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Biomedical subjects

H H Scheld

Publications and source records attributed to H H Scheld.

At least 235 records · Page 13Linked to original sources
PubMed1994

A simple technique for thoracoscopic resection of lung tumors.

Mainly incited by the bushfirelike spread of endoscopic operative techniques in general surgery, thoracoscopy has become the object of new interest in the field of thoracic surgery. Location and resection of lung tumors are problematic for several reasons and so far not standardized. The main problems are pointed out. A new technique together with the instruments and their advantages is demonstrated. Future aspects are discussed.

Humans↗
PubMed1994

Implantable cardioverter defibrillator therapy in patients with arrhythmogenic right ventricular cardiomyopathy, long QT syndrome, or no structural heart disease.

Recent technical developments in implantable cardioverter defibrillator (ICD) systems and reduced operative mortality and morbidity rates associated with ICD implantation have expanded the indications for ICD treatment of ventricular tachyarrhythmias. This review summarizes data regarding ICD therapy in patients with arrhythmogenic right ventricular cardiomyopathy, long QT syndrome, and idiopathic ventricular fibrillation and presents preliminary concepts for identification of patients who will benefit more from ICD therapy than from pharmacologic and other nonpharmacologic approaches. Recent studies suggest that ICD therapy may improve long-term prognosis by reliably terminating recurrences of life-threatening arrhythmias. Appropriate ICD therapies during mean follow-up periods of 12 to 36 months occurred in 30% of patients with idiopathic ventricular fibrillation to 50% of patients with arrhythmogenic right ventricular cardiomyopathy and long QT syndrome. At present no strict recommendations can be given for ICD implantation in these patients. However, at least in cardiac arrest survivors in whom the clinical arrhythmia is not reproducibly inducible during electrophysiologic study, ICD therapy appears to be superior to other treatment options with regard to long-term survival and thus should be considered as a first-line treatment. We are hopeful that continued study of long-term follow-up with and without ICD treatment and improved risk stratification will lead to better criteria for selection of treatment options.

Adult↗
PubMed1994

Single-incision implantation of cardioverter defibrillators using nonthoracotomy lead systems.

This study describes the placement of a newly designed implantable cardioverter defibrillator in a subpectoral device pocket using the incision for venous access in 16 patients undergoing implantation of an implantable cardioverter defibrillator with a nonthoracotomy lead system. The endocardial lead system consisted of a right atrial/superior vena cava defibrillation spring electrode and a right ventricular bipolar sensing/defibrillation electrode, inserted by cephalic venotomy or by puncturing of the subclavian vein. As a result of intraoperative testing using biphasic shocks the defibrillation threshold (DFT) had to be less than 24 J, otherwise an additional subcutaneous patch electrode was placed in the lateral chest wall near the cardiac apex through another incision. All patients received a nonthoracotomy lead system in combination with a subpectoral device placement. In 11 of 16 patients the endocardial leads alone were sufficient (DFT, 13.4 +/- 7.0 J), 5 of 16 patients (31%) required an additional subcutaneous patch electrode to achieve proper device function (DFT, 14.6 +/- 9.0 J). The operation lasted 93 +/- 20 minutes. This was a significant (p < 0.05) lower time consumption than standard nonthoracotomy approach combined with abdominal device placement (120 +/- 50 minutes). There were no postoperative complications. During follow-up period (average, 4 months), none of the patients reported major local symptoms, especially no device migration occurred. This approach, in contrast to an abdominal device placement, avoids another incision and subcutaneous tunneling of leads. In 11 of 16 patients defibrillator implantation by a single incision in the deltoideopectoral groove was possible.

Aged↗
PubMed1994

Nonthoracotomy defibrillator implantation: a single-center experience with 200 patients.

Nonthoracotomy leads for defibrillator implantation and biphasic shocking devices are under investigation. Implantation success and mortality and morbidity of the procedure determine the operative course. Lead-associated complications, late infection, and freedom of sudden cardiac death characterize the follow-up period with respect to the implanted device. From October 1989 to March 1993 in 200 patients, 205 (including five infections caused by reimplantations) transvenous or transvenous-subcutaneous lead systems were tested. Mean ejection fraction was 0.40 +/- 0.16. In 62.5% (125/200) coronary artery disease and in 19% (38/200) cardiomyopathy was the underlying disease (59 patients with prior cardiac operations). Leads were implanted with defibrillation thresholds less than 25 J in 195 patients, whereas 10 patients received intrathoracal patches. Since biphasic shocks became available, no nonthoracotomy lead system has failed in the last 115 consecutive patients. Perioperative mortality in the nonthoracotomy group was 1% (2/195). In 6.2% (12/193) of the surviving patients, perioperative complications occurred. Major problems were bleeding from the device or patch pocket (n = 6) and early infection (n = 2). During the follow-up of 20 +/- 10 months, lead-associated complications (dislocation, lead fracture, insulation defect, loss of sensing) occurred in 9 patients and in 5 patients late infection appeared. Within the follow-up period no patient died suddenly, and 134 patients received therapeutic interventions by the device. Defibrillator implantation using nonthoracotomy leads, especially combined with biphasic shocking devices, is applicable in almost every patient. During the operative course and follow-up, the defibrillator-associated morbidity and mortality is at the same level as or lower than when using patch lead systems.

Adolescent↗
PubMed1994

Successful long-term course after heart transplantation for anthracycline cardiomyopathy in a young boy despite neurological complications.

A now 14-year-old boy underwent orthotopic heart transplantation at the age of 13 for anthracycline cardiomyopathy which was a sequela of polychemotherapy for embryonal teratocarcinoma at the age of 1 year. Despite perioperative cerebellar infarction with signs of herniation which required emergency right cerebellar hemispherectomy the long-term course after 18 months turned out to be favorable with complete medical and psychosocial rehabilitation.

Adolescent↗
PubMed1994

High-frequency oscillation in an adult porcine model.

OBJECTIVE: Controversy exists as to whether high-frequency oscillatory ventilation can be used on babies and small laboratory animals only, or whether high-frequency oscillatory ventilation can also be efficient in the adult patient and large (> 65 kg body weight) laboratory animals. Moreover, controversy exists as to whether limitations in high-frequency oscillation efficiency are caused by the size and shape of the bronchial system, by the lack of low impedant intersegmental gas flow in lung parenchyma, or by inappropriate high-frequency ventilators and ancillary hardware. Therefore, our objective in this study using the adult pig as a model of the adult patient was to test whether the adult airway system is suited to the use of high-frequency oscillatory ventilation or whether there are geometrical, structural, or functional limitations to efficient ventilation by high-frequency oscillation. DESIGN: Prospective, controlled, randomized comparison over 8 to 16 hrs of ventilatory management. SETTING: Experimental thoracovascular surgery laboratory in a university hospital. SUBJECTS: Fifteen adult, female, house swine (weight 90 to 140 kg). INTERVENTIONS: We evaluated the ventilatory effect of a wide range of oscillation frequencies (10-15 to 35-45 Hz), tidal volumes (0.5 to 2.2 mL/kg), and bias flow volumes (10 to 70 L/min) at a mean airway pressure of 12 +/- 1 cm H2O in anesthetized and relaxed pigs who did not have lung injury. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases are mainly dependent on tidal volume, frequency, and mean airway pressure. A threshold bias flow volume of 35 +/- 5 L/min is required to prevent CO2 rebreathing. In the group of lightweight animals (65 to 99 kg), the most efficient frequency band for CO2 elimination was approximately 25 Hz. The most efficient frequency band for arterial oxygenation was found to vary between individuals more than the most efficient frequency band for CO2 elimination. In the group of heavy animals (100 to 140 kg), no most efficient mean frequency could be assessed, probably because the excitation system was limited. We confirmed that tidal volume on its own had an effect on CO2 elimination ("tidal-volume effect"), although CO2 elimination was mainly determined by the product of tidal volume and oscillation frequency (oscillated minute volume), at least up to a critical frequency. Beyond that frequency, CO2 elimination could not be enhanced. The most efficient mean airway pressure in unimpaired lungs was assessed at 12 +/- 1 cm H2O. CONCLUSIONS: Adult pigs with a body weight in the range of the weight of clinical adult patients can be ventilated by high-frequency oscillation at tidal volumes smaller than, equal to, or slightly more than anatomical deadspace. The most efficient frequency for gas exchange varied between individuals. Tidal volume had an enhancing effect on CO2 elimination. The frequency dependency of PaO2 may have been related to a frequency-dependent structural remodeling of the airway system, which occurred even though the mean airway pressure was kept constant. These results demonstrate that failure of adequate ventilation by high-frequency oscillation is caused by a) CO2 rebreathing, b) the avoidance of an appropriate alveolar recruitment strategy, and c) an underpowered, high-frequency ventilatory system (oscillator) that is unable to deliver appropriate pressure oscillations. These limitations led to insufficient CO2 elimination and/or inadequate arterial oxygenation.

Animals↗
PubMed1994

Transvenous-subcutaneous defibrillation leads: effect of transvenous electrode polarity on defibrillation threshold.

INTRODUCTION: The defibrillation threshold (DFT) of a transvenous-subcutaneous electrode configuration is sometimes unacceptably high. To obtain a DFT with a sufficient safety margin, the defibrillation field can be modified by repositioning the electrodes or more easily by a change of electrode polarity. In a prospective randomized cross-over study, the effect of transvenous electrode polarity on DFT was evaluated. METHODS AND RESULTS: In 21 patients receiving transvenous-subcutaneous defibrillation leads, the DFT was determined intraoperatively for two electrode configurations. Two monophasic defibrillation pulses were delivered in sequential mode between either the right ventricular (RV) electrode as common cathode and the superior vena cava (SVC) and subcutaneous electrodes as anodes (configuration I) or the SVC electrode as common cathode and the RV and subcutaneous electrodes as anodes (configuration II). In each patient, both electrode configurations were used alternately with declining energies (25, 15, 10, 5, 2 J) until failure of defibrillation occurred. The DFT did not differ between both configurations (18.3 +/- 8.2 J vs 18.9 +/- 8.9 J; P = 0.72). Eleven patients had the same DFT with both electrode configurations, 5 patients a lower DFT with the RV electrode as cathode, and 5 patients a lower DFT with the SVC as cathode. Four patients had a sufficiently low DFT (< or = 25 J) with only 1 of the 2 configurations. CONCLUSION: A change of electrode polarity of transvenous-subcutaneous defibrillation electrodes may result in effective defibrillation if the first electrode polarity tested fails to defibrillate. In general, neither the RV electrode nor the SVC electrode is superior if used as a common cathode in combination with a subcutaneous anodal chest patch.

Adult↗
PubMed1994

A prospective randomized cross-over comparison of mono- and biphasic defibrillation using nonthoracotomy lead configurations in humans.

INTRODUCTION: For current implantable defibrillators, the nonthoracotomy approach to implantation fails in a substantial number of patients. In a prospective randomized cross-over study the defibrillation efficacy of a standard monophasic and a new biphasic waveform was compared for different lead configurations. METHODS AND RESULTS: Intraoperatively, in 79 patients receiving nonthoracotomy defibrillation leads, the defibrillation threshold was determined in the initial lead configuration for the mono- and biphasic waveform. In each patient, both waveforms were used alternately with declining energies (20, 15, 10, 5 J) until failure of defibrillation occurred. Three different initial lead configurations were tested in different, consecutive, nonrandomized patients using a bipolar endocardial defibrillation lead alone (A; n = 36) or in combination with a subcutaneous defibrillation patch (B; n = 24) or array (C; n = 19) lead. The lowest successful defibrillation energy with the biphasic waveform was less than, equal to, or higher than with the monophasic waveform in 64%, 28%, and 8% of patients, respectively, and on average significantly lower with the biphasic waveform for all three lead configurations (A: 11.3 +/- 4.4 J vs 14.5 +/- 4.5 J; B: 9.7 +/- 4.7 J vs 15.1 +/- 4.5 J; C: 7.9 +/- 4.5 J vs 12.4 +/- 4.9 J). Defibrillation efficacy at 20 J was significantly improved by the biphasic waveform (91% vs 76%). CONCLUSION: In combination with nonthoracotomy defibrillation leads, the biphasic waveform of a new implantable cardioverter defibrillator showed superior defibrillation efficacy in comparison to the standard monophasic waveform. Defibrillation thresholds were improved for lead systems with and without a subcutaneous patch or array lead.

Adult↗
PubMed1994

Reconstructive vascular surgery in rotationplasty for malignant tumors of the femur.

The rotationplasty procedure of the femur, as first described by Borrgreve, is the functional improvement of an abnormally shortened lower limb. In the last 15 years this procedure has been used in its original form and as modification for tumors of the femur and proximal tibia. The reconstruction of the femoral vessels as an important part of the operation has not enough been accentuated. Principally two types of reconstructions can be performed: the vessels are dissected in the adductor canal or a segmental resection and reanastomosis are performed. Between January 1990 and April 1993 classical and modified rotationplasties were performed for malignant tumors in 34 patients in our institution. In all cases a segmental femoral vessel resection with end-to-end anastomosis were performed. No intra- and postoperative vascular related complications occurred. The authors emphasize the advantage of this method: reanastomosing resected femoral vessels by experienced vascular surgeons is a save, time-saving method. In addition, the radicality of the operation increases in order to obtain excellent long term results.

Adolescent↗
PubMed1994

[Ventilation by high frequency oscillations in adults. An experimental study of conditions and methods].

A hydraulic pump with an adjustable stroke delivering up to 145 ml at 1 to 45 Hz has been used to ventilate adult pigs of a weight between 60 and 140 kg. After tracheotomy the curarized animals were connected to the pump by a metallic tube through which a bias flow was directed. This flow (FiO2 0.35) was humidified by a special ceramic device and aspirated at the distal end of the tube. It was demonstrated that under these conditions gaz exchange was well maintained with oscillations between 15 and 35 Hz. Higher frequencies were needed for the heavier animals. Blood gas measurements of samples from segmental pulmonary veins demonstrated regional differences in gas exchange. These could be modified by adjusting the oscillation frequency. Reinhalation of gas could be prevented by an increase of the bias flow. Alveolar recruitment by initial pulmonary inflation by a pressure of 18 +/- 2 cm H2O is required for adequate oxygenation. Maintenance of adequate elimination of CO2 required a bias flow of 35 +/- 5 l/min. Mean pressure in the airways was maintained at 12 +/- 1 cm H2O. This pressure determines the value of PaO2. Ordinary endotracheal tubes tend to collapse during the sucking phase of the pressure cycle. Rigid or armed tubes are required. They must allow for aspiration of the bias flow from the distal end of the tube.

Anesthesia, General↗
PubMed1994

[Pectoral cardioverter-defibrillator implantation combined with transvenous bipolar defibrillation electrodes].

Ultimately, implantable cardioverter-defibrillators (ICD) will one day be implantable like present pacemakers. However, due to the size of the pulse generator and the low defibrillation efficacy of monophasic shocks, only a few selected patients have been implanted transvenously-pectorally. Therefore, we have prospectively investigated whether a transvenous-pectoral approach is in general feasible with a new downsized ICD capable of delivering biphasic shocks. Out of 33 patients, 76% received a bipolar transvenous defibrillation lead system. In the first 13 consecutive patients, a randomized crossover study showed that this high efficacy was above all achieved by a superior defibrillation efficacy of the biphasic waveform in comparison to the monophasic waveform (69% vs. 23%; p = 0.03). Not a single patient could be defibrillated exclusively with the monophasic waveform. In a further 15 consecutive patients, a crossover study showed that a position of the transvenous anode within the Vena anonyma instead of the Vena cava superior is, in general, not superior (87% vs. 80%; p = 0.67). Only one patient could be exclusively defibrillated with the V. anonyma position. Intraoperatively, no complications occurred and all but one patient received a pectoral implantation of the pulse generator. Postoperatively, in five patients local complications related to the ICD system were seen; two needed a surgical revision. In two patients movements of the left shoulder joint were temporarily restricted. Thus, in the majority of patients a new downsized ICD capable of biphasic shocks can be implanted transvenously-pectorally like a pacemaker.

Adult↗
PubMed1994

Comparative analysis of glutaraldehyde-preserved porcine xenografts and fresh or glutaraldehyde-treated human aortic valves by holographic interferometry.

Although calcification and degeneration are recognized as the main causes of bioprosthetic heart valve failure, the reasons for such failure are not well understood. Hidden tissue anomalies in the valves may be the origin of later calcification. Application of hologram interferometry for non-destructive testing enables the detection of such tissue anomalies. A comparative study by holographic interferometry of ten porcine bioprosthetic valves (seven Carpentier-Edwards SAV, two BioImplant and one Valcor) with five human aortic valves before and after glutaraldehyde treatment is presented. Whereas irregularities were detected in the interferograms of eight out of ten bioprostheses, no similar distorted fringe pattern was found in the holographic interferograms of human specimens. The present results suggest that tissue abnormalities exist in standard bioprosthetic valves which are absent in human ones. These irregularities may be the origin of later calcification and valvular dysfunction.

Aged↗
PubMed1994

[Cost/benefit relations in heart transplantation].

The expanding role of cardiac transplantation as well as mechanical and antiarrhythmic bridging requires a critical reflection of the economic impact of these therapeutic modalities. Based on assumptions from the pertinent literature, cardiac transplantation requires costs of about 55,000 DM per year of life gained by the procedure. Even if a maximum social and professional reintegration percentage of about 60% is assumed, it does not seem possible to perform the procedure without additional costs to the health care system. The consequences of this are the following: 1) Cardiac transplantation should only be performed by centers experienced in all aspects of terminal heart failure care including a heart failure program, high-risk conventional surgery program, mechanical and antiarrhythmia bridging program, and qualified post transplant care program. 2) In order to evaluate potentially cost-saving therapeutic strategies in cardiac transplantation, multicenter trials have to be conducted which require a continuous scientific working group and research data organization based on the consensus of all participating transplant centers. 3) An improved professional reintegration program is necessary. 4) The ethical foundation for offering cardiac replacement to patients, namely, the responsibility for the individual person's well-being, has to be emphasized by physicians active in the field. 5) The society as a whole, not the group of physicians active in the field, has to debate and decide on how many resources should be spent in this field of health care. 6) Since potential cardiac transplant recipients are, to a large extent, recruited from patients suffering from coronary artery disease, it is essential to incorporate a primary preventive perspective into this high-technology field of medicine.

Adult↗
PubMed1994

[Transvenous subcutaneous implantation technique of the cardioverter/defibrillator].

For years the high efficacy of implantable cardioverter-defibrillators (ICD) to prevent sudden cardiac death was impaired by the substantial perioperative mortality of the therapy. With the introduction of transvenous-subcutaneous defibrillation leads, thoracotomy could be abandoned and perioperative mortality was reduced to less than 1%. Despite frequent lead complications as dislocations, conductor fractures and isolation failures, long-term efficacy in termination of ventricular tachyarrhythmias remained approximately 98% and prevention of sudden cardiac death was not impaired. All nonthoracotomy defibrillation lead systems involve an endocardial right ventricular lead usually introduced from the left cephalic vein or directly via the subclavian vein. This lead has a pace/sense tip and at least one defibrillation electrode located in the right ventricle. Additionally, a second transvenous electrode and/or a subcutaneous patch or array electrode or the pulse generator shell has to be used for defibrillation. In combination with the biphasic defibrillation waveform, virtually all patients can be defibrillated using a combination of these electrodes. In most patients defibrillation is possible with transvenous electrodes alone and there is no need for an additional subcutaneous electrode. Smaller pulse generators have already been implanted in a subpectoral position--in many patients allowing a single incision approach as used for pacemaker implantation. Ultimately, with even smaller pulse generators ICDs should be implantable like present pacemakers in local anesthesia. This overview covers the history, models, practical aspects of implantation and testing, efficacy and complications of transvenous/subcutaneous defibrillation leads. Figures show the impact of the surgical approach on the frequency of de novo ICD implantations, X-rays of nearly all current bipolar and tripolar transvenous subcutaneous ICD lead systems, transvenous-epicardial hybrid systems and various complications. Additional figures cover lead complications not visible on X-rays. Defibrillation thresholds are compared for various lead configurations. Sensing amplitudes and pacing thresholds are compared for bipolar and pseudobipolar sense/pace leads as well as for different cardiac diseases. Tables summarize the main characteristics of current transvenous and subcutaneous ICD leads and external devices for intraoperative testing of ICD leads as well as the complications of transvenous/subcutaneous leads in three multicenter studies.

Defibrillators, Implantable↗
PubMed1994

Holographic interferometry: a new technique for in vitro investigations of prosthetic heart valves.

At present there are many different prosthetic models available for heart valve replacement. Postimplant dysfunction resulting from material failure has been reported in several prostheses. The prime cause of these defects is hidden abnormalities in the valve construction or materials. In order to detect these defects before implantation, preoperative non-destructive testing of individual valves is proposed. For this purpose, holographic interferometry has been applied which is a non-contact, non-destructive, highly sensitive, three-dimensional measurement technique. Samples of different types of prosthetic heart valve, both mechanical and biological, were mounted in a specially developed test chamber with optical access from four sides. The valves were loaded with a static liquid pressure of 2.5-15 kPa. Deformations of the valves as a result of small pressure differences (0.5-15% of the static pressure) applied between two exposures were recorded by double-exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of defects in the valve material.

Heart Valve Prosthesis↗
PubMed1994

[Glomus tumors: a diagnostic and surgical challenge?].

Within a population of 1150 vascular patients over a time period of 10 years we saw a carotid body tumor (synonymous chemodectoma) in only 11 cases. A correct preoperative diagnosis was found only in three patients. Before being treated by a specially trained team of vascular surgeons, eight patients had undergone inadequate operations. These were performed with a high incident of local complications. Simple bedside physical examination of the patient while looking for the signs of Fontaine and Kocher I + II (20) assures the diagnosis. Confirmation can be achieved by color-flow Doppler sonography (2). For the surgical resection, the only therapeutic alternative to the "gold standard" is angiography in digital subtraction technique which illustrates the blood supply of the tumor (70% exclusively by the external carotid artery). Also, it shows the typical intercarotid widening and the rich vascular conglomerate in between. Malignancy was detected in one case only (pulmonary metastasis). In two cases concomitant tumors of the jugular vein were seen. The interruption of the blood flow in the external carotid artery facilitates the surgical approach substantially. The ligature of this vessel (six patients) and the interposition of saphenous vein grafts (all 11 cases) for reconstruction of the internal carotid vessel were employed as the surgical strategy. Even the exstirpation of a large tumor (18 x 11 x 9 cm) extending from the skull base and almost reaching the left clavicular bone was successfully performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Comparison of frequency of aggravation of ventricular tachyarrhythmias after implantation of automatic defibrillators using epicardial versus nonthoracotomy lead systems.

The time of onset of 4,471 episodes of ventricular tachycardia (VT) or fibrillation (VF) in 40 of 65 patients with an implantable cardioverter-defibrillator (ICD) with endocardial defibrillation electrodes (group 1) and in 53 of 123 with epicardial defibrillation electrodes (group 2) was analyzed to examine whether the incidence of VT/VF immediately after surgery is greater than during further follow up and whether the site of lead placement exerts an influence on the occurrence of these arrhythmias. Actuarial survival rates free of VT/VF were 77, 65, and 54% at 1, 3 and 6 months, respectively, for group 1, and 84, 66 and 52%, respectively, for group 2. The probability of VT/VF was increased only during the first week after surgery; in that week, 12.8% of all patients had VT/VF, without significant differences between groups 1 and 2. Until the end of the first month, this percentage increased to 23%, whereas only 12 to 15% of patients had VT/VF during subsequent months. In 19 patients with third-generation devices capable of terminating tachycardias by overdrive pacing, 326 of 412 VT/VF episodes occurring in the first week after surgery were terminated by antitachycardia pacing, and only 86 had to be terminated by cardioversion or defibrillation. No postoperative exacerbation of inappropriate ICD therapies was observed in any group; 2 to 5% of patients per month received ICD therapies for atrial fibrillation or sinus tachycardia. Patients who received appropriate ICD therapies in the first week after surgery were at high risk of recurrence of VT/VF.(ABSTRACT TRUNCATED AT 250 WORDS)

Defibrillators, Implantable↗