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PubMed1986

Aminoacids and oscillatory electrocortical activity.

The effects of the local application of glutamate, aspartate, glycine, GABA and dl-alanine were studied upon the intact and isolated cortices of barbiturate anesthetized cats and upon the intact cortex of similarly anesthetized terrapin turtles. Repetitive responses following the DCR's, and the strychnine spikes, were observed, and sometimes a long duration oscillatory regular activity appeared after the treatment with those aminoacids. The oscillations had a frequency similar to that of the waves in a sleep spindle. They also occurred in the isolated cortex. The negativity of the DCR's may show different susceptibility from that of the negative component of the strychnine spikes, to the depressant action of the aminoacids. The conclusion is that the oscillatory electrocortical activity occurs in the cortex out from some subcortical influence. As a possible mechanism, it is suggested the establishment of a circus-movement type of activity involving the neurons and their dendritic apical and basilar branches. The aminoacids could act by favoring the opening of the low-resistance junctions present between dendrites, thus facilitating its synchronized activity.

Action Potentials↗
PubMed1985

[Pacing and right atrial ventricular dissociation in auricular stimulation in reciprocal tachycardia using an accessory pathway].

The effects of right atrial (RA) and coronary sinus (CS) stimulation have been studied in 13 patients with circus movement tachycardia (CMT). Tachycardia entrainment has occurred in all patients during RA pacing and in 11/13 during CS pacing, for a pacing rate 10 to 31 beats faster than the tachycardia rate. During RA pacing, short episodes of right atrial ventricular dissociation (6/13 patients) occurred but not during CS pacing. This can be explained by the anatomical proximity of the CS to the AV node (AVN) or by postulating two separate lateral inputs in the upper part of the AVN. Tachycardia entrainment is a criteria in favor of a reentry mechanism. It delineates a ranges of frequency between tachycardia rate and the slowest possible atrial stimulation rate capable of tachycardia termination which may be benefit for patients with drug resistant CMT, for whom antitachycardia pacemaker is envisaged.

Adolescent↗
PubMed1971

Physiopathology of Chagas' heart disease: correlations between clinical and experimental findings.

In penetrating the heart and developing in it, Trypanosoma cruzi produces an immunoallergic reaction that leads to changes in the histological structure of the myocardium; these changes alter the fundamental properties of the heart, causing fundamental dynamic disorders and morphological changes in the organ.In Chagas' cardiomyopathy, the velocity of impulse propagation diminishes in the auricular and ventricular musculature, altering the activation mechanism, this being shown by changes in the P-wave and in ventricular focal blocks.The functional refractory period (FRP) is shortened in the auricular and ventricular tissue and constitutes, together with changes in conductivity, the physiopathological basis that explains the circus movement-the fundamental factor of the arrhythmias of this stage of the disease. Localization of the inflammation in the A-V conduction system increases the duration of the FRP, producing all types of A-V block.The oedema and the cellular interstitial infiltration seen during this acute phase reduce the distensibility of the fibres; this, in turn, limits their contractility, producing a decrease in systolic volume and an increase in the final diastolic pressure in the chambers of the heart-fundamental factors in reducing kinesia and in increasing the heart's volume.In the chronic phase, destruction of the contractile tissue and fibroblastic proliferation bring into play compensatory mechanisms that maintain the strength of cardiac contractions; the elongation of the fibres and the nature of the dynamic pressure-volume curves explain the dilatation of the chambers of the heart and the dynamic changes seen in this phase of the disease.

Acute Disease↗
PubMed1978

[Repetitive supraventricular tachycardia. Case report and electrophysiologic bases].

A typical case of repetitive supraventricular tachycardia is reported. Periods of normal heart rate are interrupted by short bursts of supraventricular tachycardia. In the case described this phenomenon can be explained by coexistence of reentry and an automatic rhythm from a subsidiary pacemaker. This pacemaker was found to be in the bundle of His; its automaticity showed a rate somewhat faster than that of the sinus node. Careful analysis of the surface electrocardiograms allowed a definition of the electrophysiologic events starting a run of tachycardia. The circus movement entertaining the tachycardia itself was found to result from AV nodal reentry.

Bundle of His↗
PubMed1983

[Application of endocavitary mapping to the study of auricular flutter].

Many in vitro and animal experimental studies seem to support the hypothesis of reentry as the physiopathological mechanism of atrial flutter. Clinically, these studies are much more difficult because of problems in determining the different sequences of atrial depolarisation. In this study, the authors attempted to improve the technique of endocavitary atrial mapping. Three or four multi-recording electrodes were positioned in the atria using biplane 30 degrees RAO and 60 degrees LAO incidences. Right atrial angiocardiography showed up the atrial borders and enabled the recording catheters to be more accurately positioned. Thirty to 47 recordings points were thereby determined within the atrial cavities, the left atrium being studied via the coronary sinus, right pulmonary artery, patent foramen ovale or by the endooesophageal approach. This method of spatial orientation of the catheters associated with recording of the endocavitary potentials allowed the construction of an isochronic map of atrial depolarisation, which was then analysed for each case of flutter. The study confirmed two hypotheses: the asynchronism of right and left atrial depolarisation, and the circus motion of depolarisation. Three types of flutter were observed: --The first two types were similar with cirus motion within the right atrium. The wave front ascended in part or all of the septum and descended in the external free wall of the right atrium. There was a transitional zone, possibly reentrant, in the groove located anterior to the inferior vena cava. --The third type of flutter was atypical and was associated with cirus motion in the left atrium. Two transitional zones, similar to those encountered in the right atrium, were detected in one patient between the orifices of the pulmonary veins, and, in another patient, on the anterior part of the roof of the left atrium. These transitional zones seem to be at the basis of the physiopathological mechanism of flutter. Unfortunately, their small size makes their analysis by endocavitary mapping difficult.

Atrial Flutter↗
PubMed1983

Effects of diltiazem on vulnerability to atrial and ventricular reentrant arrhythmias in the normal and ischemic heart.

In experiments on 20 artificially ventilated anaesthetized dogs, the effects of the new calcium antagonist diltiazem on the stimulation thresholds to repetitive extrasystoles and fibrillation of the atria and the ventricles, respectively, and on ventricular dysrhythmias 6-24 h after acute coronary occlusion were investigated. The electrophysiological studies were performed using different methods of programmed stimulation of the heart. The results show that therapeutic doses of diltiazem provide no protection against stimulus-induced supraventricular reentrant arrhythmias with the AV-node not involved in the reentrant circus, and have no antifibrillatory efficacy in electrically induced ventricular arrhythmias in the non-ischemic heart. In acute myocardial infarction there is no antiarrhythmic effect either. Our results can be explained by the fact that diltiazem is a specific calcium antagonist and that the slow response plays only a minor role in the arrhythmias investigated.

Animals↗
PubMed1982

Verapamil in cardiac arrhythmias: an overview.

1. Verapamil remains the most widely used calcium antagonist for the treatment of cardiac arrhythmias. It is the most potent and effective drug for the acute treatment of paroxysmal supraventricular tachycardia particularly, circus movement tachycardia with or without pre-excitation. 2. As it is a powerful depressant of atrioventricular nodal conduction it reduces the ventricular rate in atrial flutter and fibrillation with reversion to sinus rhythm in a proportion of patients with these arrhythmias. Because verapamil does not increase airways resistance it can be used in patients with obstructive airways disease. The drug is also effective in supraventricular tachyarrhythmias following open-heart surgery and myocardial infarction. 3. It is not an effective drug against ventricular arrhythmias unless due to coronary artery spasm. The use of verapamil should be avoided in the presence of sick sinus node syndrome, clinical cardiac failure and treatment with other negative inotropic drugs.

Administration, Oral↗
PubMed1982

[Occult pre-excitation. Differential diagnosis between latent Wolf-Parkinson-White syndrome and concealed atrial pre-excitation (endocavitary electrophysiological study)].

Sixty patients (pts) with very disabling symptoms during supraventricular tachycardia (SVT) underwent electrophysiological study to determinate the mechanism of arrhythmia. 20 pts had, during normal sinus rythm (NSR), ECG pattern of ventricular pre-excitation (V-P); 40 pts, instead, had ECG pattern within normal limits (WNL). In V-P pts, circus movement tachycardia by overt accessory pathway (AP) was initiated. Among ECG-WNL pts group: 10 pts showed ectopic atrial rythm; 22 pts had SVT due to A-V nodal reciprocation; and 8 pts revealed the participation of concealed AP in the reentrant circuit of tachycardia. Among these latter, atrial stimulation at various sites and drugs-administration discovered extranodal by-pass liable for concealed V-P in 2 pts; in the remaining 4 pts it was possible to demonstrate concealed atrial preexcitation by ventricular stimulation, during NSR and SVT, and by atrial mapping during ventricular stimulation and SVT. Our report confirms the significative incidence of concealed AP at the basis of numerous cases of SVT (26%) and outlines the distinction between the latent W.P.W. syndrome and the atrial preexcitation, due to anomalous by-pass with anterograde block.

Arrhythmias, Cardiac↗
PubMed1982

[Ultrastructural study of the epithelium of the indifferent gonad in human embryogenesis].

Gonads from 10 human embryos (28 days -- 6 weeks of development) have been studied (stage of the indifferent gonad). The material is fixed in 3% glutaraldehyde, treated in 2% osmium tetraoxide solution and after dehydratation in alcohols embedded in araldit. Ultrathin sections are contrasted in uranyl-acetate saturated alcohol solution and then in lead citrate. The sections are studied by means of the electron microscope Tesla-613. At early stages of embryogenesis (28-32 days) the cells of the germ epithelium are polar; their main organells are localized in apical parts. The granular endoplasmic reticulum is especially well developed, its membranes have the form of either a spiral or concentric circuses, mitochondria accumulate as large clusters. The cells discharge, into the celoma, their secret containing certain structures which are morphologically identical to the elements of the agranular endoplasmic reticulum. By the 33d day of embryogenesis primary sex cords appear, their cells lose polarity. In these cells Golgi complex is especially well developed. Complex plexuses of cellular processes and powerful contacts of a lock type are formed. Divergent differentiation of the gonadal epithelium into superficial and sex cord epithelium is started. With an increasing size of the gonad, the latter predominates. It begins to perform the secretory function, while the superficial epithelium becomes less active.

Epithelium↗
PubMed1982

Concealed re-entry in the human heart.

The mechanism and electrophysiologic manifestations of concealed re-entry were studied in human electrocardiograms and intracardiac recordings. Previously described patterns of concealed re-entry were documented in 49 patients. In seven cases concealed re-entry was involved in the genesis of Wenckebach periodicity and alternating Wenckebach periodicity in the AV node, and "reversed" Wenckebach periods in the His-Purkinje system. These manifestations of concealed re-entry were not described so far. In five cases re-entry was apparently concealed. Complete (but hidden) circus movement of the supraventricular impulses in these patients were detected by intracardiac recordings and by analysing the effects of echo beats on timing of the subsequent sinus beats. Concealed re-entry of the cardiac impulse is a well-documented electrophysiologic event which explains many common and peculiar manifestations of impulse formation and impulse conduction in the human heart.

Arrhythmias, Cardiac↗
PubMed1994

[Intracardiac treatment of atrial flutter by radiofrequency currents].

Though not as common as atrial fibrillation, atrial flutter is frequently encountered in everyday cardiological practice. Though generally thought to be benign, it may be difficult to treat both in respect to its conversion to sinus rhythm and prevention of recurrences. It is often poorly tolerated. There are resistant, invalidating forms for which catheter ablation of the His bundle may be considered as a last resort. This is only a palliative measure even if effective from the functional point of view. A new technique for treating atrial flutter by a direct action on the atrial tissue has been recently introduced. The basis of this method is the concept of circus movement of the activation in the right atrium, the wave front circulating in an anti-clockwise direction in common atrial flutter. The postero-inferior region of the right atrium, at Koch's triangle, is the site of slow conduction and the target of choice for catheter ablation. The detection of this zone is determined by the endocavitary recording of fragmented, prolonged electrogrammes and by atrial stimulation techniques. The application of radiofrequency currents on these bases (high energy shocks are rarely used nowadays) results in interruption of atrial flutter. However, there are no data available concerning the long-term efficacy of this technique. Since 1992, our group has used an anatomical approach for catheter ablation. This aims to apply the radiofrequency current on the isthmus of atrial tissue between the orifice of the inferior vena cava and the tricuspid annulus through which the flutter wave front passes to reach the interatrial septum.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Flutter↗
PubMedDate not supplied

[Experimental anti-arrhythmic action of perhexiline].

The antiarrhythmic action of Perhexiline phosphate, in doses of 3 and 6 mg/kg on various experimental cardiac arrhytmias and on the physiological properties of the atrial myocardium has been studied in the anesthetized dog. Its action in concentrations of 3 and 6 mcg/ml on the transmembrane action potentials in isolated Purkinje fibers has also been analyzed. The activity of perhexiline is comparatively greater in the circus movement atrial flutter and in the arrhythmias caused by ouabain and by barium chloride intoxication than in the atrial tachysystolia caused by the local application of aconitine. Perhexiline prolongs the wave length (refractory period times conduction velocity) of the atrial impulse and depresses atrial excitability. These effects may explain its action on experimental atrial flutter. In isolated Purkinje fibers, perhexiline reduces the maximum velocity of depolarization, the overshoot, the amplitude of the action potential and its duration, measured at 50% of its repolarization phase. The relation of these electrophysiological effects of perhexiline to the genesis of each type of arrhythmia may explain its different type of activity in the experimental models studied.

Animals↗
PubMed1975

[Ventricular tachycardia due to premature supra-ventricular beats with a normal QRS complex. Analysis of a case].

Report of attacks of ventricular tachycardia in a 39 year-old man, free from heart disease. Cardiac pacing showed that the tachycardia could be induced by premature supraventricular beats normally propagated to the ventricles, and by atrial acceleration. The same part played by the cardiac rate on triggering of attacks was demonstrated during ventricular pacing. Besides, the possibility to interrupt the tachycardia by one electrically induced ventricular beat, supports the hypothesis of a re-entry machanism. The QRS configuration during the arrythmia suggested a propagation of excitation starting from the posterior-inferior area of the left ventricle. However, the absence of anomalies of the supraventricular beats initiating the tachycardia excluded a circus movement resulting from a unidirectional block on the left anterior hemibranch. More probably there existed an area of micro-reentry, stimulating the left ventricle from the posterior branches of the His-Purkinje system.

Adult↗
PubMed1993

[Electrotherapy of supraventricular tachycardia (atrial fibrillation/atrial flutter)].

Contrary to patients with the WPW-syndrome and AV nodal reentry in whom radiofrequency catheter ablation is the therapy of first choice for cure from these arrhythmias instead of life-long medical therapy, pharmacologic therapy of atrial fibrillation and atrial flutter remains the treatment of choice in these patients. If, however, atrial fibrillation with rapid atrioventricular conduction is medically intractable and associated with severe haemodynamic impairment, these patients may be offered catheter ablation of AV conduction by radiofrequency energy. Compared to DC ablation, this approach is associated by an acceptable complication rate. Including the left ventricular approach in cases where it is not possible to ablate AV conduction using the venous approach, the success rate to achieve third degree AV block approaches 100%. With the development of temperature-controlled radiofrequency catheter ablation, a further reduction of side effects is anticipated. A disadvantage of this approach is the need for permanent pacemaker implantation (usually rate-adaptive VVI stimulation) after induction of complete AV block. Therefore, the advantage of normalization of ventricular rate by ablation of AV conduction has to be weighed against the risk of life-long pacemaker treatment for complete AV block in every patient. Patients with medically intractable typical atrial flutter may be offered the following alternative modes of electric treatment: selective ablation of the area of slow conduction sustaining circus movement in the right atrium underlying atrial flutter, by radiofrequency energy without interrupting AV conduction, implantation of a permanent antitachycardia pacemaker with electrodes positioned in the right atrium, radiofrequency catheter ablation of AV conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗
PubMed1993

[Surgery for Wolff-Parkinson-White syndrome in the first year of life].

A case of surgical treatment for reentrant atrioventricular tachycardia in a 7 months old child is reported. Episodes of tachycardia were repetitive and long-lasting, often leading to signs of hemodynamic impairement, and were not controlled by antiarrhythmic drugs. The electrophysiologic study showed a circus-movement tachycardia utilizing a concealed accessory pathway located at the anterior septal aspect of tricuspid anulus. The child underwent successful surgical treatment by the endocardial technique. Few minutes after weaning from extracorporeal circulation, developed T wave inversion followed by acute right ventricular dysfunction and ventricular fibrillation. Others ischemic like episodes, maybe as a result of coronary artery spasm, occurring in the next 6 hours were successfully treated with isosorbide dinitrate. At 18 months follow-up, the child is free of tachycardia and has normal atrioventricular conduction.

Electrocardiography↗
PubMed1993

[Aneurysm spurium after resection of aortic coarctation].

25 years after reconstruction of an aortic coarctation by prosthetic material, an insufficiency of the anastomosis gave rise to the development of a false aneurysm. The aneurysm was resected and the anastomosis was reconstructed in parallel extracorporal circulation with femoral cannulation in order to prevent ischemic lesions of the spinal cord and the visceral organs. The patient who works as a circus acrobat, made a successful recovery.

Adult↗
PubMed1993

[Efficacy of adenosine triphosphate in terminating supraventricular tachycardia].

The efficacy of adenosine triphosphate (ATP) was tested in 23 patients suffering from supraventricular tachycardia; 10 patients had orthodromic circus movement tachycardia and 13 typical av nodal reentrant tachycardia. At a mean dose of 0.18 mg/kg all tachycardias were halted in less than 1 minute due to transient acute av nodal block followed by return to normal av conduction within 8 seconds. All patients had transient minor side effects. One elderly subject had a short episode of atrial fibrillation after the acute av block. In conclusion, ATP is useful and safe for rapid termination of supraventricular tachycardias incorporating the av node in their circuit.

Adenosine Triphosphate↗