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PubMed1983

Epicardial activation patterns and dispersion of refractoriness initiating ventricular tachycardia in the canine left ventricle during acute ischemia.

We examined the activation patterns in the left ventricular epicardial surface of dog hearts using multielectrode grid during the beats initiating ventricular tachycardia 5 to 120 min after coronary artery occlusion. The grid was placed on the ischemic border zone (the area was confirmed by ST-isopotential mapping) to record simultaneously 36 unipolar epicardial potentials. Under the control conditions almost radial spread of activation from the central stimulating electrode of the grid was observed. Activation during acute ischemia showed crowded isochrone lines in the ischemic area, especially during the premature beats with shorter coupling intervals. In 8 out of 15 episodes, where ventricular tachycardia was induced by a single premature stimulus, the conduction delay during premature beats culminated in the local conduction block accompanied by circus movement of activation. Subsequent initial beats of ventricular tachycardia also showed similar activation patterns indicating reentry of excitation. In the remaining 7 episodes, however, we could not obtain such circus movement of activation under the grid. We also measured the effective refractory period at 5 sites under the grid. The results showed greater dispersion of the effective refractory period in the ischemic border zone throughout 5 to 120 min after coronary occlusion in the cases where ventricular tachycardia developed. These findings suggest that reentry of excitation, which is most probably caused by inhomogeneity of refractoriness in the ischemic border zone, may play an important role in the genesis of ventricular tachyarrhythmias during acute ischemia.

Animals↗
PubMed1995

From delirium cordis to atrial fibrillation: historical development of a disease concept.

In 1874, the electrical stimulation of animal hearts made known the existence of atrial fibrillation, but atrial fibrillation was not associated with its clinical counterpart, arrhythmia perpetua, until 1909, by which time simultaneous recordings of the human heartbeat, the venous and arterial pulses, and electrocardiographic activity had revealed the common origin of these events. After the electrical basis of atrial fibrillation was found and after atrial fibrillation was clearly distinguished from ventricular fibrillation, investigation into its mechanism ensued. Two contrasting theories, that of circus movement and that of tachysystole from a single focus, led to 30 years of research and debate. Pivotal to the argument was the notion of blocked conduction. Although the theory of circus movement prevailed for a long time, it appeared to be demolished by electrophysiologic experiments done between 1948 and 1950. The realization that blocked conduction could later reenter led to more recent research in animals and humans that revived the notion of circular conduction, although in a much more sophisticated form.

Animals↗
PubMed1994

[Evaluation of velopharyngeal function after later surgical repair of cleft palate. ]

This study detected 60 cases of patients of later surgical cleft palate repairing with different operative procedures,based on nasopharyngeal fiberscope and image processing detective system of nasopharyngeal function.They were divided into two groups,30 cases with Furlow's double reversing Z plasty,and others with traditional palatoplasty.The results were as follows:the type of velopharyngeal closure with later palatoplasty mainly were circus,semi-circus,and the rate of operative success only was 46.6%,which was lower than other reports.Author described that compensation of lateral and posterior pharyngeal wall made the type of velopharyngeal closure.The elder the age,the more the compensation is.For the late cleft palate repair,although the variable surgical procedure made a condition for speech improvement, patients with later cleft palate repair still can't improve their phonation.

Journal Article↗
PubMed2004

Blue ocean strategy.

Despite a long-term decline in the circus industry, Cirque du Soleil profitably increased revenue 22-fold over the last ten years by reinventing the circus. Rather than competing within the confines of the existing industry or trying to steal customers from rivals, Cirque developed uncontested market space that made the competition irrelevant. Cirque created what the authors call a blue ocean, a previously unknown market space. In blue oceans, demand is created rather than fought over. There is ample opportunity for growth that is both profitable and rapid. In red oceans--that is, in all the industries already existing--companies compete by grabbing for a greater share of limited demand. As the market space gets more crowded, prospects for profits and growth decline. Products turn into commodities, and increasing competition turns the water bloody. There are two ways to create blue oceans. One is to launch completely new industries, as eBay did with online auctions. But it's much more common for a blue ocean to be created from within a red ocean when a company expands the boundaries of an existing industry. In studying more than 150 blue ocean creations in over 30 industries, the authors observed that the traditional units of strategic analysis--company and industry--are of limited use in explaining how and why blue oceans are created. The most appropriate unit of analysis is the strategic move, the set of managerial actions and decisions involved in making a major market-creating business offering. Creating blue oceans builds brands. So powerful is blue ocean strategy, in fact, that a blue ocean strategic move can create brand equity that lasts for decades.

Commerce↗
PubMed2004

Refractoriness of cardiac muscle as affected by intercalated disks: a model study implications for fibrillation and defibrillation.

It is generally agreed that inhomogeneities of the recovery process in cardiac tissue play an important role in the genesis of reentrant arrhythmias. Regarding cardiac muscle as an assembly of discrete cells connected by gap junctions, differences in recovery may result from a nonuniformity of membrane or cable properties. In this study, a computer model of a one-dimensional cardiac muscle fiber including a periodic intercalated disk structure is used to study the influence of disk resistance (Rj) and stimulus strength (J) on refractoriness. Stimulating currents are applied externally in a bipolar arrangement. The basic effect of a current pulse is local de- and hyperpolarizations at the ends of an individual cell. Polarization develops very rapidly and increases with increasing values of Rj or J so that an interaction with membrane current kinetics becomes possible. When a premature stimulus is applied during repolarization of a conditioning action potential, multiple Na currents can occur, either caused by depolarization of the cathodal end of a cell or in the form of anode break excitation at the hyperpolarized end. Those currents affect the response of a fiber such that, at a given value of J, the refractory period is shortened by an increase in Rj. In a ring fiber model with different Rj values in the two halves of ring an extrastimulus timed between the refractory periods of the two branches results in a sustained circus movement. Varying stimulus strength yields an upper limit of vulnerability characterized by a "synchronized extrasystole". The ring model also implies the suppression of circus movement by an external shock. The minimal shock strength required for suppression is close to the upper limit of vulnerability. The simulations suggest that discrete effects of junctional resistance may be involved in fibrillation and defibrillation.

Action Potentials↗
PubMed1991

Mechanisms of ventricular arrhythmias: a perspective.

The most important ventricular arrhythmias, the ventricular tachycardias (VTs) and ventricular fibrillations (VFs), are thought to underlie the majority of cases of sudden cardiac death. In ischemic heart disease, they can be divided into several pathophysiological entities: (a) arrhythmias occurring during the acute reversible phase of ischemia, (b) arrhythmias taking place during reperfusion of acutely ischemic myocardium, (c) arrhythmias occurring 24-72 h after acute infarction, and (d) arrhythmias associated with chronic infarction. In all three settings, the mechanisms sustaining ventricular arrhythmias need to be distinguished from initiating mechanisms. With the exception of the 24-72-h stage, these arrhythmias are sustained by circus movement with reentry: the electrophysiological determinants of circus movements at a cellular level and, consequently, the appearance of the circulating wave fronts, differ according to the ischemic phase. In acute ischemia, multiple circulating waves, with somewhat large diameters, change their vortexes from beat to beat. In chronic infarction, the location of the stable circuits with elongated central zones of block are closely related to myocardial fiber architecture and probably to scar tissue. These differences indicate that (a) in acute ischemia, the conduction disturbances are mainly determined by the development of inexcitability at the level of cardiac membranes; and (b) in chronic infarction, the site of conduction block and the pivoting points of the wave fronts are determined by impairment of electrical cell-to-cell coupling. In contrast to the mechanisms sustaining VT and VF, the initiating mechanisms are less well defined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

[Verapamil in the study and treatment of supraventricular tachycardias, with special reference to pre-excitation].

Verapamil is a novel antiarrhythmic agent which appears to act as a calcium-ion antagonist, blocking calcium transport across the myocardial cell membrane. It was given intravenously, in a dose of 10 mg, to thirty-two patients suffering from paroxysmal supraventricular tachycardia, and sinus rhythm was achieved promptly in all. Identical results were obtained in a further ten patients with supraventricular tachycardias associated with the Wolff-Parkinson-White or other pre-excitation syndromes. In a separate group of eighteen patients in whom A-V junctional tachycardias were induced during intracardiac electrography, conversion to sinus rhythm was achieved in fifteen patients, with prolongation of the cycle length in the others. Circus-movement tachycardias were induced in eight patients with the Wolff-Parkinson-White syndrome, and conversion to sinus rhythm was achieved in seven. The results were less consistent in patients with other supraventricular arrhythmias including ectopic atrial tachycardia and atrial flutter, and, in the single patient with supraventricular and ventricular tachycardias, only the former was controlled. In the single patient with atrial fibrillation complicating the wolff-Parkinson-White syndrome who received Verapamil, sinus rhythm was restored. Side effects were few and mild, with rare exceptions of profound hypotension, bradycardia and asystole; their management is discussed, and reasons are advanced why their occurrence is likely to be related either to the concomitant administration of beta-adrenergic blockers or to the presence of sinoatrial disease. It appears that Verapamil is particularly suitable for the treatment of supraventricular tachycardias due to a circus movement as calcium antagonism is likely to be most effective in the N region of the atrioventricular node.

Adrenergic beta-Antagonists↗
PubMed1980

[Parasites of Austrian birds of prey (Falconiformes)].

During the examination of 158 birds of prey -- Buteo buteo (85), Falco tinnunculus (30), Accipiter gentilis (19), Accipiter nisus (18), Circus aeruginosus (2), Circus pygargus (1), Pandion haliaetus (1), Pernis apivorus (1), Falco subbuteo (1) and faeces samples of Falco tinnunculus 4 protozoan species, 1 trematode species, 2 cestode species, 13 nematode species, 2 acanthocephalan species and 5 mallophaga species could be detected. In the buzzard, kestrel and goshawk a new species of Capillaria could be found and described as Eucoleus suppereri spec. nov. A new species of Synhimantus, Synhimantus (Dispharynx) falconis spec. nov. was diagnosed. The infestation frequency of endo- and ectoparasites was relatively high, whereas the infestation intensity was small or mediocre on an average. The highest rate of infestation was found with trematodes and cestodes. The significance of the analysis of crop- and stomach-cntents as a guarantee of diagnosis "psuedoparasitism" was pointed out.

Animals↗
PubMed1995

Diagnosis and treatment of tachycardias with a long BP interval.

The differential diagnosis of tachycardias with a long RP interval is reviewed and the methods of treatment of these arrhythmias catheter ablation are described. Electrocardiographic and electrophysiologic criteria for the correct diagnosis of atrial tachycardia, circus movement tachycardia using retrogradely an accessory pathway with decremental conduction properties and the uncommon form of atrioventricular nodal reentrant tachycardia are discussed. First results of our institution of radiofrequency catheter ablation of atrial tachycardias and circus movement tachycardias using retrogradely an accessory pathway with decremental conduction properties are presented. We concluded that both electrocardiographic and electrophysiologic criteria give a better understanding of the mechanism and arrhythmic site which are important markers for a safe and successful ablation procedure.

Catheter Ablation↗
PubMed1981

A congenital abnormality in the arrangement of muscle bundles in a segment of the distal ileum, producing obstruction: a variant of the so-called "giant Meckel's diverticulum".

This 4-year-old male child was diagnosed at birth as having several minor congenital anomalies. X-rays taken during the first year of his life showed a single, massively dilated loop of bowel in the upper abdomen, not appreciated at the time. In 1980 he was admitted to Jackson Memorial Hospital with the diagnosis of small bowel obstruction. An upper gastrointestinal series showed one tremendously dilated loop of distal ileum. At laparotomy, the patient was found to have extreme segmental dilatation of one loop of distal ileum which ended abruptly; there was no evident external cause for obstruction. The resected loop contained in excess of 200 cc of watery brown liquid. The mucosal folds and underlying smooth muscle bundles, in the dilated portion only, were not arranged circumferentially but rather in a distinctive finger-print-like pattern with trifurcations, whorls, and intricate interdigitations which had probably produced contractions of a circus type rather than normal peristaltic waves. We have been able to find only three reports in the literature in which, as was the case here, the so-called "giant Meckel's diverticulum" presented as a single tremendously dilated segment of ileum, sharply demarcated at its distal end. In none of them is there any description of the orientation of muscle bundles. We believe that the abnormal arrangement of smooth muscle in the muscular coat in this specimen, and perhaps in the others, probably represents the underlying cause for the extreme localized dilatation.

Child, Preschool↗
PubMed1985

Evaluation of flecainide acetate in rapid atrial fibrillation complicating Wolff-Parkinson-White syndrome.

Flecainide is reported to be effective in patients with paroxysmal tachycardias, but its effect on rapid ventricular response over accessory atrioventricular pathway during atrial fibrillation is not known. The influence of flecainide on various electrophysiological properties of the accessory pathway with special emphasis on ventricular rate during atrial fibrillation was investigated in 9 patients with severe symptomatic Wolff-Parkinson-White syndrome. The shortest ventricular response during atrial fibrillation increased from 218 (190-270) to 320 (240-block) ms. In 4 patients sustained rapid atrial fibrillation converted to sinus rhythm. The rate of circus movement tachycardia decreased from 166/min to 130/min after flecainide, due to a lengthening of retrograde ventriculoatrial conduction time over the accessory pathway. Flecainide caused a significant prolongation of the effective refractory period of the accessory pathway in our subgroup with extremely fast AV conduction during atrial fibrillation and induced a depressant effect on retrograde accessory pathway conduction. This makes the drug very promising for the emergency treatment of dangerous rapid tachyarrhythias complicating this syndrome.

Adolescent↗
PubMed1994

Termination of pacemaker-mediated tachycardia by adenosine.

A 30-year-old woman was referred for follow-up right- and left-heart catheterization 4 years after cardiac transplantation. She had an implanted epicardial pacemaker for bradycardia; this was programmed to the DDD mode. At the time of her catheterization, as a pigtail catheter was pulled back across the aortic valve, runs of premature ventricular complexes occurred and tachycardia with ventricular pacing spikes and ventricular capture was initiated at a rate of 126 beats/min. Adenosine 6 mg was given intravenously through a femoral venous sheath and within 20 s the tachycardia broke. The tachycardia was consistent with pacemaker-mediated tachycardia (PMT), a circus movement tachycardia occurring when ventricular pacing causes retrograde atrial depolarization followed by triggering of ventricular pacing. With reprogramming of the pacemaker to an AV delay of 160 ms and a postventricular atrial refractory period of 300 ms, no further episodes of PMT have occurred. This case illustrates that intravenous adenosine can effectively terminate PMT by causing ventriculoatrial block, thus interrupting the reentrant circuit by eliminating retrograde atrial activation.

Adenosine↗
PubMed2005

Conjoined twins.

Conjoined twins have been a source of fascination for both the general public and the medical profession since time immemorial. Their birth was initially viewed as an ominous sign of impending disaster. This was followed by a prolonged period through the Middle Ages and into the nineteenth century when they were regarded as freaks or monstrosities and were exhibited with substantial financial reward at circuses and sideshows. Recently, conjoined twins have attracted intense media interest, which has coincided with increasing success in their separation. This article gives an overview of the role of prenatal ultrasound in assessing the prognosis and discusses the post-natal surgical management and outcome.

Female↗
PubMed1991

Diversity in motile responses of human neutrophil granulocytes: functional meaning and cytoskeletal basis.

Different agonists induce motility and shape changes, but only a specific polarized shape is correlated with directed migration. An intact and dynamic actin network appears to be important for motility and migration. Motility is usually associated with an increased level of F-actin, and a specific location of F-actin into surface protrusions. For locomotion, a specific location of F-actin, rather than a large net increase in F-actin appears to be of importance. Three major groups of responses can be distinguished on the basis of the type of shape changes, functional activity and organization of F-actin. 1. Agents capable of polarizing cells, such as chemotactic peptides, and microtubule-disassembling agents elicit, at appropriate concentrations, a marked chemokinetic response, but little if any fluid pinocytosis. F-actin shows a polar location, being concentrated mainly in the protrusions at the leading front. Chemotactic peptide also induces an increase in the level of F-actin and cytoskeleton-associated actin. It is, however, not clear if front-tail polarity and locomotion, induced by chemotactic peptide after longer time of stimulation, correlate with an actual increase in the level of cytoskeleton-associated actin. 2. Activators of protein kinase C such as PMA and diacylglycerols, induce nonpolar cells with surface projections. PMA and diacylglycerols stimulate pinocytosis substantially. All three agents tend to inhibit locomotion or chemotaxis as an immediate response. They also increase the percentage of cytoskeletal actin, and induce an enrichment of F-actin in surface projections. 3. Circus movement may occur in response to D20. These cells show little or no stimulation of locomotion or pinocytosis. Thus the functional significance of this motor response remains to be elucidated. We conclude that different agonists can induce motility and shape changes, but not necessarily chemotaxis. Only a polarized shape is correlated with directed locomotion. An intact and dynamic actin network appears to be important for motility including locomotion. Motility is usually associated with an increased level of F-actin, and a specific location of F-actin into surface protrusions. The actin-associated proteins alpha-Actinin, myosin and actin-binding protein appear also to be important for pseudopod formation. For locomotion, a specific location of F-actin, rather than a large net increase in F-actin may be of importance.

Actins↗
PubMed1989

Cardiac arrhythmias modelled by Cai-inactivated Ca2+ channels.

A model of cardiac cells incorporating the membrane potential and the intracellular calcium concentration as the two dynamical variables is developed. This model is applied to simple systems of cells to investigate its behavior as a function of the model parameters. Rational entrainment is observed in systems of two coupled pacemaker cells. The propagation of the membrane potential and intracellular calcium concentration through a sheet is simulated. Behavior suggestive of circus movement tachycardias is observed.

Arrhythmias, Cardiac↗
PubMed1990

Estimation of the total surface area in Indian elephants (Elephas maximus indicus).

Twenty-four adult Indian elephants (Elephas maximus indicus) of both sexes and different ages and weights, belonging to the Temple Devaswoms, the Forest Department of the Government of Kerala and the Gemini Circus formed the experimental subjects from which formulae were derived to predict the total surface area from either body measurements or areas of individual regions. Several models, using the parameters studied either singly or in combination, were tried independently for males and females and also for adults irrespective of sex. The best prediction of total surface area (S) in m2 was obtained for adults irrespective of sex by using the two parameters, the height at the shoulders (H) in m and forefoot pad circumference (FFC) in m in the formula S = -8.245 + 6.807H + 7.073FFC. No significant improvement in the accuracy of prediction resulted from the use of the independent best fit formulae for males and females. The conventional method of using the exponential of body weight (kg) for predicting surface area was not found to yield an equivalent accuracy in these animals.

Animals↗
PubMed1989

Estimation of body weight in Indian elephants (Elephas maximus indicus).

Thirty-nine adult Indian elephants (Elephas maximus indicus) of both sexes and various ages and weights, belonging to the Forest Department of the Government of Kerala (India), Temple Devaswoms, Gemini Circus and other private agencies, were used to derive formulae to predict body weight and height from body measurements. Several models were fitted separately for males and females and also for adults irrespective of sex. The best prediction of body weight (W) in kg was obtained for adults irrespective of sex by using two parameters, the body length (L) in cm from the base of the forehead to the base of the tail, and the chest girth (G) in the formula W = -1010 + 0.036 (L x G). No single parameter gave as accurate a prediction of the body weight, and the inclusion of height as a third parameter did not improve the prediction. No significant improvement in the accuracy of prediction resulted from the use of different formulae for males and females. An equation to predict the height at the shoulders (H) in cm from the right forefoot circumference (C) in cm in adult elephants irrespective of sex was also derived. This was H = -1.60 + 1.99 C.

Animals↗
PubMed1992

A perceptual investigation of polytonality.

Four experiments investigated the perception of tonal structure in polytonal music. The experiments used musical excerpts in which the upper stave of the music suggested a different key than the lower stave. In Experiment 1, listeners rated the goodness of fit of probe tones following an excerpt from Dubois's Circus. Results suggested that listeners were sensitive to two keys, and weighted them according to their perceived importance within the excerpt. Experiment 2 confirmed that music within each stave reliably conveyed key structure on its own. In Experiment 3, listeners rated probe tones following an excerpt from Milhaud's Sonata No. 1 for Piano, in which different keys were conveyed in widely separate pitch registers. Ratings were collected across three octaves. Listeners did not associate each key with a specific register. Rather, ratings for all three octave registers reflected only the key associated with the upper stave. Experiment 4 confirmed that the music within each stave reliably conveyed key structure on its own. It is suggested that when one key predominates in a polytonal context, other keys may not contribute to the overall perceived tonal structure. The influence of long-term knowledge and immediate context on the perception of tonal structure in polytonal music is discussed.

Adult↗