The pre-stenotic Doppler shift signature.

In two series of measurements the Doppler shift signatures of 10 healthy volunteers were studied at varying distances proximal to a total reflection site, in order to describe parameters which are predictive for downstream lesions. Characteristic changes both in amplitude and time parameters were found; the most marked changes being the abolishment of a DC-component for monophasic signatures, the development or the augmentation of early diastolic reverse flow amplitudes together with a highly significant reduction in the signatures' systolic deceleration time. Maximum changes however tended to be localized at 2 to 4 centimeters upstream from the reflection site. Further upstream propagation was limited. Hence the time course of a Doppler signature and particularly its systolic deceleration should be taken into account in addition to the known resistance indices, if downstream lesions shall be predicted from upstream Doppler signatures. The limited upstream propagation of pre-stenotic Doppler signature changes restricts its diagnostic value to vascular segments where the region adjacent to a lesion is routinely scanned; thus diagnostic benefit can be expected for extracranial carotid artery disease but hardly for peripheral (lower limb) lesions.

How useful are acceleration- and deceleration-based Doppler indices? A trial on patients with percutaneous transluminal angioplasty.

The usefulness of indices commonly used in Doppler sonography is limited; the aim of this study was to investigate if inclusion of systolic acceleration and deceleration patterns in Doppler indices will result in practical diagnostic advantages. Systolic delay time index (SDTI) and height-width index (HWI) are compared to Gosling's pulsatility index (PI) and to PI-based damping factors (DF) in patients with isolated lesions in the distal superficial femoral artery before and after percutaneous transluminal angioplasty (PTA). Before PTA, all indices distal to the lesion differ significantly from proximal indices. After successful PTA, none of the indices is able to detect the PTA outcome with sufficient sensitivity. The additionally defined curve broadening index (CBI) shows a 100% sensitivity for detecting PTA success in the examined patient population.

[Lack of fatigue of the musculature in patients after immobilization--a paradox?]. / Fehlende Ermüdung der Muskulatur bei Patienten nach Immobilisation--ein Paradoxon?

The isometric strength of knee extensors was measured in patients six weeks after cruciate ligament surgery over a contraction period of 30 sec. The characteristics of the graph obtained form the measurement system were compared to the graphs of uninjured knee extensor muscles. Apart from strength reductions, as expected for atrophic muscle, the pattern of the strength graph led to the impression that these muscles did not fatigue during prolonged contraction. This paradoxical phenomenon can be explained by the existence of central inhibitory mechanisms.

[Changes in the ultrasound power spectrum due to concentric stenoses of the femoral artery of the dog]. / Veränderungen des Ultraschall Power-Spektrums durch konzentrische Stenosen in der Femoralarterie des Hundes.

An artificial stenosis model consisting of a revolving centric cylinder with six boreholes (10-60% diameter reduction) was implanted in the superficial femoral artery of anaesthezised beagles (n = 10). Range gated pulsed Doppler signals were recorded at 7 sites between three diameters upstream to ten diameters downstream the Angle corrected parameters derived from the contour of spectral lines between 3 and 21dB on both sides of mode frequency were calculated for different time windows. Two groups of dogs could be distinguished. Group A showed marked downstream power spectrum changes which did not correlate to the degree of stenosis. In Group B, in contrast, the degree of power spectral disturbances correlated to the degree of stenosis. It was suggested that partial thrombosis of the stenoses during measurement provides an acceptable explanation for the missing correlation in Group A.

[What does 31 phosphorus magnetic resonance spectroscopy measure?A validation in healthy probands]. / Was leistet die 31Phosphor-Kernspinspektroskopie? Eine Validierung an gesunden Probanden.

With 31P nuclear magnetic resonance spectroscopy skeletal muscle metabolism can be measured noninvasively. Aim of this study was to investigate intraindividual reproducebility, interindividual variability, and the correlation of the NMR parameters PCr, alpha-, beta-, gamma-ATP to graded exercise. Reproducebility and variability of PCr values were comparabel to changes of the pH value. Alpha-, beta-, gamma-ATP did not change during measurements. Correlations between the workload and the changes of the NMR parameters were rare. It was found that the intraindividual reproducebility is low and the interindividual variability is high. No systematic correlation between the NMR parameters and the workload could be seen. The termination of exercise in healthy volunteers is not explained by energy depletion but due to other mechanisms. There is no evidence that 31P NMR spectroscopy presents remarkable advantages for clinical purposes compared to well established diagnostic methods.

[The value of 31 P nuclear magnetic resonance spectroscopy in follow up of Fontaine stage IIb peripheral arterial occlusive disease]. / Zur Wertigkeit der 31p Kernspinspektroskopie bei der Verlaufskontrolle der peripheren arteriellen Verschlusskrankheit im Stadium IIb nach Fontaine (PAVK IIb).

The method of nuclear magnetic resonance (NMR) spectroscopy compared to the parameters absolute-, pain-free walking distance and ankle/arm coefficient in Doppler pressure was used for observation of patients with peripheral arterial occlusive disease stage IIb according to Fontaine. While the classic parameters (walking distances, ankle/arm coefficient) described a homogenous group, NMR-spectroscopy parameters showed marked inter- and intraindividual variations during exercise. Further studies on high magnetic power fields, exercise patterns and muscle recreation analysis have to be carried out to develop a reliable system of non invasive muscle energy monitoring in vascular diseases.

Myocardial performance and metabolism in non-ketotic, diabetic rat hearts: myocardial function and metabolism in vivo and in the isolated perfused heart under the influence of insulin and octanoate.

The influence of a non-ketonic, chronically diabetic state (60 mg/kg streptozotocin) on cardiac function and metabolism was studied under in vivo conditions by inserting a Millar-tip catheter into the left ventricle and in the model of the isolated perfused heart. In vivo heart rate and maximal left ventricular systolic pressure were reduced after a diabetes duration of 4 and 12 weeks. The maximal rise and fall in left ventricular pressure progressively declined with the duration of diabetes. The reduced myocardial function was associated with a loss in ATP and adenine nucleotides. In the perfused heart of chronically diabetic rats, heart function was also impaired and could not be restored in vitro by perfusion with glucose and insulin. In the presence of octanoate--a substrate which can be metabolized independently from insulin--heart function of diabetic rats was improved, but remained lowered as compared to controls. Since the content of myocardial creatine phosphate was reduced in diabetic hearts perfused with octanoate, these findings indicate that the suppression of cardiac performance is not only a result of an impaired glucose metabolism, but of a more general defect in energy provision and utilization. In contrast to hearts of acutely diabetic, ketotic rats most often used, the rate of lipolysis of endogenous triglycerides and the contribution of fatty acids to energy production was low in the chronically diabetic state. Inhibition of fatty acid oxidation by an inhibitor of carnitine palmitoyltransferase (CPTI) did not restore the reduced responsiveness of diabetic hearts to insulin. Analysis of intracardiac metabolites revealed that in the perfused heart of chronically diabetic rats glucose-6-phosphate and citrate do not accumulate as in hearts of ketotic, diabetic rats. Therefore, the impaired glucose metabolism presumably reflects a reduced uptake of glucose rather than in inhibition of glycolysis as in hearts of ketotic, diabetic rats.