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H Baumgartner

Publications and source records attributed to H Baumgartner.

At least 37 records · Page 2Linked to original sources
PubMed1999

Assessment of coronary stenoses by Doppler wires: a validation study using in vitro modeling and computer simulations.

The present study evaluates the use of intracoronary velocity measurements by Doppler guidewires for assessing coronary obstructions. In vitro experiments were performed in a flow model using acrylic phantoms of coronary stenoses with different configurations (stenosis area: 56%, 75% and 89%; stenosis length: 1 and 5 mm; stenosis border: tapering or abrupt). Nonpulsatile laminar flow conditions of a test fluid were established at flow rates ranging from 0.5 to 2.0 mL/s to simulate baseline flow and flow after vasodilation. Peak Doppler velocity was measured proximal to, within and distal to the model stenoses. Computer simulations were employed to calculate radial flow profiles with and without a Doppler wire aligned with the vessel center. In 84 in vitro flow experiments, peak Doppler velocity correlated well with the average flow velocity as calculated from the actual flow rate and the vessel's cross-sectional area proximal to (r = 0.98, SEE = 1.4, p < 0.001) and within (r = 0.97, SEE = 16.4, p < 0.001) the stenosis. However, the ratio of calculated average velocity to Doppler-measured peak velocity was significantly different from 0.5, the expected value for a parabolic flow profile (0.76+/-0.08, 0.81+/-0.14; p < 0.001). Acceptable accuracy was found for the Doppler estimation of stenosis severity using the continuity equation (error: 0.9+/-1.2% and -4.6+/-3.5% for stenosis with a length of 5 mm and 1 mm, respectively). Doppler velocity reserve significantly underestimated the true flow reserve for the 56% and 75% stenoses (p < 0.01). Computer simulations demonstrated significant alterations of flow profiles by the wire, which explained the observed underestimation of the true flow reserve by the Doppler velocity reserve. Thus, Doppler guidewire measurements of intracoronary flow velocities are useful to assess the severity of coronary stenoses. However, the in vitro results and computer simulations indicate that guidewires alter the flow profile, so that Doppler velocity reserve may underestimate the true flow reserve.

Analysis of Variance↗
PubMed1999

Artificial neural networks and spatial temporal contour linking for automated endocardial contour detection on echocardiograms: a novel approach to determine left ventricular contractile function.

This study investigated the use of artificial neural networks (ANN) for image segmentation and spatial temporal contour linking for the detection of endocardial contours on echocardiographic images. Using a backpropagation network, the system was trained with 279 sample regions obtained from eight training images to segment images into either tissue or blood pool region. The ANN system was then applied to parasternal short axis images of 38 patients. Spatial temporal contour linking was performed on the segmented images to extract endocardial boarders. Left ventricular areas (end-systolic and end-diastolic) determined with the automated system were calculated and compared to results obtained by manual contour tracing performed by two independent investigators. In addition, ejection fractions (EF) were derived using the area-length method and compared with radionuclide ventriculography. Image quality was classified as good in 12 (32%), moderate in 13 (34%) and poor in 13 (34%) patients. The ANN system provided estimates of end-diastolic and end-systolic areas in 36 (89%) of echocardiograms, which correlated well with those obtained by manual tracing (R = 0.99, SEE = 1.44). A good agreement was also found for the comparison of EF between the ANN system and Tc-radionuclide ventriculography (RNV, R = 0.93, SEE = 6.36). The ANN system also performed well in the subset of patients with poor image quality. Endocardial contour detection using artificial neural networks and spatial temporal contour linking allows accurate calculations of ventricular areas from transthoracic echocardiograms and performs well even in images with poor quality. This system could greatly enhance the feasibility, accuracy and reproducibility of calculating cardiac areas to derive left ventricular volumes and ejection fractions.

Adult↗
PubMed1999

"Overestimation" of catheter gradients by Doppler ultrasound in patients with aortic stenosis: a predictable manifestation of pressure recovery.

OBJECTIVES: This study sought to evaluate whether pressure recovery can cause significant differences between Doppler and catheter gradients in patients with aortic stenosis, and whether these differences can be predicted by Doppler echocardiography. BACKGROUND: Pressure recovery has been shown to be a source of discrepancy between Doppler and catheter gradients across aortic stenoses in vitro. However, the clinical relevance of this phenomenon for the Doppler assessment of aortic stenosis has not been evaluated in patients. METHODS: Twenty-three patients with various degrees of aortic stenosis were studied with Doppler echocardiography and catheter technique within 24 h. Using an equation previously validated in vitro, pressure recovery was estimated from peak transvalvular velocity, aortic valve area and cross-sectional area of the ascending aorta and compared with the observed differences between Doppler and catheter gradients. Doppler gradients were also corrected by subtracting the predicted pressure recovery and then were compared with the observed catheter gradients. RESULTS: Predicted differences between Doppler and catheter gradients due to pressure recovery ranged from 5 to 82 mm Hg (mean +/- SD, 19 +/- 16 mm Hg) and 3 to 54 mm Hg (12 +/- 11 mm Hg) for peak and mean gradients, respectively. They compared well with the observed Doppler-catheter gradient differences, ranging from -5 to 75 mm Hg (18 +/- 18 mm Hg) and -7 to 48 mm Hg (11 +/- 13 mm Hg). Good correlation between predicted pressure recovery and observed gradient differences was found (r = 0.90 and 0.85, respectively). Both the noncorrected and the corrected Doppler gradients correlated well with the catheter gradients (r = 0.93-0.97). However, noncorrected Doppler gradients significantly overestimated the catheter gradients (slopes, 1.36 and 1.25 for peak and mean gradients, respectively), while Doppler gradients corrected for pressure recovery showed good agreement with catheter gradients (slopes, 1.03 and 0.96; standard error of estimate [SEE] 8.1 and 6.9 mm Hg; mean difference +/- SD 0.4 +/- 8.0 mm Hg and 1.1 +/- 6.8 mm Hg for peak and mean gradients, respectively). CONCLUSIONS: Significant pressure recovery can occur in patients with aortic stenosis and can cause discrepancies between Doppler and catheter gradients. However, pressure recovery and the resulting differences between Doppler and catheter measurements may be predicted from Doppler velocity, aortic valve area and size of the ascending aorta.

Adult↗
PubMed1999

Large-scale synthesis of hematoregulatory nonapeptide SK&F 107647 by fragment coupling.

Linear and convergent routes for the large-scale preparation of the hematoregulatory nonapeptide (Glp-Glu-Asp)2-DAS-(Lys)2 (2, SK&F 107647) were investigated. A convergent approach ('3 + 2'-route employing Boc-and benzyl ester protecting groups) was selected for the preparation of multihundred-gram quantities of 2. Key steps were the preparation and the coupling of tripeptide hydrochloride (HCl.H)2-DAS-(Lys(Z)-OBn)2 (6, DAS-2,7-L,L-diaminosuberic acid) and tripeptide Glp-Glu(OBn)-Asp(OBn)-OH (26). Several coupling reagents were investigated in order to reduce the amount of epimerization of this fragment coupling. TDBTU [O-(3,4-dihydro-4-oxo-1,2,3-benzotriazin-3-yl-1,1,3,3-tetrameth yluronium tetrafluoroborate] was identified as the condensation reagent of choice. Using this synthetic route > 97% pure final product in an overall yield of 35% calculated on di-Boc protected 2,7-L,L-diaminosuberic acid was prepared.

Indicators and Reagents↗
PubMed1998

Assessment of myocardial viability by dobutamine echocardiography, positron emission tomography and thallium-201 SPECT: correlation with histopathology in explanted hearts.

OBJECTIVES: We examined the relationship among viability assessment by dobutamine echocardiography (DE), positron emission tomography (PET) and thallium-201 single-photon emission computed tomography (TI-SPECT) to the degree of fibrosis. BACKGROUND: DE, PET and TI-SPECT have been shown to be sensitive in identifying viability of asynergic myocardium. However, PET and TI-SPECT indicated viability in a significant percentage of segments without dobutamine response or functional improvement after revascularization. METHODS: Twelve patients with coronary artery disease and severely reduced left ventricular function (EF 14.5+/-5.2%) were studied with DE prior to cardiac transplantation: 5 had additional PET and 7 had TI-SPECT studies. Results of the three techniques were compared to histologic findings of the explanted hearts. RESULTS: Segments with >75% viable myocytes by histology were determined to be viable in 78%, 89% and 87% by DE, PET and TI-SPECT; those with 50-75% viable myocytes in 71%, 50% and 87%, respectively. Segments with 25-50% viable myocytes showed response to dobutamine in only 15%, but were viable in 60% by PET and 82% by TI-SPECT. Segments with <25% viable myocytes responded to dobutamine in 19%; however, PET and TI-SPECT demonstrated viability in 33% and 38%, respectively. Discrepant segments without dobutamine response but viability by PET and SPECT had significantly more viable myocytes by pathology than did those classified in agreement to be nonviable but had significantly less viable myocytes than those classified in agreement to be viable (p < .001). CONCLUSIONS: These findings suggest that contractile reserve as evidenced by a positive dobutamine response requires at least 50% viable myocytes in a given segment whereas scintigraphic methods also identify segments with less viable myocytes. Thus, the methods may provide complementary information: Nuclear techniques appear to be highly sensitive for the detection of myocardial viability, and negative tests make it highly unlikely that a significant number of viable myocytes are present in a given segment. Conversely, dobutamine echo may be particularly useful for predicting recovery of systolic function after revascularization.

Aged↗
PubMed1998

[Manual medicine in pain treatment].

To diagnose the source of pain, a very refined segmental technique is employed in manual medicine. The evaluation of static and dynamic functions is complemented by palpatory and functional testing of the joint mechanics. A reversible hypomobility of a joint causes a swelling of the surrounding soft tissue, a stiffening of the muscle tissue and a change in turgor and trophicism. The various techniques of manual medicine restore the physiological joint play, causing thereby reflectory phenomena, often the source of pain, to disappear quickly. Trivial trauma or inappropriate coordination of movement sequences interfere with joint mechanics. The nociceptive stimulus from all joint structures activates segmentally connected muscular fiber bundles through the posterior horn complex via alpha- and gamma-motoneurons. The joint play of other segments and/or peripheral components can be disturbed via interneurons and become a source of pain. Mobilisation of the joint activates inhibitory neurons, the normal joint mechanics are reestablished and the nociceptive stimulus reduced.

Chronic Disease↗
PubMed1997

[Aortic coarctation--long-term follow-up in adults].

Surgical repair of coarctation of the aorta has been performed since 1945. Although surgical techniques have improved, problems such as restenosis and aneurysm at the operation site or hypertensive cardiovascular disease, still remain. To evaluate the long-term results after surgical repair of coarctation, 41 patients, 25 male and 16 female patients (mean age: 28 +/- 11 years, range 14-57 years), were studied 16 +/- 8 years after surgery (range 3-44 years). Mean age at surgery was 12 +/- 9 years (range 0.5-35 years). In 24 patients resection and end-to-end anastomosis had been performed, patch graft aortoplasty in nine patients, tube interposition graft in seven patients and one patient had undergone the subclavian flap technique. All patients were assessed by exact physical examination, the resting arm-to-leg systolic pressure gradient was measured by Doppler sonography, a bicycle exercise test and an echocardiogram were performed. Twenty-one patients reported postoperative symptoms such as dizziness (n = 12), headache (n = 3), cold legs (n = 10) and/or dyspnea (n = 8). In two patients the resting arm-to-leg pressure gradient was greater than 30 mm Hg, in two patients it was greater than 20 mm Hg. Gradient calculated by Doppler echocardiography ranged from 0 to 80 mm Hg (21 +/- 17 mm Hg) and showed poor correlation with the arm-to-leg pressure difference. The mean functional capacity was 89 +/- 18% (range 42-110%). In 18 patients exercise-induced hypertension was found, while in only eight patients arterial hypertension had already been known. To evaluate the morphology of the aorta MRI was performed in 28 patients. No aneurysm was found. In five patients a minimal lumen diameter as small as 9-11 mm was measured. Patients were divided into two groups according to their age at operation, group I: < 9 years (n = 19) and group II: > 9 years (n = 22). Resting blood pressure was significantly higher in group II (135 +/- 27 mm Hg vs 114 +/- 20 mm Hg, p < 0.009), anti-hypertensive medication (43% vs 11%, p < 0.04) and symptoms were more frequent in these patients (15/22 vs 6/19, p < 0.04). However at time of follow-up examination the age of patients of group II was significantly higher (33 +/- 12 vs 22 +/- 5 years, p < 0.0005). Between these two groups there was no difference in follow-up time and results of echocardiography or stress test. In conclusion, despite good long-term results after surgical repair of coarctation of the aorta, patients should be followed on a regular basis primarily in order to recognize systemic hypertension as early as possible and to improve the long-term outcome in these patients by antihypertensive treatment.

Adolescent↗
PubMed1997

Transesophageal versus intracoronary Doppler measurements for calculation of coronary flow reserve.

OBJECTIVE: The present study was performed to compare coronary flow reserve by transesophageal Doppler echocardiography and intracoronary Doppler flow wire measurements in patients with LAD disease. METHODS: 17 patients with various degree of LAD stenosis were studied. Intracoronary LAD Doppler measurements were performed at baseline and after intracoronary injection of 18 micrograms adenosine. Transesophageal coronary sinus and LAD Doppler measurements were performed at baseline and after intravenous dipyridamole (0.6 mg/kg/5 min). Coronary flow reserve was calculated as the ratio of hyperemic to baseline average peak velocities. RESULTS: Coronary flow reserve was 2.44 +/- 0.62 and 2.19 +/- 0.76 for proximal and distal intracoronary measurements and was 2.25 +/- 0.64 and 1.74 +/- 0.63 for transesophageal LAD- and coronary sinus measurements. Proximal intracoronary flow reserve significantly correlated with transesophageal coronary sinus (r = 0.73, p < or = 0.001) and LAD (r = 0.70, p < or = 0.005) measurements, whereas distal intracoronary flow reserve only correlated with transesophageal coronary sinus flow reserve (r = 0.56, p < or = 0.02). Receiver operating characteristic curve analysis demonstrated similar diagnostic accuracy of all applied techniques for detection of a significant LAD stenosis. CONCLUSIONS: Coronary flow reserve by both transesophageal techniques correlated with intracoronary Doppler flow wire measurements, however considerable discrepancies may occur in the individual patient.

Adenosine↗
PubMed1997

Influence of anaesthesia and muscle relaxation on intubating conditions and sympathoadrenal response to tracheal intubation.

BACKGROUND: The study aimed to assess the relative influence of anaesthesia and muscle relaxation on intubating conditions and the haemodynamic and catecholamine responses to tracheal intubation. METHODS: Sixty ASA 1 or 2 patients were randomly assigned to one of four groups (15 patients each) that differed in the depth of anaesthesia (thiopentone plus fentanyl 2.5 microg x kg(-1) or thiopentone alone) and the degree of vecuronium-induced neuromuscular block (100% or > or =65%) at intubation. Muscle relaxation was measured at 0.1 Hz by means of mechanomyography. Heart rate (HR) and mean arterial blood pressure (MAP) were measured before and after induction of anaesthesia, and 1 min and 5 min following intubation, while adrenaline (A) and noradrenaline concentrations (NA) were determined from arterial blood samples. RESULTS: Intubating conditions were improved primarily by providing complete muscle relaxation at the adductor pollicis muscle (P<0.001) and to a lesser extent by adding fentanyl to thiopentone (P=0.04). The response of HR and MAP to tracheal intubation was attenuated mainly by fentanyl (P<0.001). Complete muscle relaxation further diminished the response of MAP to intubation (P=0.03). Changes in A and NA were dependent on the depth of anaesthesia only (P < or =0.01). CONCLUSION: The results of the study demonstrate that the sympathoadrenal response to intubation is attenuated by adding fentanyl (2.5 X kg[-1]) to an induction regimen with thiopentone, whereas provision of complete muscle relaxation at the adductor pollicis muscle is necessary to attain smooth intubating conditions.

Adolescent↗
PubMed1997

Relation between left atrial size and secondary atrial arrhythmias after successful catheter ablation of common atrial flutter.

Catheter ablation provides an effective cure for patients with typical atrial flutter. However, these patients may have the potential to develop atrial tachyarrhythmias other than common atrial flutter. This study examines clinical and echocardiographic predictors for the occurrence of uncommon atrial flutter or atrial fibrillation after abolition of common atrial flutter. The study population comprised 17 patients (12 men, 5 women, age 32-74 years) who underwent successful radiofrequency catheter ablation of common atrial flutter. Common atrial flutter did not recur in any patient during a median follow-up time of 8 (range 1-25) months. Within a median of 7 (range 1-223) days, however, symptomatic atrial tachyarrhythmias occurred in 8 of 17 patients (47%): uncommon atrial flutter (n = 4); atrial fibrillation (n = 3); and both uncommon atrial flutter and atrial fibrillation in one patient. Preablation left atrial volume was significantly larger in patients who developed secondary arrhythmias compared with patients who remained in sinus rhythm (57.9 +/- 15.6 vs 43.7 +/- 16.4 cm3, P < 0.05). Enlarged left atrial volume dichotomized at 51 cm3 independently predicted postablation atrial arrhythmias (X2 = 5.11, rel. risk = 5.3, P < 0.05). On Kaplan-Meier analysis, time to occurrence of postablation atrial arrhythmias was significantly shorter in patients with enlarged left atrium (P < 0.02). In conclusion, symptomatic uncommon atrial flutter and atrial fibrillation develops in a substantial proportion of patients after successful ablation of common atrial flutter. Out of a series of clinical and echocardiographic parameters, preablation left atrial size is the best predictor for the occurrence of these postablation atrial arrhythmias.

Adult↗
PubMed1997

Efficacy and safety of meloxicam in patients with rheumatoid arthritis.

OBJECTIVE: To evaluate the efficacy and safety of meloxicam, a new acidic enolic nonsteroidal anti-inflammatory drug, at doses of 7.5 and 15 mg once daily in patients with rheumatoid arthritis (RA). METHODS: Meloxicam 15 and 7.5 mg daily was administered for 21 days in this double blind, randomized, placebo controlled study. 159 patients received meloxicam 7.5 mg, 162 received meloxicam 15 mg, and 147 received placebo. RESULTS: Meloxicam 15 mg once daily was significantly superior (p < 0.05) to placebo in 3 of the 4 primary endpoints (disease activity assessed by the investigator, disease activity assessed by the patient, and reduction of the number of tender/painful joints). No difference was observed regarding number of swollen joints. The difference between meloxicam 7.5 mg once daily and placebo reached statistical significance in 2 of the 4 primary endpoints, disease activity assessed by the patient and number of tender/painful joints. A statistically significant difference between meloxicam 1.5 mg and 7.5 mg was not observed for any primary endpoint. The rating of global tolerance by investigators and patients at the end of the study was similar in the 3 treatment groups, indicating that meloxicam and placebo were generally similarly well tolerated. However, there was a slightly higher incidence of gastrointestinal (GI) disturbances reported by patients receiving meloxicam 15 mg. GI adverse events were reported by 11, 11, and 16% of patients in the placebo, meloxicam 7.5 mg, and meloxicam 15 mg groups, respectively. None were serious. CONCLUSION: Meloxicam in daily doses of 7.5 and 15 mg is effective in treating the signs and symptoms of RA.

Aged↗
PubMed1996

[Lumbar pain in old age].

In advanced age, lumbar pain is less frequently caused by occupational stress and psychosomatic factors. Unstable segments and spondylo-arthrotic degeneration can lead to muscular strain whenever insufficient secondary stability and missing muscular equilibrium are involved. In the differential diagnosis one must distinguish between osteoporosis and spinal stenosis, which increases in frequency with age. Pain due to internal or gynecological problems must be excluded. From the therapeutic point of view, patients should be instructed in ergonomics and the simple application of physiotherapeutic procedures, e.g. heat and cold. Analgetics become increasingly important with age, consequently resulting in reduced use of antirheumatics. There exists enough evidence to show that muscular training of the lumbar muscles play an important role in the secondary prevention of lumbar pain in elderly people as well. Essentially, it can be stated that physical age is not directly related to possible ailment. The change of occupational obligations, with possibilities to adapt to personal stress levels, as well as the positive attitude towards everyday life in retirement have a major influence in accepting and handling ability of problems, concerning pain. In the department of Physical Medicine, Rehabilitation and Rheumatology of the Clinic Wilhelm Schulthess it was found that among 7806 patients with lower back pain (1990-1995) 43.3% involved the ages of 40 to 60 and 31.3% the ages of 60 to 80. More distinctly than in younger patients, older aged patients tend to show a marked discrepancy between radiological findings and effective pain. Lower back pains of elderly patients are of a different nature from those found in younger or middle-aged people. Ischialgia due to the protrusion of an intervertebral disk or an acute lumbovertebral syndrome caused by muscular instability are found much less frequently.

Aged↗
PubMed1996

Importance of pressure recovery for the assessment of aortic stenosis by Doppler ultrasound. Role of aortic size, aortic valve area, and direction of the stenotic jet in vitro.

BACKGROUND: Pressure recovery has been shown to occur distal to aortic stenoses in experimental and clinical studies. However, its clinical relevance in this setting has not yet been evaluated. METHODS AND RESULTS: To address the hypothesis that pressure recovery can cause significant differences between Doppler and catheter gradients in aortic stenosis and to examine the effects of aortic size, aortic valve area, and direction of the stenotic jet on these differences, stenoses with valve areas from 0.5 to 1.25 cm2 and aortic diameters from 1.8 to 5.0 cm were studied in a pulsatile flow model. Jets entered the aorta centrally or eccentrically with angles of 15 degrees, 30 degrees, or 45 degrees. Overall, good correlation was found between Doppler and catheter gradients. However, when the various combinations of orifices and aortas were analyzed separately, slopes varied from 1.0 to 1.86, and the Doppler-catheter gradient differences ranged from -2 (small valve area with a large aorta) to 66 mm Hg (80% overestimation by Doppler echocardiography) when the stenosis was moderate and the aorta was small. Mild eccentricity of the jet did not significantly alter the results. However, overestimation by Doppler decreased with increasing jet eccentricity. Finally, differences between Doppler and catheter gradients could be predicted by estimating pressure recovery from Doppler measurements. CONCLUSIONS: Significant pressure recovery can occur in aortic stenosis and can cause differences between Doppler and catheter gradients. These differences may reach clinical relevance, particularly when the stenosis is moderate and the aorta is small and can be predicted from Doppler measurements.

Aorta↗
PubMed1996

Diagnosis and management of prosthetic valve dysfunction.

Immediate and long-term prognosis of patients with prosthetic valves critically depends on prevention, rapid diagnosis, and optimal treatment of complications. This review describes the current practice in management of prosthetic dysfunction and discusses unresolved or controversial issues such as: what is the optimal anticoagulation regimen in both mechanical and bioprosthetic heart valves? Is thrombolysis superior to surgery in thrombotic valve obstruction? Is valve replacement superior to conservative therapy for prosthetic valve endocarditis? In addition, recently obtained data relating to the incidence of early and late mortality, thromboembolism, anticoagulation-related hemorrhage, valve thrombosis, hemolysis, paravalvular leakage, and the necessity and risk of reoperation are presented.

Bioprosthesis↗
PubMed1996

Stenotic lesions.

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Aortic Valve Stenosis↗