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At least 613 records · Page 34Linked to original sources
PubMed1979

[Short-term and average-term automatic control of re-entry arrhythmias].

The AA. described an external stimulator to be utilized instead of invasive pharmacological treatment, as a short and middle-time therapeutic approach to re-entry tachycardia, in Departments of cardiology. The device must be connected with an electrode placed in atrium or in coronary sinus or in ventricle, according to individual request. A frequency discriminant device recognizes tachycardia and activates automatic scanning stimulator, synchronized on R or P waves, with progressive 5 msec stop delay; tachycardia interruption zone is automatically individuated. Stimulation has an automatic stop when tachycardia is interrupted; in case of persistent tachycardia scanning-function cycle will star again automatically. The device, which can be programmed for a simple or a double impulse emission, is equipped with a demand stimulator working if post-tachycardia asystole is present. Frequency discriminant device activates the scanning function beyond a defined threshold which can be varied within a wide range of frequencies.

Arrhythmias, Cardiac↗
PubMedDate not supplied

[Automatism: an intrinsic property of cardiac tissues].

Automaticity is an intrinsic property of some types of cardiac tissues, like the nodes and the conducting fibers. Automatic cells are characterized by the appearance, during diastole, of a slow depolarization which is capable of reaching threshold and generate an action potential. This depolarization is the so-called slow diastolic depolarization, or pacemaker potential. Tissues with automaticity do not have the same intrinsic firing frequency, which determines the existence of a true pacemaker; normally this role is assumed by the sinus node and several latent, or subsidiary pacemakers. The latter do not give any manifestation, because, since they have a slower firing frequency than that of the true pacemaker, the impulses generated by the latter will activate them before they can reach threshold. The ionic mechanisms that originate the pacemaker potential are just some of the processes that constitute the electrophysiological properties of the cardiac cell membranes. The mechanism includes the slow inactivation of an outward current combined with a constant inward current. Recently published evidence suggests that the pacemaker potential could be the resultant of an inward current that is slowly activated during the final part of the repolarization, but these data are still controversial and difficult to interpret. The factors that regulate heart rate modify the electrophysiological characteristics of the membrane by means of three major mechanisms: the slope of the pacemaker potential, the voltage of the threshold potential and, the maximum diastolic potential. Some of the most important factors that modulate heart rate include the neurotransmitters of the automatic nervous system, the plasmatic levels of some ions, like potassium and calcium, and changes in the intrinsic properties of the membrane, like the influence of heart rate on the activity of the sodium pump.

Animals↗
PubMed1983

[Agreement of automatically and manually determined parameters of the electronystagmogram].

Prerequisite for clinical use of programs for automatic analysis of nystagmus is a similar accuracy in determining parameters of electronystagmograms in comparison with manual evaluation. For examination of accuracy and reliability of our program NYSLYS, we compared maximal values of the slow phase velocity (SPV) and the number of beats in 10 s of responses from thermal tests, with 100 patients with equilibrium disturbances. The average difference between the automatically and manually evaluated values for SPV and the number of beats in 10 s is in the range of +/- 15%. Correlation coefficients are 0.97 for SPV and 0.95 for the number of beats in 10 s. Similar correlation coefficients are obtained for the ratio of responses after left and right ear stimulation. These results show that our automatic analysis can replace tedious manual evaluation in most cases. In addition the temporal course of SPV is obtained as a good aid in the judgement of nystagmus. Automatic analysis, however, cannot fully replace the ability to examine electronystagmograms. Especially if curves are disturbed by many artifacts or in cases with very irregular reactions the original electronystagmogram must be considered, too.

Caloric Tests↗
PubMed1983

Trials of the automatic implantable defibrillator in man. A three-year program report.

Since February, 1980, 65 survivors of multiple arrhythmic cardiac arrests unresponsive to therapy were referred for implantation of the automatic defibrillator. In 37 patients (Group I), automatic defibrillator implantation alone was performed by subxiphoid insertion (20 patients) or thoracotomy (17 patients). In another 28 patients (Group II), implantation was combined with definitive cardiac procedures--coronary artery bypass grafting in seven patients, bypass grafting and mitral valve replacement in four patients, and left ventricular aneurysmectomy with endocardial resection in 17 patients. There were no surgical deaths in Group I; four operative deaths occurred in Group II. The longest follow-up has been 34 months, average 15.6 months. Following hospital discharge, 44 episodes of automatic out-of-hospital resuscitation were observed in 11 Group I patients. Similarly, four resuscitations were observed in two Group II patients. Hypothetical survival curves based on the assumption that these out-of-hospital resuscitations were lifesaving indicated expected 1 year survivals rates of 45% in Group I and 85% in Group II. Excluding the perioperative deaths that were unrelated to the defibrillator, the actual 1 year survival rates observed were 75% and 95% in Groups I and II, respectively. Although definitive operation markedly reduced the number of out-of-hospital arrhythmic episodes, the automatic defibrillator appears to increase survival both when implanted alone and when used in combination with cardiac procedures.

Adolescent↗
PubMed1983

Compared efficacy of quinidine, GABA and N-trimethyl GABA upon a model of ventricular automaticity.

The effects of GABA, its quaternary derivative N-trimethyl GABA and quinidine have been studied in a model of ventricular automaticity induced in the isolated right ventricle of the rat. GABA shows low anti-automatic activity. N-trimethyl GABA and quinidine were, however, very effective drugs in the reduction of the automatic ventricular rate. The efficacy of the latter two drugs at 5 X 10(-5) M was not significantly different. We conclude that N-trimethyl GABA has some anti-automatic activity in this experimental model, similar to a classic antidysrhythmic drug such as quinidine, that would warrant further research.

Animals↗
PubMedDate not supplied

[Determination of the permissible error of a photoelectric concentration meter for an automatic biochemical analyzer].

On the ground results derived from an analysis of metrological characteristics of the biochemical automatic unit systems and of their influence on the end-result with due regard for actual operating conditions a formula for the automatic unit error was deduced. The specificity of technical requirements to be met by automatic meters is shown and a new complex set of metrological characteristics of the concentration meter are given. At the same time permissible values for metrological characteristics of the meter satisfying medical requirements are defined. The new complex set of metrological characteristics for the biochemical automatic unit concentration meter allows it to make a change from the absolute photometric scale of the device to the one in relative units.

Autoanalysis↗
PubMed1995

Specific effects of zatebradine on sinus node function: suppression of automaticity, prolongation of sinoatrial conduction and pacemaker shift in the denervated canine heart.

We evaluated the cardiac electrophysiological effects of zatebradine in eight anesthetized and autonomically denervated canines, with particular emphasis on the effects on sinus node automaticity and sinoatrial conduction (SACT), both at rest and after atrial overdrive pacing. Sinus node function was assessed by using the recorded sinus node electrogram and also by applying a previously validated mathematical model of sinus node function which allows separate evaluation of effects of pacing on SACT and suppression of automaticity. Other standard electrophysiological parameters also were measured. Tests were performed before and after incremental doses of zatebradine (0.0625, 0.125 and 0.25 mg/kg). Zatebradine caused a significant, dose-related increase in cardiac cycle length. There also was a significant, dose-related increase in both suppression of automaticity and SACT (independent of changes in cycle length) after zatebradine. The only other significant electrophysiological effect was a relatively minor increase in the ventricular effective refractory period (13%). Higher doses of zatebradine were associated with spontaneous pacemaker shift characterized by loss of the sinus node electrogram and variation in P-wave morphology. Our results confirm that the effects of zatebradine are relatively specific for the sinus node. These included: 1) prolongation of resting sinus cycle length; 2) enhanced suppression of automaticity after overdrive pacing; 3) prolongation of SACT; and 4) induction of sinus node pacemaker shifts. This agent should be used cautiously in patients with possible sinus node dysfunction.

Animals↗
PubMed1994

An algorithm for automatic tracking of nuclear boundaries.

An image segmentation algorithm, based on boundary tracking, was introduced to achieve automatic segmentation of nuclei. This will improve reliability and reproducibility for the computer-assisted grading of routinely stained material, especially from biopsies, which often offer only scanty clinical material. Nuclear grading systems using karyometric features were developed earlier. However, hematoxylin and eosin-stained tissues have proven difficult for automatic segmentation, which is a crucial part of an objective grading system. In this paper we describe an automatic tracking method that traces nuclear boundaries on the basis of edge information and local boundary features. There were two phases to the procedure. First, approximate boundaries were extracted by automatic thresholding; then, boundaries were refined through interactive tracking. The results are encouraging.

Algorithms↗
PubMed1994

[The pectoral implant of an automatic defibrillator by cardiologists in an electrophysiology laboratory].

We have performed 2 implantations of transvenous automatic cardioverter defibrillator in a cardiac laboratory devoted to electrophysiology and pacemaker implantation. This is a preliminary experience with a novel implant strategy. Cardiologists were the primary operators. The automatic cardioverter defibrillator were placed in a subcutaneous pectoral region, with a non-thoracotomy lead system. The automatic cardioverter defibrillator were two Medtronic 7219D PCD Jewel, with a Transvene system. There were no perioperative complications. Acceptable defibrillation threshold were obtained in both patients, 12 and 20 J, respectively. Leads were inserted percutaneously through the left subclavian vein. After 8 months of follow-up the patients continue to tolerate the device satisfactorily. Implantation of automatic cardioverter defibrillator systems by trained cardiologists in an electrophysiology laboratory is safe and feasible. Moreover, its cost-effectiveness is superior, the saving includes the surgeons, and the reduction of stay in unit of intensive care and hospitalization.

Defibrillators, Implantable↗
PubMed1994

Automatic identification of surgical and orthodontic instruments.

Surgical instruments are becoming increasingly expensive and represent an important component of the costs of operating theatres. The use and processing of surgical instruments in decontamination and packaging units and in the operating theatre need to be monitored, both to improve efficiency and to allow measurement of the effectiveness of training in operative technique. Automatic identification of surgical and orthodontic instruments was therefore performed using two standard methods: the two-dimensional bar-code and matrix code. Encryption (the formulation of codes), was carried out prior to bar and matrix coding using acid-etch and laser techniques respectively. 'Reading' of the two types of code was more difficult with bar-codes because of the high reflectivity of background polished stainless steel, and only large instruments had sufficient area for bar-coding. Consistent, accurate, automatic identification of the instruments was possible with the matrix code for which a surface of only 4 sq mm is necessary. After 50 cycles of decontamination and packaging, neither code showed obvious deterioration and it was possible to read the matrix code as easily as prior to this process. Automatic instrument identification is possible using recently developed methods and could facilitate economies in the processing of instruments in health facilities and the automatic recording of instrument usage in the operating theatre.

Electronic Data Processing↗
PubMed1993

[Transcatheter ablation with high-frequency currents as a method for creating useful experimental models in the study of cardiac conduction and automatism].

PURPOSE: analyze the utility of transcatheter ablation with high-frequency currents to create different experimental models of altered cardiac automatism and conduction. METHOD: the results were obtained in six anesthetized dogs subjected to electrophysiological study after selectively applying transcatheter radiofrequency ablation to different zones of the specific cardiac conduction system. Ablation was carried out using conventional bipolar 7F catheter-electrodes. High-frequency currents (0.7 MHz) were emitted through the distal electrode, with variable intensity and duration according to the aim of the experiment. Anatomic (fluoroscopic) and electrophysiological criteria were used to position the electrode within the ablation zone. RESULTS: selective radiofrequency application to the atrioventricular junction zone affords complete A-V blocks with escape rhythms located in the A-V node or His-Purkinje system, together with different degrees of infra- and intra-hisian and intranodal blocks. The modification of intranodal refractoriness and conduction without interrupting atrial pulse transmission may manifest atypical patterns with truncated nodal conduction curves. The abolition of sinus function through ablation in the zone of the sulcus terminalis makes it possible to obtain supraventricular subsidiary rhythms. The obtaining of intranodal complete blocks with supra-Hisian escape rhythms demonstrates phenomena such as the modulation of subsidiary automatism by non-transmitted atrial pulses, analyzed by constructing phase-response curves. CONCLUSION: transcatheter ablation using high-frequency currents is useful in demonstrating phenomena related to intranodal and His-Purkinje conduction, subsidiary pacemaker automatism or the modulation of automatism and conduction via non-transmitted pulses.

Animals↗
PubMedDate not supplied

[The evaluation of a digital system for the automatic analysis of the density of abdominal radiograms].

This paper reports the results of the evaluation of an automatic system developed to analyze radiographic densities. This system, called RADEN, has been implemented at the Institute for Information Processing of the Italian National Research Council in Pisa. Forty-three pairs of abdominal X-ray films were obtained before and after the administration of ionic iodate contrast medium (i.i.c.m.) during urographic examinations. The 86 X-ray films were acquired and digitized using a computer-controlled optoelectronic device with a sampling step ranging 125 microns to 250 microns. The resulting images were arrays of 512 x 512 pixels, each one quantified on a byte (256 gray levels). The computing system included a high-performance personal computer equipped with a video RAM board having built-in facilities for image processing and with an optical disk to archive the images. Automatic and semi-automatic procedures were developed to segment, recognize and classify the images and to characterize three homogeneous regions--i.e., bone, water and air. The output data were compared with the area values of the air densities computed directly on the X-ray films by a radiologist. Furthermore, both data sets were compared with the scores given in a blind study by four observers. The subsequent statistic analysis showed the increase in air density areas after i.i.c.m. administration and the applicability of the implemented system to the automatic examination of abdominal radiographic densities. The results encourage to believe that the proposed approach could be employed as a first step for the development of quite a more complex system oriented to X-ray image understanding and to assisted diagnosis.

Contrast Media↗
PubMed1995

[An attempt of applying the image processing for the automatic estimation of sampled airborne pollen].

Development of techniques to rapidly and easily estimate an airborne pollen quantity is necessitated in order to make out a appropriate prescription for an allergy patient from medical clinical viewpoints, and in order to research a movement of allergen from medical basic viewpoint. The measurement of airborne pollen quantity required a large labour and time, because the amount of pollen grains is visually measured by naked eye. This paper, as a first step to estimate an airborne pollen quantity full-automatically, discuss techniques to measure the quantity of sampled airborne cedar pollen automatically and rapidly using the image processing techniques. As a result, the following facts are cleared. Automatic measurement is possible to some degree without any special image processing. It is important to eliminate a noise on image as blurs on basefilm for high accuracy measurement. The precision has improved fairly with level correction for image. Sharpening filter is the most appropriate process to improve the accuracy of automatic measurement of sampled airborne pollen. This filtering process has a merit that the operativeness is easy.

Air Pollutants↗
PubMed1995

Automatic 3D segmentation and characterization of brain tissues in multiparametric MR image sequences.

In this paper a new segmentation method for automatic differentiation of normal and pathological brain tissues, based on multidimensional relaxation parameter histograms, is introduced. The developed histogram pyramid algorithm, which is an extension of histogram-based cluster analysis methods, is used for automatic analysis of multiparametric image data from several body slices simultaneously. The achieved segmentation results are improved by a following merging algorithm, which merges split tissue parts. Furthermore, tissue specific relaxation parameter values are computed within each 3D tissue segment and can be stored in a data base. Based on the tissue database, automatic tissue classifications are performed using statistical pattern recognition methods. Classified tissues are marked with tissue-specific colors and visualized in tissue class images. For clinical applications, the algorithms for 3D segmentation, visualization, and classification of tissue structures are integrated in the software system SAMSON (System for AutoMatic Segmentation and ClassificatiON of Tissue in Magnetic Resonance Tomography). With the software system SAMSON, a tissue database for intracranial tissues has been established based on the examination of 15 volunteers and 100 patients with neoplastic and other lesions--all verified histologically.

Algorithms↗
PubMedDate not supplied

Automatic quantitation of venous hemodynamics with an electrically calibrated strain gauge plethysmograph.

Strain gauge plethysmography has permitted noninvasive quantitation of altered venous hemodynamics in the legs of patients with venous disease. A new plethysmograph has been developed which avoids previous problems of mechanical calibration of gauges and the necessity for a recorder for calculating blood flows. This instrument permits accurate electrical calibration of mercury-in-Silastic gauges which are effectively at the corners of the Wheatstone bridge and are supplied by constant current for linear output. A timer and follow-and-hold circuit allow automatic calculation of rates of change in limb circumference and, thus, blood flow, from a panel meter. The accuracy of the automatic versus the graphic methods of quantitating venous outflow and reflux flow was determined in 20 normal subjects. Venous outflows were 15.1 +/- 0.5 (mean +/- 1 S.E.M.) and 15.9 +/- 0.4 cc/min/100 cc by automatic and graphic methods, respectively (r = 0.96, p less than 0.01). Reflux flows were 2.1 +/- 0.2 and 2.3 +/- 0.2 cc/min/100 cc by the automatic and graphic methods, respectively (r = 0.93, p less than 0.01). This plethysmograph may prove to be a simple, rapid, and accurate device for evaluating altered hemodynamics in venous disease.

Hemodynamics↗
PubMed1998

Mood influences on automatic and controlled semantic priming.

Mood effects on automatic and controlled components of semantic priming were examined. After a neutral or positive mood manipulation, subjects underwent two blocks of a priming task. Automatic and strategic priming processes were operationally differentiated by the assumption that automatic priming remains constant during the task, whereas controlled priming develops slowly during the course of the experiment. In the first block the priming effect was greater for happy than for neutral mood participants. In the second block the priming effect was greater for neutral mood than for happy participants. The results confirm the hypothesis of a mood-dependent processing change: During early trials priming is based on automatic processing facilitated by positive mood. This processing mode is later superseded by controlled processes aided by neutral mood.

Adult↗
PubMedDate not supplied

[Digit span, automatic speech and orientation: amplified norms of the Barcelona Test].

BACKGROUND: Digit span, automatic speech and orientation are screening tests of interest in neurology due to their high sensitivity in cerebral pathologies and easy applicability. These tasks assess attention, concentration, mental control, orientation and short-term memory. OBJECTIVES: To analyze the impact of age and education on the results of the following subtest included in the Barcelona Test: digit span, automatic speech and orientation. PATIENTS AND METHODS: 275 normal subjects were evaluated. Mean (SD) age: 52 (17.7), range (18-19). Mean education: 9 (5.5) years, range (0-25). Subjects were stratified into 7 groups by age and education. Nine items of Barcelona Test were used: digits span forward and backward, automatic speech, forward and backward, with and without time, and person, time and place orientation. RESULTS: Statistical description, parametric and non parametric test. The Kruskal Wallis test was used, showing that aged and education are significant difference in the automatic speech forward or backward, with or without time, while it did not showed a significant difference in the different groups in the orientation tests. Analysis of Variance for group of age and education showed significant differences in the digit span forward and backward (F = 19.92; p < 0.001; F = 18.44, p < 0.001), respectively. CONCLUSIONS: Both age (inversely) and education (directly) influenced on the scores of the analyzed items, except to person, place and time orientation that are not affected for them.

Adolescent↗
PubMed1964

AUTOMATISM.

Individuals can carry out complex activity while in a state of impaired consciousness, a condition termed "automatism". Consciousness must be considered from both an organic and a psychological aspect, because impairment of consciousness may occur in both ways. Automatism may be classified as normal (hypnosis), organic (temporal lobe epilepsy), psychogenic (dissociative fugue) or feigned. Often painstaking clinical investigation is necessary to clarify the diagnosis. There is legal precedent for assuming that all crimes must embody both consciousness and will. Jurists are loath to apply this principle without reservation, as this would necessitate acquittal and release of potentially dangerous individuals. However, with the sole exception of the defence of insanity, there is at present no legislation to prohibit release without further investigation of anyone acquitted of a crime on the grounds of "automatism".

Automatism↗