Atrioventricular Tachycardia Research Articles

Successful catheter ablation by radiofrequency energy of posteroseptal accessory pathway in a patient with drug refractory Wolff--Parkinson--White syndrome

A 45-year-old patient with the Wolff-Parkinson-White syndrome suffering from recurrent intractable reciprocating atrioventricular tachycardia (RAVT) is reported. He used amiodarone, sotalol, quinidine, propafenone and flecainide unsuccessfully. An electrophysiological study (EPS) performed with four catheters localized the site of the anomalous pathway in the ostium of the coronary sinus. In this region we could also record a Kent potential. In the ostium of the coronary sinus, radiofrequency energy was repeatedly applied until the conduction over the accessory pathway was abolished both in the anterograde and the retrograde direction. The Kent deflection detectable before ablation, could not be detected after it. During follow-up (1 month) the patient remained asymptomatic and the control EPS showed no evidence of pre-excitation, either anterogradely or retrogradely.

Diagnosis and Surgical Treatment of Tachycardias in Patients with Nodoventricular Fibers

From May, 1982 to April, 1991 25 patients were examined and 23 had open heart surgery for tachycardia with nodoventricular fibers (NVF) participation. All patients suffered tachycardia for more than 5 years. Most patients had syncope. The patients had: true NVF tachycardia (11), atrioventricular node reentry tachycardia (5), orthodromic atrioventricular tachycardia (AVT) (5), and atrial flutter (1) all with passive propagation through NVF, pseudonodoventricular tachycardia (AVT with slow accessory pathways) two patients. In 18 out of the 23 who had surgery there were no signs of preexcitation or tachycardia events in the follow-up period.

Diagnostic Value of Synchronized Transesophageal Atrial Pacing

Synchronized transesophageal atrial pacing (single and double extrastimuli) was used in 137 patients with various tachycardias inducible by atrial pacing during transesophageal electrophysiological study (EPS). This pacing mode in five patients initiated atrioventricular tachycardias with ipsilateral bundle branch block not seen when using other pacing modes. During the tachycardia, single or double extrastimuli caused ipsilateral bundle branch block disappearance in two patients with atrioventricular tachycardia, and changed AV activation ratio in one patient with atrioventricular junctional reentrant tachycardia. This pacing mode causes very little discomfort, what is important in children, and enhances diagnostic abilities of transesophageal EPS. So, this pacing mode should be used routinely as one of the steps of transesophageal EPS.

Signal averaging of the electrocardiogram in the remote differential diagnosis of broad complex tachycardias

The diagnosis of the origin of a broad complex tachycardia may be difficult, especially in the absence of a 12-lead electrocardiogram of the tachycardia. This study investigates the value of signal averaging in the differential diagnosis of broad complex tachycardia. Signal averaging during sinus rhythm was performed in 102 consecutive patients who presented with broad complex tachycardia (QRS width greater than 110 ms), in whom a definitive electrophysiological diagnosis was made. The presence of late potentials was determined on the basis of two definitions, the second including total QRS duration. The patients studied included 75 with ventricular tachycardia; 33 of these patients had suffered previous myocardial infarction, five had dilated cardiomyopathy, and 37 had a 'normal' heart. Of the 27 patients with supraventricular tachycardia, 22 had an atrioventricular accessory pathway (seven with a delta wave in sinus rhythm), three had atrioventricular nodal tachycardia and two had atrial tachycardia. The sensitivity of late potentials for the diagnosis of ventricular tachycardia was low utilizing both definitions (28% and 45%) although specificity was high (96% and 95%). The sensitivity for the diagnosis of ventricular tachycardia was higher for patients with ischaemic heart disease (43% and 70%) but very low for patients with ventricular tachycardia and a normal heart (16% and 22%). In conclusion, signal averaging in the remote diagnosis of broad complex tachycardia is specific but not sensitive for ventricular tachycardia, which limits its usefulness in selecting patients for electrophysiological study.

Antiarrhythmic Treatment of Atrioventricular Tachycardias

Atrioventricular (AV) tachycardia includes both AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT) using an accessory pathway. The treatment of the acute attack is different from the long-term treatment of both AVNRT and AVRT. Verapamil and adenosine, by prolonging the refractory period of the AV node, are highly effective in terminating acute attacks of AVNRT and orthodromic AVRT. Conversion to sinus rhythm is achieved in approximately 90% of the episodes of tachycardias with both agents given intravenously. The initial dose of verapamil is 0.075-0.1 mg/kg and a subsequent bolus of 5 mg can be given to a maximal dose of 15-20 mg. The initial dose of adenosine is 3 or 6 mg, but doses of 9 or 12 mg can be administered if smaller dosages have been unsuccessful. Other agents producing lengthening of the refractory period of the accessory pathway in AVRT or of the fast pathway in AVNRT often terminate reentry tachycardia. Such agents are class IC antiarrhythmic drugs such as flecainide or propafenone and class IA drugs such as procainamide. In patients with accessory pathways and antidromic tachycardia or atrial fibrillation conducting via an accessory pathway, treatment with verapamil or digoxin should be avoided because these agents may enhance the conduction properties of the accessory pathway, thereby leading to an increase of the ventricular rate or even to ventricular fibrillation. Prevention of AVNRT episodes can be obtained with various antiarrhythmic drugs. Digoxin alone or in combination with beta-blockers is effective in approximately 50% of the cases and especially when the combination proved to be successful during electrophysiological testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic discrimination between antidromic tachycardia and atrioventricular nodal tachycardia with pre-excitation

Electrophysiologic discrimination between antidromic tachycardia and atrioventricular nodal tachycardia with pre-excitation

Anatomically guided surgery to the AV node *1AV nodal skeletonization: experience in 46 patients with AV nodal reentrant tachycardia

We report our combined experience with operative therapy for atrioventricular nodal tachycardia using an anatomically guided procedure. The operative rationale was to dissect the AV node with the intent of modifying perinodal tissues (skeletonization). The anterior septal and posterior septal regions were initially approached epicardially to facilitate endocardial dissection. Under normothermic cardiopulmonary bypass, the right atrial septum was mobilized and the intermediate AV node was exposed anterior to the tendon of Todaro. Ablation of concomitant accessory pathways was done prior to AV nodal skeletonization. Forty-six patients aged 9-71 years (mean 36) were operated upon. Five patients had accessory pathways in addition to AV nodal reentry. At electro-physiological study prior to discharge, no patient had an AV block although anterograde and retrograde Wenckebach cycle lengths were significantly prolonged. Ten patients had a retrograde AV block. The 46 patients were free of arrhythmia and not taking antiarrhythmic medication after a follow-up of 1-45 months (mean 17). Three patients had a recurrence of the tachycardia 10 days, 2 months and 7 months post-operatively, respectively. All patients had a subsequently successful reoperation.

Management of Stokes-Adams Syndrome

Stokes-Adams attacks are related to paroxysmal or chronic atrioventricular (AV) block (50-60%), sinoatrial (SA) block (30-40%) or paroxysmal tachycardia or fibrillation (0-5%). In between attacks most patients present with sinus rhythm, a large part with widened QRS complex. A minor proportion of patients present with chronic AV block. ECG is very rarely normal. Diagnosis is based on ECG recording during fainting. In patients with sinus rhythm and bundle-branch block or AV block, ECG monitoring should be performed in hospital, since Stokes-Adams syndrome in these patients is a potentially life-threatening disease. In sick sinus syndrome where the suspected arrhythmia is not life-threatening, ambulatory ECG by Holter monitoring can be performed to establish the diagnosis. In cases where ECG monitoring leaves doubt, an electrophysiologic study including His bundle electrography and sinus node recovery time may support the diagnosis, although normal findings do not preclude the diagnosis. Pacemaker implantation should be performed in Stokes-Adams syndrome, as oral drug treatment is ineffective. The dual-chamber pacemaker presents the advantages of both physiological heart rate and AV synchrony, but has troublesome side effects. Most patients with tachycardia/bradycardia syndromes require supplementary anti-arrhythmic treatment, and in some patients additional long-term anticoagulation should be considered.

Entrainment of Ventricular Tachycardia by Sinus Rhythm

Entrainment of ventricular tachycardia (VT) may be manifest as fixed and progressive QRS fusion with ventricular and, rarely, atrial pacing. Only a single example of spontaneous VT entrainment by another rhythm, rapid atrioventricular nodal tachycardia, has been reported. This article describes an example of fixed and progressive QRS fusion between conducted sinus rhythm and VT consistent with entrainment. In contrast to entrainment with pacing, entrainment of VT by sinus rhythm occurred with drug-mediated arrhythmia slowing and demonstrated progressive QRS fusion at a constant cycle length. However, it did not demonstrate unfused but entrained QRS complexes. The resulting short PR interval and wide QRS mimicked a preexcited rhythm.

Treatment of atrioventricular node reentrant tachycardia with encainide: Reversal of drug effect with isoproterenol

To determine the efficacy of encainide in the treatment of atrioventricular (AV) node reentrant tachycardia, Holter electrocardiographic (ECG) monitoring, exercise treadmill testing and programmed electrical stimulation were performed in 16 patients while they were taking no medication and after steady state levels were reached during treatment with encaini+de (75 to 200 mg/day; mean 117 ± 47). In addition, to study the possible reversal of drug effects by sympathetic stimulation, AV node conduction and tachycardia induction were reassessed during isoproterenol infusion (1 to 3 μg/min), a dose calculated to increase the rest heart rate by 25 ± 10%.Sustained AV node reentrant tachycardia could be initiated in all 16 patients in the control state, in 2 patients after encainide and in 10 patients during isoproterenol infusion. The shortest mean atrial paced cycle length sustaining 1:1 AV conduction was 358 ± 57 ms during the control study, which increased to 409 ± 59 ms with encainide (p < 0.01 versus control) and decreased to 313 ± 31 ms during isoproterenol infusion (p < 0.01 versus control and encainide). he shortest mean ventricular paced cycle length with 1:1 ventriculoatrial conduction was 337 ± 56 ms in the control study, 551 + 124 ms with encainide infusion (p < 0.01 versus control) and 354 ± 72 ms during isoproterenol infusion in the encainide-loaded state (p < 0.01 versus both control and encainide).During a mean follow-up period of 19 ± 10 months, significant clinical recurrences occurred in 4 of the 10 patients in whom tachycardia could still be initiated with encainide (with or without isoproterenol). In contrast, no significant episodes occurred in the six patients in whom tachycardia could not be induced with encainide despite isoproterenol infusion. Suppression of atrial or ventricular ectopic activity with encainide during Holter ECG monitoring did not appear to correlate with clinical recurrence. It is concluded that: 1) encainide is an effective agent for control of AV node reentrant tachycardia, primarily by virtue of its depressant effect on retrograde pathways; and 2) failure to induce tachycardia in the medicated state despite isoproterenol infusion predicts freedom from tachycardia recurrence.

Complete atrioventricular dissociation and His bundle tachycardia in a newborn: problems in prenatal diagnosis and postnatal management

A newborn infant with complete atrioventricular dissociation and infranodal tachycardia, detected at 33 weeks gestation by fetal echocardiography, is described. In the perinatal period, infra or juxta-nodal tachycardia was noted, compromising the hemodynamic state of the newborn. A combination of flecainide and propranolol terminated the arrhythmia.

Ventricular paired pacing to control intractable junctional tachycardia following open heart surgery in a child

A 5-month-old girl presented postoperatively with an atrioventricular (A-V) junctional tachycardia at a rate of 245/min following surgical repair of tetralogy of Fallot. The systolic blood pressure dropped to 60 mmHg with this rapid heart rate, and the infant became shocked. Drugs and overdrive pacing were ineffective in suppressing the A-V junctional tachycardia and in improving cardiac output. Ventricular paired pacing was used successfully to halve the mechanically effective ventricular rate and to restore cardiac output. When ventricular paired pacing was stopped after 12 h, the spontaneous rhythm was an atrial rhythm with 1-1 A-V conduction. The patient was discharged in sinus rhythm on the 5th postoperative day.

Experience with flecainide for the treatment of cardiac arrhythmias in children.

We treated 22 children, aged 3 days to 16 years 6 months (median 11 years 1 month), with flecainide for a variety of arrhythmias where a Class I agent was indicated. In 16, conventional antiarrhythmic treatment had failed. Structural heart disease was present in nine. The arrhythmia was paroxysmal re-entry atrioventricular tachycardia in nine; paroxysmal atrial tachycardia, flutter or fibrillation in five; paroxysmal ventricular tachycardia in five and frequent ventricular extrasystoles (with couplets) in three. Sinus rhythm was achieved in all four children who received flecainide during tachycardia (three received intravenous flecainide, one oral). During follow-up of 3-24 months (median 12 months), arrhythmia control was obtained in 13 children (59%). Combination therapy was used in seven of these; with digoxin in four and a beta blocker in three. Flecainide doses used in this study ranged from 1-11 mg kg-1 day-1 (median 4 mg kg-1 day-1), 25-297 mg m-2 day-1 (median 113 mg m-2 day-1). The median, pre-dose flecainide concentration in those responding to therapy was 225 micrograms l-1 and in those failing to respond was 417 micrograms l-1. An arrhythmogenic effect occurred in one child.

Electrophysiologic and clinical effects of flecainide for recurrent paroxysmal supraventricular tachycardia

The antiarrhythmic effects of flecainide acetate were evaluated in 9 patients with paroxysmal atrioventricular (AV) nodal tachycardia and 17 patients with AV tachycardia. An electrophysiologic study was performed before and after intravenous flecainide acetate, 2 mg/kg body weight, was infused over 15 minutes and was followed by a maintenance infusion of 1.6 mg/kg given over 1 hour to 26 patients and during oral treatment to 15. Treatment with oral flecainide acetate was continued for 14 ± 5 months. Intravenous flecainide acetate terminated AV nodal tachycardia by blocking the retrograde fast pathway conduction in 7 of 7 patients and AV tachycardia by blocking retrograde conduction in the extranodal pathway in 10 of 10 patients. AV nodal tachycardia and AV tachycardia were noninducible in 8 of 9 patients (90%, p < 0.001) and 11 of 17 patients (65%, p < 0.001), respectively. Long-term treatment with oral flecainide acetate suppressed AV nodal tachycardia and AV tachycardia in 8 of 9 patients (90%, p < 0.001) and 11 of 17 patients (65%, p < 0.001), respectively. A favorable outcome was associated with block in the accessory pathway after intravenous flecainide acetate and noninducibility during oral treatment. Recurrences preferentially occurred in the younger patients. Flecainide acetate is effective in the acute and long-term management of paroxysmal supraventricular reentry tachycardia by suppressing conduction through the retrograde fast limb of the tachycardia circuit. The clinical effect can be predicted by electrophysiologic testing.

Subthreshold atrial pacing in patients with a left-sided accessory pathway: An effective new method for terminating reciprocating tachycardia

This study investigated the possibility of terminating reciprocating atrioventricular (AV) tachycardia using subthreshold atrial pacing. Ten patients with a left-sided accessory pathway and sustained AV tachycardia underwent suhthreshold atrial pacing from the coronary sinus site closest to insertion of the accessory pathway. In seven of these patients, the tachycardia could be reliably terminated with subthreshold atrial overdrive pacing. When pacing at a cycle length of 80 ± 23% of the tachycardia cycle length, the minimal subthreshold current that was effective in tachycardia termination was 64 ± 14% of threshold current and the maximal ineffective current was 49 ± 17% of threshold (p < 0.05). In all cases, the tachycardia was terminated by one or two instances of atrial capture that resulted in a premature atrial impulse (20 ± 4% advancement of the atrial cycle) that blocked the AV node limb of the tachycardia. Anterograde conduction over the accessory pathway never occurred, either during the tachycardia or during subthreshold pacing after a return to normal sinus rhythm. No instances of atrial fibrillation were provoked by suhthreshold pacing. Possible explanations for the intermittent atrial capture with critically placed subthreshold impulses include supernormal atrial conduction or summation of impulses at the atrial insertion site of the accessory pathway.It is concluded that subthreshold pacing is effective in selected patients with AV tachycardia due to an accessory pathway. Furthermore, because neither atrial fibrillation nor anterograde conduction over the accessory pathway is seen with subthreshold pacing, this modality may hold significant promise for permanent antitachycardia pacing in these patients.

Clinical electrophysiologic effects of flecainide acetate.

Flecainide acetate depresses the rate of depolarization of action potential (Vmax), the so-called "membrane stabilizing action." In the intact heart it has a unique profile of substantial effect on conduction with modest effect on refractoriness. After intravenous administration, clinical electrophysiologic studies show that conduction through atrial myocardium, atrioventricular (AV) node, His-Purkinje system, and ventricular myocardium is depressed, the most prominent effect being on the His-Purkinje system. Refractorines of the normal atrial and AV nodal myocardium is not prolonged while that of the ventricular muscle is slightly increased. Atrial fibrillation (60% to 70%), atrial tachycardia (90% to 100%), and nodal and AV tachycardia (80% to 90%) are generally terminated, while flutter is usually slowed, but in a small proportion of patients (10% to 20%) might be terminated by the intravenous use of flecainide acetate. This drug has also been shown to be effective in terminating stable ventricular tachycardia (70%). However, it appears to be slightly less effective in suppressing inducibility of ventricular arrhythmias. Administered orally, flecainide is very effective in decreasing ventricular ectopic activity (80% to 95%) and nonsustained ventricular tachycardia. Thus, flecainide has a wide range of antiarrhythmic properties, making it a useful agent in the management of a variety of supraventricular and ventricular arrhythmias. In a small proportion of patients, however, its use can lead to apparent arrhythmogenic effects, the most dangerous being exacerbation of ventricular tachycardia.

The Supraventricular Tachycardias

Most supraventricular tachycardias can be diagnosed confidently using the standard 12-lead electrocardiogram, the more so if such a tracing in sinus rhythm is also available. The underlying mechanisms may often be determined and these may have important therapeutic consequences. This chapter reviews the electrocardiographic appearances of the supraventricular arrhythmias. Extrasystoles are common but rarely require specific treatment. Automatic atrial tachycardias are common and usually amenable to simple management. Reentrant circuits related to atrial and atrioventricular tachycardias are also described, and where possible, treatment is related to underlying mechanisms.

Arrhythmia and prognosis in infants, children and adolescents with hypertrophic cardiomyopathy

In adults with hypertrophic cardiomyopathy, the annual mortality rate from sudden death is 2 to 3%, and the finding of nonsustained ventricular tachycardia during electrocardiographic (ECG) monitoring provides a marker of the patient who is at increased risk. In the young, the annual mortality rate from sudden death is even higher, approximately 6%, but the prognostic significance of arrhythmia is unknown. To determine the prevalence of arrhythmia and its relation to prognosis, 2 days of ECG monitoring was performed in 6 infants, 14 children and 33 adolescents with hypertrophic cardiomyopathy receiving no cardioactive medications. An additional 1 to 9 days (median 2) of monitoring was performed in 29 patients. All patients had sinus rhythm; 4 adolescents had episodes of paroxysmal supraventricular tachycardia, a child with the Wolff-Parkinson-White syndrome had symptomatic reentrant atrioventricular tachycardia and 5 adolescents had asymptomatic nonsustained ventricular tachycardia.During follow-up of 1 week to 7 years (median 3 years), five patients died suddenly and two had successful resuscitation from out-of-hospital ventricular fibrillation; none of these seven patients had ventricular arrhythmias during 2 to 7 days (median 3) of ECG monitoring. The two patients with ventricular fibrillation, the five with ventricular tachycardia, the one with Wolff-Parkinson-White syndrome and the seven with recurrent syncope or adverse family history, or both, received low dose amiodarone. None of these “high risk” patients died during 6 months to 6 years (median 3 years) of follow-up.In summary: 1) arrhythmias were rare in infants and children with hypertrophic Cardiomyopathy; 2) in adolescents, the prevalence rate of nonsustained ventricular tachycardia was 18%; 3) seven patients (15%) experienced sudden cardiac death (two were resuscitated) and none of these had significant supraventricular or ventricular arrhythmias. In contrast to adults, in the young with hypertrophic cardiomyopathy, the absence of ventricular arrhythmia during ambulatory ECG monitoring does not indicate a low risk of sudden death.

Train stimulation at the atria for prevention of atrioventricular tachycardia: Dependence on accessory pathway location

In 12 patients with accessory pathway-mediated supraventricular tachycardia, programmed electrical stimulation with a rapid train of 10 stimuli was assessed for prevention of tachycardia induction. Tachycardia was induced with one or two extrastimuli from both the right and the left atrium (by way of the coronary sinus). Preventive train stimulation, with the train delivered after the tachycardia-initiating stimulus, was attempted at the site of tachycardia induction as well as at the opposite site. Prevention at the site of tachycardia induction was successful in all patients when the length of the train (90 ms) exceeded the effective refractory period of the tachycardia-initiating stimulus to achieve single atrial capture within the "preventive zone." However, in patients with a left-sided accessory pathway, preventive stimulation at the right atrium failed when tachycardia was induced from the coronary sinus because of interatrial conduction delay. It is concluded that train stimulation is an effective mode for supraventricular tachycardia prevention, yet the site of preventive stimulation should lie as close as possible to the anatomic site of the reentrant circuit to reduce interatrial conduction delay.

Value of the 12-lead electrocardiogram in discriminating atrioventricular nodal reciprocating tachycardia from circus movement atrioventricular tachycardia utilizing a retrograde accessory pathway

The value of the 12-lead electrocardiogram for distinguishing atrioventricular (AV) nodal reciprocating tachycardia from circus movement AV tachycardia utilizing a retrograde accessory pathway was studied in 100 patients with narrow QRS complex tachycardia. Intracardiac electrograms showed AV nodal reciprocating tachycardia in 40 patients and circus movement AV tachycardia in 60. The 12-lead electrocardiograms recorded during tachycardia were randomly sorted and reviewed by 4 experienced cardiac electrophysiologists who were blinded to the diagnosis associated with each tracing, the relative proportion of each arrhythmia and the hypotheses to be tested. Each reviewer was asked to indicate the location of the P wave relative to the QRS complex, electrical axis of the P wave in the frontal and horizontal planes and presence or absence of QRS alternation, and to interpret the most likely mechanism. The performance of published electrocardiographic criteria to differentiate AV nodal reciprocating tachycardia from circus movement AV tachycardia was evaluated. The overall accuracy of the reviewers' interpretations was 75%, similar to the accuracy of the predefined criteria when applied by these observers (71% correct, difference not significant). Interobserver agreement of reviewer interpretations was 76% and the intraobserver agreement was 78%. Features associated with circus movement AV tachycardia by univariable analysis were P waves after the QRS complex, faster tachycardia rates and QRS alternation. Multivariable analysis showed that only the location of the P wave relative to the QRS complex was independently associated with the mechanism of tachycardia (p = 0.002). QRS alternation was found by multivariable analysis to be associated with the rate but not the mechanism of the tachycardia.