Biomedical subjects

D Roser

Publications and source records attributed to D Roser.

4 recordsLinked to original sources

PubMed1998

The Ross operation: do native aortic, native pulmonary, and homograft pulmonary valve size and form differences influence results?

BACKGROUND: The pulmonary autograft approaches the ideal aortic valve substitute but numerous technical modifications are debated. The valves involved often differ in diameter and shape of the recipient annulus. We previously reported simplified surgical rules and early results of 52 patients and here we extend the report to 76 patients and analyze the mid-term results with respect to valve mismatch. METHODS: We studied the influence of geometric discrepancies. Valve regurgitation and gradient are compared for size discrepancies up to or more than 3 mm between recipient annulus and pulmonary autograft. The normal tricuspid recipient aortic annulus is compared with the flat circular redo-prosthetic or bicuspid annulus. Patients with plication of the aortic annulus and remodeling of the distal aorta are reviewed, and lastly donor homograft to pulmonary autograft discrepancies up to and more than 3 mm are compared. RESULTS: The results were comparable in all groups and no significant differences were observed. CONCLUSION: The pulmonary autograft operation may be simplified, with good results at the least in the first year despite operative tailoring due to valve discrepancies.

Adolescent↗

PubMed1997

The influence of geometric mismatch between the native aortic, native pulmonary and homograft pulmonary valve on the results of the pulmonary autograft operation.

BACKGROUND: The pulmonary autograft operation has achieved broad acceptance and may be the ideal aortic valve substitute. Both the pulmonary autograft and the aortic homograft are more complicated procedures than prosthetic valve replacement. The trend to insert the pulmonary autograft as a root replacement rather than in the subcoronary position has achieved greater uniformity in the results, but there is still confusing diversity in opinions on technical details and anatomical dimensions. The importance of both size and shape mismatches between the three valves involved has received little attention. The valves often differ in diameter and in the shape of the recipient aortic annulus. This uncertainty and the diversity of opinions on essential technical details was disconcerting when we proceeded from aortic homograft-to-pulmonary autograft operations, this was compounded by only a single homograft being available for every operation as we have no homograft bank. METHODS: We compared the hemodynamic results regarding various geometric mismatches. All operative details were the same and patients were studied at regular intervals. Comparisons were made in patients with mismatch between recipient aortic annulus and pulmonary autograft. Patients with a normal tricuspid aortic annulus were compared to those with either a circular redo prosthetic valve annulus or a bicuspid recipient annulus. Thirdly we compared the patients with plication of the aortic annulus to those with remodeling of the distal aorta. Lastly we compared mismatch between donor homograft and pulmonary autograft. RESULTS: No influence of geometric mismatch between the three valves could be found on the results of the pulmonary autograft operation. CONCLUSIONS: Good results are obtainable without a painful learning curve if one keeps to certain surgical principles. It need not be a complicated operation and geometric mismatches between the three valves involved may be compensated for adequately.

Adolescent↗

PubMed1987

Changes in haemodynamics and left ventricular function during intravenous nifedipine infusion with and without additional propranolol in patients with coronary artery disease. A randomized, placebo controlled trial.

The haemodynamic effects of a combined intravenous treatment of nifedipine and propranolol in ten patients with coronary artery disease compared to a single treatment with nifedipine or placebo were investigated. Nifedipine infusion resulted in a reduction of left ventricular (LV) afterload and LV volumes with an increase in heart rate and EF and no change of the double product, coronary sinus flow, LV diastolic parameters and dp/dtmax. Addition of propranolol lowers myocardial oxygen demand by reducing heart rate and dp/dtmax together with a sustained afterload reduction with no change in LV volumes and EF. The vasodilatatory action of nifedipine pretreatment balanced the negative effects of acute beta-receptor blockade on LV function and allows the reduction of myocardial oxygen demand without a deterioration of LV function.

Angiography↗

PubMed1984

A note on 'plotless' methods for estimating bacterial cell densities.

' Plotless ' techniques for determining population densities have been developed for, and applied to, higher plant populations. They can often be carried out more rapidly than techniques involving total counts of individuals in plots, or quadrants, but such plotless techniques have not been generally applied to the estimation of densities of bacterial cells. Direct microscopical counting of cell numbers in a field of view, an example of a plot-related method, has been traditionally used for microbial cell counts. In this study 'plot' and ' plotless ' methods on a variety of bacterial samples are compared. Estimates of bacterial cell density were obtained by measuring the distance of cells from a fixed point in a field of view. The values, which were more rapidly obtained, were directly correlated with total cell counts. Although there was some apparent deviation from a perfect 1:1 relationship with total counts, as indicated by a correlation coefficient less than 1.0, there were no significant differences between the replicated counts of bacteria on samples of tissue from the surface of Hypholoma basidiocarps (P less than 0.05). This indicated that the methods of enumeration were comparable. The distance-related estimates could readily be obtained from fields of view with cell densities varying over several orders of magnitude. It was more rapidly applied, particularly at high density, and the method was applicable not only to random cell distributions but also to the non-random distributions encountered when microbial cells aggregated into microcolonies. The method appears to be particularly well-suited for automated, digitized, direct counting procedures, as well as to estimating bacterial numbers on membrane filters and natural substrates.

Bacteria↗