1/27. Paroxysmal supraventricular tachycardia caused by 1:2 atrioventricular conduction in the presence of dual atrioventricular nodal pathways.One-to-two atrioventricular conduction, ie, the double response to a single sinus or atrial impulse, resulting in two QRS complexes for one P wave, is a rare manifestation of dual atrioventricular (AV) nodal pathways. This report describes the case of a 61-year-old woman with continuous episodes of supraventricular tachycardia caused by independent conduction to the ventricles of sinus impulses over both the fast and the slow AV nodal pathway, giving rise to a ventricular rate that was twice the sinus rate. A wide spectrum of electrocardiographic manifestations of 1:2 AV conduction was observed on the surface electrocardiogram. The diagnosis was suggested by several elements including evidence of dual AV nodal pathways during sinus rhythm and cycle length alternans during tachycardia. The patient underwent successful slow pathway ablation with complete disappearance of symptoms and electrocardiographic manifestations of 1:2 AV conduction.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
2/27. Electrophysiologic characteristics and radiofrequency ablation of concealed nodofascicular and left anterograde atriofascicular pathways.INTRODUCTION: True nodoventricular or nodofascicular pathways and left-sided anterograde decremental accessory pathways (APs) are considered rare findings. methods AND RESULTS: Two unusual patients with paroxysmal supraventricular tachycardia were referred for radiofrequency (RF) ablation. Both patients had evidence of dual AV nodal conduction. In case 1, programmed atrial and ventricular stimulation induced regular tachycardia with a narrow QRS complex or episodes of right and left bundle branch block not altering the tachycardia cycle length and long concentric ventriculoatrial (VA) conduction. Ventricular extrastimuli elicited during His-bundle refractoriness resulted in tachycardia termination. During the tachycardia, both the ventricles and the distal right bundle were not part of the reentrant circuit. These findings were consistent with a concealed nodofascicular pathway. RF ablation in the right atrial mid-septal region with the earliest atrial activation preceded by a possible AP potential resulted in tachycardia termination and elimination of VA conduction. In case 2, antidromic reciprocating tachycardia of a right bundle branch block pattern was considered to involve an anterograde left posteroseptal atriofascicular pathway. For this pathway, decremental conduction properties as typically observed for right atriofascicular pathways could be demonstrated. During atrial stimulation and tachycardia, a discrete AP potential was recorded at the atrial and ventricular insertion sites and along the AP. Mechanical conduction block of the AP was reproducibly induced at the annular level and at the distal insertion site. Successful RF ablation was performed at the mitral annulus. CONCLUSION: This report describes two unusual cases consistent with concealed nodofascicular and left anterograde atriofascicular pathways, which were ablated successfully without impairing normal AV conduction system.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
3/27. Is it safe to program a long tachycardia detection interval?Implantable cardioverter defibrillator (ICD) therapy is used frequently in patients with "slow" ventricular tachycardia (VT). Hence, the tachycardia detection interval is programmed within the range of the physiologic heart rate, but this may cause serious problems. If a fast VT is converted to sinus tachycardia with a cycle length shorter than the tachycardia detection interval, the episode is not terminated and the success counter is not reset. If this happens repeatedly, therapies will be exhausted without termination of the episode. If VT recurs within such an episode, it will not be treated. This report describes a patient who died suddenly in a scenario similar to the one described. Although all documented VT/ventricular fibrillation episodes were terminated by the device, the episode was not terminated because of the ongoing supraventricular tachycardia. Therefore, no further therapies were available and the patient probably died of fast untreated VT. Programming of a long tachycardia detection interval is dangerous in currently available ICDs.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
4/27. 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.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
5/27. Reentrant and nonreentrant forms of atrio-ventricular nodal tachycardia mimicking atrial fibrillation.BACKGROUND: atrial fibrillation (AF) manifests disorganized atrial activity and irregular R-R intervals on electrocardiogram (ECG). Variation in R-R intervals can also be seen with other supraventricular tachycardias that may mimic AF. OBJECTIVE: We report our observations on three patients who were referred to our center to undergo pulmonary vein (PV) isolation for erroneously diagnosed AF in the setting of dual atrio-ventricular (AV) nodal pathways manifesting as AV nodal reentrant tachycardia (AVNRT) and/or double response during sinus rhythm. methods AND RESULTS: These three subjects (two females) were derived from a group of 456 consecutive patients undergoing AF ablation at our center over a 3-year period. All three patients had been symptomatic for over 2 years, having failed two or more antiarrhythmic medications. In each case AF was initially diagnosed on ECG and/or recordings from ambulatory monitoring. However, in all three cases the correct diagnosis was established during the invasive electrophysiologic study. In one patient during the stimulation protocol, two narrow complex tachycardias were serially induced (cycle lengths: 305 and 360 msecs; VA time: 60 and 240 msecs). The latter was confirmed to be atypical AVNRT and during this tachycardia, block in upper pathway was observed. In the other two patients, sinus rhythm with repetitive runs of double response and isolated junctional beats were observed in the absence of retrograde conduction. Successful slow pathway modification was performed in each subject and all three patients have remained arrhythmia free over a mean follow-up of 31 /- 16 months off antiarrhythmic medications. CONCLUSIONS: AF can be erroneously diagnosed in patients with dual AV nodal pathways manifesting double response and/or AVNRT. Incorporating a stimulation protocol as a part of the AF ablation procedure may help in diagnosing these rare clinical presentations that can be cured by slow pathway modification alone.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
6/27. Reentrant fascicular tachycardia with cycle length alternans: insights into the tachycardia mechanism and origin.This report details the electrophysiology of a unique case of reentrant fascicular tachycardia in a patient without structural heart disease. Persistent cycle length alternans, with constant fluctuation in alternate RR intervals, occurred during tachycardia. A distinct mode of spontaneous termination of tachycardia was observed. The findings were consistent with the presence of decremental conduction properties in the tachycardia circuit or decremental dual functional pathways within one limb of the circuit. These observations provide further evidence in support of a fascicular origin of the tachycardia.- - - - - - - - - - ranking = 5keywords = cycle (Clic here for more details about this article) |
7/27. Opposite effects of propafenone and flecainide in a patient with reciprocating supraventricular tachycardia.A 46 year-old woman with wolff-parkinson-white syndrome (postero-septal accessory pathway), symptomatic for recurrent episodes of nonsustained paroxismal supraventricular tachycardia (PSVT), was empirically treated with propafenone (600 mg/day). After a week of therapy the patient returned to the hospital after an episode of syncope. She referred a significant increase in duration and frequency of "palpitations". Under treatment with propafenone a sustained PSVT could be induced during transesophageal testing. During the electrophysiologic study performed off drugs, only a nonsustained PSVT could be induced. After flecainide infusion (1 mg/kg) anterograde block of the accessory pathway was observed and only few beats (less than 8) of PSVT could be induced. The patient was discharged on flecainide (200 mg/day) and 1 month later a transesophageal testing was repeated showing an anterograde block of the accessory pathway at a pacing cycle length of 500 ms; no arrhythmias were induced. The patient has been asymptomatic on chronic oral therapy with flecainide during a follow-up period of 8 months. This case shows that 2 1c class antiarrhythmic drugs may have opposite effects (proarrhythmic and antiarrhythmic). Failure, or even the proarrhythmic effect of one drug, does not necessarily exclude the efficacy of another drug of the same subclass in preventing recurrence of PSVT.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
8/27. Modulation of atrioventricular junctional parasystole during atrial pacing.In this report we describe a case of a 68-year-old man with atrioventricular junctional parasystole in whom atrial pacing caused marked changes in the arrhythmic pattern. During atrial pacing at a cycle length of 960 ms, the duration of the ectopic cycle length was influenced by the interval between the parasystolic and nonparasystolic beat. A shorter interval from nonparasystolic to ectopic beat prolonged the ectopic cycle length and a longer one shortened it. Pacing at a cycle length of 900 ms completely suppressed the parasystole. Both of these changes are most likely due to modulation and entrainment of the parasystolic rhythm. During spontaneous variation of the sinus cycle length over 24 hours of ambulatory ECG recording, modulation could not be confirmed; however, there was parallel variation of the ectopic and sinus cycle lengths which suggests that both pacemakers were under the influence of the autonomic nervous system.- - - - - - - - - - ranking = 6keywords = cycle (Clic here for more details about this article) |
9/27. Automatic implantable scanning burst pacemakers for recurrent tachyarrhythmias.Ninety patients (13 patients with supraventricular tachycardia and 72 patients with ventricular tachycardia) underwent electrophysiological study. Six out of 18 patients with supraventricular tachycardia (33%) and one out of 72 patients with ventricular tachycardia (1.4%) were considered suitable candidates for the scanning pacemaker. However, only six of the seven patients underwent implantation. The seventh patient decided not to undergo implantation and continued to have recurrent episodes of supraventricular tachycardia. The scanning pacemaker delivers extrastimuli at preset initial and coupled delay after four cycles of tachycardia. If tachycardia is not terminated, another set of extrastimuli are delivered with a decrement in the coupling cycle. During the follow-up period of 7-25 months (mean, 14.3 months), tachycardia cycle lengths and termination windows changed in four patients. The pacemakers in these patients were reprogrammed multiple times (2 to 6 times with a mean of 3.5) as the previous number of extrastimuli and intervals were ineffective in the termination of tachycardias. The major limitations of the extrastimulus pacemaker were: 1) only a small percentage of patients were suitable candidates for its use; (2) the initially selected termination window in the majority of patients was ineffective during the follow-up period due mainly to the changes in tachycardia cycle length and subsequent termination windows; and (3) the majority (five out of six patients in this series) of patients needed additional pharmacologic therapy to modify their tachycardia rates. However, despite these limitations, the scanning pacemaker may be an additional tool in the management of recurrent tachyarrhythmias in selected patients.- - - - - - - - - - ranking = 4keywords = cycle (Clic here for more details about this article) |
10/27. Evaluation and management of a supraventricular tachycardia with a standard bradycardia support pacemaker.A standard dual chamber pacemaker with the ability to telemeter intracardiac electrograms and to perform noninvasive electrophysiological studies was implanted in a patient with previously documented complex ventricular arrhythmias treated with amiodarone who later presented with a hypersensitive carotid sinus syndrome and syncope. Subsequently, he developed a supraventricular tachyarrhythmia with an atrial cycle length of 320 ms. Its diagnosis was facilitated by the ability to noninvasively telemeter atrial endocardial electrograms directly from the implanted pacemaker. Its management was aided by utilizing the already implanted bradycardia support pacemaker to stimulate the patient with premature extrastimuli coupled to his intrinsic atrial rhythm (PS1 and S1S2 each 170 ms.) by connecting the pacemaker to an electrophysiological stimulator via the pacemaker programmer. This particular pacemaker was not chosen because of this capability at the time of its original implantation. However, this capability facilitated the patient's evaluation and subsequent management.- - - - - - - - - - ranking = 1keywords = cycle (Clic here for more details about this article) |
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