Effect of body position on the ability to initiate paroxysmal supraventricular reentry tachycardias and on the conduction system properties of the reentry circuit

The obtainability as well as the maintenance and termination of paroxysmal supraventricular reentry tachycardias depend upon the interaction of the individual components of the reentry circle, in which cases the properties of the pathway are influenced by the changing preponderance of the sympathetic and parasympathetic tonus and thus also by the body position. In 29 investigations by means of highly frequent and programmed transoesophageal atrial stimulation the influence of the body position on the initiation possibility of the paroxysmal supraventricular tachycardia and on the pathway properties of the individual components of the reentry circle are analysed. The investigations were performed either in the standing position or in lying position, in 16 patients for the objectivation of anamnestically reported paroxysms of tachycardia and in 13 patients for the therapy control after medicamentous stabilisation. In 6 patients supraventricular reentry tachycardias could be initiated only in standing position, in lying position only a few echo systoles appeared. In 9 patients in whom we obtained a tachycardia both in standing position and in lying position in upright posture an in most cases clear increase of the frequency of tachycardia was found. The evocation mode of the tachycardia was partly alleviated in the standing position, but also rendered difficult in several cases. It seems to be indicated to repeat the investigation under orthostatic conditions, when an adequate anamnesis of the tachycardia is present and an initiation possibility in lying position is lacking, or when a great subjective impairment in a paroxysm of tachycardia is reported and there is a relatively low frequency of tachycardia in lying position.     

Electrical therapeutic procedures in recurrent, drug refractory tachycardias. II. Electrical transvenous catheter ablation

In 6 patients with medicamentously therapy-refractory tachycardias (3 times auricular flutter/auricular fibrillation with very rapid atrioventricular conduction, once focal atrial tachycardia, once paroxysmal atrioventricular reentry tachycardia, once recurrent ventricular tachycardia on the basis of an interventricular reentry) percutaneous transvenous catheter ablations of the atrioventricular conduction region (bundle of His ablation, 5 cases) and the right Tawara branch (1 case), respectively, were performed. During a follow-up period of 2-26 months (on an average 10.5 +/- 8.0 months) a permanent total block in 4 cases could be obtained (3 times AV-block III. once complete right bundle branch block). In two other patients the total AV block receded to the AV block I. and II. respectively, within 2 and 8 days, respectively; in the first case the AV node reentry tachycardias were no more to be evoked, in the second case a tolerable ventricular frequency was the result during the auricular flutter recidivations. In all patients treated by means of catheter ablation after the intervention an impressive improvement of the clinical symptomatology developed. Due to possible complication and the dependence upon the pacemaker of the patients concerned which is to be expected the indication to the ablation should be made only after the exhaustion of all medicamentous possibilities and taking into consideration other electric therapy methods.     

Anti-tachycardia radiofrequency pacemakers. Experience with 44 cases

Programmed cardiac stimulation may be performed externally using implanted radiofrequency receiving capsules. Between 1979 and 1984, 44 patients underwent implantation of these devices, 12 with atrial leads for supraventricular tachycardias (8 orthodromic reciprocating tachycardias, 1 intranodal junctional tachycardia and 3 atrial tachycardias), and 32 with ventricular leads for ventricular tachycardias. In the first case the transmitter was given to the patients so that they could terminate the tachycardias themselves. In the second case, the transmitter was kept in the cardiology department. All patients were also prescribed prophylactic antiarrhythmic drugs. The radiofrequency method was effective in 11 out of 12 cases of supraventricular tachycardia with a follow-up period ranging from 24 to 65 months (average 45 +/- 11 months). In the ventricular tachycardia group, the device was used in 11 patients to terminate ventricular tachycardia and in all patients to evaluate the efficacy of the antiarrhythmic therapy by provocative programmed stimulation with a follow-up ranging from 2 to 81 month (average 24 +/- 20 months). This palliative therapeutic method has reduced the number of hospital admissions in these patients. The indications are relatively few because of the efficacy of currently available antiarrhythmic agents and the possibility of radical treatment of tachyarrhythmias by surgery or catheter ablation.     

Intravenous flecainide acetate for the clinical management of paroxysmal tachycardias

Intravenous flecainide acetate (2 mg/kg) was administered to 40 patients undergoing routine electrophysiological evaluation for the investigation of recurrent paroxysmal tachycardias. Ten patients had recurrent atrial flutter, 11 patients had recurrent atrial fibrillation, one of whom also had paroxysmal left atrial tachycardia, and 19 patients had recurrent ventricular tachyarrhythmias (17 with recurrent ventricular tachycardia and 2 with recurrent fascicular tachycardia). Flecainide was administered during tachycardia (over 5 to 10 minutes) to all patients with atrial flutter, to 10 patients with atrial fibrillation, and to 17 patients with ventricular tachyarrhythmias. In the remaining 3 patients with ill-sustained arrhythmias flecainide was administered during sinus rhythm and reinitiation of tachycardia was then attempted. Flecainide restored sinus rhythm in only 2 patients with atrial flutter (20%), in 9 patients with atrial fibrillation (90%), in 12 patients with ventricular tachycardia (80%), and in one of the 2 patients with fasicular tachycardia. Flecainide also successfully terminated the left atrial tachycardia. Two patients experienced proarrhythmic side effects during flecainide administration, one of whom required intervention by cardioversion. Minor dose effects included oral paresthesia, transient drowsiness or dizziness, and occasional visual blurring. Flecainide acetate is an effective antiarrhythmic agent for the acute termination of recent onset paroxysmal atrial and ventricular tachyarrhythmias.     

Predictive value of induction of atrial flutter or fibrillation in paroxysmal junctional tachycardia

The association of different types of tachycardia in a given patient is a well-known phenomenon and the development of ablative methods rises hopes that treatment of one of them may suppress the others. The aim of this study was to determine the significance of induction of atrial flutter or fibrillation (AF) during electrophysiological investigation of patients investigated for paroxysmal junctional tachycardia. The initial population of 500 patients was limited to 485 patients, aged 12 to 86, with a normal intercritical ECG and without a Wolff-Parkinson-White syndrome, who underwent electrophysiological investigation for junctional tachycardias since 1978 and in whom the tachycardia could be reproduced. The study was performed by the endocavitary approach in 262 cases and by the transoesophageal approach in 213 cases with a similar protocol, programmed atrial stimulation with 1 and 2 extrastimuli under basal conditions, eventually completed by the repetition of the protocol with low doses of isoproterenol. The electrophysiological study showed that the tachycardia involved a latent bundle of Kent in 103 cases, a double nodal pathway in 343 cases or another circuit in 39 cases. During this study, sustained AF was induced in 66 cases (13.5%) with a similar incidence in Kent bundles (14.5%), intranodal reentry (11%) and other forms of reentry (11%). During follow-up, ranging from 6 months to 10 years, 7 patients with induced AF and 9 without inducible tachycardia, developed permanent AF. The occurrence of the arrhythmia was significantly correlated with the mechanism of reentry (latent Kent 8/103 cases, intranodal reentry 8/343 cases, p < 0.05), and with the induction of the same arrhythmia by oesophageal investigation alone (p < 0.001). The initiation of the arrhythmia by endocavitary stimulation did not seem to have any positive predictive value. In conclusion, the induction of atrial flutter or fibrillation during investigation of a subject with paroxysmal junctional tachycardia without a patent Wolff-Parkinson-White syndrome, does not seem to be predictive of future development of atrial flutter or fibrillation, unless the investigation was undertaken by the oesophageal approach.     

Transitory or permanent regular wide QRS complex tachycardia induced by atrial stimulation in patients without apparent heart disease. Significance

Objectives. - The purpose of the study was to evaluate the frequency of transitory or permanent bundle branch block (BBB) associated with a paroxysmal tachycardia induced by atrial stimulation in patients without heart disease and its significance.Methods. - Esophageal atrial stimulation was performed in 447 patients suspected to have supraventricular tachycardias (SVT). Sustained regular tachycardia was induced in all of them but three, either in control state (75%) or after administering isoproterenol. In 346 patients, only narrow complex SVTs were induced (77%); in 259 of them, the reentry occurred in the AV node and in remaining patients within a concealed accessory pathway. In 62 patients, a transitory functional BBB was recorded at the onset of the tachycardia (14%). In 33 of them, the reentry occurred in the AV node and in the remaining 29 patients within a concealed accessory pathway. In 36 patients (8%), a permanently wide QRS complex tachycardia was induced. Three patients had also inducible narrow complex SVT. Atrial pacing induced a BBB similar to the aberrancy in tachycardia in 22 patients: the reentry occurred in the AV node in 17 patients, within a concealed accessory pathway in three patients and in a Mahaim bundle in two patients. In other patients, QRS complex remained normal during atrial pacing: all 14 patients had a ventricular tachycardia (VT), either a verapamil-sensitive VT (n = 7) or catecholamine-sensitive VT (n = 4) or bundle branch reentry (n = 3). Followed from 2 to 12 years, the prognosis of these patients was excellent.Conclusion. - Transitory BBB at the onset of an SVT is noted in 14% of the population, is more frequent in patients with accessory pathway reentrant tachycardia, but is helpful for this diagnosis in only 12% of cases. A regular tachycardia with permanent left or right bundle branch morphology induced by atrial stimulation in a patient without heart disease and without BBB during atrial pacing is due to a VT even if this patient has also narrow complex tachycardias. This mechanism does not affect the excellent prognosis of this population.     

Ventriculoatrial intervals: diagnostic use in paroxysmal supraventricular tachycardia.

Reciprocating tachycardias due to reentry either within the atrioventricular (AV) node or using an accessory AV pathway are a common cause of paroxysmal supraventricular tachycardia in humans. Unfortunately, although of potential therapeutic value, differentiation of these forms of reciprocating tachycardia may be difficult and require detailed electrophysiologic study. To develop diagnostic criteria that permit exclusion of participation of an accessory AV pathway in reciprocating tachycardia without extensive laboratory testing, results of electrophysiologic studies were examined in 50 patients with Wolff-Parkinson-White syndrome, 15 patients with accessory AV pathways that conducted only in the ventriculoatrial direction, and 15 patients with reentry within the AV node. The interval between onset of ventricular activation and both earliest recorded atrial activity (V-Amin) and high lateral right atrial electrogram (V-HRA) was measured during tachycardia. A V-Amin of 61 ms or less or V-HRA of 95 ms or less did not occur in patients with accessory AV pathways, but occurred frequently (12 of 15 and seven or eight, respectively) in patients with reentry within the AV node. Therefore, in patients with paroxysmal reciprocating tachycardias, V-A interval measurements provide a screening test capable of excluding participation of an accessory AV pathway.     

The Response of Paroxysmal Supraventricular Tachycardia to Overdrive Atrial and Ventricular Pacing:

Pacing During Supraventricular Tachycardia. Introduction: Standard electrophysiologic techniques generally allow discrimination among mechanisms of paroxysmal Supraventricular tachycardia. The purpose of this study was to determine whether the response of paroxysmal Supraventricular tachycardia to atrial and ventricular overdrive pacing can help determine the tachycardia mechanism. Methods and Results: Fifty-three patients with paroxysmal Supraventricular tachycardia were studied. Twenty-two patients had the typical form of atrioventricular (AV) junctional (nodal) reentry, 18 patients had orthodromic AV reentrant tachycardia, 10 patients had atrial tachycardia, and 3 patients had the atypical form of AV nodal reentrant tachycardia. After paroxysmal Supraventricular tachycardia was induced, 15-beat trains were introduced in the high right atrium and right ventricular apex sequentially with cycle lengths beginning 10 msec shorter than the spontaneous tachycardia cycle length. The pacing cycle length was shortened in successive trains until a cycle of 200 msec was reached or until tachycardia was terminated. Several responses of paroxysmal Supraventricular tachycardia to overdrive pacing were useful in distinguishing atrial tachycardia from other mechanisms of paroxysmal Supraventricular tachycardia. During decremental atrial overdrive pacing, the curve relating the pacing cycle length to the VA interval on the first beat following the cessation of atrial pacing was flat or upsloping in patients with AV junctional reentry or AV reentrant tachycardia, but variable in patients with atrial tachycardia. AV reentry and AV junctional reentry could always be terminated by overdrive ventricular pacing whereas atrial tachycardia was terminated in only one of ten patients (P < 0.001). The curve relting the ventricular pacing cycle length to the VA interval on the first postpacing beat was flat or upsloping in patients with AV junctional reentry and AV reentry, but variable in patients with atrial tachycardia. The typical form of AV junctional reentry could occasionally be distinguished from other forms of paroxysmal Supraventricular tachycardia by the shortening of the AH interval following tachycardia termination during constant rate atrial pacing. Conclusions: Atrial and ventricular overdrive pacing can rapidly and reliably distinguish atrial tachycardia from other mechanisms of paroxysmal Supraventricular tachycardia and occasionally assist in the diagnosis of other tachycardia mechanisms. In particular, the ability to exclude atrial tachycardia as a potential mechanism for paroxysmal Supraventricular tachycardia has important implications for the use of catheter ablation techniques to cure paroxysmal Supraventricular tachycardia.     

Catheter ablation of monomorphic ventricular tachycardia

PURPOSE OF REVIEW: Patients with ventricular tachycardia are subject to frequent recurrences and antiarrhythmic drug therapy has been disappointing. Catheter ablation offers an alternative means of controlling ventricular tachycardia. RECENT FINDINGS: The origin and pathophysiology of ventricular tachycardia are being defined for newly recognized types of ventricular tachycardia as well as scar-related ventricular tachycardias. The approach to mapping and ablation of ventricular tachycardia depends on the nature of the arrhythmia substrate, which is largely determined by the underlying heart disease. Focal origin ventricular tachycardias often occur in patients without structural heart disease. The right ventricular and left ventricular outflow tracts are common locations. Ablation is usually successful unless the focus is epicardial in location or in close proximity to the ostia of a coronary artery. The reentry path for idiopathic left ventricular reentrant ventricular tachycardia is now defined. In patients with heart disease, most ventricular tachycardias are scar related, with areas of fibrous tissue forming the border for reentry paths. Substrate mapping defines areas of scar, abnormal conduction, and reentry circuit exits during sinus rhythm. Ablation of multiple ventricular tachycardias and unstable ventricular tachycardias performed largely during sinus rhythm is often possible. Ablation is usually adjunctive therapy to an ICD in these patients. Epicardial mapping and ablation are needed in some patients. SUMMARY: Ablation is a reasonable alternative to antiarrhythmic drug therapy for controlling frequent ventricular tachycardia episodes in many patients. Further technological advances can be anticipated.     

食管心房调搏诱发与终止房室折返性心动过速的研究

目的探讨经食管心房调搏诱发与终止房室折返性心动过速的价值。方法选择255例有心动过速发作史,并且既往心电图证实有阵发性室上性心动过速(PSVT)的患者行食管心房调搏检查。结果在被检的255例患者中诱发房室折返性心动过速229例,占89.8%(其中顺向型217例,占94.8%,逆向型12例,占5.2%)。诱发成功的最佳刺激方法为程序期前刺激法(S1S2、S1S2S3),诱发率为88.2%。诱发的必备条件是旁路有效不应期长于房室结有效不应期。在诱发房室折返性心动过速的229例中215例经电刺激成功终止,转复为窦性心律,成功率为93.9%,其中64例采用短阵快速刺激一次性成功终止,转复成功率达100%。结论食管心房调搏能有效地诱发与终止房室折返性心动过速,诱发顺向型房室折返性心动过速的关键因素是旁路不应期大于房室结有效不应期,终止发作的最有效的刺激方法为短阵快速刺激。本法可作为急诊终止阵发性室上性心动过速的首选方法。     

Diagnosis of the mechanism of reciprocating tachycardia by a simplified electrophysiological study

The authors attempted to identify the parameters which best differentiated intranodal reentry from tachycardias associated with an accessory pathway during a simplified electrophysiological study. The data were obtained by using two catheters, one recording right atrial activity and the other delivering programmed stimulation in the right ventricle. Sixty-four patients in whom the mechanism of their tachycardias had previously been determined were studied. There were 19 intranodal and 45 accessory pathway tachycardias. The following parameters were studied: the ventriculo-atrial interval during tachycardia; the prematurity of atrial activity in response to programmed ventricular stimulation; the shortest ventriculo-atrial interval when the atrial activity was premature; the difference between the shortest ventriculo-atrial interval with atrial prematurity and the ventriculo-atrial interval during tachycardia; in the absence of prematurity the ventriculo-atrial interval with the shortest ventricular coupling was used. The ventriculo-atrial interval during tachycardia was shorter in intranodal reentry (43 ms vs 170 ms, p less than 0.001). This interval was greater than 120 ms only in accessory pathway tachycardias and was only under 75 ms in patients with intranodal tachycardias. Premature atrial activation was observed in 42% of intranodal and 98% of accessory pathway tachycardias (p less than 0.001). The predictive value for tachycardias involving an accessory pathway was 85% when the auriculogramme was premature and, conversely, it was 92% for intranodal tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)     

A technique for the rapid diagnosis of atrial tachycardia in the electrophysiology laboratory

OBJECTIVE: The purpose of this study was to determine if the atrial response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction during paroxysmal supraventricular tachycardia is a useful diagnostic maneuver in the electrophysiology laboratory. BACKGROUND: Despite various maneuvers, it can be difficult to differentiate atrial tachycardia from other forms of paroxysmal supraventricular tachycardia. METHODS: The response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction was studied during four types of tachycardia: 1) atrioventricular nodal reentry (n = 102), 2) orthodromic reciprocating tachycardia (n = 43), 3) atrial tachycardia (n = 19) and 4) atrial tachycardia simulated by demand atrial pacing in patients with inducible atrioventricular nodal reentry or orthodromic reciprocating tachycardia (n = 32). The electrogram sequence upon cessation of ventricular pacing was, categorized as "atrial-ventricular" (A-V) or "atrial-atrial-ventricular" (A-A-V). RESULTS: The A-V response was observed in all cases of atrioventricular nodal reentrant and orthodromic reciprocating tachycardia. In contrast, the A-A-V response was observed in all cases of atrial tachycardia and simulated atrial tachycardia, even in the presence of dual atrioventricular nodal pathways or a concealed accessory atrioventricular pathway. CONCLUSIONS: In conclusion, an A-A-V response upon cessation of ventricular pacing associated with 1:1 ventriculoatrial conduction is highly sensitive and specific for the identification of atrial tachycardia in the electrophysiology laboratory.     

Pathophysiology of ventricular tachyarrhythmias

On 11 patients at the age between 11 and 60 years with ventricular tachyarrhythmias (6 times relapsing ventricular tachycardia, twice relapsing ventricular fibrillation, 3 times massive polytopic ventricular extrasystoles) complex intracardiac electrophysiological and haemodynamic examinations, including heart catheterization with angiography (and in 6 patients selective coronarography) were performed. In no case we succeeded in evoking a ventricular tachycardia by stimulation. Also the spontaneous long-lasting ventricular tachycardias could not be interrupted by a single or manifold stimulation. By multiple right- and left-ventricular potential deviations we succeeded in differentiating the ventricular tachycardia and ventricular extrasystoles, respectively, according to the place of origin in all patients. As cause of the ventricular tachycardia and of the ventricular fibrillation, respectively, in 4 patients an ectopic focus with increased impulse formation, in the other patients, apart from an increased ectopic automatism, also reentry tachycardia is assumed.     

Spectrum of regular tachycardias with wide QRS complexes in patients with accessory atrioventricular pathways

Reciprocating tachycardia and atrial flutter or fibrillation are the rhythm disorders most frequently documented in patients with accessory atrioventricular (A-V) pathways. Reciprocating tachycardia typically results in a regular tachycardia (140 to 250/min) with a normal QRS pattern, although on occasion bundle branch block aberration occurs. Atrial flutter or fibrillation may result in an irregular ventricular response, with the QRS configuration being normal or exhibiting bundle branch block or various degrees of ventricular preexcitation, or both. Although much less common than either reciprocating tachycardia or atrial flutter/fibrillation, regular tachycardias with a wide QRS complex suggestive of ventricular preexcitation are observed in patients with accessory pathways. Excluding functional or preexisting bundle branch block, several arrhythmias may cause these electrocardiographic findings which may mimic those of ventricular tachycardia.In the present study a variety of arrhythmias that resulted in tachycardias with a wide QRS complex were examined in 163 patients with accessory pathways who underwent clinical electrophysiologic study for evaluation of recurrent tachyarrhythmias. Twenty-six patients (15 percent) manifested a regular tachycardia with a wide QRS complex suggesting ventricular preexcitation. Atrial flutter with 1:1 anterograde conduction over an accessory pathway (15 of 26 patients, 58 percent) was the most frequent arrhythmia and was usually associated with a heart rate of 240/min or greater (12 of 15 patients). Reciprocating tachycardia with conduction in the anterograde direction over an accessory pathway (antidromic reciprocating tachycardia) occurred in 7 of 26 patients (27 percent), and resulted in a slower ventricular rate than atrial flutter (217 ± 22 versus 262 ± 42, P < 0.01). Other arrhythmias included reciprocating tachycardia with reentry utilizing a fasciculoventricular or nodoventricular connection (two patients, 8 percent), reciprocating tachycardia with reentry in the atrium or A-V node and anterograde accessory pathway conduction (one patient, 4 percent) and ventricular tachycardia (one patient, 4 percent).In this study the clinical electrophysiologic diagnostic features of several arrhythmias which cause tachycardias with a wide QRS compex suggesting ventricular preexcitation are outlined. It is apparent that definitive arrhythmia diagnosis during these tachycardias is often complex and usually requires careful study using intracardiac electrode catheter techniques.     

Initial experience with a fully implantable,programmable, scanning,extrastimulus pacemaker for tachycardia termination

Summary: A fully implantable automatic scanning pacemaker designed for tachycardia termination has been used in three patients with regular paroxysmal supraventricular tachycardia. The pacemaker recognizes tachycardia and delivers one or two extrastimuli which automatically scan inwards if tachycardia continues. A memory is incorporated to retain and immediately reuse a successful pacing sequence if tachycardia recurs. Ventricular pacing has been used in two patients and atrial stimulation in one. Although all had suffered frequent attacks of tachycardia after implantation no sustained episodes of tachycardia have been appreciated. No unwanted arrhythmias have been induced and drug treatment has been stopped in all three patients. Fully implantable scanning pacemakers which automatically recognize and revert tachycardia offer an effective and versatile form of treatment for recurrent paroxysmal tachycardias.     

Value of esophageal pacing in evaluation of supraventricular tachycardia

Esophageal stimulation was performed in 40 patients who had spontaneous paroxysmal supraventricular tachycardias (SVTs). The purpose of this study was to look for the most sensitive stimulation protocol and criteria that would help to define the mechanism of reentry. In 20 patients (group I) atrial pacing up to second-degree atrioventricular block was performed under control conditions and isoproterenol, and SVT was induced in 14 patients (70%), 11 in the control state and 3 while receiving isoproterenol. In 20 patients (group II) atrial pacing and programmed atrial stimulation using 1 and 2 extrastimuli delivered at 2 cycle lengths (600 and 500 ms) was performed in the control state and while receiving isoproterenol. SVT was induced in all patients, in 13 patients in the control state and in 7 while receiving isoproterenol. Programmed stimulation always induced SVT and was the only method capable of tachycardia induction in 14 patients. The mechanism of SVT could be established in 91%. The measurement of the ventriculoatrial interval was the most useful sign to define the site of reentry. Occurrence of a bundle branch block helped to delineate the mechanism in 4 patients. When a positive P wave in V1 preceded the esophageal atrial electrocardiogram, it suggested that there was reentry through a left-sided accessory atrioventricular connection in 6 patients. SVT could always be induced by programmed atrial stimulation in the control state and under isoproterenol. The location of the P wave in V1 compared to the ventriculogram and the esophageal electrocardiogram helped to define the mechanism of tachycardia.     

Combined anti-bradycardia/anti-tachycardia pacemaker-cardioverter-defibrillator systems in patients with recurrent ventricular tachyarrhythmias]

In 41 patients with recurrent sustained ventricular tachycardia and/or ventricular fibrillation an integrated pacemaker-defibrillator-system (PCD, Medtronic, model 7216 A or 7217 B) was implanted. In 21 out of 24 (88%) patients a new transvenous implantation technique in combination with a subcutaneous patch electrode was used. The implanted devices comprise antibradycardiac pacemaker functions, two different forms of antitachycardiac pacemaker functions (ramp and burst pacing), and internal cardioversion or defibrillation capabilities. During a mean follow-up of 8 months 147 episodes of ventricular tachycardia were detected, 131 of them were terminated successfully by antitachycardiac pacing; in 13 episodes internal cardioversion was applied to revert ventricular tachycardia. Twenty-seven episodes of ventricular fibrillation or rapid ventricular tachycardia (greater than 200/min) were detected and successfully terminated by internal defibrillation. In six patients with intermittent rapid atrial fibrillation, change of antiarrhythmic therapy was required to avoid activation of the device. The new integrated pacemaker-defibrillator systems improve therapy in patients with life-threatening tachyarrhythmias by reducing the number of internal cardioversions/defibrillations; the non-thoracotomy approach reduces the post operative risk.     

Bundle branch reentry tachycardia: a possible mechanism of flecainide proarrhythmia effect

A 42-year old man with non-obstructive myocardiopathy complicated by paroxysmal atrial fibrillation treated with amiodarone (200 mg per day) received flecainide in daily doses of 400 mg for undocumented palpitations. Ten syncopes and numerous malaises occurred during the following two months. Electrophysiological testing was performed, showing prolongation of HV to 80 ms and discreet widening of QRS to 100 ms. Programmed atrial stimulation failed to demonstrate a second degree subnodal block and to induce tachycardia. In contrast, ventricular stimulation elicited a critical SH delay (260 ms), always followed by a left delay-type complex preceded by His bundle deflection which suggested reentry within the His-Purkinje system. Three extrasystoles on imposed rhythm started sustained ventricular tachycardia with the same 270 ms cycle morphology and reproducing the symptoms. Each V wave was preceded by an H potential, with HV varying from 100 to 300 ms. Three weeks after flecainide was discontinued, HV was 60 ms, and no ventricular tachycardia could be triggered by programmed stimulation. The patient remained symptom-free throughout the 5-month follow-up. This case illustrates the proarrhythmic effect of the flecainide-amiodarone combination. The mechanism of provoked tachycardia probably involves ventricular reentry through the His bundle branches, induced by a critical depression of conduction below the His bundle.     

Diagnostic value of the isoproterenol test in effort tachycardia

An isoproterenol test was performed in 69 patients during electrophysiological investigation to assess its diagnostic value in adrenergic supraventricular or ventricular tachycardia. Sixteen control subjects had no symptoms on exercise and routine exercise stress testing did not trigger any hyperexcitability. Sixteen patients had reproducible documented supraventricular tachycardia induced by exercise (13 paroxysmal junctional tachycardias, 3 focal atrial tachycardias). Eight patients had ventricular hyperexcitability related to effort. Twenty-nine patients had supraventricular and/or ventricular hyperexcitability only at rest. Electrophysiological investigations included paired atrial stimulation during sinus rhythm and paced rhythm followed by programmed ventricular stimulation using one and then two extrastimuli delivered during sinus rhythm and paced ventricular rhythm. These stimulation studies were carried out under basal conditions and then during low dose isoproterenol infusion (10 to 40 micrograms) which accelerated the heart rate to 130/mn. Electrophysiological and conduction parameters and the mode of induction of the tachycardia (defined as at least 5 successive echos with a configuration similar to the clinical tachycardia) were studied. We observed an acceleration of anterograde and retrograde conduction and a shortening of the effective atrial and ventricular refractory periods but these changes were found equally in the different groups of patients and were not related to the induction of tachycardias. The induction of paroxysmal junctional tachycardia by isoproterenol was a very sensitive (92%) and specific (100%) diagnostic method. Its diagnostic value was much greater than Holter monitoring (25%) and exercise stress testing (12.5%). Induction of ventricular tachycardia by isoproterenol was also very sensitive (75%) and specific (95%). The diagnostic value was higher than exercise stress testing (71%) and Holter monitoring (62%). Isoproterenol did not affect the induction of spontaneous tachyarrythmias unrelated to effort and even suppressed the triggering of some episodes. In conclusion, the induction by atrial or ventricular pacing or spontaneous supraventricular or ventricular tachycardia during isoproterenol infusion was very specific and correlated with the concept of tachycardia induced by exercise and therefore of adrenergic nature. The sensitivity of this test was excellent in patients with supraventricular tachycardia (95%) and very good in ventricular tachycardia (75%). On the other hand, the changes in the electrophysiological parameters were not specific for a group of patients.     

Cryoablation of a Nodoventricular Mahaim Fiber

An 11-year old female presented with paroxysmal tachycardia and was diagnosed with a Mahaim fiber during electrophysiologic study. A preexcited tachycardia and the typical variety of AV nodal reentry tachycardia were induced at different times. During preexcited tachycardia, the His bundle electrogram followed the ventricular electrogram, and, introduction of atrial premature beats at different coupling intervals, advanced the peri-AV nodal atrial tissue, with no change in the ventricular cycle length, leading to a diagnosis of an antidromic tachycardia due to a nodoventricular fiber. Cryoablation at a mid-septal location under three-dimensional guidance successfully eliminated both tachycardias without detrimental effects to the AV node.