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Biomedical subjects

R Fries

Publications and source records attributed to R Fries.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Associations between farm characteristics in fattening pigs and occurrence of lesions at meat inspection].

A revised inspection system for fattening pigs in the EU has been proposed emphasizing the need for a more detailed documentation of the fattening process. It is supposed that the availability of such information enables a discrimination of conspicuous and non-conspicuous lots of fattening pigs delivered to the abattoir allowing for a modified, only visual inspection of non-conspicuous lots. This proposal motivated a study performed in 1996 on about 22,000 pigs, searching, among other things, for first hints on associations between management/farm conditions for fattening pigs and lesions found at meat inspection, which can be used for discrimination. Taking the two lesions 'pneumonia' and 'callous affections of the legs' as examples this contribution demonstrates the use of regression trees to visualize association structures and to develop hypotheses on relations between lesions and farm characteristics. An association of 'callous affections of the legs' with flooring systems is clearly shown in the generated tree. The occurrence of 'pneumonia' seems to be associated with the application of disinfection measures in this data set. However, this result should be interpreted with caution as some problems for data analysis arise because of the low number of farms in this study in relation to the high number and complexity of farm characteristics considered. A further problem is the high variability of daily deliveries within farms that cannot be explained referring to farm characteristics common to all deliveries. As a conclusion data from this study have been useful to develop hypotheses on associations between farm characteristics and lesions at meat inspection. However, there is need for further, more specific studies before such associations can be utilized to discriminate between conspicuous and non-conspicuous lots of fattening pigs.

Animal Husbandry↗
PubMed1998

Influence of beta-blockers on the frequency of arrhythmia recurrences in patients with implantable cardioverter-defibrillator: an intraindividual comparison.

We studied retrospectively 60 consecutive recipients of an implantable cardioverter-defibrillator and identified 16 patients who were temporarily on and off beta-blockers (further medication unchanged). An intraindividual analysis revealed that 56% of the patients experienced more arrhythmic episodes during follow-up off beta-blockers compared to 44% while being on beta-blockers. Also, the mean episode frequency during follow-up time on and off beta-blockers was comparable (0.4+/-0.6 vs. 0.5+/-0.5, ns).

Adrenergic beta-Antagonists↗
PubMed1998

[Clinical significance of sleep apnea disorders after implantation of a cardioverter-defibrillator in patients with cardiac disease and sustained ventricular tachyarrhythmia].

The purpose of our study was to determine the prevalence of sleep related breathing disorders (SRBD) in patients with an implantable cardioverter-defibrillator (ICD) and to evaluate prospectively the possible influence of SRBD on arrhythmia recurrence and circadian arrhythmia variation as well as on cardiac mortality during long-term follow-up. Forty consecutive ICD recipients with cardiac disease and a documented history of spontaneous, life-threatening, ventricular tachyarrhythmias underwent full-night polysomnography and were followed for 2 years. In 16 of 40 patients (40%), SRBD were diagnosed (Apnea/Hypopnea Index (AHI) > 10); in 9 of these 16 patients (56%) central sleep apneas (CSA) occurred (in 8 of these 9 patients in combination with Cheyne-Stokes respiration). Seven of the 16 patients with SRBD (44%) revealed obstructive sleep apneas (OSA). AHI was 32 +/- 15 (12-60) in patients with CSA and 32 +/- 27 (11-86) in patients with OSA. Patients with and without SRBD were comparable concerning left ventricular ejection fraction, NYHA classification, cardiac disease, ICD indication, and concomitant medication. ICD registered ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA. The numbers and circadian variation of episodes registered during follow-up in patients without SRBD, with OSA or CSA were comparable (14 +/- 25, median 4 vs 15 +/- 15, median 7 vs 4 +/- 5, median 2.5). The 2-year cardiac mortality was highest in patients with CSA (4/9 (44%) vs. 0/7 patients (0%) with OSA vs 3/24 patients (12.5%) without SRBD. Thus, the prevalence of SRBD in patients with chronic heart failure and a history of malignant ventricular tachyarrhythmias is high (40%) and the occurrence of CSA seems to be predictive for cardiac mortality in these patients. An influence of moderate SRBD on arrhythmia recurrence and circadian variation of spontaneous sustained tachyarrhythmic events could not be demonstrated.

Aged↗
PubMed1998

[Reproducibility of the effectiveness of defibrillation for terminating induced ventricular fibrillation using intraoperatively measured defibrillation threshold energy in patients with implanted cardioverter-defibrillator].

The aim of the present study was to assess the long-term reproducibility of the defibrillation efficacy of energies set at the intraoperatively measured defibrillation threshold using a modified testing protocol. Between December 1993 and January 1996, 83 patients receiving an implantable cardioverter-defibrillator (ICD) in combination with a non-thoracotomy lead system and having an intraoperatively measured defibrillation threshold (DFT) < or = 15 J were enrolled in a substudy of a prospective, randomized multicenter trial ("Low Energy Endotak Trial" (LEET)). Step-down DFT testing was performed intraoperatively (15, 10, 8, 5 J). It was mandatory to reproduce a successful conversion of ventricular fibrillation at the DFT energy during implantation (DFT+). At the end of implantation, at predischarge, and after one year, assessment of the defibrillation efficacy of DFT+ energy was repeated (first shock: DFT+, second shock: 2 x DFT+). Mean DFT+ at implant was 9.6 + 3.3 J. Immediately after implantation, successful conversion of induced ventricular fibrillation was achieved in 70/79 (89%) patients using DFT+ energies. In 7/8 (89%) patients only the second shock set at 2 x DFT+ and in one patient only the third shock set at maximum energy (34 J) was successful. At predischarge, defibrillation efficacy of DFT+ was reproducible in 61/77 (79%) patients. The remaining 16 patients were successfully converted using a second shock set at 2 x DFT+. One year after implantation, conversion of ventricular fibrillation was achieved at energies set at DFT+ in 52/62 (84%) patients and in the remaining 10 patients at energies set at 2 x DFT+. A total of 183/218 (84%) episodes of induced ventricular fibrillation were terminated successfully using DFT+ energies. There was no correlation between the intraoperatively determined DFT+ or the underlying cardiac disease and the defibrillation efficacy. These results demonstrate that the defibrillation efficacy for termination of induced ventricular fibrillation using DFT+ energies is reproducible at implantation, at predischarge, and one year after ICD insertion. Energies set at twice DFT+ seems to allow for reliable defibrillation within the first year after ICD implantation.

Adult↗
PubMed1998

Valve-preserving replacement of the ascending aorta: remodeling versus reimplantation.

OBJECTIVE: Aortic valve regurgitation in combination with dilatation of the ascending aorta and root requires a combined procedure to restore valve function and eliminate pathologic dilatation of the proximal aorta. Two techniques have been proposed for this purpose; the aortic root may be either remodeled with an especially configured vascular graft or replaced with reimplantation of the aortic valve within the graft. We have used both techniques depending on the individual pathologic condition of the aortic root. METHODS: Of 107 patients undergoing operation for proximal aortic disease between October 1995 and November 1997, 40 patients had morphologically intact aortic valve leaflets in conjunction with dilatation of the aortic root. Of these, 15 patients underwent an operation as a surgical emergency for acute aortic dissection type A. In 29 instances, root remodeling in conjunction with ascending aortic replacement was performed; 11 patients underwent radical replacement of the proximal aorta with reimplantation of the aortic valve. Partial or total arch replacement was performed additionally in 27 of these patients. Other concomitant procedures were coronary artery bypass grafts (n = 11) and mitral reconstruction (n = 1). RESULTS: Two patients died after repair of acute aortic dissection, for a total operative mortality rate of 5%. No patient died after elective surgery. Aortic valve function could be effectively restored with both techniques. No patient underwent reoperation on the proximal aorta; freedom from aortic regurgitation of grade II or more at 1 year is 88% with both techniques. CONCLUSIONS: Depending on individual root pathologic condition, both the remodeling and the reimplantation techniques appeared to have their individual merits. Both result in adequate restoration of aortic valve function and elimination of pathologic aortic dilatation.

Adult↗
PubMed1998

Construction and characterisation of a gridded chicken cosmid library with four-fold genomic coverage.

Gridded genomic libraries are crucial for the positional candidate gene approach. For this purpose we constructed a gridded genomic library from a female chicken using the vector sCos 1. About 110,000 cosmid clones were grown and replicated in 384-well plates. An average insert size of 39 kb was calculated from the analysis of 68 randomly selected clones. No chimerism could be observed from 31 in situ hybridisations. One replica of the library (number 125) has been transferred to the Resource Centre/Primary Database (RZPD) of the German Human Genome Project (DHGP). The whole library was gridded onto four nylon filters at high density for efficient identification of cosmid clones by colony hybridisation. Twenty-two probes were used for screening the library and each of them gave at least one positive signal. This result is in good agreement with a four-fold coverage of the genome as estimated from the insert length and number of recombinant clones. This library provides a powerful tool for rapid physical mapping and complex analysis of the chicken genome.

Animals↗
PubMed1998

Assessment of intersignal variability for discrimination of atrial fibrillation from atrial flutter.

The analysis of endocardial signals obtained from an electrode located in the right atrium enabled by new dual chamber implantable cardioverter defibrillators may be helpful to provide additional therapies such as overdrive pacing or low energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Algorithms for discrimination of atrial tachyarrhythmias based on rate counting are of limited efficacy. The aim of this study was to assess the intersignal variability by using fast discrete wavelet transforms (FDWT) as a new method of discrimination of AF from AFL. Patients with spontaneous episodes of AF/AFL or patients who developed AF/AFL during an electrophysiological study were studied. The endocardial signals were recorded from the high right atrium using a transvenous 5 Fr bipolar electrode catheter (interelectrode spacing: 1 cm). The signals were digitized (2 kHz, 12-bit resolution) after amplification and filtering (40-500 Hz). Within data segments of 10-second duration, 25 consecutive signals were selected and normalized and FDWT was applied. Standard deviations of the wavelet coefficients (SD) from coarse scales (scale 4-8) were calculated. A total of 94 data segments (AF: 52, AFL: 42) from 28 patients were analyzed. SD at each considered scale was higher for AF than for AFL (P < 0.001). SD at scale 8 discriminated between AF from AFL with 100% sensitivity and specificity. We conclude that assessment of intersignal variability of bipolar endocardial recordings using FDWT is an effective method for the discrimination of AF from AFL. The implementation of this tool in a discrimination algorithm of an implantable device may help provide the appropriate differential therapy for atrial tachyarrhythmias.

Algorithms↗
PubMed1998

Discrimination of sinus rhythm, atrial flutter, and atrial fibrillation using bipolar endocardial signals.

INTRODUCTION: Analysis of endocardial signals obtained from an electrode located in the right atrium as realized in newly designed dual chamber, implantable cardioverter defibrillators might be used to provide additional therapeutic options, such as overdrive pacing or low-energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Therefore, we developed a computer algorithm for discrimination of normal sinus rhythm (NSR), AFL, and AF that may lead to adequate differential therapy of atrial tachyarrhythmias in an automated mode. METHODS AND RESULTS: During an electrophysiologic study, bipolar endocardial signals from the high right atrium were obtained in 28 patients during sustained AFL or AF and after restoration of NSR. A total of 286 data segments of 5-second duration were recorded (NSR: 96, AFL: 86, AF: 104). Mean atrial cycle length (MCL), standard deviation of mean atrial cycle length (SDCL), and index of irregularity (IR), defined as the ratio between MCL and SDCL, were calculated for each data segment. A cutoff of 315 msec for MCL allowed discrimination of NSR from atrial tachyarrhythmias with 100% sensitivity and specificity. For discrimination of AF from AFL by using SDCL, a cutoff value of 11.5 msec led to a sensitivity of 99% and a specificity of 90%. Best discrimination of AF from AFL was found for the criterion IR > or = 7.5%, resulting in a sensitivity of 100% with a specificity of 95% for AF detection. CONCLUSION: The investigated algorithm provides discrimination of NSR, AFL, and AF with high sensitivity and specificity. Incorporation of this algorithm in an implantable automated antitachycardia device may lead to adequate differential therapy in patients suffering from spontaneous episodes of AF and AFL.

Algorithms↗
PubMed1998

Influence of thermal stress on the incidence of acute myocardial infarction in a temperate climate.

Using a Poisson regression model the relative incidence of acute myocardial infarctions (AMI) prospectively registered in 8 hospitals within a radius of 50 km during a 2-year period was correlated with the outside conditions characterized by a complete thermophysiological model (Klima-Michel Model) defining thermal stress. An increase in the incidence of AMI related to thermal stress could be demonstrated neither by splitting the study period into 12 equally sized 'felt-temperature' classes by months of the year nor by single days. This was confirmed by correlation of the AMI rate with the mean felt-temperature level during the preceding 14 days. Thermal stress caused by the atmospheric conditions in a temperate climate may be too weak to influence significantly the incidence of AMI.

Aged↗
PubMed1997

Antitachycardia pacing in patients with implantable cardioverter-defibrillators: inverse circadian variation of therapy success and acceleration.

We analyzed spontaneous ventricular tachycardias treated by antitachycardia pacing during long-term follow-up in 138 recipients of an implantable cardioverter-defibrillator. An inverse circadian variation of the antitachycardia pacing termination and acceleration rates with the worst antitachycardia pacing success during the time period with the highest episode frequency (morning hours) was demonstrated.

Circadian Rhythm↗
PubMed1997

Tolerability of internal low-energy shock strengths currently needed for endocardial atrial cardioversion.

There seems to be no relation between shock strength and patient's tolerability using energy levels currently needed for low-energy internal atrial cardioversion. Every patient felt that the second delivered shock, independent of the amount of energy, was more uncomfortable than the first one, which indicates that psychological conditioning may also play an important role in determining discomfort.

Atrial Fibrillation↗
PubMed1997

Incidence and clinical significance of short-term recurrent ventricular tachyarrhythmias in patients with implantable cardioverter-defibrillator.

Aims of the present study were (1) to investigate the clinical significance of short-term recurrent tachyarrhythmias (STRTs) in ICD recipient, (2) to identify basic characteristics of the subgroup of patients with STRTs and (3) to compare the frequency and circadian pattern of single arrhythmic events and STRTs. We reviewed data from 119 consecutive patients with late generation ICD. All registered spontaneous ventricular tachyarrhythmias were divided into STRTs (defined as two or more consecutive episodes separated by < or =1 h of sinus rhythm) and single events. During a mean follow up of 36+/-18 months (range 2-67 months) 1849 ventricular arrhythmic events were detected in 57 out of 119 ICD recipients (48%). 202 STRTs consisting of 1128 single detection (6+/-7/STRT, range 2-52) occurred in 34/57 patients (60%; 6+/-6 per patient, range 1-21). Recurrent ventricular tachycardias before device implantation and a high number of single arrhythmic events during follow-up distinguished patients with STRTs. Cardiac mortality was significantly higher in patients with STRTs (26 vs. 4%, P<0.05). The majority of both single episodes and STRTs were registered between 8 a.m. and noon and in the evening. This study reveals a high incidence of STRTs in ICD recipients with spontaneous tachyarrhythmias during follow-up and identifies STRTs as prognostic significant events. Comparable circadian variations suggest that similar triggering factors may be involved in the genesis of STRTs and single tachyarrhythmias.

Adult↗
PubMed1997

Factors influencing heart rate variability in patients with severe aortic valve disease.

BACKGROUND AND HYPOTHESIS: Heart rate variability (HRV) is an accepted tool for the assessment of cardiovascular autonomic tone. There are no sufficient data concerning its application to patients with severe aortic valve disease (AVD) requiring cardiac surgery. METHODS: It was the aim of this study to examine HRV and its physiologic correlates in patients with severe aortic valve disease requiring cardiac surgery. The correlates of time domain indices of HRV obtained from 24-h Holter electrocardiographic recordings were analyzed in 36 consecutive patients (23 men and 13 women, mean age 62 +/- 11 years) with AVD prior to cardiac surgery (aortic stenosis: 17 patients, aortic valve regurgitation: 3 patients, combined aortic valve disease: 16 patients). RESULTS: Low values of HRV were found in the entire study group: SDNN 96.8 +/- 30.9 ms, SDNNI 39.3 +/- 14.4 ms, SDANN 86 +/- 28.9 ms, and RMSSD 30 +/- 18.1 ms. In a univariate analysis, there was no significant correlation between the time domain measures of HRV and age, gender, medication, left ventricular ejection fraction, peak aortic pressure gradient, fraction of aortic valve regurgitation, and left ventricular mass assessed by echocardiography. Patients in advanced functional classes of heart failure [New York Heart Association (NYHA) III or IV] had significantly lower values for SDNN (83.8 +/- 33.6 vs. 107.3 +/- 24.7 ms; p < 0.05) and SDANN (72.7 +/- 29.4 vs. 96.6 +/- 24.3 ms; p < 0.05) than patients in NYHA class I or II. Reassessment of HRV 1 week after aortic valve replacement was performed in 17 patients and showed a significant further decrease of SDNN (102.4 +/- 29.7 vs. 61.5 +/- 23.5 ms; p < 0.001), SDNNI (40.7 +/- 13.6 vs. 23.4 +/- 12.4 ms; p < 0.001) and SDANN (91.8 +/- 29.2 vs. 54.2 +/- 22.8 ms; p < 0.001). CONCLUSION: Patients with AVD requiring cardiac surgery reveal reduced time domain indices of HRV. This observation is pronounced in patients with a progressed clinical class of heart failure, whereas hemodynamic and echocardiographic parameters seem to have no significant influence on HRV parameters in this population. In addition, there is evidence of a further reduction of HRV time domain indices 1 week after uncomplicated aortic valve replacement.

Aortic Valve↗