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Biomedical subjects

P Ritter

Publications and source records attributed to P Ritter.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Auriculoventricular block disclosed in the exercise test].

Sixteen patients, 14 of whom described stress related symptoms, present a severe atrio-ventricular block (A-V B), identified during a stress test while the ECG at rest showed a 1/1 atrioventricular conduction (AV). The electrophysiological study (EPS) creates the A-B Block through atrial stimulation and specifies the location of the A-V B: intra-hissian in 8 patients (7 with small QRS an 1 with widened QRS) and infra-hissian in 8 patients (all with widened QRS). Non-invasive methods constitute the prime approach in the diagnostic work-up of stress symptoms. The ideal treatment consists of a dual-chamber cardiac stimulation.

Adult↗
PubMed1989

Pharmacokinetics of the progestin dienogest (STS 557) in rabbits.

Disposition and excretion of the progestin Dienogest (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4,9-dien-3-one, STS 557) were investigated in female rabbits. Following single and repeated administration of the tritium-labelled compound the plasma concentration courses of total radioactivity (Dienogest + metabolites) and of the parent drug alone were estimated and also the urinary and fecal excretion of total radioactivity. From these data basic pharmacokinetic parameters were calculated. Additionally, the enterohepatic recirculation of biliary excreted metabolites was studied using bile of donors for oral administration to recipients. Following oral administration the high bioavailability of Dienogest which was already found in other animal species and in man could also be confirmed with rabbits. The parameters of Dienogest disposition do not differ significantly from those of the progestin levonorgestrel. Thus, the different effects of the both progestins in the McPhail-Clauberg assay in the rabbit cannot be attributed to differences in pharmacokinetics.

Animals↗
PubMed1989

Studies on the biotransformation of the progestagen dienogest in the rabbit.

Following administration of 14 alpha, 15 alpha-3H-Dienogest (STS 557, 17 alpha-cyanomethyl-17 beta-hydroxy-4, 9-estradien-3-one) to female rabbits, extracts from urine, bile and plasma were separated by means of HPLC. Urinary and biliary metabolites are characterized by patterns of high complexity. From the mass spectra and UV absorption data of the urinary Dienogest metabolites a variety of biotransformation reactions has been derived like: hydroxylation in different positions of the Dienogest molecule, among these the 11-position; reduction of the 3-oxo group to 3-hydroxy; introduction of 2 and 4 hydrogen atoms; aromatization of ring A; transformation of 17 alpha-CH2CN to CH2OH, and formation of compounds with a 5(10), 9(11)-diene structure. Some of these reactions occur simultaneously resulting in a very complicated metabolite spectrum. Possibly the multiple effects of Dienogest established in animals are partially caused by metabolites.

Animals↗
PubMed1989

Haemodynamic benefit of a rate-adapted A-V delay in dual chamber pacing.

In dual chamber pacing, an improvement of exercise capacity is expected when the atrial refractory period is shortened, because the 2/1 point is increased. This objective can be achieved by greatly reducing atrioventricular delay (AVD) on exercise. Are such variations (up to 100-120 ms) detrimental from a haemodynamic standpoint? This study was performed to analyse this particular aspect of DDD pacing. Three DDD pacing modes, differing by their AVDs (fixed 200 ms AVD, fixed 150 ms AVD, and rate-adapted AVD) were tested in random order, with a haemodynamic protocol including ten patients with chronic atrio-ventricular (A-V) block. For the rate-adapted AVD pacing mode, AVD was reduced by 20 ms every 10 beats min-1 increment (from 220 ms at 90 beats min-1 to 100 ms at 150 beats min-1). Pacing rate was increased from 90 to 150 beats min-1 by increments of 10 beats min-1 every 5 min. Cardiac performance was significantly improved with the rate-adapted AVD above the two fixed AVDs, despite a large AVD variation. When AVD was rate adapted, cardiac index, stroke volume index and left ventricular systolic work index were generally higher and pulmonary capillary wedge pressure, pulmonary arterial pressure and systemic vascular resistances were generally lower, especially at 120, 130 and 140 beats min-1. Comparing the two fixed AVDs, 200 AVD improved cardiac function more at lower heart rates, whereas 150 AVD improved cardiac function more at higher heart rates. Despite its limitations, this study demonstrates that the potential benefits of reducing AVD with increasing heart rates should be twofold in dual chamber pacing: (a) haemodynamic, optimizing cardiac performance on exercise for all heart rates, especially in cases of organic heart disease; (b) electrophysiologic, permitting a sufficiently rapid maximal tracking rate in cases with long post-ventricular atrial refractory periods, allowing a satisfactory level of exercise.

Aged↗
PubMed1989

[Results of cisplatin-based polychemotherapy and analysis of prognostic factors in ovarian cancer. Apropos of 106 cases].

One hundred and six patients with stage Ic to IV ovarian carcinoma were treated by a protocol consisting of optimal debulking surgery followed by 9 cycles of CHAP chemotherapy. Clinical response was confirmed by a second-look procedure. Sixty-nine patients (65%) responded with 54 histological complete remissions (50.8%). Nineteen patients did not receive any complementary treatment due to a negative reaction, or prolonged neutropenia. Seven patients received maintenance chemotherapy, 10 an abdominal radiotherapy, 22 intraperitoneal chemotherapy and 11 autologous bone marrow transplantation. The 5-year survival rate was 32.5% and disease-free survival rate was 39.7%. Prognostic-factor analysis showed that age, initial staging, residual disease and cytological grading were significant. The authors propose a classification based on the risk of relapse, and different therapeutic indications for improving response rate and patient survival.

Adult↗
PubMed1989

[Forensic use of polymorphism St 14.1].

The DNA-fragment (St 14.1) from the human X-chromosome recognizes a series of approximately 10 alleles after Taq I digestion. The presence of constant bands simplifies the assignment of the alleles to a definite Kb-size when small differences exist between the alleles. 348 individuals were investigated and included 120 mother/child combinations. The verification of the Hardy-Weinberg equilibrium gave a value of 32 in the chi square test by 20 degrees of freedom and therefore a P-value of 95-97.5. The allele frequencies range from 1%-40% with an expected exclusion rate of 77.3% (for mother/daughter combinations).

Alleles↗
PubMed1988

Failure of the exercise test to predict the anterograde refractory period of the accessory pathway in Wolff Parkinson White syndrome.

Modifications of the delta wave on the surface ECG during an exercise stress test were compared to electrophysiological variations in accessory pathway (AP) refractoriness and in AV node conduction, during intravenous isoproterenol infusion in ten patients with WPW syndrome. In one patient, the delta wave persisted unchanged at the end of exercise and, with isoproterenol, there was a greater reduction in the AP anterograde effective refractory period (AERP) than in AV node conduction time. In three patients, the delta wave became less and less apparent but without completely disappearing; in these patients, the slight reduction of the AERP in the accessory pathway with isoproterenol was comparable to the reduction in AV node conduction time, explaining the progressive fusion between the two activation fronts. In the six other patients, the delta wave completely disappeared during exercise: in two cases, suddenly from one cycle to the next with strong concordance between the measured (isoproterenol) and the estimated (exercise test) AERP in the AP; in four cases, the disappearance was progressive with a significantly greater reduction in the AV node conduction time than in the measured AERP of AP which was nonetheless very short, 190 to 225 ms, during isoproterenol infusion. These findings confirm the limitations of the exercise test to predict the AERP of the AP. In addition, they demonstrate that modifications in the delta wave during exercise result from a balance between the relative effects of sympathetic stimulation on refractoriness of AP and normal AV conduction.

Adult↗
PubMed1988

Relationship between heart rate and minute ventilation, tidal volume and respiratory rate during brief and low level exercise.

The correlation between heart rate (HR) and three respiratory parameters, minute ventilation (VE), tidal volume (Vt), and respiratory rate (RR), were studied. Four healthy subjects performed four exercise tests (duration 30 seconds at 50, 100, 150, or 200 W), in random order. Cardio-respiratory parameters were recorded respiratory cycle by respiratory cycle. The results of these low level exercise tests showed that oxygen consumption (VO2) was strongly correlated with VE (r = 0.91 +/- 0.10; P less than 0.01) (except in one test) and Vt (r = 0.91 +/- 0.07; P less than 0.001) (except in one test). There was no significant correlation between VO2 and RR. At exercise onset HR, VE, and Vt were modified in a matter of a few heart beats while RR varied depending on the subject and the level of exercise. During exercise average HR, VE, and Vt were significantly higher than at rest in most cases; but RR was not significantly changed by exercise. The correlations between HR and VE, Vt and RR varied from one individual to another. Nevertheless, the correlation coefficients were positive for VE and Vt, while they were negative for RR. Sensing respiratory rate thus appears to be insufficient for responsive pacing at exercise onset, but sensing respiratory volumes (Vt, VE) should give satisfactory results.

Adult↗
PubMed1987

A comparative study of immuno-blotting techniques for the detection of Gc-subtypes after isoelectric focusing on agarose and polyacrylamide gels.

A comparison of separation and detection techniques has been carried out to determine the most suitable combination for use in Gc-subtyping. The best results (i.e., high sensitivity, distinct bands, especially with reference to the 1S and 1F separation) were achieved using isoelectric focusing in polyacrylamide gel (pH 4.5-5.4) followed by transfer to nitrocellulose membrane by electroblotting and finally detection with enzyme-linked antibody complex.

Electrophoresis↗
PubMed1987

[New forms of work in general practice].

A trial with job rotation between repetitive jobs failed within a year after initial enthusiasm among the workers. Stress may increase to an intolerable level with the number of tasks, with higher qualified work and due to the lack of familiarity with fellow workers in ever changing settings.

Adolescent↗
PubMed1986

Prospective study of computed tomography in initial management of blunt abdominal trauma.

Physical examination is often unreliable in the evaluation of blunt abdominal trauma. The utility of computed tomography (CT) in the early management of abdominal trauma in the absence of definite signs is controversial. CT was prospectively evaluated as an adjunct to physical examination in the initial assessment of blunt abdominal trauma. Indications for emergency abdominal CT were a stable patient with an equivocal abdominal examination, closed head injury, spinal cord injury, hematuria, or pelvic fracture. One hundred twenty patients were studied. CT was accurate in 98.3% of these patients. With associated head injury, combining head and abdominal CT proved to be expeditious. Splenic, hepatic, and renal injuries were reliably detected with CT. Minor injuries which did not require laparotomy were reliably diagnosed. Patients with acute pancreatic injuries may have normal CT findings. Eighty-six per cent of laparotomies were therapeutic. In conjunction with close clinical monitoring, CT was reliable in evaluation of blunt abdominal trauma in a selected group of patients.

Abdominal Injuries↗
PubMed1986

Physiological relationship between AV interval and heart rate in healthy subjects: applications to dual chamber pacing.

The purpose of this paper is to specify the mathematical relationship between spontaneous AV interval (AVI) and heart rate (HR), the amplitude and rate of variation of AVI, and the physiological factors likely to affect these characteristics. Ten patients with healthy hearts were studied. Two catheter electrodes were positioned in the right atrium and at the tip of the right ventricle respectively, allowing the detection of endocardial signals. The AV and AA intervals for each heart cycle were digitized to an accuracy of +/- 1 msec. Measurements were made at rest, then during a stress test on an exercise bicycle, and finally during the recovery phase. The results show that adaptation is very precise and takes place instantly. Any variation in heart rate causes an immediate, inversely proportional variation in AVI. Adaptation follows a linear pattern, generally with relatively low amplitude and an average AVI reduction of 27.5 +/- 11.2 msec for an average HR increase of 78.7 +/- 22.5 bpm, i.e., a decrease of 4 +/- 2.1 msec for an HR variation of 10 bpm. The amplitude and variation rate of AVI seem to be independent of the age and base value of the PR interval. These observations may be useful for designing new VDD or DDD pacemakers that automatically adapt the AV interval to the instantaneous heart rate. The hemodynamic benefits of this adaptation were also demonstrated.

Adolescent↗