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Biomedical subjects

A Neumann

Publications and source records attributed to A Neumann.

At least 73 records · Page 4Linked to original sources
PubMed1993

Fluorescence in-situ hybridisation and molecular studies used in the characterisation of a Robertsonian translocation (13q15q) in Prader-Willi syndrome.

A patient with classical Prader-Willi syndrome was found to have a Robertsonian translocation 45,XY,t(13q15q)mat. On CBG banding, the translocation chromosome had a large centromere with one primary constriction. Using fluorescence in situ hybridisation, positive signals were obtained with chromosome 13 and chromosome 15 centromere probes, proving that the translocation was dicentric. NOR banding was negative in this chromosome, suggesting that the breakpoints were at 13p11 and 15p11. DNA studies showed that, while there was no deletion involving 15(q11-13), maternal uniparental disomy for chromosome 15 was present. We compare our findings with the five other cases of familial Robertsonian translocation PWS that have been reported.

Adult↗
PubMed1992

Effects of simultaneous alterations in preload and afterload on measurements of left ventricular contractility in patients with dilated cardiomyopathy: comparisons of ejection phase, isovolumetric and end-systolic force-velocity indexes.

OBJECTIVES: The study was designed to critically evaluate the clinical utility of ejection phase and nonejection phase indexes of contractile state in patients with severe left ventricular dysfunction. BACKGROUND: Ejection phase indexes of left ventricular systolic performance are unable to differentiate contractility changes from alterations in loading conditions. Isovolumetric and end-systolic force-velocity indexes have been proposed as alternative measurements of contractile state that are load independent. METHODS: Seventeen patients with nonischemic dilated cardiomyopathy were studied during cardiac catheterization. High fidelity central aortic and left ventricular pressure measurements were made with simultaneous echocardiographic recordings of chamber minor- and long-axis dimensions and wall thickness. Data were acquired under control conditions, during nitroprusside infusion and with dopamine (6 micrograms/kg per min). RESULTS: Patients were classified into those without (group 1, n = 10) and those with (group 2, n = 7) a decrease in end-diastolic circumferential wall stress in response to dopamine. There were no baseline differences between the groups in functional class, left ventricular chamber geometry or cardiovascular hemodynamics. Ejection phase indexes were variably altered by changes in preload, afterload and heart rate, thereby complicating physiologic interpretation of data. Dopamine increased the commonly used isovolumetric index, maximal rate of rise in left ventricular pressure (dP/dtmax), by 64% for group 1 but by only 16% for group 2 (p less than 0.001), resulting in an underestimation of contractile state change in 41% of patients. In contrast, the left ventricular end-systolic circumferential wall stress-rate-corrected velocity of fiber shortening relation, which incorporates afterload, ventricular wall mass and heart rate in its analysis, was a sensitive contractility measurement that was preload independent and equally augmented by dopamine for both groups. CONCLUSIONS: Of the left ventricular contractility indexes evaluated, the end-systolic circumferential wall stress-rate-corrected velocity of fiber shortening relation was the most physiologically appropriate for assessing pharmacologically induced changes in inotropic state that were accompanied by complex alterations in loading conditions in patients with dilated cardiomyopathy.

Cardiac Catheterization↗
PubMed1992

Influence of histamine receptors on basal left ventricular contractile tone in humans: assessment using the H2 receptor antagonist famotidine and the beta-adrenoceptor antagonist esmolol as pharmacologic probes.

Histamine has a positive inotropic action in humans. Recent controversial data have suggested that histamine2 (H2) receptor blockade depresses overall left ventricular systolic performance in healthy volunteers. To explore the possibility that H2 receptors positively influence basal left ventricular contractile tone, 10 normal subjects were studied by using imaging and Doppler echocardiography and calibrated subclavian pulse data in a blinded, randomized, two-period crossover trial with measurements obtained at the end of each 7-day period. Oral drug administration consisted of either the potent H2 antagonist famotidine (40 mg/day) or placebo. Left ventricular circumferential end-systolic wall stress-rate-corrected velocity of fiber shortening (Vcfc) relations were generated over a range of loads with methoxamine. Contractility was assessed by using Vcfc at a common end-systolic wall stress. During each study, data were obtained before and during high dose intravenous esmolol administration to determine the contributions, if any, of sympathetic reflex responses. Famotidine did not alter blood pressure, left ventricular percent fractional shortening, circumferential end-systolic wall stress, stroke volume index, cardiac index, total vascular resistance or ventricular contractile state in comparison with placebo but did decrease heart rate by 3 beats/min (p less than 0.05). With beta-adrenergic blockade, no differences in contractility were evident between esmolol alone and famotidine plus esmolol. Thus, H2 receptor blockade with famotidine does not alter myocardial mechanics or cardiac sympathetic tone, suggesting that in humans basal left ventricular contractile state is not physiologically dependent on the H2-mediated effects of histamine.

Adolescent↗
PubMed1992

A time-course study of the effects of pentobarbital, fentanyl, and morphine chloralose on myocardial mechanics.

Cardiovascular physiological studies in anesthetized animals may be confounded by the hemodynamic actions of the anesthetic agents themselves. To identify an anesthetic regimen that does not significantly influence cardiovascular physiology, the hemodynamic responses of 28 dogs were studied. Animals were equally divided among groups with 1) no anesthesia (i.e., trained conscious preparation), 2) pentobarbital sodium, 3) fentanyl citrate, and 4) a combination of morphine sulfate and alpha-chloralose. Anesthesia was maintained for 3 h. Data were acquired with the use of ultrasound imaging of the heart in conjunction with invasive pressure measurements. Left ventricular ejection phase indexes and end-systolic force-velocity relations were used to evaluate the effects of each anesthetic agent on overall systolic performance and myocardial contractility. Compared with the conscious animals, pentobarbital profoundly depressed systolic performance (P less than 0.05 vs. control) because of a reduction in myocardial contractility (P less than 0.01) and an increase in left ventricular afterload (end-systolic wall stress, P less than 0.05). Fentanyl increased myocardial contractility (P less than 0.05) but also tended to increase afterload with the net result that overall systolic performance remained unchanged. Morphine-chloralose did not affect overall ventricular systolic performance or its individual determinants. Pentobarbital and fentanyl also caused progressive time-dependent deteriorations in all parameters of systolic function during prolonged anesthesia. In contrast, cardiac function was stable for greater than or equal to 3 h after induction of morphine-chloralose anesthesia. The hemodynamic profile of dogs anesthetized with morphine-chloralose most closely resembled that of the conscious animals. Morphine-chloralose is recommended when prolonged anesthesia is required for studies of cardiovascular physiology.

Anesthetics↗
PubMed1992

[Osteoid osteoma of the elbow].

The osteoid osteoma is a rare, benign neoplasm of bone, most frequently located in the lower extremity (head of the tibia). Because of its rarity and its mostly rather unspecific clinical symptoms, diagnosis of the tumor is frequently problematic. Ideally, osteosclerosis surrounding a central focus (nidus) is revealed by radiology. Radiological imaging seems to be the most effective tool in reaching the correct diagnosis. Operative resection of the nidus is the only known curative therapy for osteoid osteoma.

Adult↗
PubMed1991

Left ventricular mechanics in preeclampsia.

Increased systemic vascular resistance and contracted blood volume are characteristic findings in preeclampsia. These alterations in cardiovascular hemodynamics can adversely affect ejection phase indices of left ventricular performance making it difficult to separate abnormalities resulting from changes in load from those caused by depressed myocardial contractility. To address this issue the contractility-sensitive, load-independent relationship between left ventricular end-systolic wall stress and rate-corrected velocity of fiber shortening was assessed in 10 nulliparous patients with preeclampsia. Comparisons were made with data obtained from 10 age-matched normotensive women with uncomplicated pregnancies (control subjects). Studies were performed by means of two-dimensionally targeted M-mode echocardiography and calibrated carotid pulse tracings during early labor, 1 day after delivery, and 4 weeks after delivery. During early labor and 1 day after delivery, patients with preeclampsia had elevated blood pressure and increased total systemic resistance. These parameters returned to normal by 4 weeks after delivery. Before delivery and 24 hours after delivery, the patients with preeclampsia had lower overall left ventricular performance (as measured by cardiac output and rate-corrected velocity of fiber shortening) and higher left ventricular afterload (as measured by left ventricular end-systolic wall stress) when compared with control subjects. These differences were no longer present 4 weeks after delivery. Despite the time-related intergroup differences in hemodynamics, left ventricular contractility was similar between normotensive and preeclamptic subjects at all stages of the study. Thus when load is eliminated as a confounding variable, the decrements in overall left ventricular performance measured in patients with preeclampsia reflect a mechanically appropriate response to increased afterload rather than an abnormality in the ventricular contractile state.

Adult↗
PubMed1991

Parathyroid hormone and myocardial performance in dialysis patients.

Whether parathyroid hormone (PTH) has a clinically important effect on myocardial performance is unclear. Previous investigations of cardiac function before and after parathyroidectomy have failed to control for ionized calcium, other biochemical parameters, or heart rate and cardiovascular loading conditions. We performed load- and rate-independent measurements of myocardial contractility in seven stable hemodialysis patients before and after surgical parathyroidectomy under identical conditions of blood ionized calcium (Ca2+), electrolytes, pH, PO2, and hematocrit. Mid-molecule PTH decreased from 44 +/- 8 to 2 +/- 1 ng/mL. Aortic systolic and diastolic pressures, left ventricular chamber dimensions, end systolic wall stress, left ventricular contractility at a common level of afterload, and contractile reserve evaluated with dobutamine were similar before and after parathyroidectomy. Thus, PTH appears not to have a direct effect on myocardial contractile state in dialysis patients.

Adult↗
PubMed1991

A physiological approach to drug therapy in dilated cardiomyopathy. Echo-Doppler evaluation of cardiac mechanics, myocardial energetics, and ventriculo-vascular coupling.

Cardiac ultrasound imaging can be used in conjunction with calibrated external pulse recordings to provide detailed information regarding cardiovascular hemodynamics. This review establishes a physiological framework for the echo-Doppler assessment of cardiac mechanics, left ventricular energetics, and ventriculo-systemic vascular coupling in patients with dilated cardiomyopathy. The section on cardiac mechanics concerns the evaluation of overall cardiac performance and its individual determinants. Particular emphasis is placed upon the use of noninvasive methodology to identify the relative contributions of altered loading conditions and intrinsic myocardial contractility to cardiac performance. The noninvasive evaluation of left ventricular energetics is based on the physiological premise that myocardial oxygen consumption is a function of three major determinants, i.e., heart rate, contractility, and the integral of left ventricular systolic load (or wall stress). Following a brief discussion of the vascular properties that determine the relationship between pressure and flow in the systemic circulation, noninvasive methods for determination of systemic vascular resistance and arterial compliance are described. At the end of each section, practical clinical applications of these techniques to the evaluation and management of patients with dilated cardiomyopathy are presented.

Cardiomyopathy, Dilated↗
PubMed1991

Doppler and electromagnetic comparisons of instantaneous aortic flow characteristics in primates.

Assessment of the pulsatile mechanical behavior of the coupled left ventricle and the peripheral arterial circulation requires accurate estimation of instantaneous aortic flow. Before the availability of Doppler technologies, this could only be achieved by invasive techniques. The purpose of this study was to assess the accuracy of Doppler-based measurement of instantaneous aortic blood flow and waveform morphology throughout ventricular ejection when compared with an established invasive method. Accordingly, data from electromagnetic flow and continuous-wave aortic Doppler recordings were simultaneously acquired and compared in five monkeys over a wide range of flows generated by intravenous infusions of the beta-adrenoceptor agonist dobutamine and the alpha-receptor agonist methoxamine. Instantaneous aortic pressure was measured using a high-fidelity micromanometer-tipped catheter placed in the ascending aorta. Excellent correlations were noted for stroke volume, cardiac output, left ventricular ejection time, maximal flow velocity, and maximal rate of change of flow velocity (dQ/dtmax). When compared with electromagnetic flows, continuous-wave aortic Doppler had significantly lower times to maximal flow velocity and dQ/dtmax. Frequency domain analysis indicated that both the magnitude and phase were within +/- 6% up to the third harmonic. Instantaneous comparison disclosed that during early systole (up to 10% of ejection) Doppler was higher than electromagnetic flow rate by 11 +/- 19% (p less than 0.05). At 20-30% of systolic ejection, electromagnetic flow rates were slightly higher than Doppler (5 +/- 4% at 20% of ejection, p less than 0.001 and 2 +/- 3% at 30% of ejection, p less than 0.05). From 40% of ejection to the end of systole, flow rates using both techniques were virtually identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Venous air embolism. Diagnosis by spontaneous right-sided contrast echocardiography.

This report describes the definitive diagnosis of venous air-embolism by documentation of spontaneous echo contrast in the right cardiac chambers following removal of a jugular venous catheter in a patient with hepatic failure. This complication was potentiated by the presence of concurrent hepatic coagulopathy which prejudiced effective hemostasis at the central venous puncture site.

Catheterization, Central Venous↗
PubMed1991

[Knee joint hemarthrosis. An absolute indication for operation?].

The degree of severity of an injury of the knee joint is estimated mainly on the basis of the history given by the patient, stability testing and hemarthrosis. Once these are known the surgeon usually decides whether an arthroscopy should be done or not. In a group of 365 patients who had undergone arthroscopy after acute knee injury, we made a retrospective check of the indications. The purpose of the study was to evaluate the sensitivity of hemarthrosis as an indicator of severe injury of the knee joint necessitating operative treatment. For stability testing we used the varus and valgus stress test, the Lachman test, the Anterior drawer test, the pivot shift test and the anterior drawer test with medial and lateral rotation. The Lachman test was repeated under general anesthesia in the majority of patients just before the arthroscopy. The results were evaluated retrospectively with the aid of electronic data processing. In nearly 70% of cases the arthroscopy was indicated because of positive signs of instability together with a typical history provided by the patient or hemarthrosis. In another 27%, the hemarthrosis was the sole reason for the surgeon's decision to perform an arthroscopic investigation of the injured knee joint. In 80.5% of all cases the clinical diagnosis of lesion of the anterior cruciate ligament (ACL) or combined injury to ligaments and menisci was confirmed by the arthroscopy. In addition to this group, in another 10.8% we found other severe lesions necessitating by operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Prediction of aortic annulus diameter by two-dimensional echocardiography. Application in the preoperative selection and preparation of homograft aortic valves.

The preoperative selection and preparation of an appropriately sized homograft aortic valve would allow delay of surgery if a suitable valve were unavailable, thus pre-emptying inventory limitations, and a decrease of ischemic time in cases of isolated aortic valve replacement. An accurate preoperative measurement of the aortic annulus diameter is the prerequisite for such selection. The aortic annulus diameter was measured retrospectively in a blinded fashion from the two-dimensional echocardiograms of 62 patients who underwent aortic valve replacement with mechanical or bioprosthetic valves. Measurements were obtained with electronic calipers by two observers. Confidence in the accuracy of the measurement obtained was ranked on a scale from 1 to 5. The mean difference between echocardiographic measurements and prosthetic valve sizes was 0.39 +/- 0.46 mm (mean +/- 2SD) for observer 1 and -0.26 +/- 1.44 mm for observer 2. Ninety-eight percent of observer 1 measurements and 80% of observer 2 measurements were within 1.5 mm of the prosthetic valve size (p less than 0.01 for differences between observers). Confidence scores were higher for observer 1 and for both observers were related to accuracy. The aortic annulus diameter of eight patients scheduled for homograft aortic valve replacement was measured prospectively with the same technique. There was an excellent agreement between the two-dimensional echocardiographic measurements and the surgical measurements. In the last 5 consecutive patients, the echocardiographic measurement was used for the preoperative selection and preparation of the appropriate valve. In conclusion, measurement of the aortic annulus diameter by two-dimensional echocardiography is feasible and clinically useful for the preoperative selection and preparation of homograft aortic valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1991

[Standards for preclinical resuscitation--requirements for efficient therapy and scientific analysis. A prospective study using as an example the combined emergency medical service of the Munich administrative district and capital].

A standardized treatment protocol is essential for scientific evaluation of parameters influencing the outcome and survival of patients who have suffered cardiac arrest in a non-hospital situation. In addition, a standardized therapy algorithm permits effective, time-saving interaction of all members of the emergency team who work together to perform cardiopulmonary resuscitation (CPR) in any emergency outside the hospital. This paper gives the results obtained in 50 patients in whom on-the-spot resuscitation was performed by a specially trained team [emergency medical team (EMT) + on-scene physician] using an ACLS (advanced cardiac life support) protocol modified from the AHA (American Heart Association) standard. Two different algorithms were used one for ventricular fibrillation (VF) and pulseless ventricular tachycardia and one for asystole and pulseless bradycardia. When indicated, countershocks were first administered at a continuous energy level of 360 J, up to three times one after the other. All patients then received epinephrine intratracheally, 2 mg, immediately after intubation. In the case or persisting asystole a further 2-mg dose of epinephrine and then one 5-mg dose were given i.v. in keeping with the ACLS protocol. In the case of persisting VF or pulseless tachycardia we gave one 100-mg dose of lidocaine i.v. and then performed the next countershock at the same energy level. The time the team members actually needed for the single steps of the ACLS protocol was meticulously documented with the aid of a stop watch.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1990

Myocardial mechanics in young adult patients with diabetes mellitus: effects of altered load, inotropic state and dynamic exercise.

The disease entity "diabetic cardiomyopathy" has been extensively described in young patients with diabetes in the absence of ischemic, hypertensive or valvular heart disease. The most convincing data have been a 30% to 40% incidence of decreased radionuclide angiographic left ventricular ejection fraction response to dynamic exercise. In the current study, the hypothesis was tested that this abnormal ejection fraction response was due to alterations in ventricular loading conditions or cardiac autonomic innervation (extrinsic factors), or both, rather than to abnormalities in intrinsic ventricular systolic fiber function (contractility). Twenty normotensive patients with diabetes (mean age 30 +/- 5 years, mean duration 15 +/- 6 years) and 20 age-matched normal subjects were studied. All patients with diabetes had a normal treadmill exercise tolerance test without evidence of myocardial ischemia. By radionuclide angiography, all normal subjects increased ejection fraction with exercise (62 +/- 4% to 69 +/- 6%; p less than 0.001). In contrast, 11 (55%) of 20 patients with diabetes maintained or increased ejection fraction with exercise (group 1; 62 +/- 4% to 69 +/- 6%; p less than 0.001) and 9 (45%) of 20 showed an exercise-induced decrease (group 2; 73 +/- 4% to 66 +/- 6%; p less than 0.001). No difference in the incidence of microangiopathy, as noted by funduscopic examination, was present between the diabetic groups. Despite the abnormal ejection fraction response to exercise in the group 2 patients with diabetes, all patients with diabetes had a normal response to afterload manipulation, normal baseline ventricular contractility as assessed by load- and heart rate-independent end-systolic indexes and normal contractile reserve as assessed with dobutamine challenge. Autonomic dysfunction did not explain the disparate results between the group 2 patients' radionuclide angiographic data and their load-independent tests of ventricular contractility and reserve. In addition, the high ejection fraction at rest in group 2 patients (73 +/- 4% versus 62 +/- 4% for normal subjects; p less than 0.001) was not related to the abnormal tests of autonomic function. Thus, when left ventricular systolic performance was assessed by load- and rate-independent indexes, there was no evidence for cardiomyopathy in young adult patients with diabetes who have normal blood pressure and no ischemic heart disease.

Adult↗
PubMed1990

Parasympathetically modulated antiarrhythmic action of lidocaine in atrial fibrillation.

Clinical experience has shown that the antiarrhythmic effect of lidocaine on atrial arrhythmias, and specifically for the conversion of atrial fibrillation to normal sinus rhythm, is minimal. This study summarizes our experience in 30 dogs in which atrial fibrillation was initiated and sustained (greater than or equal to 15 minutes) under increased vagal tone achieved by either alpha-chloralose anesthesia (26 dogs) or pentobarbital sodium anesthesia combined with direct external electrical vagal stimulation (four dogs). Under increased vagal tone (regardless of the procedure), an intravenous bolus of lidocaine (2 to 3 mg/kg) was 100% effective (101 of 101 episodes) in pharmacologically converting atrial fibrillation to normal sinus rhythm. This was associated with marked slowing of intra-atrial electrical activity, as shown by fast Fourier analysis of intra-atrial electrograms. Over a period of 3 to 5 minutes, lidocaine progressively shifted the peak frequency content from 84 +/- 18 mV2/Hz in the 10 to 20 Hz frequency band during the pre-lidocaine phase to 110 +/- 34 mV2/Hz in the 0 to 10 Hz frequency band immediately prior to conversion to normal sinus rhythm. When atropine was administered or electrical vagal stimulation was discontinued, the conversion of atrial fibrillation to normal sinus rhythm followed a similar electrophysiologic pattern. When isoproterenol was infused, it was difficult to induce atrial fibrillation; when the arrhythmia was initiated, it could not be sustained even with concomitant electrical vagal stimulation. Thus in this model of parasympathetically sustained atrial fibrillation, lidocaine was 100% effective in converting atrial fibrillation to normal sinus rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗