Search PubMed⌕ Search

Biomedical subjects

A Markewitz

Publications and source records attributed to A Markewitz.

61 records · Page 4Linked to original sources
PubMed1986

What is the most appropriate stimulation mode in patients with sinus node dysfunction?

Sinus node disease (SND) has caused many controversies about the appropriate stimulation mode. We compared the advantages and disadvantages of VVI, AAI, DDD, and DDI mode. In an additional study, left ventricular function at rest (R) and during exercise (E) was investigated in dual chamber and ventricular stimulation mode with a stimulation rate of 70 ppm (R) and 110 ppm (E). A total of 223 patients (pts) was investigated (67 AAI, 87 VVI, 69 DDI). Hemodynamic disadvantages in VVI mode resulted in a 55% actuarial incidence of atrial fibrillation after five years. In AAI mode, we found another 25% complication rate due to impaired AV conduction (n = 9) or a bradyarrhythmia (n = 6) with slow ventricular response. DDI mode implies the possibility of sustaining a pacemaker mediated tachycardia. Single ventricular stimulation with a high stimulation rate (110 ppm) under E showed a worse left ventricular performance as compared to dual chamber stimulation. DDI mode shows none of the aforementioned disadvantages. To sum it up: Until a dual chamber rate responsive pacemaker becomes available, the DDI mode represents the best stimulation mode for patients with a SND.

Atrial Fibrillation↗
PubMed1985

Late (11 to 19 years) assessment of hemodynamic and prosthetic valve function in patients with Starr Edwards ball valves: a non-invasive study utilizing 99m-technetium pertechnetate scintigraphy.

This is an account of 2 groups of 10 patients each who received Starr Edwards ball valves in either the mitral (M) or aortic (A) position on average 14.7 +/- 3 or 14.9 +/- 2.4 years ago, respectively. Non-invasive scintigraphic studies were performed using the first pass of 18 to 20 mCi 99 m-Technetium Pertechnetate. Enddiastolic and endsystolic volumes were found elevated at rest: (M) EDV 135 +/- 50 ml, ESV 63 +/- 30 ml; (A) EDV 163 +/- 41 ml, ESV 69 +/- 25 ml. The response to maximum exercise--during which the heart rate increased from 85 +/- 23 min-1 to 133 +/- 33 min-1--was abnormal, since none of the volumes changed significantly. During exercise, therefore, the increase of the cardiac output was totally heart rate dependent: (M) 6.1 +/- 2.3 to 9.3 +/- 2.3 l/min; (A) 7.0 +/- 1.9 to 10.9 +/- 3.1 l/min. The dynamics of the rapid diastolic filling rate of the left ventricle (RFR) and the mean pulmonary transit time (MTT) served as functional parameters of the Starr Edwards ball valves in the mitral position. The rapid filling rate increased from 205 +/- 98 to 321 +/- 58 ml/sec, whereas MTT decreased from 7.4 +/- 1.4 to 5.4 +/- 2.1 sec. In patients with aortic valve replacement the left ventricular ejection rate was assessed, it rose from 233 +/- 80 to 459 +/- 232 ml/sec. The significant changes of the parameters proved that the Starr Edwards ball valve mechanism functions satisfactorily 11 to 19 years post-operatively.

Aortic Valve Insufficiency↗
PubMed1985

[Potential danger to pacemaker patients during transurethral operations. Clinical and experimental studies].

The high sensitivity of modern demand pacemakers to HF-currents, as used for the TUR, could be shown by an in vitro model, animal experiments and clinical investigations. It was possible to characterise the type specific HF-sensitivity by means of individual functions. Furthermore, it could be proven that almost every external HF-signal could be blocked by switching the demand pacemaker to its fixed magnet frequency, a most important procedure in order to maintain patient safety during a transurethral resection.

Animals↗
PubMed1980

[Results of radiation therapy in 214 primary cerebral tumors and 27 metastases to the brain (1969--1978) (author's transl)].

The results of radiation therapy in 241 patients with a cerebral tumor are reported. A total of 214 primary cerebral tumors and of 27 metastases to the brain was irradiated at the medical radiation institute of the University of Tübingen within the period from 1969 to 1978. Of the cases, 56% underwent primary radiation therapy, and 44% postoperative treatment. Histologically verified diagnoses are existing for 68.5% of all the cases. The average survival rate (months) for the different tumor groups--according to the classification of Zülch--is compared with data in literature. The problems concerning the indication of radiation therapy are discussed. The results underline the merely palliative character of actual radiation therapy in the treatment of most cerebral tumors. Its value is to be found in the prevention resp. retardation of recurrences. Irradiation, even palliative irradiation, or cerebral metastases may be recommended without restriction, as special importance has to be attached to the aspect of an improvement of life quality.

Adolescent↗
PubMedDate not supplied

The influence of gastrointestinal agents on resorption and metabolism of cyclosporine after heart transplantation: experimental and clinical results.

The clinical effectiveness of cyclosporine is limited by changes in resorption and metabolism of cyclosporine and by possible drug interactions. This study examined the influence of five gastrointestinal agents on duration and resorption of cyclosporine and dosage/level relations: cimetidine, famotidine, pirenzepine, aluminum hydroxide, and omeprazole. These gastrointestinal agents were studied in 64 rat experiments, in which the impact of each single drug and of drug combinations on cyclosporine resorption and metabolism was tested. A standardized dosage of cyclosporine was given orally, and the duration was calculated for the maximum whole blood level of cyclosporine to be achieved; the dosage/level quotient was calculated. Cimetidine, famotidine, pirenzepine, and combination treatment prolonged duration of cyclosporine resorption. Furthermore, cimetidine, famotidine, and omeprazole lowered the dosage/level quotient, thus leading to higher cyclosporine levels with the same dosage; pirenzepine increased the dosage/level quotient. For clinical comparison, 163 heart transplant patients who had received standard triple-drug immunosuppressive therapy were analyzed. The time interval until a therapeutic cyclosporine level was achieved and the dosage/level quotient were once again calculated. Similar to the results in the animal experiments, cimetidine and famotidine significantly delayed the resorption of cyclosporine; cimetidine, famotidine, and omeprazole lowered the cyclosporine dosage/level quotient, thus leading to higher cyclosporine levels with the same dosage. Aluminum hydroxide did not lead to any changes in the resorption or metabolism of cyclosporine. Most examined gastrointestinal agents, and particularly H2-blocking drugs, led to significant prolongation of cyclosporine resorption and cyclosporine level alterations. The initial prolongation of cyclosporine resorption was successfully avoided by intravenous administration of cyclosporine for the first 4 postoperative days in 40 consecutive patients.

Absorption↗