PubMed Health⌕ Search

Biomedical subjects

F K Schmiel

Publications and source records attributed to F K Schmiel.

14 recordsLinked to original sources
PubMed1979

Flow measurements and simultaneously performed angiography of aorto-coronary bypass grafts during bypass surgery.

The function of aorto-coronary bypass grafts is usually assessed by the run-off, determined from postoperatively performed cineangiograms. The reliability of this method was tested by comparing the electromagnetically measured graft flow with the run-off, qualitatively estimated from cineangiograms. The electromagnetic flow measurements and cineangiography were performed simultaneously during bypass surgery. The run-off was classified by three independent observers into three classes (poor, moderate, and good). The average mean flow rates corresponding to the three classes were: poor: Q = (43 +/- 11)ml/min; moderate: Q = (48 +/- 14)ml/min; good; Q = (63 +/- 22)ml/min. Although the differences between the flow rates of the three classes were found significant (except between poor and moderate run-off), there was a wide range of overlapping. Especially in grafts with low flow rates (Q less than 70 ml/min) there were pronounced disagreements between the qualitative estimation of flow and the electromagnetically measured flow. Using videodensitometric flow measurements as a check test, the uncertainties in classification proved to be caused by the lack of reliability of the observer. The flow rates in aorto-coronary bypass grafts can be determined reliably only by means of quantitative methods, e.g., electromagnetic or videodensitometric flow measurements.

Angiography↗
PubMed1979

[A model analysis on the effects of left ventricular hypertrophy and dilatation on pump function and myocardial force and shortening (author's transl)].

The effects of hypertrophy and dilatation on myocardial force and shortening were analysed using Wong's formula for equatorial midwall stress in a thick-walled ellipsoid of revolution. Wall thickness, chamber volume and ejection fraction were treated as independent variables. An isolated increase in wall thickness reduces wall stress and, to a lesser extent, myocardial fiber shortening, i.e. myocardial function is overestimated from ventricular pressures and ejection fraction. Ventricular dilatation without a proportional increase in myocardial mass leads to an increase of myocardial force and shortening, i.e. myocardial performance is underestimated from ventricular function. A decrease of ejection fraction increases total systolic myocardial force considerably, leading to a shift to the right on the inverse relation of force and shortening. Therefore the efficiency of myocardial contraction is reduced and myocardial performance is better than ventricular pump function would indicate.

Cardiac Output↗
PubMed1975

A new method for automated detection of the R-on-T phenomenon.

The detection of premature ectopic beats coinciding with the T-wave of the antecedent beat is important for patient monitoring. In the method described here, the difficulties of direct measurement of QT time are avoided by evaluating the changes of QT time according to heart rate by use of a diode function generator. An analog circuit is used for comparing the computed QT time with the coupling interval of successive beats. In case of a R-on-T-phenomenon an alarm is given. The frequency of alarms is registered on a trend recorder. The methods is based on empirical equations which all contain a constant factor. Our investigations showed that the variability of this factor during longer periods of monitoring was small enough to allow sufficient exactness of the evaluation procedure.

Adult↗
PubMed1975

[Estimation of ventricular volume derived from three transverse diameters and the longitudinal axis, compared with an area-longitudinal axis method (author's transl)].

The difficulty of automatic volume estimations of the left ventricle from cine-ventriculography lies in the accurate definition of the ventricular contour during the whole of the cardiac cycle. On the other hand, automatic determination of the long axis of the ventricle, and of three transverse diameters, is feasible. An attempt was therefore made to see whether accurate ventricular volume estimations could be obtained from these measurements. Two different geometrical models were examined: a) A complete rotational ellipsoid b) A half rotational ellipsoid. Examination of ten cine-ventriculograms (totalling 546 frames) has shown that the ventricular volume can be determined with an adequate accuracy by this method. The half ellipsoid model produced better mean results than the full ellipsoid. Its mean deviation from the area-long axis method was only minus 1.2%, that of the complete ellipsoid was minus 3.3%.

Heart Function Tests↗
PubMedDate not supplied

Measurement of flow velocity in the model circulation by videodensitometry. Methodological investigations.

The relation between videodensitometrically measured front velocity and electromagnetically assessed flow was examined in a circulatory model with continuous as well as pulsatile flow (89 experiments). The diameter of the tubes in the videodensitometric measuring section was 0.305 to 0.518 cm. A linear correlation was proved in flow velocities up to Reynold's number Re = 225. The exact flow, measured electromagnetically, was overestimated in continuous flow by 21% (r = 0.99, Syx = +/- 14.5 ml/min) and in pulsatile flow by 24% (r = 0.98, Syx = +/- 20.8 ml/min). In view of these results the phasic and average flow can be calculated accurately using videodensitometric techniques.

Blood Flow Velocity↗