam axis between the anterior and posterior aortic walls, and averaged over 8 beats. Flow times were derived from the flow curves and normalised by the ejection period as determined from the carotid pulse tracing. Thus, relative ejection time (% SEP) was calculated at the anterior (gate 4) and the posterior aortic wall (gate 13) as well as at the axis of the vessel (gate 9). In normals % SEP was 92 +/- 3% in gate 4, 95 +/- 4% in gate 9 and 93 +/- 3% in gate 13 (NS). In patients with HOCM % SEP was 92 +/- 5% in gate 4 and 83 +/- 4% (NS) in gate 9. At the posterior aortic wall (gate 13) % SEP amounted to 68 +/- 5% and was significantly lower than in gate 9 (P less than 0.05) and in gate 4 (P less than 0.001) respectively. It is concluded that in contrast to normals systolic flow time in hypertrophic obstructive cardiomyopathy varies along the sound beam in the ascending aorta. Flow time recorded at the posterior aortic wall is most abbreviated.

Blood Flow Velocity↗
PubMed1987

Differential regulation of a Thy-1 gene in transgenic mice.

We have generated Thy-1.1-transgenic Thy-1.2 mice to study the developmental expression of the Thy-1 gene in detail by transcriptional and immunological methods. In brain, the expression of the injected gene was identical to that of the endogenous gene in a tissue- and development-specific manner. In lymphoid tissue, the transferred gene was also expressed correctly in the early phases of T-cell lineage development; however, as the T cells matured, the transcription of the transferred gene, but not the endogenous gene, was suppressed. This result shows that different regulatory elements are used to express the Thy-1 gene in early and late lymphoid development.

Age Factors↗
PubMed1987

The use of invasive techniques, angiography and indicator dilution, for quantification of valvular regurgitations.

Angiographic techniques have been used for the quantification of mitral or aortic and rarely tricuspid regurgitation. Mitral or aortic regurgitant volume per beat and the regurgitation fraction (fao and fm, respectively) are obtained from the angiographic determination of total left ventricular stroke volume (TSV) and forward stroke volume (FSV) estimated by a different technique. Although this procedure is generally accepted as the gold standard for quantification of left heart regurgitations, there are several limitations: In the presence of mitral and aortic regurgitation no separate quantification of fao and fm is feasible; heart rate at the time of determination of FSV (from Fick or dye dilution cardiac output) and of TSV (angio) may be different; there is a tendency to consistently overestimate stroke volume by angio techniques; repeated estimations of TSV by angio are influenced by the circulatory effects of the contrast dye. In contrast indicator dilution techniques, where upstream and downstream sampling allow the simultaneous estimation of forward and regurgitant flow, the accuracy of the determination of FSV is well established and repeated estimations of fao and fm are possible because the indicators do not have cardiovascular effects. These methods are, however, crucially dependent on thorough mixing of the regurgitant volume with the blood in the upstream chamber. In 23 patients with isolated aortic regurgitation there was a positive correlation between fao evaluated by thermodilution and fao determined by the biplane angio-Fick method (r = 0.59). fao by thermodilution averaged 0.40 and fao by angio-Fick 0.46 (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiocardiography↗
PubMed1987

Pain relief after arthroscopy: naproxen sodium compared to propoxyphene napsylate with acetaminophen.

We compared naproxen sodium (550 mg) and propoxyphene napsylate with acetaminophen (PN/A, 100 mg with 650 mg) for pain relief after arthroscopy or arthroscopic meniscectomy. Fifty-two patients entered this multicenter, double-blind, randomized, parallel trial. In each drug group, pain intensity values dropped consistently throughout this six-hour study from mean baseline levels of approximately 55 on a scale of 0 to 100. Pain intensity values were lower at each hour in the naproxen sodium than in the PN/A group and significantly lower at hour 1 (P = .008). Pain intensity differences (PID, reflecting change from baseline) mirrored this trend: greater mean PIDs were seen in the naproxen sodium group at each hour, and this difference between drug groups was statistically significant at hour 1 (P = .017). One patient in the naproxen sodium group and seven patients using PN/A took a second dose within the six hours. Patients in each drug group reported five complaints.

Acetaminophen↗
PubMed1987

[Relation between systolic and diastolic elastic muscle properties and the morphology of the hypertrophic pressure-loaded left ventricle].

According to Maxwell's model, left ventricular (LV) systolic elastic properties are characterized by a series-elastic element and LV diastolic properties by a parallel-elastic element. It is not known whether this functional concept is reflected by some morphological counterparts. In 12 patients with aortic stenosis (AS) before and 19 months after aortic valve replacement, and in ten controls, LV biplane volume and simultaneous high-fidelity pressure measurements were performed during diagnostic catheterization. The constant (k) of systolic myocardial stiffness was determined from LV peak wall stress, the maximum rate of systolic stress rise and instantaneous LV midwall circumferential fiber shortening rate at peak stress. The constant (k*; circ-1) of diastolic stiffness was assessed from the diastolic stress-stiffness relationship, using a viscoelastic model. In AS patients pre- and postoperative endomyocardial biopsies were taken to assess muscle fiber diameter, interstitial fibrosis and LV fibrous content. Systolic myocardial stiffness constant was 15 circ-1 in controls, 14 circ-1 in preoperative and 12 circ-1 in postoperative AS patients (P less than 0.01 vs. controls). Diastolic myocardial stiffness constant was 19 circ-1 in controls, 23 circ-1 in preoperative AS patients and increased slightly but not significantly to 33 circ-1 after valve replacement. Parallel to the postoperative decrease in systolic stiffness, muscle fiber diameter decreased significantly from 33 to 27 mu (P less than 0.05). The slight increase in diastolic stiffness was accompanied by a significant increase in interstitial fibrosis from 15% to 26% (P less than 0.05); LV fibrous content remained essentially unchanged after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve Stenosis↗
PubMed1987

Trocar introduction performed during laparoscopy of the obese patient.

Obesity, especially morbid obesity, is reported to be a relative contraindication to laparoscopy. A technique for trocar introduction and laparoscopy of the obese patient to eliminate this contraindication is described. The technique presented herein differs from the traditional method by: 1, primary trocar entry at a 90 degree angle to the horizontal plane, and 2, confirmation for intraperitoneal position of the instruments before creating the pneumoperitoneum. A retrospective study was done to compare demographic, medical and surgical data of obese and non-obese patients. No important differences were found and it was also found that obesity was not a relative contraindication to laparoscopy. Obesity was defined by a ponderal index of less than 11.7. No operative complications were found for the 344 obese patients studied and all laparoscopy procedures were completed as intended. These differences in technique can avoid the pitfalls commonly reported concerning laparoscopy of the obese patient.

Adult↗
PubMed1986

[The stunned myocardium: ischemia-induced reversible myocardial dysfunction].

The "stunned" myocardium is the result of an ischemic insult which is not of sufficient severity to produce myocardial necrosis but affects myocardial function, biochemical processes and ultrastructure for a prolonged period of time. A "stunned" myocardium can be expected when preoperative asynergic wall motion is normalized after successful coronary bypass surgery under similar loading conditions. Forty-five patients (mean age 51 years) underwent diagnostic cardiac catheterization before and 9.5 months after successful bypass surgery. Patients with perioperative myocardial infarction and/or occluded vein grafts were excluded from the study. Preoperatively 17 of the 45 patients had a reduced systolic ejection fraction. These patients were further divided into the following two groups: group 1 consisted of 6 patients without or with only a small increase in regional ejection fraction (6 regions of the left ventricle in the right anterior oblique projection) after surgery (control group), and group 2 of 11 patients with a postoperative increase in preoperatively reduced regional ejection fraction (preoperatively "stunned" myocardium). In regard to duration of symptoms, functional classification (NYHA), number of myocardial infarctions, unstable angina pectoris and physical working capacity on the bicycle ergometer, there were no significant differences between the two groups. A mean 2.8 and 3.6 vein grafts (ns) were implanted in groups 1 and 2, respectively. Postoperatively, NYHA class decreased significantly and physical working capacity increased in both groups. Left ventricular end-diastolic and peak systolic pressure remained unchanged after surgery; left ventricular ejection fraction was unchanged in group 1 (49 vs. 51%, ns) but increased significantly in group 2 (38 vs. 50%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Artery Bypass↗
PubMed1986

Cefotetan in the treatment of obstetric and gynecologic infections.

The efficacy, tolerance, and safety of cefotetan--a new 7-alpha-methoxy cephalosporin--was assessed in controlled and uncontrolled evaluations involving 131 evaluable patients hospitalized with obstetric and gynecologic infections. The 99% satisfactory clinical response rate obtained with this drug was equivalent to that obtained with either moxalactam or cefoxitin, yet the mean amount of cefotetan given was lower than that of the other two drugs. Cefotetan was well tolerated and produced no major adverse reactions. In this era of Diagnosis Related Groups and cost containment, the twice-daily dosage schedule of cefotetan is a decided cost benefit.

Adult↗
PubMed1986

Myasthenia gravis: immunohistological heterogeneity in microenvironmental organization of hyperplastic and neoplastic thymuses suggesting different mechanisms of tolerance breakdown.

Four samples of thymoma obtained from patients affected by myasthenia gravis have been immunohistologically analysed on cryostat sections using a panel of antisera and monoclonal antibodies specific for antigens which define different stages of intrathymic lymphocyte differentiation and antigens specific for different types of thymic epithelial cells (cortical, medullary). When the thymoma samples were compared to age-matched normal thymuses and hyperplastic thymuses obtained from patients with myasthenia gravis some evident microenvironmental differences could be demonstrated using these reagents. In all the thymoma samples in fact the neoplastic lobules appeared as grossly enlarged cortical-type areas, formed by accumulations of T lymphocytes exhibiting the cortical immature phenotype (TdT+, T6+, etc.) within a network of putatively neoplastic epithelial cells characterized by cortical phenotype as defined by reactivity with various monoclonal antibodies (RFD4-, MR3+). These 'cortical' epithelia showed some abnormal features such as lack or irregular distribution of HLA-DR and enhanced keratin expression. Small areas of 'medullary' differentiation could be observed in 3/4 thymoma samples. In thymic hyperplasia, on the other hand, the cortical areas appeared somewhat compressed (but comparable to those observed in normal age-matched samples) by enlarged medullary areas. The expansion of medullary areas was due to the infiltration of 'peripheral' lymphoid tissue intruding through the extraparenchymal zone and forming organized B and T areas. These observations are discussed in the light of the clinical heterogeneity observed in myasthenia gravis.

Adolescent↗
PubMed1986

Vasoconstriction of stenotic coronary arteries during dynamic exercise in patients with classic angina pectoris: reversibility by nitroglycerin.

To study the vasomotility of normal and diseased coronary arteries during dynamic exercise, symptom-limited supine bicycle exercise during cardiac catheterization was performed by 18 patients with classic angina pectoris. The cardiovascular response was assessed by hemodynamic measurements and computer-assisted determination of normal and stenotic coronary artery luminal areas from biplane coronary angiograms made before, during, and after exercise. After baseline measurements were recorded, 12 patients (group 1) performed bicycle exercise for 3.4 min (mean), reaching a maximum workload of 81 W (mean); at the end of exercise they received 1.6 mg sublingual nitroglycerin. After measurements at rest in six other patients (group 2), 0.1 mg intracoronary nitroglycerin was given, followed by exercise (3.8 min, 96 W; NS) and sublingual nitroglycerin as in group 1. During exercise in group 1, luminal area of the coronary stenosis decreased to 71% of resting levels (p less than .001), while area of the normal coronary artery increased to 123% of control (p less than .001). After sublingual nitroglycerin at the end of exercise, area of the normal vessel further increased to 140% of control (p less than .001), while luminal area of the stenosis dilated to 112% of resting levels (p less than .001 vs exercise, NS vs rest). Pretreatment with intracoronary nitroglycerin increased both normal (121%; p less than .05) and stenotic (122%; p less than .05) luminal areas, while preventing the previously observed narrowing of stenosis during exercise (114%; NS). Exercise resulted in a similar heart rate-systolic pressure product and caused angina pectoris in two-thirds of the patients in each group. However, patients pretreated with intracoronary nitroglycerin (group 2) had a lower mean pulmonary arterial pressure during maximum exercise (35 mm Hg) than those patients (group 1) not receiving pretreatment (47 mm Hg; p less than .001). Group 2 patients reached a percentage of their predicted work capacity (65%) that was about the same as that during previous upright bicycle exercise (71%; NS), while group 1 patients had a significantly lower work capacity (51% of predicted) than that before catheterization (82%; p less than .001). Hence, narrowing of coronary artery stenosis during dynamic exercise is attributable to active vasoconstriction due to its reversibility by preexercise intracoronary nitroglycerin. Patients who did not experience narrowing of stenosis during exercise (group 2) had less evidence of myocardial ischemia (lower mean pulmonary arterial pressure) and maintained their work capacity.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗