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Biomedical subjects

R Erbel

Publications and source records attributed to R Erbel.

At least 307 records · Page 17Linked to original sources
PubMed1995

Noninvasive visualization of an apparent patent intracoronary stent by transesophageal echocardiography.

In the area of increasing interventional techniques there is a need for noninvasive imaging modalities to provide postinterventional follow-up. We were able to visualize the apparent patency and measure the dimensions of an intracoronary Palmaz-Schatz stent in the left circumflex coronary artery using transesophageal two-dimensional echocardiography. This report indicates the potential of echocardiography to directly assess coronary stents.

Angioplasty, Balloon, Coronary↗
PubMed1995

Has transesophageal echocardiography changed the approach to patients with suspected or known infective endocarditis?

Infective endocarditis is still a great clinical challenge. Its diagnosis is difficult to establish, and mortality has remained around 30%. Early diagnosis and optimal treatment are crucial fo prognosis improvement. Echocardiography plays an indispensable role in the management of this disease, especially with the recently introduced approach, transesophageal echocardiography (TEE). TEE can overcome the limitations of transthoracic echocardiography (TTE) and is superior to TTE in almost every way in providing earlier and more information for the diagnosis and treatment of infective endocarditis. TEE detects valve vegetations with much higher sensitivity and specificity than TTE. It can demonstrate smaller vegetations in the early stage of the disease and vegetations on atypical locations (e.g., mitral valve annulus), and provides detailed characterization of vegetations (e.g., location, size, mobility, and changes during treatment). Such information is of great prognostic value and may help in selecting proper treatment. TEE is more sensitive for detecting complications, such as mitral valve perforation, abscess, and subaortic complications, which respond poorly to medicine and for which timely surgery may be the best treatment. For those with prosthetic valve endocarditis, TEE is especially useful because TTE is greatly limited by the acoustic shadow of prostheses. Both positive and negative results of TEE examination are valuable for confirming or excluding infective endocarditis. TEE also plays a unique role in intraoperative monitoring and can assess surgical results before the chest is closed. TEE has become an invaluable tool for the diagnosis and management of patients with suspected or known infective endocarditis.

Diagnosis, Differential↗
PubMed1995

High wall shear stress proximal to myocardial bridging and atherosclerosis: intracoronary ultrasound and pressure measurements.

BACKGROUND: Studies have shown that myocardial bridging may prevent coronary atherosclerosis and that the segment proximal to the bridge is often sclerosed. The underlying mechanism is still unknown. METHODS: Intracoronary ultrasound and pressure measurements were performed in a patient with myocardial bridging in the left anterior descending coronary artery. A 3.5 F, 20 MHz probe was used to measure the change in cross sectional area of the lumen during the cardiac cycle. Intracoronary pressure was measured with a Double tip, end mounted pressure transducer system, the catheter having two pressure sensors located at the end of the catheter 3 cm apart. Intracoronary pressure was recorded as the catheter was slowly advanced and pulled back through the left anterior descending coronary artery. RESULTS: Systolic compression of the bridge segment was clearly visualised on ultrasonography and an eccentric plaque with calcium deposit was found in the segment proximal to the bridge. The pressure in the segment proximal to the bridge (160/26 mm Hg) was higher than that of the proximal normal segment (126/68 mm Hg). The pressure distal to the bridge was 68/30 mm Hg. A highly characteristic "sucking effect" was found in the bridge segment. The pressure in the bridge segment was 102/-40 mm Hg. CONCLUSION: The pressure in the segment proximal to the myocardial bridging was higher than aortic pressure. Disturbance of blood flow and high wall stress proximal to myocardial bridging was a main contributor to the development of atherosclerosis in the segment proximal to the bridge.

Aged↗
PubMed1995

[Recent morphofunctional findings on the left atrium: their relations to thromboembolic risk].

In the past, the left atrial appendage has been considered a "useless" structure but associated to thromboembolic complications; its physiologic role is still undefined. Owing to its great distensibility, left atrial appendage positively influences atrial compliance and left ventricular performances. In addition this structure seems to play an important role in circulatory homeostasis by the release of atrial natriuretic factor in response to volume loading and atrial stretch. Transesophageal echocardiography provides a detailed anatomical characterization of this structure and, by means of Doppler flow velocities recordings, supplies relevant functional data. Despite their anatomical contiguity, the left atrium and atrial appendage result from a separate embryonic development; likewise, their function may differentiate. In the left atrial appendage a quadriphasic flow pattern has been described in subjects with sinus rhythm; however, as we reported, in some patients a more complex Doppler pattern can be observed, with an additional systolic forward flow wave which is presumably due to reflection phenomena. In patients with atrial fibrillation, an irregular flow pattern has been detected, which is mostly dependent on the duration of the arrhythmia, the underlying heart disease and the left atrial pressure. By transesophageal echocardiography a clear correlation has been established between the left atrial appendage slow flow and the occurrence of thromboembolic events; however, while waiting data from large studies, stratification of patients according to thromboembolic risk and decisions about anticoagulant prophylaxis should be performed by clinical information and transthoracic echocardiographic findings. No clinical or echocardiographic parameter has been found to be predictive of the thromboembolic events after cardioversion; in this setting the exclusion of atrial or atrial appendage thrombi by transesophageal echocardiography does not rule out the need for anticoagulation in patients with atrial fibrillation undergoing electrical or pharmacological cardioversion.

Atrial Function, Left↗
PubMed1995

[Reliability of digital transesophageal echocardiography in imaging the left coronary artery].

Fifty consecutive patients (mean age 56 years) were examined to evaluate the reliability of transesophageal echocardiography in the evaluation of the left proximal coronary artery. Results of 28 cases were compared to selective coronary angiography. Echocardiography was able to visualize the left main artery for the length of 1.0 +/- 0.6 cm in all patients (100%), the left circumflex artery for maximal 3.1 +/- 1.4 cm in 86% and the left anterior descending artery as long as 2.3 +/- 0.9 cm in 58%. The intraluminal diameter of the most proximal localized segments measured by echocardiography and angiography in the LAO and RAO-projection was in terms of the left main artery 4.1 +/- 0.9 mm, 4.1 +/- 0.9 mm and 4.0 +/- 0.9 mm (n.s.), of the left circumflex artery 2.8 +/- 0.5 mm, 3.3 +/- 0.8 mm and 3.3 +/- 0.9 mm (n.s.) and of the left anterior descending artery 3.0 +/- 0.8 mm, 3.4 +/- 0.7 mm, and 3.6 +/- 1.0 mm (n.s.). In respect of detection of coronary artery stenoses in correspondence to the coronary angiogram sensitivity was 81%, specificity 93% and positive predictive accuracy 86%. Quantitative analyses of the coronary anatomy and the correlation to angiography could contribute to the validation of transoesophageal echocardiography.

Adult↗
PubMed1995

Initial experience with a steerable intravascular ultrasound catheter in the aorta and pulmonary artery.

The aim of this protocol was to test the feasibility and safety of a prototype steerable intravascular ultrasound (IVUS) catheter (Boston Scientific, Waterton, MA) in comparison with standard IVUS catheters. A 3.5F, 20-MHz mechanical echo transducer was incorporated into a bendable sheath with a blunt tip. The flexible IVUS catheter was compared with a standard IVUS catheter in 13 patients. Seven patients underwent catheterization of the left side of the heart, and six patients had catheterization of the right side of the heart for suspected recurrent pulmonary embolism. In the aorta, three lumen area measurements were made: (1) midway between the aortic arch and the aortic root, (2) at the most cranial part of the aorta, and (3) in the descending aorta at the level of the diaphragm. Evaluation of the accuracy of luminal dimension measurements by both types of catheters in perpendicular positions to the vessel wall was evaluated in a hollow rubber cast of an human aorta and its side branches, representing luminal diameters from 3 to 26 mm. We performed 20 measurements with each type of catheter. The results were compared with ruler measurements, after the cast had been cut in slices. The equation for the standard 3.5F IVUS catheter was: y = 0.89x + 0.15; SE = 0.17; r = .97; for the 4.8F 20-MHz standard IVUS catheter: y = 0.97x + 0.05; SE = 0.18; r = .98; and for the steerable catheter, y = 0.94x + 0.09; SE = 0.12; r = 0.97.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1995

[Diagnosis of coronary heart disease using echocardiography 3D reconstructions. Diagnosis of global and regional left ventricular function].

The technique of tomographic 3D-echocardiographic reconstructions allows, beside the morphological description of cardiac structures, a left ventricular quantification concerning the diagnosis of the coronary heart disease. The advantage of the tomographic 3D-reconstruction and tomographic quantification is that the left ventricular volume is determined directly by manual planimetry during the whole heart cycle and will not be approximated by geographical algorithms as used for 2D-techniques and alternative 3D-techniques. We worked with the Echoscan reconstruction unit (TomTec) equipped with a pentium-processor and a 64 RAM memory for the acquisition and digitalization of a 3D-echocardiographic image data set (Figures 2a and 2b). Automatic image acquisition is performed using a unit existing of a common ultrasound transducer and a special rotational motor device. All the examinations described in this publication are performed by a transthoracic approach. Examining asymmetric model hearts with aneurysm an experimental study sustentiated the high accuracy of determining asymmetric ventricle volumes (mean of difference [3D--true dimensions] = 0.91 ml; SD of differences = +/- 6.17 ml) and aneurysm volume (mean of difference = 0.43 ml; SD of difference = +/- 2.14 ml). Also high reproducibility of 2 repeated 3D-measurements was documented (ventricular volumetry: mean of difference = -0.09 ml; SD of difference = 3.15 ml. Aneurysm volumetry: mean of difference = 0.24 ml; SD of difference = 0.17 ml). The principle of quantification by tomographic planimetry is usable the same way in vivo (Figures 3 and 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Volume↗
PubMed1995

Three-dimensional reconstruction of coronary arteries with intravascular ultrasound.

Three-dimensional (3D-) reconstruction of intravascular ultrasound (IVUS) images is a recently introduced technical method which has rapidly grown in science and clinical practice. In the catheterization laboratory it is particularly important to obtain the 3D-reconstruction on-line, since the dimensions measured and the plaque attributes displayed may guide the therapeutic decision. Off-line reconstruction, however, provides very accurate and reproducible area and volume measurements of lumen and plaque and is thus exceptionally qualified for studying progression/regression of atherosclerosis or restenosis after catheter-based interventions. Complementary 3D-reconstruction methods, revealing specific advantages and limitations, meet the requirements by slightly different technical approaches, but each 3D-reconstruction of two-dimensional IVUS images requires some basic procedural steps. The IVUS images can be acquired during continuous or ECG-gated withdrawals of the IVUS imaging catheter. The latter permits even to visualize the cyclic pulsation of the reconstructed arteries. As an alternative approach a sensing device recognizes the insertion depth of the IVUS catheter and permits reliable measurements even during manual handling of the IVUS catheter. A discrimination between the blood-pool and structures of the vascular wall, performed in the digitized images, can be achieved by the application of different techniques. This processing step which is called segmentation and the image acquisition are particularly crucial with regards to the final quality of the 3D-reconstruction. Currently there are still limitations of 3D-IVUS, but a new approach combining data obtained from 3D-IVUS and biplane angiography offers a promising potential to solve most of the remaining problems in the future. Thus, three-dimensional IVUS offers a great clinical and scientific potential since it provides spatial visualization of vascular pathology, longitudinal and volumetric measurement of luminal and plaque dimensions, and facilitated guidance of catheter-based interventions. Assuming a technical development similar to the progress of the previous years. 3D-IVUS has a realistic chance to gain significant importance and to become a routine technique in the future.

Computer Graphics↗
PubMed1995

[Stress echocardiography--a new test for evaluating the anti-ischemic effect of medication].

Exercise echocardiography and exercise electrocardiography were performed to test the anti-ischemic effects of isosorbide dinitrates (2 x 40 mg) und nisoldipine (2 x 10 mg) using a randomized, double-blind, placebo-controlled crossover trial. A total of 24 patients with symptomatic coronary artery disease and exercise-induced ST segment depression underwent 144 investigations (6 in each patient) at the first placebo treatment, 1st and 8th day during treatment with the first drug and the second placebo treatment 1st and 8th day during treatment with the second drug. A wall motion score (sum of 14 segments; wall motion grading: normal = 1, hypokinetic = 2, akinetic = 3, dyskinetic = 4) and ST depression at the exercise were used to assess the anti-ischemic effects. Both drugs reduced the number of exercise-induced wall motion abnormalities on the maximal comparable exercise level in comparison to placebo treatment. The wall motion score on the maximal comparable exercise level during placebo treatment was 25.5 +/- 6.9, during isosorbide dinitrate treatment (1 day) 23.5 +/- 7.2 and 23 +/- 6.7 (8th day; for both treatment days, p < or = 0.001 vs. placebo treatment), and during nisoldipine treatment (1st day) 23.6 +/- 5.9 and 23 +/- 6.8 (8th day; p < or = 0.001). ST segment depression changed at exercise during first placebo treatment to 0.153 +/- 0.068 mV, during ISDN treatment to 0.102 +/- 0.055 (1st day, p < 0.001) and to 0.117 +/- 0.056 (8th day, p < 0.001). ST segment depression during nisoldipine treatment was 0.121 +/- 0.075 mV on the 1st day (p < or = 0.002) and 0.120 +/- 0.071 mV on the 8th day (p < 0.001). Exercise echocardiography can be used to test anti-ischemic drug effects. There were no differences in the reduction of exercise-induced ischemia between the two drugs.

Aged↗
PubMed1995

[Alternative methods in interventional therapy of coronary heart disease].

Percutaneous high-frequency coronary rotablation using the rotablator is able to remove arteriosclerotic material from the vessel wall. A diamond-coated (30-80 microns) brass burr drill fastened to a flexible drive shaft rotating and tracking along a drill coaxial guide wire is used. The turbine rotates the drive shaft in excess of 150,000-190,000 rpm. High-frequency rotational angioplasty was successful in > 90% of patients, but in about 90% additional PTCA is necessary. No increase of bypass surgery compared to PTCA is observed. CK and CR-MB elevation is more often found than after PTCA. Vessel perforation is rarely observed. All vessels were open at 24-h control. The restenosis rate seems not be increased. The main indications for high-frequency rotational angioplasty are rigid and calcified sclerotic lesions which cannot be passed by conventional balloon catheters. Whether the restenosis rate can be reduced by this method will be judged in part by the COBRA study. In order to avoid acute complications of PTCA and to reduce restenosis rate, coronary stents were developed. Self-expandable and balloon expandable stents are available. It could be demonstrated that these stents can be used as a bail-out system and can block elastic recoil of coronary arteries. The major remaining problem is subacute closure of coronary vessels. In order to prevent thrombosis treatment with coumarine, acetylsalicylic acid, and dipyridamol is necessary. Coronary stents can be successfully delivered in more than 90% of the patients. In a highly selected patient group using single stents restenosis rate could be significantly reduced.

Angioplasty, Balloon, Coronary↗
PubMed1995

[Tissue Doppler echocardiography: a new stage in the study of myocardial function].

Tissue Doppler echocardiography is a new technique that allows selective visualization and measurement of myocardial velocities, affording a new perspective on cardiac function. It has been showing promising and exciting preliminary results on coronary artery disease, hemodynamics, cardiomyopathies, right ventricular and aortic diseases and arrhythmias, opening a new era in the analysis of regional myocardial function.

Aorta↗
PubMed1995

[Experimental ultrasound angioplasty: in vitro resolution of thrombi].

A new ultrasonic angioplasty ablation catheter connected to a 19.5 kHz. 25 W transducer was tested in vitro for its ability to disrupt 12-h. 24-h, and 5-day-old whole blood thrombi (n = 45.697 mg +/- 223 mg) and fibrin thrombi (n = 45.338 mg +/- 133 mg), as well as 5-day-old cadaver thrombi (n = 8.270 mg +/- 71 mg) within 10 min. Five of each age were used as control thrombi in which the catheter was moved back and forth without ultrasound emission. The size of ablated thrombus particles was measured by a laser device. The power output at the end of the catheter was assessed calorimetrically. The loss of weight of whole blood thrombi was between 429 (74%) and 524 mg (91%) (p < 0.01, whole blood thrombi vs. control thrombi) and between 302 (85%) and 314 mg (95%) (p < 0.05) for fibrin thrombi, respectively. Thrombus age did not prove to be a highly significant influencing factor. The disruption rate for whole blood thrombi was 0.75 to 1.05 mg/s and for fibrin thrombi 0.69 to 0.7 mg/s. It was only 0.09 mg/s for the cadaver thrombi. 93% of all particles ablated from whole blood thrombus ranged between 0-5 micron, less than 0.2% between 30-150 microns. For fibrin thrombi 69% of all particles were < 10 microns (25% between 10-20 microns). Only 0.02% ranged between 300-600 microns, which was similar for cadaver thrombi. The mean measured power output at the catheter tip was 5.9 W compared to the power output of 25 W at the ultrasound generator.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1995

[PTCA-induced myocardial ischemia for detection salvaged myocardium after thrombolytic therapy of acute myocardial infarct].

In 43 patients (ages 55.8 +/- 9.0 years) with myocardial infarction treated with thrombolytic therapy presenting with one-vessel coronary artery disease, the monitoring-ECGs during PTCA (17.0 +/- 12.7 days after infarct) were analyzed. Patients with ST-segment deviations > or = 0.1 mV (group A, n = 33) were compared with those < 0.1 mV (group B, n = 10). To answer the question, if these ischemic signs might be interpreted as salvaged myocardium, parameters of infarct size were evaluated. The maximal CK-activity in group A was 867 +/- 567 IU/l, in group B 1452 +/- 992 IU/l (p < 0.05), whereas the maximal GOT-activity was 113 +/- 69 IU/l and 174 +/- 102 UI/l (p < 0.05). The number of pathologic segments of the ventriculographies in the acute phase were 9 +/- 2 and 14 +/- 3 (p < 0.05), shortly after PTCA, 12 +/- 2 and 16 +/- 2 (p = 0.06), and after 6 months, 11 +/- 4 and 13 +/- 1 (N.S.). At the same time points EDV was analyzed in both groups and revealed the following: 103 +/- 20 ml, 98 +/- 21 ml, 104 +/- 23 ml and 103 +/- 25 ml (N.S.), 101 +/- 21 ml (N.S.), 116 +/- 46 ml (N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

[Noninvasive evaluation of the patency of coronary vessel stents using electron beam tomography segment images with administration of contrast media].

The implantation of intracoronary stents is increasingly employed in interventional cardiology. Even with high-resolution x-ray equipment the tiny struts of stainless steel stents can usually not be visualized. Coronary angiography is required to prove stent patency, and correct localization and deployment of the stent can only be assessed with intravascular ultrasound. In this setting a non-invasive diagnostic method would be of great advantage to document patency of the stented vessel segment. Herein we describe two patients with stent implantation in whom contrast-medium-enhanced electron beam tomographic scanning was applied to check for vessel patency. A pathological finding with reduced contrast enhancement could be distinguished from a normal finding, as was confirmed subsequently as a highly obstructed and a patent stented vessel segment by angiography. Thus, for the first time an alternative non-invasive diagnostic method may provide information on patency of stented vessel segments and may be useful for sequential follow-up investigations.

Angina Pectoris↗
PubMed1995

Microscopic evaluation of an occluded intracoronary Palmaz-Schatz stent removed before coronary artery bypass grafting.

Intracoronary implantation of stent devices is a new interventional technique with a promising role in the treatment of acute coronary occlusions caused by intimal dissection and suboptimal results of percutaneous transluminal coronary angioplasty. However, the prolonged presence of stent material embedded in the arterial wall may generate unknown late consequences. Major complications consist of subacute to chronic occlusion and restenosis. To elucidate the underlying cause we removed an angiographically occluded intracoronary artery Palmaz-Schatz stent before coronary artery bypass grafting. Scanning electron microscopy showed thorough coating of the metal struts of the stent by normal neoendothelial cells. Side branches arising at the level of the stent were patent. According the specific angiographic feature thrombotic occlusion originated distally of the stent.

Aged↗