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Biomedical subjects

W H Knapp

Publications and source records attributed to W H Knapp.

103 records · Page 6Linked to original sources
PubMed1977

[Experimental coronary bypass operation: distribution of myocardial blood flow early and after one year].

In 10 dogs a stenosis greater than 75% of the left circumflex coronary artery is induced (Ameroid) in the course of 40 days. Within 1 hour after coronary artery bypass operation (n = 6) maldistribution of myocardial blood flow (MBF), consisting of a subendocardial perfusion deficit, is improved but not completely abolished. One year after coronary bypass operation (n = 4) MBF and its endo/epi-distribution is normal. Bypass flow and its flow profile are useful indicators of MBF and its intramyocardial distribution only when coronary dilation is induced.

Animals↗
PubMed1977

[Heart diagnosis using M-mode-echocardiography. Continuous registration of the left ventricular transversal internal diameter. III. Measurements on highly trained athletes (author's transl)].

"Relative Cross-sectional area Differences" (RCD) and "Relative Velocities of Contraction" (RVC) permit a differentiation between normal subjects and patients with different degrees of myocardial failure, as previously described. Important determinants of the parameters RCD and RVC are changed, if ventricular volume and stroke volume increase and heart rate decreases, as is commonly observed in athletes. Examinations were performed at rest and after exercise on 31 athletes and 33 untrained normal subjects. Ventricular volumes were clearly increased in athletes. RCD, however, which is an equivalent to the ejection fraction, showed only slight alterations with physical training. RVC was obviously not changed by athletic training. After exercise athletes showed a significant increase in RCD. In untrained subjects only small changes in RCD were observed. In conclusion, the results show that RCD and RVC can quantitatively assess the degree of myocardial failure in cases of left ventricular dilatation without having to take into account the patients' degree of physical training.

Adolescent↗
PubMed1977

[Automated method of determining blood circulation time in nuclear medicine cardiology].

In this paper a method of computer-assisted evaluation of circulation times using a scintillation camera is described. Eight segments of the central circulation are defined on a graphic display unit. Then the analysis of time-activity curves and the normalization of circulation times to hear rate is performed. The automatic analysis is based upon the hydrodynamic meaning of the first inflection point of a time-activity curve. The differences between inflection points are nearly identical with appearance time differences under the experimental conditions used in 131 cases. A mathematical model is presented to defined the conditions for this behaviour and to explain some deviations observed if time differences exceeded a certain value. It can be shown that the method described is largely independent of extraneous influences. It offers haemodynamically relevant parameters that correspond to the minimal cardiac transit times.

Blood Circulation Time↗
PubMed1977

[Heart diagnosis using m-mode-echography. Continuous registration of transverse left-ventricular internal diameters. IV. Patients with coronary artery disease (author's transl)].

"Relative Cross-sectional area Differences" (RCD) and "Relative mean Velocity of Contraction" (RVC) can precisely be determined by means of impulse-reflected ultrasound. They are highly invariant under physiological conditions and closely related to the degree of non-ischemic myocardial disorders. To evaluate the diagnostic information of these parameters in coronary artery disease (CAD), echocardiographic examinations were performed on 105 subjects. The results were compared with the angiocardiographically determined ejection fraction and with minimal cardiac transit times. The heart-dynamic data were grouped according to the manifestation of CAD and correlated to each other. Furthermore the parameter's capability in identifying differences in hemodynamics in normals and in patients with CAD was tested. In more than 90 per cent of patients with CAD, RCD and RVC exceeded the normal range. For clinical diagnosis the results lead to certain limitations in the validity of the echocardiographic parameters. In cases of infarction localized at the apex and in myocardial aneurysmas, RCD and RVC reflect the function of the whole myocardium, not the ejection fraction of the left ventricle. In those cases of infarction of the posterior or posterolateral wall, the value of RCD and RVC could not be verified. If infarction occurs at other localizations (septum, anterior wall), RCD and RVC show the degree of reduced myocardial function without any limitation.

Adult↗
PubMed1976

[Heart diagnostics using M-mode echography. Continuing registration of transverse internal left ventricular diameters. II. Determination in patients with myocardial insufficiency with special reference to ischemic heart disease].

Relative Cross-sectional area Differences (RCD) and Relative mean Velocity of Contraction (RVC) are easily, quickly and precisely determined by means of impulse-reflected ultrasound. They were recognized to be highly invariant under physiological conditions and thus were considered as sensitively regulated heart-dynamic-parameters. (his paper reports about a total of 395 examinations on patients with myocardial disease and on normal subjects. Various pathogenic factors are included excepting patients with myocardial infarction. In all subgroups there is a decrease of RCD and RVC with increasing degrees of cardiac disease. Correlating the angiocardiographically determined left-ventricular ejection fraction with both parameters, they show a significant linear relationship. Even in clinically latent myocardial disease the echocardiographic parameters are defnitely reduced. Small changes of myocardial function, e.g. under digoxin and in different degrees of uremic heart disease with uremic cardiomyopathy, can be recognized by RCD and RVC under exclusion of extracardiac factors. Physical tests during exercise confirm the observed trends. The typical changes of the echocardiographic parameters in myocardial disease, permitting a sharp discrimination of pathologic values with their small physiological variability, identify RCD and RVC as sensitive parameters of the mechanical function of the myocardium in the range of validity that was examined. The described properties and the lack of discomfort to the patient suggest a number of important indications of this method.

Cardiomyopathies↗
PubMed1975

[Heart diagnosis using M-mode echocardiography. Continuing registration of transverse left ventricular inner diameters. I. Measurement in healthy persons].

Transversal internal diameters of the left ventricle can be determined simply, quickly, precisely and continuously by external application of impulse reflected ultrasound. These measurements permit the calculation of "relative cross-sectional area differences" between end-diastole and end-systole (RCD); peak and mean velocity of circumferential fiber contraction can be equally determined. The present report gives an analysis of 133 measurements on 81 healthy individuals. All persons were examined at rest, a part of them during exercise. All measurements were taken while supine position. The transversal internal diameters averaged 4.9 cm with considerable standard deviations. There was only a trend showing diminution of diameters during exercise. The "relative cross-sectional area differences" (RCD) between end-diastole and end-systole have only small standard deviations compared with the diameters. The average 58.3% and show a slight increase during exercise. The RCD were only slightly influenced by heart rate at rest. In contrast, peak and mean velocity of circumferential fiber contraction are obviously dependent on the heart rate. The results indicate a linear correlation between mean velocity and heart rate. The "relative mean velocities of contraction" (RVC), defined by normalization of the values to a rate of 60/min, average 1.0 and have small standard deviations like the RCD. The small physiological variety and the excellent reproducibility of data offer RCD and RVC determined by echocardiography as sensitive dynamic heart parameters applicable in clinical cardial diagnosis without any stress for the patient.

Anthropometry↗