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At least 847 records · Page 47Linked to original sources
PubMed1988

DDD pacing: an effective treatment modality for recurrent atrial arrhythmias.

We performed atrial EP studies (atrial substrate evaluation) on 10 patients. These patients had evidence of paroxysmal, sustained, recurrent atrial arrhythmias (7 men and 3 women with a mean age of 64 +/- 15 years). All patients combined a brady-tachy syndrome; 7 patients had a sick sinus syndrome (SSS) and 3 patients a typical vagally induced atrial arrhythmia. No anti-arrhythmic drug was allowed in 3 patients with SSS, 1 drug failed in 4 patients and the combination of 2 drugs failed in 3 patients during the first to eighth years prior to pacemaker implantation. Atrial substrate evaluation was feasible in all these patients off anti-arrhythmic therapy and showed important abnormalities of atrial loco-regional conduction parameters and long refractory periods (RP). The remarkable point was, in 7 patients, a paradoxical improvement in intra-atrial conduction delay at rapid pacing rate. The DDD pacing mode was chosen in all patients. No technical problem occurred during implantation. Atrial pacing rate was programmed to be slightly higher than the mean diurnal heart rate calculated on Holter monitoring. After implantation, the mean follow-up period was 18 +/- 25 months with an average of one Holter every 4 months during the first 2 years. The 7 patients who improved intra-atrial conduction at rapid pacing rate were controlled without drugs, 2 patients were controlled with 1 drug, and 1 patient with 2 drugs. Atrial pacing in the DDD mode in a selected group of patients prevents paroxysmal and drug-resistant atrial arrhythmias. Atrial substrate evaluation is a sensitive tool for assuring the long-term benefit of atrial pacing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Catheter ablation of atrioatrial conduction as a cure for atrial arrhythmia after orthotopic heart transplantation.

OBJECTIVES: We present three patients in whom atrial arrhythmia was treated by ablation of electrical conduction across a surgical suture line. BACKGROUND: Conduction across the suture line separating the donor and native right atria has recently been described after orthotopic heart transplantation. METHODS: Mapping and pacing of both grafted and recipient right atrium was performed to assess the relation between both atria and its relevance to clinical arrhythmia, prior to successful radiofrequency at the site of electrical communication. RESULTS: In cases 1 and 3, atrioatrial conduction was bidirectional. In both, two types of P waves were observed during sinus rhythm. In case 2, conduction from the recipient to the grafted atrium yielded a very particular surface ECG pattern of atrial extrasystole. The block being unidirectional, the recipient atrial sinus rhythm was not perturbed and behaved like an atrial parasystole. Ablation was performed during sinus rhythm in case 1, recipient right atrial pacing in case 2 and grafted right atrial pacing in case 3 at the site with the shortest conduction time to the other tissue. At the successful ablation site multiple component potentials were recorded. Respectively, 1, 4 and 2 radiofrequency pulses were followed by total atrioatrial conduction interruption. No tachycardia could be induced at the end of the procedure and late follow-up was event free. CONCLUSIONS: The existence of arrhythmogenic atrioatrial conduction should be taken into account when evaluating atrial arrhythmias in the transplanted heart because it is potentially curable by radiofrequency catheter ablation.

Adolescent↗
PubMed1986

A new animal model of atrial flutter.

A new, simple and reliable model of atrial flutter utilizing postpericardiotomy pericarditis was developed in the dog. Using a sterile technique, the pericardium was opened by way of a right thoracotomy, Teflon-coated, stainless steel wire electrodes were fixed to three selected sites on the atria and exteriorized, the atrial surfaces were generously dusted with talcum powder and a single layer of gauze was placed on the free left and right atrial walls. The dogs were allowed to recover. Subsequently, the inducibility of atrial flutter and selected electrophysiologic properties of the atria were determined by daily programmed atrial stimulation studies with the dogs in the conscious, nonsedated state. Atrial flutter could be induced in 23 of 25 dogs initially studied. It was sustained (that is, lasting greater than or equal to 5 min) in 17 of the 23. Neither atrial excitability, intraatrial conduction time nor atrial refractoriness determined by pacing and recording from the three fixed sites predicted the inducibility of atrial flutter. One hundred thirty-nine episodes of atrial flutter induced in these 23 dogs were analyzed. The mean sustained atrial flutter cycle length was 131 +/- 20 ms (mean +/- SD) (range 100 to 170); the atrial flutter cycle length was 150 ms or more in 23 episodes, between 120 and 150 ms in 64 episodes and 120 ms or less in 52 episodes. In five dogs, the stability of the atrial flutter cycle length during sustained atrial flutter was studied and shown to be remarkably stable in all five until interrupted by rapid atrial pacing 35 to 95 minutes after its induction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Emergency transvenous ablation of atrioventricular conduction to control refractory atrial tachycardia.

Three patients were referred for urgent investigation and treatment of refractory arrhythmias. Each patient had failed to respond to antiarrhythmic drugs and in two patients direct current cardioversion was also unsuccessful. Transvenous ablation of atrioventricular conduction was therefore thought appropriate. With a temporary ventricular pacing system in situ, a second electrode was used to record His and atrial electrograms. A 270 watt-second shock was delivered through this lead when the His potential was maximized. The tachycardia was controlled in two patients and the procedure was without deleterious effects.

Bundle of His↗
PubMed1994

[A case report of the maze procedure with mitral valve replacement].

The maze procedure was performed simultaneously with mitral valve replacement for atrial fibrillation and mitral stenosis in a 66-year-old female. On the first postoperative day, the cardiac status deteriorated suddenly due to a very rapid heartbeat which was later diagnosed as a 1:1 AV conduction of atrial flutter. The atrial flutter responded to an injection of verapamil and changed to a 2:1 conduction. Although atrial flutter had continued until the thirteenth postoperative day, the heart achieved sinus rhythm on that day. Since then it has continued without any antiarrhythmic drugs except digitalis. It was difficult to make a diagnosis of the rapid heartbeat on the 12-lead ECG because P waves could not be seen clearly on the ECG. Recording the electrical cardiac status by using the temporal atrial pacing leads, which were placed during the operation, was helpful in diagnosing the heartbeat as atrial flutter. The electrophysiological examination eight weeks after the operation revealed that the sinus node function was normal and atrial flutter or atrial fibrillation could not be induced. The patient is well and in sinus rhythm 12 months after the operation.

Aged↗
PubMed1991

Transesophageal versus intracardiac atrial stimulation in assessing anterograde conduction properties of the accessory pathway in Wolff-Parkinson-White syndrome.

Electrophysiologic intracardiac and noninvasive transesophageal testing, used to evaluate parameters of anterograde conduction across the accessory pathway, the refractory period and shortest atrial cycle length with 1:1 conduction over the pathway, were compared to assess the reliability of the noninvasive technique in identifying patients with Wolff-Parkinson-White syndrome, at risk of rapid ventricular response during atrial fibrillation when this arrhythmia is not inducible. Sixteen patients with Wolff-Parkinson-White syndrome were submitted both to invasive and transesophageal atrial stimulation. We evaluated both the functional and effective refractory periods of the accessory pathway, using the same drive cycle length, and the shortest cycle length with 1:1 atrioventricular conduction over the accessory pathway. There were no differences between the parameters obtained by intracardiac atrial stimulation and by transesophageal atrial stimulation. The two approaches correlated well: mean functional refractory periods of the accessory pathway were 285 +/- 42 msec and 289 +/- 32 msec, respectively (NS, r = 0.88); mean effective refractory periods of the accessory pathway were 267 +/- 41 msec and 271 +/- 32 msec, respectively (NS, r = 0.89); mean shortest cycle lengths with 1:1 conduction over the accessory pathway were 255 +/- 48 msec and 255 +/- 44 msec, respectively (NS, r = 0.94). These data demonstrate the reliability of transesophageal atrial stimulation in estimating the parameters for anterograde conduction across an accessory pathway. These results, and the already documented ability of transesophageal atrial stimulation to induce atrial fibrillation, suggest this noninvasive technique should be taken as a first approach in screening patients with Wolff-Parkinson-White syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Radiofrequency catheter ablation and modulation of atrioventricular conduction in patients with atrial fibrillation.

We attempted radiofrequency ablation of the AV junction with a sequential right- and left-sided approach in 78 patients affected by severely symptomatic, drug refractory atrial fibrillation. Stable third-degree AV block was obtained in 99% of cases and, after 3 months, persisted in 92% of cases. Single session, stepwise, radiofrequency modulation of the AV node was attempted in 13 patients with paroxysmal atrial fibrillation. During sinus rhythm, ablation of the slow and fast AV node pathways was performed in order to increase the nodal refractory period or to slow conduction. Clinically successful modulation of AV conduction was achieved in 15% of cases and persisted during a 3-month follow-up. In conclusion, AV junction ablation is a well-established means of treating atrial fibrillation, but implies the implant of a permanent pacemaker. AV node modulation avoids the pacemaker implant, but is efficacious only in a minority of patients. Thus, in patients affected by paroxysmal atrial fibrillation, AV modulation should be attempted first; if this is ineffective, AV ablation can be performed during the same session.

Aged↗
PubMed1991

[Estimation using unipolar transesophageal recording of the interatrial conduction time in patients with paroxysmal atrial flutter and fibrillation].

Twenty-three consecutive subjects (age 46.7 +/- 21, range 13-78) addressed to our attention for symptoms attributed to documented or suspected supra ventricular arrhythmias underwent transesophageal electrophysiologic study. On the basis of the preliminary investigations 15 proved free from organic heart disease, 2 were affected with ischemic heart disease (secondary angina), 6 with hypertensive cardiomyopathy. In each patient the sensibility, specificity and positive predictive value of the following reports regarding the occurrence of paroxysmal fibrillation and flutter (Ffap) were evaluated: a) echo reports of left atrial enlargement; b) ECG signs of atrial enlargement; c) interatrial conduction time (TCIA) assessed with unipolar transesophageal recording. As TCIA we adopted the time interval intercurrent from the first low-voltage deflection of the esophageal P wave (far field) and the apex of the intrinsecoid deflection of the same wave. TCIA proved significantly longer in the 12 patients affected with Ffap compared with those free from documented paroxysmal or inducible arrhythmias or affected with paroxysmal junctional reciprocating tachycardias: 76.6 +/- 11 vs 51.8 +/- 11.7; p less than 0.001. A TCIA greater than 63 msec characterizes with satisfactory sensibility and specificity the occurrence of Ffap: sens. 75%, spec. 91%, positive predictive value 90%. Echo and ECG reports of atrial enlargement behave as highly specific but not sufficiently sensitive indexes of the occurrence of Ffap: sens. 42%, spec. 100%, pos. pred. val. 100% and sens. 17%, spec. 100%, pos.pred.val. 100% resp. We concluded that TCIA is an index correlated with and predictive of the occurrence of Ffap in patients symptomatic for cardiopalmus or neurologic symptoms in the absence of other arrhythmias detectable with Holter monitoring which are able to produce clinical symptoms.

Adolescent↗
PubMed2003

[Feasibility of combination mapping utilizing a duo-decapolar electrode catheter and the CARTO system for incisional reentrant atrial tachycardia with cycle length alternation: a case report].

A 43-year-old woman had undergone patch closure operation for atrial septal defect 27 years ago. She was referred to our hospital for evaluation of frequent palpitations since 1 year ago. Electrophysiological study was performed with recording of the coronary sinus, His bundle, and low lateral right free wall electrography utilizing a steerable duo-decapolar electrode catheter(Livewire, Daig). Supraventricular tachycardia with cycle length alternation of 300 and 320 msec similar to atrial flutter was reproducibly provoked by burst pacing from the coronary sinus. During the supraventricular tachycardia, abnormal atrial potentials occurred in the low lateral right free wall region with very low amplitude and splitting potentials. The cycle length alternation of the supraventricular tachycardia depended on the occurrence of the splitting potentials, that is, the splitting potentials were present during the supraventricular tachycardia with a long cycle and the splitting potentials were absent during the supraventricular tachycardia with a short cycle. This phenomenon suggested that the splitting potentials resulted from 2:1 functional intra-atrial local conduction block. In addition, during sinus rhythm the abnormal electrograms revealed fractionated activity. Thus, these findings strongly imply that the supraventricular tachycardia is due to a macro-reentrant right atrial tachycardia utilizing an anatomical obstacle caused by the atrial septal defect operation as a central area, namely incisional reentrant atrial tachycardia. Three-dimensional electroanatomical mapping using the CARTO system(Biosense-Webster) was conducted to investigate whether the low lateral right free wall area possessed the critical isthmus essential to the reentry circuit. Electroanatomical mapping revealed that the very low amplitude potentials and the splitting potentials corresponded to the scars and the functional conduction block area detected by mapping using the multipolar catheter, respectively. According to the propagation mapping, the incisional reentrant atrial tachycardia slowly conducted the channel created by multiple neighboring scars clockwise and the alternation of the tachycardia cycle length was dependent on the development of the functional local intra-atrial conduction block within the channel. An approximately 1.5 cm successful linear lesion was created by radiofrequency catheter ablation to transect the isthmus based on the electroanatomical mapping findings. Afterwards, the incisional reentrant atrial tachycardia could not be induced by burst stimuli from the coronary sinus even under administration of isoproterenol. The use of three dimensional electroanatomical mapping(CARTO system) to evaluate the reentry circuit after the detection of abnormal potentials by using multipolar catheter in advance is a very useful method to determine optimal target site of ablation for a patient with incisional reentrant atrial tachycardia.

Adult↗
PubMed1985

N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165), a new antiarrhythmic agent: effects on cardiac conduction.

Effects of N-(2,6-dimethylphenyl)-8-pyrrolizidineacetamide hydrochloride hemihydrate (SUN 1165) on cardiac conduction were studied in anesthetized, anesthetized open-chest and conscious dogs and rabbit Langendorff hearts following either intravenous (i.v.) bolus injection and continuous infusion or intraarterial injection. SUN 1165 at antiarrhythmic doses (or concentrations), prolonged PQ interval in dogs inherently showing broad QRS complex without affecting QRS duration, but prolonged both PQ interval and QRS duration in dogs showing narrow QRS complex, in a dose-dependent manner. At higher doses (or plasma concentrations), SUN 1165 caused a marked prolongation of PQ interval together with QRS duration and subsequently, in most cases, elicited conduction block within the atrial muscle as evidenced by disappearance of P wave. SUN 1165 caused the dose-related prolongations of atrio-ventricular conduction time and intra-atrial conduction time, and at the highest dose it blocked conduction within the atrial muscle in some cases. In the rabbit Langendorff hearts, SUN 1165 tended to prolong intraatrial and His-Purkinje-ventricular conduction time in preference to atrio-ventricular one. At higher concentrations, SUN 1165 produced conduction block in the Purkinje-ventricular system. These results suggest that SUN 1165, at the antiarrhythmic doses (or plasma concentrations), causes a delay of cardiac conduction by acting on the atrial muscle and His-Purkinje-ventricular system without affecting conduction through A-V node region, and at higher doses (or concentrations) produces conduction block by acting again on the atrial muscle or on His-Purkinje-ventricular system without impairing conduction in the A-V node.

Animals↗
PubMed1978

Electrophysiological demonstration of concealed conduction in the human atrium.

In the course of electrophysiological evaluation of six patients with sick sinus syndrome, two patients with chronic conduction system disease and four patients with paroxysmal supraventricular tachycardia or atrial flutter-fibrillation, the phenomenon of concealed conduction within the atrium (At) was repeatedly observed. One pair of intracardiac electrodes was used to deliver electrical stimulus (St) to the high right At and two additional pairs of electrodes were utilized to record high right and low septal right atrial electrograms. The interelectrode distances were 10 mm apart. In all 12 patients, high right atrial capture could be accomplished at a pacing rate of greater than or equal to 200 beats/min. Concealed intra-atrial conduction was evident when the intra-atrial conduction time of the propagated St during 2:1 St-At block was more than 40 msec longer than that during 1:1 St-At conduction at half the St frequency. This indicated that the nonpropagated St during 2:1 St-At block partially penetrated the At and in turn, delayed conduction of the subsequently propagated St. Futher observations revealed that a gradual increase in the St frequency resulted in a progressive prolongation of the intra-atrial conduction time and a shifting of 2:1 to 3:1 St-At block (alternating Wenckebach periodicity in the At) in five patients. These findings clearly demonstrate the occurrence of concealed conduction in the human At.

Adult↗
PubMed2004

Digital 3D reconstruction of two parahissian accessory bundles in a case of Wolff-Parkinson-White syndrome.

Three-dimensional reconstruction of digitized histological serial sections of the cardiac conduction system yielded two accessory pathways in a case of a 24-day-old male infant who died after a short period of illness with ECG findings of Wolff-Parkinson-White syndrome. In infants, the differential diagnosis of possible accessory pathways connecting the AV conduction system, atrial or ventricular septum includes dispersed conduction system tissue without connecting features. This is why three-dimensional reconstruction is necessary in order to refute or establish connectivity of cell groups as found in histological serial slice images.

Autopsy↗
PubMed1985

Ventricular tachycardia and sudden death in myotonic dystrophy: clinical, electrophysiologic and pathologic features.

A 37 year old man who presented with a cardiomyopathy, conduction defects and atrial and ventricular arrhythmias was found to have the neuromuscular manifestations of myotonic dystrophy. Despite implantation of a permanent cardiac pacemaker, antiarrhythmic drug therapy and antiarrhythmic surgery, sudden death occurred. The results of electrophysiologic studies, coronary arteriography and pathologic findings are described. This case confirms previous observations that ventricular arrhythmias, in addition to atrial arrhythmias and conduction disturbances, are cardiac manifestations of myotonic dystrophy and can lead to sudden death.

Adult↗
PubMed1992

Voltage-dependent gating and single-channel conductance of adult mammalian atrial gap junctions.

In the heart, the rapid propagation and synchronization of action potentials necessary for a normal heart rhythm and an effective cardiac output are mediated by specialized ionic channels that link adjacent cells and are known collectively as gap junctions. Cardiac gap junctions are gated by various physiological and pharmacological agents, but the role of voltage in their gating is unclear. Whereas embryonic or neonatal ventricular cells have voltage-gated gap junctions, adult cells are reported to have only voltage-independent gap junctions. We studied the voltage dependence of adult rat atrial gap junctions by individually voltage clamping each cell of a connected cell pair and controlling the transjunctional voltage (Vj), measuring transjunctional current (Ij), and calculating junctional conductance (gj). Two distinct populations of cell pairs were observed: highly coupled pairs with the peak gjs ranging from 3.4 to 40 nS and weakly coupled pairs with the peak gjs ranging from 0.3 to 2.0 nS. gj was dependent on Vj, and Ij decayed exponentially, with the time constants being voltage dependent. Voltage dependence was most apparent when cells were poorly coupled. The gj did not decrease to zero. The normalized conductance--Vj plot was fit with a two-state Boltzmann model as a first approximation, resulting in a half-inactivation potential and gating charge of 42.5 mV and 1.14 eV, respectively, for the weakly coupled cell pairs. For highly coupled cell pairs, the half-inactivation potential shifted to 53.3 mV. Single gap junctional channels had a gj of 36.2 +/- 7.6 pS (range, 27-49 pS), which was Vj independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Evidence of specialized conduction cells in human pulmonary veins of patients with atrial fibrillation.

UNLABELLED: Specialized Conducting Cells in Human PV. INTRODUCTION: Depolarizations similar to those from the sinus node have been documented from the pulmonary veins after isolation procedures. We assessed the hypothesis that sinus node-like tissue is present in the pulmonary veins of humans. METHODS AND RESULTS: Pulmonary vein tissue was obtained from five autopsies (four individuals with a history of atrial fibrillation and one without a history of atrial arrhythmias) and five transplant heart donors. Autopsy veins were fixed in formaldehyde and processed for light microscopy to identify areas having possible conductive-like tissue. Areas requiring additional study were extracted from paraffin blocks and reprocessed for electron microscopy. Donor specimens were fixed in formaldehyde for histologic sections and glutaraldehyde for electron microscopy. Myocardial cells with pale cytoplasm were identified by light microscopy in 4 of the 5 autopsy subjects. Electron microscopy confirmed the presence of P cells, transitional cells, and Purkinje cells in the pulmonary veins of these cases. CONCLUSION: Our report is the first to show the presence of P cells, transitional cells, and Purkinje cells in human pulmonary veins. Whether these cells are relevant in the genesis of atrial fibrillation requires further study.

Adolescent↗
PubMed2000

The effect of a residual isthmus of surviving tissue on conduction after linear ablation in atrial myocardium.

The aim of this study was to determine the relationship between the size of discontinuities in lines of ablation and wavefront propagation. Discontinuities in linear radiofrequency lesions used for the treatment of atrial fibrillation may be proarrhythmic and a major clinical problem. A better understanding of the electrophysiological properties of these discontinuities (isthmuses) may assist in their detection and treatment. Linear lesions were made in the right atrial free wall using a Nd:YAG laser in 12 dogs. Conduction properties across the discontinuities were studied by pacing from either side of the lesion. Two of the three isthmuses less than 0.8 mm(2) in cross section (smallest 0.2 mm(2)) conducted at extrastimulus intervals of 300 ms. All three failed to conduct at cycle lengths close to the atrial effective refractory period. Isthmuses above 0.8 mm(2) (n¿=8) conducted at all cycle lengths. Conduction slowing (mean slowest conduction 0.5 +/- 0.3 m/s) occurred in the region of the isthmus but the overall delay was only 6 +/- 6 ms where propagation through the isthmus occurred. The effect on conduction of small discontinuities in linear lesions is dependent on the size of the residual isthmus. All but the very smallest of discontinuities in linear lesions conduct and therefore have the potential to participate in reentrant arrhythmias. Efforts should be directed toward the development of ablation techniques that reliably produce continuous transmural linear lesions for cure of atrial fibrillation and flutter.

Animals↗