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Biomedical subjects

R Erbel

Publications and source records attributed to R Erbel.

At least 91 records · Page 5Linked to original sources
PubMed2001

Microgenerators for energy autarkic pacemakers and defibrillators: fact or fiction?

BACKGROUND: Implantable devices for medical use like permanent pacemakers, defibrillators, and fluid pumps depend on an energy provided by batteries. Unfortunately, the battery usually determines the duration of life of these devices, while technical problems occur infrequent. Device replacement for battery exhaustion requires surgical procedures and account for up to 1/3 of all pacemakers sold. Attempts to provide unlimited power support using radio transmission, nuclear energy etc. did not gain clinical acceptance. METHOD: We therefore evaluated the potential role of a microgenerator (designed for use in wrist watches) to recharge pacemaker batteries. We used the Epson-Seiko Caliber 5M22 that uses a "Gold-Cap" for energy storage. The mass of the actuator is 1.6 g and an angle of > 10 degrees is needed to overcome friction. Output at a rotor frequency of 200 Hz is 1.8 mWatt To measure the power provided, various experiments were made with the microgenerator taped to the chest of a normal person working in an office. Range of 11 experiments over 8 hours each was 0.2 to 3.1 microWatt (median 0.5 microWatt). Therefore, the power generated was 10 to 100 times less than the calculated power needed to recharge a typical pacemaker battery. A second type of generator (Mondaine, Zurich, Switzerland) with less mechanical parts, available in a "black box" version only, generated not more power. CONCLUSION: Thus, commercially available, yet not optimized microgenerators provided only between 1 to 10% of the power requirements of a pacemaker. However, modifications in design and mainly the orientation and weight of the actuator to generate more power from the G-forces during walking, would result in a more meaningful energy output.

Costs and Cost Analysis↗
PubMed2001

[Progression of coronary arteriosclerosis as monitoring the therapeutic success of hyperlipidemia].

BACKGROUND: Coronary calcium represents an integral part of coronary atherosclerosis. It results from an actively regulated process and already appears in early stages of the disease. Studies using electron-beam computed tomography (EBCT) have demonstrated that an accelerated progression of coronary calcified atherosclerosis is associated with an increased rate of clinical events. In experimental animal models, effective lowering of LDL cholesterol stops the progression of coronary calcified atherosclerosis. LDL CHOLESTEROL AND PROGRESSION OF CORONARY CALCIUM: A number of EBCT-derived retrospective analyses have consistently reported that LDL cholesterol values are the most important factor influencing the progression of coronary calcified atherosclerosis. In high-risk patients with no clinical coronary artery disease who were not specifically treated, a mean annual progression of coronary calcium of 52% was observed. In the presence of statin drug therapy, progression ranged from -7% through 22%, depending on the LDL cholesterol levels during therapy. A preliminary prospective investigation has confirmed these results and, in particular, suggested that reaching low LDL cholesterol levels < 100 mg/dl effectively stops the progression of coronary calcified atherosclerosis. LDL cholesterol independent ("pleiotropic") effects of statin drugs could not be demonstrated by using EBCT. At present, two large prospective, randomized trials are being conducted which analyze the effects of intensified versus standard statin drug therapy on the progression of coronary calcified atherosclerosis by EBCT. CONCLUSIONS: Serial EBCT studies enable analysis of the interaction between therapeutic measures, progression of coronary calcified atherosclerosis and clinical course of the patients by virtue of direct visualization of the activity of coronary plaque disease. This has already been successfully implemented in small patients groups. Validation in the individual patient is pending. Prospective, randomized therapeutic trials are expected to yield valuable knowledge for clinical practice.

Cholesterol, LDL↗
PubMed2001

[Metallic biomaterials for coronary stents].

The introduction of coronary stents is a milestone in interventional cardiology. Two landmark studies have shown that stainless steel stents significantly decrease the restenosis rate as compared to balloon angioplasty. This fact led to a marked increase of stent implantation since the first stent implantation by Jacques Puel in 1986. Although the concept of coronary stenting significantly improved the interventional therapy of coronary artery disease, restenosis remains a major unsolved drawback of this technique. In addition to procedure and disease related factors like implantation pressure and plaque burden, data suggest that the stent as a medical implant plays a crucial role in the process of neointima formation. Since its introduction in cardiology, more than 50 different stents of different configuration and material have been developed. Although recent publications report of promising results using biodegradable materials, almost all coronary stents commercially available at the moment are made of metallic alloys. Whereas first generation stents were made exclusively from stainless steel and only minor interest was focussed on the stent material in the manufacture of coronary stents, recent studies strongly suggest that the metallic alloy used has a direct impact on the extent of neointima formation. Thus, metallic alloys differ not only with respect to mechanical features, but also by their biocompatible properties. These two factors are of major importance in the induction of vessel wall injury, inflammatory processes and cell proliferation. In the first part, the present paper reviews the metallurgic characteristics of metallic materials, which are currently used or under investigation in the production of coronary stents. In the second part, clinical and experimental results are summarized with respect to their biocompatibility and impact on the process of restenosis formation.

Biocompatible Materials↗
PubMed2001

[Late stent thrombosis after intracoronary brachytherapy. A case report and review of the literature].

Intracoronary irradiation is currently the most promising approach to reduce restenosis after percutaneous transluminal coronary angioplasty. Meanwhile numerous data are available concerning efficacy and safety of this novel method. These data confirm the results of preclinical studies that reported a dramatic reduction of neo-intima proliferation and negative remodeling. However, the number of reports on an elevated incidence of late stent thrombosis (> 30 days post intervention) are increasing. It is commonly suggested that the delayed neo-intima formation within vascular stents is responsible for this new phenomenon. We report the case of a 48-year-old man who underwent coronary irradiation therapy after stent placement in a de-novo/restenotic lesion. Despite an explicit recommendation of a combined anti-aggregatory therapy consisting of ticlopidine and acetysalicylic acid for at least 6 months, ticlopidine was withdrawn after 4 weeks. Two weeks later, the patient was readmitted to an external hospital with an acute myocardial infarction and successfully treated with thrombolysis. The angiographic and intravascular control, which was conducted after another two weeks, showed absolutely no neointima formation within the implanted stent. Thus, a late thrombotic occlusion of the implanted stent appears most likely to be the cause underlying the myocardial infarction. This case underlines, together with other existing reports, the importance of a prolonged, combined anti-aggregatory therapy after stent placement and subsequent intracoronary irradiation.

Angina Pectoris↗
PubMed2001

Ambulatory norepinephrine treatment of severe autonomic orthostatic hypotension.

OBJECTIVES: This study was designed to establish a patient-controlled, ambulatory norepinephrine treatment of refractory orthostatic hypotension due to primary autonomic failure. BACKGROUND: Autonomic dysfunction leads to disabling postural hypotension. Particularly in primary autonomic dysfunction, repeated syncope and immobilization can be the result. Medical treatment of orthostatic hypotension often fails in advanced cases. METHODS: Ambulatory, patient-controlled norepinephrine therapy was initiated in six patients with orthostatic hypotension due to primary autonomic failure that had been refractory to conventional treatment. Before this therapy, three patients were bedridden; one was immobilized in a wheelchair. All had recurrent syncope and tolerated upright tilt-table testing for less than 15 min despite extensive medical treatment. For ambulatory treatment, a port-a-cath system was implanted and, using a CADD ambulatory infusion pump, norepinephrine was infused in individually adjusted dosages. RESULTS: Norepinephrine infusion therapy enabled all patients to sit, stay and walk around for more than 45 min. One patient died after a five-year treatment period, another after nine months because of nonhemorrhagic brain stem infarctions, both in the absence of norepinephrine treatment. The remaining four patients are still mobile after a period of 19, 10, 9 and 7 months, respectively. None of them has suffered complications due to arterial hypo- or hypertension, and there has been no infection of the infusion system. CONCLUSIONS: In these selected patients with refractory orthostatic hypotension due to primary autonomic dysfunction, ambulatory norepinephrine infusion therapy has proved to be a promising new therapeutic option. Further long-term studies including more patients are necessary to assess additional indications, reliability and safety of this new method.

Aged↗
PubMed2001

Changes in QRS voltage in cardiac tamponade and pericardial effusion: reversibility after pericardiocentesis and after anti-inflammatory drug treatment.

OBJECTIVES: The goal of this study was to define the association between low QRS voltage and cardiac tamponade or pericardial effusion and to assess the reversibility of low QRS voltage after therapeutic procedures. BACKGROUND: It is unclear whether low QRS voltage is a sign of cardiac tamponade or whether it is a sign of pericardial effusion per se. METHODS: In a prospective study design, we recorded consecutive 12-lead electrocardiograms and echocardiograms in 43 patients who were referred to our institution for evaluation and therapy of a significant pericardial effusion. Cardiac tamponade was present in 23 patients (53%). Low QRS voltage (defined as maximum QRS amplitude <0.5 mV in the limb leads) was found in 14 of these 23 subjects (61%). Nine of these 14 patients were treated by pericardiocentesis (group A). Five patients received anti-inflammatory medication (group B). Group C consisted of nine patients with pericarditis and significant pericardial effusion who had no clinical evidence of tamponade. RESULTS: In group A, low QRS voltage remained largely unchanged immediately after successful pericardiocentesis (0.36 +/- 0.17 mV before vs. 0.42 +/- 0.21 mV after, p = NS), but QRS amplitude recovered within a week (0.78 +/- 0.33 mV, p < 0.001). In group B, the maximum QRS amplitude increased from 0.40 +/- 0.20 mV to 0.80 +/- 0.36 mV (p < 0.001) within six days. In group C, all patients had a normal QRS amplitude initially (1.09 +/- 0.55 mV) and during a seven-day follow-up (1.10 +/- 0.56 mV, p = NS). CONCLUSIONS: Low QRS voltage is a feature of cardiac tamponade but not of pericardial effusion per se. Our findings indicate that the presence and severity of cardiac tamponade, in addition to inflammatory mechanisms, may contribute to the development of low QRS voltage in patients with large pericardial effusions.

Aged↗
PubMed2001

Reproducibility of two coronary calcium quantification algorithms in patients with different degrees of calcification.

PURPOSE: To evaluate the reproducibility of coronary calcium quantification algorithms by electron beam CT (EBT) in patients with different amounts of calcified plaque using the conventional (Agatston) score and an area score and to demonstrate a potential application of these results for evaluation of follow-up scans. METHODS: In 50 consecutive patients. the conventional calcium score (CCS = Agatston score) and the area score (AS) were summed for each artery and patient. Data were analyzed in four groups according to degrees of calcification: 0 (absent-minimal): CCS 0-9, I (mild): CCS 10-99, II (moderate): CCS 100-399, III (severe): CCS > or = 400. We determined and compared the reproducibility for each algorithm within and among groups. RESULTS: Median percent reproducibility improved with increasing amounts of calcified plaque for the CCS and the AS (p = 0.002 and p = 0.004, respectively). We demonstrate how these reproducibility values can be used to evaluate long-term follow-up studies. The reduction of median reproducibility per patient using the AS vs. the CCS was 32% (13 vs. 19%, respectively). On a vessel-by-vessel basis, the reduction of median reproducibility was 7% (24.3 vs. 22.6%, CCS vs. AS, p < 0.02), which was attributable to a 45% reduction in reproducibility in arteries with mild scores (46.1 vs. 25.5%, CCS vs. AS, p < 0.005). CONCLUSION: The AS has an improved reproducibility compared with the CCS, especially in patients with small amounts of coronary calcifications which may prove clinically useful. Different reproducibility values in different degrees of calcification can be used for an individual assessment of changes in amounts of coronary calcification.

Adult↗
PubMed2001

Myocardial lactate release after intracoronary verapamil application in humans: acute effects of intracoronary verapamil on systemic and coronary hemodynamics, myocardial metabolism, and norepinephrine levels.

Coronary and systemic hemodynamic effects of verapamil have been investigated previously in detail. The acute impact of intracoronary verapamil on coronary hemodynamics has, however, not been correlated to simultaneously changes in myocardial metabolism or norepinephrine levels in humans. After bolus application of 1 mg verapamil into the left coronary artery of 52 patients scheduled for routine coronary angiography, heart rate (HR) remained unchanged, whereas mean arterial blood pressure (MAP) decreased (93.8 +/- 14.9 mmHg to 85.1 +/- 13.7 mmHg, p = 0.001). Coronary blood flow (CBF), calculated from intracoronary Doppler measurements and quantitative coronary angiography, increased after verapamil administration (28.5 +/- 16.7 ml/min to 66.2 +/- 41.8 ml/min, p < 0.001), whereas coronary vascular resistance index (CVRI) decreased (1.43 +/- 0.92 to 0.46 +/- 0.23, p < 0.001). Blood samples, taken simultaneously from the aorta (Ao) and coronary sinus (CS) at baseline and at maximal flow velocity, showed an increase in norepinephrine concentrations in Ao (209 +/- 151 ng/l to 283 +/- 195 ng/l, p < 0.001) and CS (233 +/- 162 ng/l to 323 +/- 248 ng/l, p = 0.004). Myocardial metabolism of pyruvate and free fatty acids were not affected. Glucose release was augmented and initial lactate consumption changed to a net lactate release into the CS (Ao to CS differences: glucose: -1.92 +/- 9.9 mg/dl to -12.8 +/- 22.8 mg/dl, p < 0.001; lactate: 0.07 +/- 0.2 mmol/l to -0.08 +/- 0.3 mmol/l, p = 0.001). Similar results were obtained for the extraction ratios and flux of these metabolites. There was a weak correlation between the increase in CBF and lactate release into the CS. This is the first report of unexpected myocardial lactate release following intracoronary verapamil administration in humans. This lactate release was paralleled by an increased glucose release into the CS at an unchanged metabolism of free fatty acids and pyruvate. One explanation for this unexplained lactate release during increased coronary blood flow might be a wash out phenomenon of lactate from previous ischemic areas, other explanations might be the induction of paradox myocardial ischemia and/or a steal effect. Further studies are necessary to explain these unexpected findings of increased coronary flow and myocardial lactate release. Until reliable explanations are pending, studies using only lactate release as a marker of myocardial ischemia, without taken coronary and systemic hemodynamic parameters into account, should be interpreted with caution.

Adult↗
PubMed2001

Occurrence of ventricular late potentials in patients with active acromegaly.

OBJECTIVE: Patients with acromegaly have an increased risk of ventricular dysrhythmias and sudden death. Late potentials in a signal-averaged electrocardiogram (SAECG), a predictor of ventricular dysrhythmias, are frequently seen in patients after previous myocardial infarction, but little is known about the prevalence of late potentials in acromegaly. The aim of our study was to investigate the prevalence of late potentials in patients with acromegaly and their relation to the activity of the disease and to myocardial hypertrophy. PATIENTS: The study included 48 patients with acromegaly [27 males, 21 females, mean age 52.3 +/- 14.2 years, 16 active disease, 32 cured or 'well controlled', under treatment with sandostatin analogues (12/32)] and 38 healthy volunteers as a control group. RESULTS: Late potentials were detected in 9/16 (56%) patients with active acromegaly vs. 2/32 (6%) with cured/well controlled acromegaly (P = 0.001), defined as normal age-related IGF-1 levels and GH levels suppressible below 1 microg/l after an oral glucose load (75 g). Late potentials were not related to muscle mass index (127 +/- 35 active vs. 123 +/- 34 g/m2 cured/well controlled). The association of disease activity with the detection of late potentials was independent of age, gender, duration of the disease and body mass index. In comparison to the control group, the prevalence of late potentials was significantly higher in patients with acromegaly (23%) than in the control group (0%; P < 0.001). CONCLUSIONS: Late potentials in the SAECG are frequently seen in active acromegaly and may represent an early and sensitive parameter to detect myocardial injury in acromegaly.

Acromegaly↗
PubMed2001

Prevalence and clinical significance of accidental findings in electron-beam tomographic scans for coronary artery calcification.

AIMS: To analyse the prevalence, and diagnostic and therapeutic consequences, of accidental findings in electron-beam tomographic scans performed for evaluation of coronary artery calcification. METHODS AND RESULTS: A total of 1812 consecutive patients with known or suspected coronary artery disease underwent electron-beam tomography. In 583 (32%) of the patients, i.v. contrast was also administered for non-invasive coronary angiography. A total of 2055 non-coronary pathological findings were observed in 953 (53%) of the patients. The prevalence of extra-cardiac disease, as shown in native scans and contrast studies, was assessed separately. In 583 (32%) patients, cardiac structures or the pericardium were affected, in 423 (23%) aortic disease was found. Lung disease was found in 357 (20%), and pathology of other organs in 273 patients (15%). The most frequent findings were aortic calcium in 423 (23%) patients and heart valve calcification in 317 patients (17%). Malignant disease could be detected in three patients. Further diagnostic investigations were done in 191 (11%) patients, 141 (74%) of which concerned the heart. In 22 (1.2%) patients, specific therapy was initiated following electron-beam tomographic findings. CONCLUSION: Accidental non-coronary pathology is a frequent finding in electron-beam tomographic calcium scanning, and often requires diagnostic or therapeutic action. Profound knowledge of the radiological differential diagnosis of the thoracic organs is necessary for reporting electron-beam tomographic scans, in order to avoid misdiagnosis and to receive a high quality interpretation.

Adult↗
PubMed2001

Full performance of modern echocardiography within the heart: in-vivo feasibility study with a new intracardiac, phased-array ultrasound-tipped catheter.

BACKGROUND: Intracardiac echocardiography with full performance of high-resolution two-dimensional-, M-mode-, colour, pulsed and continuous wave Doppler and Doppler tissue imaging has not been previously demonstrated. AIMS: This first European in-vivo study was designed to determine the utility and feasibility of a new ultrasound-tipped catheter for intravascular and intracardiac echocardiography. METHODS: The miniaturized, multi-modal, multiple-frequency (5-10MHz) transducer tipped 10Fr (3.3mm) catheter was tested in five anaesthetized mongrel dogs linked to a standard echocardiographic platform. The catheter was introduced through an 11 Fr femoral venous sheath into the inferior vena cava and right heart chambers and the pulmonary artery under limited fluoroscopic and catheter ultrasound guidance. RESULTS: Abdominal and thoracic aorta as well as their branches, both ventricles and atrias with their appendices, all valves, pulmonary arteries and all veins could be visualized with excellent quality. All Doppler signals and the determined haemodynamics, global and regional wall motion and Doppler tissue imaging were of high diagnostic quality. Coronary flow reserve could also be determined. CONCLUSIONS: Intracardiac echocardiography is feasible and potentially useful for assessing functional and morphological disorders, and probably for the guidance of interventional procedures as well as monitoring of cardiac function. A new window to the heart has been opened.

Animals↗
PubMed2001

Echocardiographic detection of coronary artery fistula into the pulmonary artery.

A rare case of left coronary artery--pulmonary artery fistula is reported. Transoesophageal echocardiography was capable of precisely demonstrating the origin, the course and the drainage site of the fistula. In contrast, transthoracic echocardiography could visualise a drainage flow in the pulmonary artery only. In conclusion, transoesophageal echocardiography may be helpful in the diagnosis or exclusion of the form of coronary artery fistula.

Arterio-Arterial Fistula↗
PubMed2001

Stimulation of the left ventricle through the coronary sinus with a newly developed 'over the wire' lead system--early experiences with lead handling and positioning.

AIMS: This report describes the initial clinical results with a newly designed guiding catheter and an 'over the wire' pacing lead based on angiolasty technology to stimulate the left ventricle using the transvenous route via the coronary sinus (OTW-CV lead). METHODS AND RESULTS: In 75% of the 15 patients (6 males, 9 females, mean age of 53 +/- 9 years) with congestive heart failure, access to coronary sinus required less than 2 min; in one patient. the attempt failed. Mean R wave amplitudes plus or minus the standard deviation, measured at apical, mid-ventricular and basal positions the anterior (11.4 +/- 9.2, 10.8 +/- 6.2, 9.3 +/- 6.3 mV) and lateral or posterior veins (10.1 +/- 10.7, 8.6 +/- 6.4, 7.7 +/- 4.3 mV) showed a trend favouring the apex without statistical significance. Pacing impedance, measured at the same sites and vein tributaries, ranged from 670 +/- 191 to 915 +/- 145 ohms. Pacing thresholds measured at apical and mid ventricular sites were significantly lower than at the base in the anterior vein 2.5 +/- 2.8 and 2.8 +/- 1.8 vs 5.6 +/- 2.7 V at 0.5 ms, P<0.001). Thresholds in the lateral/posterior veins showed a similar trend but did not reach statistical significance (3.0 +/- 1.7, 3.6 +/- 1.4 +/- 1.8 V at 0.5 ms). In patients, in whom thresholds were determined in more than one vein, the 'best' mean threshold was 1.6 +/- 0.7 V. CONCLUSION: The new 'over the wire' lead and guiding catheter system allows uncomplicated access to the coronary sinus and the depth of the coronary vein tributaries. Left ventricular sensing and pacing thresholds are acceptable for chronic use in implanted cardiac rhythm management systems.

Adult↗