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Biomedical subjects

W Kupper

Publications and source records attributed to W Kupper.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of intravenous coronary angiography using synchrotron radiation with selective coronary angiography.

Intravenous coronary angiography with synchrotron radiation is a novel and minimally invasive technique for coronary imaging. At the Hamburger Synchrotronstrahlungslabor HASYLAB at DESY, a dedicated angiography system has been developed, which has been shown to provide detailed images of coronary artery segments. For each scan, two monochromatic X-ray images below and above the K-edge of iodine were recorded simultaneously. The two images were subtracted logarithmically to produce a maximal contrast enhancement of the iodine. To date, the procedure has been carried out on 379 outpatients. No complications occurred during or after the angiographic procedure, and hospitalization was not required in any subject. The acceptance by patient is extremely high. Five outside reviewers, blinded as to the clinical data or prior angiographic interpretation, reviewed the images for the presence or absence of 70% or more occlusion of a vessel. They reached a sensitivity of 79% and a specificity of 99%. The study has demonstrated that the synchrotron method has satisfactory sensitivity and very high specificity for severe stenoses. The new method has several advantages over magnetic resonance imaging (MRI), electron beam computed tomography (EBCT), and multi-slice computed tomography (MSCT). Neither vascular calcification (CT) nor the presence of metal stents (MRI) impairs the evaluation of perfusion of segments of the coronary arteries. Furthermore, the spatial resolution is three or four times higher using synchrotron angiography, and problems due to respiratory motion are eliminated.

Adult↗
PubMed2001

[Amlodipine versus nifedipine retard. A randomized double-blind comparative study on long-term efficacy and safety of amlodipine and nifedipine retard in the monotherapy of chronic stable angina pectoris].

PATIENTS AND METHOD: This double-blind study compared the efficacy and safety of once daily amlodipine (5-10 mg/day) vs twice daily nifedipine (40-80 mg/day) in 244 patients with chronic stable angina pectoris. Efficacy was assessed after 4 and 24 weeks by bicycle exercise test. RESULTS: No statistically significant differences were found between the two treatment groups at the end of treatment with regard to the ergometry parameters determined (maximum ST segment deviation, maximum workload in watts, maximum exercise duration and time to 0.1 mV ST segment depression). Furthermore, the two treatment groups were comparable with regard to the effected reduction in anginal attacks and short acting nitrate consumption. The incidence of adverse events was lower in the amlodipine relative to the nifedipine group (11.5% vs 19.1%). CONCLUSION: The results of this study show that once daily amlodipine offers comparable antianginal and antiischemic efficacy as twice daily sustained release nifedipine in the monotreatment of chronic stable angina pectoris. Given the lower incidence of adverse events with amlodipine and its convenient once daily dosing regimen, however, amlodipine may help to enhance patient compliance.

Adult↗
PubMed2001

Intravenous coronary angiography using synchrotron radiation: technical description and preliminary results.

BACKGROUND: Standard coronary angiography requires an arterial access and catheters; intravenous coronary angiography may image coronary arteries noninvasively and without catheters. The aim of this study was the assessment of the diagnostic accuracy of intravenous coronary angiography validated by selective coronary angiography. METHODS: Seventy outpatients (80% males, mean age 62 +/- 8 years) underwent both standard and intravenous coronary angiography after a previous coronary intervention. Intravenous coronary angiography was performed within 6 weeks before or after selective coronary angiography. Two different projections were used to obtain 6-8 sequences per patient. Images were taken after injection of the contrast agent into the brachial vein or into the superior vena cava. During image acquisition, patients were moved through the scanning beam on a special chair. Thereafter, images were evaluated and compared to selective coronary angiograms for the following criteria: no stenosis, subsignificant stenosis (< 70%), significant stenosis (> or = 70%), and occlusion. RESULTS: One hundred eighty-seven target vessels were analyzed. In 50 target vessels one or more stents had been implanted. Seventeen target vessels were not analyzable due to inadequate image quality. The sensitivity of intravenous coronary angiography for the detection of lesions was 80% and the specificity was 95%. The sensitivity for the detection of significant lesions in the left anterior descending coronary artery was 84% (specificity 93%), in the left circumflex coronary artery 67% (specificity 90%), in the right coronary artery 85% (specificity 97%), and in bypass grafts 85% (specificity 97%). No complications were observed. CONCLUSIONS: Intravenous coronary angiography is efficacious and safe and allows quantification of lesions of the coronary arteries and of bypass vessels. Further advances in image processing are needed to improve sensitivity especially in the left circumflex coronary artery.

Contrast Media↗
PubMed2001

[Turbulence and high intensity transient signals (HITS) as a parameter for optimum orientation of mechanical heart valves].

BACKGROUND: In previous studies, the impact of valve orientation on the hemodynamic performance of mechanical aortic valves has been demonstrated. This study investigates Turbulence (RNS values) and High Intensity Transient Signals (HITS) as a new and objective parameter for hemodynamics in various orientations of Medtronic Hall (MH) and St. Jude Medical (SJM) aortic valves. METHODS: Rotation devices carrying a MH or SJM valve were implanted into four pigs. The device allowed valve rotation without reopening the aorta. In various orientations, turbulent shear stresses (RNS values) and HITS were measured. RESULTS: RNS and HITS changed for both valve designs in the different orientations, with superior results for the MH in the hemodynamically best orientation. Downstream turbulence (RNS) and HITS varied in the same direction, but a one to one correlation was not observed. CONCLUSIONS: RNS and HITS vary with respect to valve orientation and design with superior results for the tilting disc valve. Both MH and SJM valves showed lower turbulence and HITS counts in their hemodynamically best orientations. HITS were related to downstream turbulence and the hemodynamic performance of the mechanical aortic valves.

Animals↗
PubMed2000

[Intravenous coronary angiography with synchrotron radiation].

INTRODUCTION: Coronary artery disease still remains the primary cause of death in the western industrialized world. Although the clinical value of selective coronary angiography (SCA) is beyond dispute, the associated risk of an invasive approach, the inherent costs and the necessary hospitalization have lead to the development and investigation of novel non-invasive techniques for coronary imaging. Intravenous coronary angiography (ICA) has been shown to permit non-invasive imaging of the coronary arteries. METHODS: In 66 pts (80% male, age 62 (+/- 8.5 yrs) after interventional therapy/CABG operation, ICA and a SCA were carried out within a time interval of < 6 weeks. After determination of the individual circulation time, contrast media (370 mg iodine/ml, 15 ml/s, 21 ml) was injected via a sheath in the cubital vein while the patient was sitting in an upright position in a specially designed scanning chair. In two different projections 6-8 images/patient were obtained for further image processing and evaluation. 182 target vessels had to be evaluated (LAD 55, Cfx 21, RCA 54, Grafts 52). In 50 target vessels one or more stents were implanted. RESULTS: 182 target vessels were evaluated according to the following criteria: no stenosis, < 70%, > = 70%, occlusion. Evaluation of the ICA and SCA images was performed by two independent investigators. Due to poor image quality, 17 vessels were not evaluated. The ICA findings were compared to that of SCA. For the LAD a sensitivity of 84% (specificity 93%), for the RCA a sensitivity of 85% (specificity 97%), for the Cfx a sensitivity of 67% (specificity 90%), and for grafts a sensitivity of 85% (specificity 97%) was calculated. CONCLUSION: ICA proved to be a feasible and safe technique for follow-up after coronary intervention/CABG operation on an outpatient basis. Evaluation of stents and severe calcification is possible. A good image quality provided, LAD RCA and grafts can be evaluated with an acceptable sensitivity and specificity. Due to superimpositioning the low sensitivity for the Cfx has to be compensated by further image processing.

Aged↗
PubMed1996

Intravenous coronary angiography with dichromography using synchrotron radiation.

Dichromography represents a digital subtraction angiography mode based on energy substraction which allows imaging of fast moving subjects like the heart. For logarithmic subtraction 2 images with X-rays just below and above the iodine K-edge (33.17 keV) are simultaneously obtained in a line scan mode. Monochromatic X-rays of sufficient intensity to visualize coronary arteries of 1 mm diameter with extremely low iodine concentrations (1 mg/cm2) after venous injection is only provided by synchrotron radiation. The system NIKOS (non-invasive coronary arteriography with synchrotron radiation) at the Deutsches Elektronen Synchrotron (DESY) consists of 6 components: a wiggler, a monochromator, a safety system, a scanning device, a detector and a computer system. After experimental studies in dogs patients are imaged since 1990. Initial results demonstrate feasibility and safety of synchrotron radiation coronary angiography. Large scale studies are designed to further evaluate sensitivity and specificity. When compact synchrotron radiation sources become available, this technique could be used for follow-up studies and for evaluation of certain high coronary risk populations.

Angiography, Digital Subtraction↗
PubMed1994

Efficacy of high dose intravenous heparin for treatment of left ventricular thrombi with high embolic risk.

OBJECTIVES: This study was performed to assess the efficacy of high dose intravenous heparin to treat mobile or protruding left ventricular thrombi as detected by serial echocardiography. BACKGROUND: The presence of mobile and protruding left ventricular thrombi greatly increases the risk of arterial embolization, yet optimal therapy, be it thrombolysis, anticoagulation or surgical removal, has not been defined. METHODS: Full dose heparin, 31,291 +/- 7,980 (mean +/- SD) IU/day, to prolong partial thromboplastin time to at least twice normal, was administered intravenously to 23 consecutive patients with 25 mobile and protruding thrombi. Patients were prospectively evaluated for hemorrhagic complications and embolic events during therapy. The presence or absence of thrombi and their size and characteristics were assessed by serial echocardiography. RESULTS: In all 23 patients left ventricular thrombi decreased in size, with disappearance of the high risk features. The duration of high dose heparin infusion was 7 to 22 days (mean 14 +/- 4). Thrombus size was reduced from 3.9 +/- 2.6 to 0.16 +/- 0.38 cm2, and thrombus disappeared entirely in 19 (83%) of 23 patients. No embolic events were detected during treatment, and the only complication was an upper gastrointestinal hemorrhage that was successfully treated medically. CONCLUSION: High dose intravenous heparin is a highly effective and safe treatment for completely resolving left ventricular thrombi with high risk features for embolization. Most such thrombi disappear completely within 1 to 3 weeks of this treatment without embolic or hemorrhagic complications.

Echocardiography↗
PubMed1993

Noninvasive estimation of regurgitant flow rate and volume in patients with mitral regurgitation by Doppler color mapping of accelerating flow field.

OBJECTIVES: This study was designed to examine the accuracy of proximal accelerating flow calculations in estimating regurgitant flow rate or volume in patients with different types of mitral valve disease. BACKGROUND: Flow acceleration proximal to a regurgitant orifice, observed with Doppler color flow mapping, is constituted by isovelocity surfaces centered at the orifice. By conservation of mass, the flow rate through each isovelocity surface equals the flow rate through the regurgitant orifice. METHODS: Forty-six adults with mitral regurgitation of angiographic grades I to IV were studied. The proximal accelerating flow rate (Q) was calculated by: Q = 2 pi r2.Vn, where pi r2 is the area of the hemisphere and Vn is the Nyquist velocity. Radius of the hemisphere (r) was measured from two-dimensional or M-mode Doppler color recording. From the M-mode color study, integration of accelerating flow rate throughout systole yielded stroke accelerating flow volume and mean flow rate. Mitral regurgitant flow rate and stroke regurgitant volume were measured by using a combination of pulsed wave Doppler and two-dimensional echocardiographic measurements of aortic forward flow and mitral inflow. RESULTS: The proximal accelerating flow region was observed in 42 of 46 patients. Maximal accelerating flow measured from either two-dimensional (372 +/- 389 ml/s) or M-mode (406 +/- 421 ml/s) Doppler color study tended to overestimate the mean regurgitant flow rate (306 +/- 253 ml/s, p < 0.05). Mean Doppler accelerating flow rate correlated well with mean regurgitant flow rate (r = 0.95, p < 0.001), although there was a tendency toward slight overestimation of mean regurgitant flow by mean accelerating flow in severe mitral regurgitation. However, there was no significant difference between the mean accelerating flow rate (318 +/- 304 ml/s) and the mean regurgitant flow rate (306 +/- 253 ml/s, p = NS) for all patients. A similar relation was found between accelerating flow stroke volume (78.27 +/- 62.72 ml) and regurgitant flow stroke volume (76.06 +/- 59.76 ml) (r = 0.95, p < 0.001). The etiology of mitral regurgitation did not appear to affect the relation between accelerating flow and regurgitant flow. CONCLUSIONS: Proximal accelerating flow rate calculated by the hemispheric model of the isovelocity surface was applicable and accurate in most patients with mitral regurgitation of a variety of causes. There was slight overestimation of regurgitant flow rate by accelerating flow rate when the regurgitant lesion was more severe.

Blood Flow Velocity↗
PubMed1993

Usefulness of transesophageal echocardiography in identifying small left ventricular apical thrombus.

OBJECTIVES: The aim of this study was to determine whether transesophageal echocardiography could clarify the nature of equivocal echodense structures in the left ventricular apical region frequently found on transthoracic echocardiography by directing the ultrasound beam from the left ventricular base to the apex and achieving better image quality. BACKGROUND: Transthoracic echocardiography often reveals an echogenic structure suggesting thrombus in the left ventricular apical region because of limited near-field resolution and echo vibration artifact in apical views. METHODS: Thirty-six patients with coronary artery disease or dilated cardiomyopathy who had apical wall motion abnormalities and equivocal transthoracic echodense structures were studied with transesophageal echocardiography using special manipulation of the transesophageal probe for adequate imaging of the apical region. Left ventricular thrombus was defined when echogenic structures with a clearly delineated margin adjacent to but distinct from the endocardium were observed in at least two different tomographic views in the four-chamber and left ventricular long-axis views during both systole and diastole. RESULTS: Left ventricular thrombus (mean size 1.3 +/- 0.7 cm2) was defined by transesophageal echocardiography in 19 (53%) of 36 patients with suspected thrombus on transthoracic echocardiography in the four-chamber or left ventricular long-axis view. Heavy trabeculation or extremely high echo reflection, or both, was observed in the apical region in 12 patients (33%). No extra structures in the apical region were found in five patients. In 19 patients with transesophageal echocardiographically defined thrombus, 6 patients (31%) experienced arterial embolic events before the transesophageal procedure. In contrast, none of 17 patients without transesophageal echocardiographically defined thrombi had systemic embolism (p < 0.03). CONCLUSIONS: 1) Transesophageal echocardiography is useful in identifying left ventricular apical thrombus in patients with unclear echogenic structures on transthoracic apical images; and 2) the high incidence of arterial embolism in patients with transesophageal echocardiographically detected left ventricular thrombus indicates the clinical importance of such thrombus.

Adult↗
PubMed1992

[Floating intracardiac metastasis].

Two years after the removal of an embryonic testicular tumour from a now 26-year-old man, his general health deteriorated and a holosystolic murmur was heard over the tricuspid valve area. A chest X-ray film demonstrated lung metastases. Biochemical tests were within normal limits, but the human chorionic gonadotrophin level was elevated to 81,030 mU/ml. Echocardiography revealed mild tricuspid regurgitation and a floating mass between the right atrium and ventricle, in contact with the tricuspid valve. The described findings did not support the diagnosis of embolus or inflammatory vegetation. Because of the danger of embolization and obstruction of the pulmonary outflow tract the mass was removed surgically. Enzyme-histological examination identified the tissue as a metastasis of the testicular tumour. The patient's condition at first improved, but he soon died of bleeding from the lung which was infiltrated by trophoblast-containing metastases of the testicular tumour.

Adult↗
PubMed1992

Intermittent infusion of dobutamine in the therapy of severe congestive heart failure--long-term effects and lack of tolerance.

Twenty patients with refractory heart failure NYHA class IV were randomly assigned to infusion therapy with 9.25 micrograms/kg/min dobutamine over 24 hours or placebo. Eight infusions over a 4-week period were performed in the hospital; between infusions breaks of 3 days were scheduled. A dose titration was performed before study during which dobutamine was infused at 2.5 micrograms/kg/min and increased by 2.5 micrograms/kg/min steps every 15 minutes up to a maximum dosage of 10 micrograms/kg/min. After dobutamine, exercise duration on the treadmill stress test increased from 177 +/- 110 seconds to 251 +/- 120 seconds (p less than 0.05). The heart-rate response to exercise increased (91 +/- 20 to 116 +/- 26 beats/min at baseline, 88 +/- 17 to 132 +/- 26 beats/min after therapy). Body weight decreased from 70.9 +/- 15.5 to 68.9 +/- 14.2 kg (p less than 0.03). On placebo, no significant changes were evident. Systolic time intervals and hemodynamic parameters showed only minor and not significant changes in both groups. No excess mortality emerged during intermittent dobutamine therapy. No clinical or hemodynamic signs of tolerance development were evident during control assessment 3 days after the last infusion. Intermittent therapy with dobutamine seems to be a promising concept in the management of refractory severe heart failure.

Adult↗
PubMed1992

Effect of dobutamine on pulmonary gas exchange in patients with severe heart failure.

Twenty patients (two female, 18 male, mean age 57 +/- 11 years) with severe heart failure NYHA IV (7 coronary artery disease, 13 congestive cardiomyopathy) were treated with 8.8 +/- 1.7 micrograms.kg-1 x min-1 of dobutamine. Pulmonary gas exchange was analysed by withdrawal of blood samples from a central venous catheter and a radial artery cannula. Dobutamine increased SvO2 from 58.7 +/- 11.2% to 72.2 +/- 6.3% (P = 0.0001) and decreased avDO2 from 7.7 +/- 2.45 Vol% to 4.97 +/- 1.34 Vol% (P = 0.0001). PaO2 and PaCO2 were not changed. Qs/Qt increased slightly from 9.1 +/- 8.3% to 11.3 +/- 6.4% (P = 0.035). Cardiac index increased by 51% (P = 0.0001), pulmonary capillary wedge pressure decreased by 28% (P = 0.0001). In patients with severe heart failure, dobutamine improved haemodynamics without detrimental effects on arterial oxygen concentration.

Dobutamine↗
PubMed1992

Residual platelet function under acetylsalicylic acid and the risk of restenosis after coronary angioplasty.

Restenosis after percutaneous transluminal coronary angioplasty (PTCA) was shown not to be preventable by antiplatelet therapy; residual platelet function under treatment with platelet inhibitors could be one cause of this. Therefore, in a prospective investigation, residual platelet function was assessed in 98 patients treated with acetylsalicylic acid (ASA) on three occasions during the first 3 months after successful PTCA. Control cardiac catheterization was obtained in 75 of these patients (77%) with 82 dilated stenoses 173 +/- 117 days after PTCA. Restenosis, defined as diameter stenosis greater than or equal to 50% at control angiography, occurred in 41% of the dilated vessels, and 43% of patients experienced restenosis in at least one vessel. The in vitro platelet aggregatory response to either ADP (0.5, 1, and 10 microM) or collagen (1 and 5 mg/L) as aggregating agents did not differ between patients with and without restenosis. In addition, neither the collagen-stimulated in vitro synthesis of thromboxane nor the basal or prostaglandin E1-stimulated concentrations of cyclic AMP in platelet-rich plasma (PRP) was different in the two groups. There was no significant correlation between any of the parameters of platelet function assessed and the change in coronary luminal diameter observed between immediately after PTCA and control coronary angiography. The mean dose of ASA ingested during follow-up was also not a determinant of the occurrence of restenosis. Thus, residual platelet function under treatment with ASA as measured in vitro in this study, did not influence the occurrence of restenosis after successful PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1992

[Cardiovascular risk factors and restenosis after PTCA].

We prospectively investigated the influence of the cardiovascular risk factors hypercholesterolemia, smoking, diabetes mellitus, and arterial hypertension on the occurrence and extent of restenosis after successful coronary dilatation (PTCA). Of the 103 patients included in the study, control coronary angiography was obtained in 75 (73%) after 173 +/- 117 days. The restenosis rate (82 stenoses), defined as greater than or equal to 50% loss of initial gain in percent diameter stenosis, was 37%. Older age, male gender, and a history of diabetes mellitus were associated with a significantly increased mean extent of restenosis (p less than 0.05). In patients with hypertension, the initial success of dilatation was less than in controls without hypertension (p less than 0.05), and restenosis tended to be enhanced (p = 0.06). The risk of restenosis was unaffected by smoking and the presence of hypercholesterolemia. In spite of the mostly insignificant influence of single cardiovascular risk factors, the extent of restenosis clearly increased with the number of risk factors.

Aged↗
PubMed1991

Age, cardiovascular risk factors and coronary heart disease as determinants of platelet function in men. A multivariate approach.

Older age, the cardiovascular risk factors and arteriosclerosis have been reported to be associated with stimulated platelet function. To evaluate the relative importance of these factors in determining platelet function, a cross-sectional multivariate study in 191 men, 113 healthy subjects and 78 patients with angiographically documented coronary heart disease, was performed. In healthy subjects, stepwise multiple linear regression identified age to be a major determinant of platelet aggregability. After induction with both ADP and collagen the platelet aggregatory response markedly increased with age. In the patients, platelet function was not age dependent. In multivariate analysis of variance, neither smoking status nor hypercholesterolemia (greater than or equal to 240 mg/dl) were determinants of platelet function in either group. An increase in systolic blood pressure was associated with slightly more inhibited ADP induced aggregation in both healthy subjects and patients with coronary heart disease. In patients compared to healthy subjects, aggregation after induction with ADP and collagen was markedly enhanced and the in vitro formation of thromboxane after collagen stimulation increased. Thus, by multivariate analysis, age and the presence or absence of coronary heart disease were found to be major determinants of platelet function. In contrast, the cardiovascular risk factors smoking, hypercholesterolemia and hypertension were associated with only minor or no alterations of platelet function.

Adult↗
PubMed1991

Interrupting the adaptive changes in congestive heart failure.

Circulating plasma concentrations of norepinephrine, renin, angiotensin and vasopressin are increased in congestive heart failure. By increasing ventricular afterload, heart failure is further worsened, which in turn--in a vicious cycle--stimulates neurohumoral vasoconstrictor mechanisms. Furthermore, because of the compensatory but excessive stimulation of the sympathomimetic system, a down-regulation and desensitization particularly of the myocardial beta 1 receptors and depletion of myocardial catecholamine occurs in chronic heart failure. These defects may be restored toward normal by interventions that attenuate the activity of the sympathetic nervous system. A direct approach to modify the excessive vasoconstriction is to administer systemic vasodilator drugs, but despite favorable short-term effects, tolerance developed to most of these drugs during long-term treatment. One reason for the loss of effectiveness is the reflex activation of the sympathetic system, which increases vasoconstrictor hormone concentrations. Activation of the renin-angiotensin system can be modified effectively by angiotensin-converting enzyme inhibitors that have shown favorable responses in patients with chronic heart failure. Beta-blocking agents interfere with endogenous sympathetic activation and have produced beneficial effects in patients with congestive cardiomyopathy. Long-term treatment is associated with up-regulation of the number of beta receptors and an improved responsiveness to catecholamines. Owing to the negative inotropic effects of beta-blocking agents, some of the patients with severe heart failure deteriorated hemodynamically and clinically. Theoretically, it should be advantageous to have a substance that combines protection against excessive beta stimulation with a mild inotropic support to prevent cardiac decompensation. This may be achieved by a selective beta 1-partial agonist like xamoterol.

Adrenergic beta-Agonists↗