Magnetocardiographic localization of an accessory pathway in patients with WPW syndrome

The usefulness of magnetocardiography (MCG) in determining the location of an accessory pathway (Kent bundle) was examined by the isomagnetic map at the time of a delta wave, and by gated magnetic resonance imaging (MRI). MCG was performed at 36 points on the anterior chest wall in eight cases with Wolff-Parkinson-White (WPW) syndrome using a SQUID (superconducting quantum interference device) system with the second derivative gradiometer. Based on these records, isomagnetic maps during the QRS and T waves were constructed, and the depth of the accessory pathway from the coil was calculated mathematically. The locations of the accessory pathways were estimated using these data and the MRI findings. The locations of the accessory pathways thus determined were compared with findings obtained by body surface maps. A dipole directed towards the left was deduced, because the maximum was located more superiorly than the minimum in an isomagnetic map 10-40 msec after onset of the delta wave in cases with WPW syndrome, indicating an accessory pathway to be located in the right ventricle. A dipole directed towards the right was deduced, because the maximum was located more superiorly than the minimum in an isomagnetic map 10-40 msec after onset of the delta wave of cases with WPW syndrome indicating an accessory pathway to be located in the left ventricle. Assuming the electric current source is a single dipole, the location of a current dipole might be determined by positions of the maximum and the minimum in the isomagnetic maps. In the present study, the locations as determined by analysis of the isomagnetic map 40 msec after onset of the delta wave and the gated MRI were concordant with the findings obtained by body surface isopotential maps. Furthermore, some cases showed two opposing dipoles on the isomagnetic map at the peak of the T wave in lead II of the standard ECG leads; one directed to the left expressing normal repolarization; the other directed to the right presumably expressing repolarization of the myocardium which was excited by an impulse via the accessory pathway. The location of the current dipole as determined by analysis of the isomagnetic map at the peak of the T wave in lead II was nearly the same as the position of the current dipole as determined by analysis of the isomagnetic map 40 msec after onset of the delta wave.(ABSTRACT TRUNCATED AT 400 WORDS)     

Problems concerning assessment of anatomical site of accessory pathway in Wolff-Parkinson-White syndrome.

Twp patients with type B WPW syndrome and reciprocal tachycardias have been studied using intracardiac electrograms and programmed electrical stimulation of the heart. One patient, who had a right-sided accessory pathway giving the surface electrocardiographic appearances of type B WPW syndrome, was shown to have an additional left-sided accessory pathway as occurs in type A WPW syndrome. This concealed left-sided atrioventricular connexion formed the retrograde pathway during reciprocal tachycardia. In the second patient the appearances of type B WPW syndrome were shown to be caused by an accessory pathway between the atrial septum and the right side of the interventricular septum rather than an accessory pathway in the right atrioventricular groove. The significance of these findings when considering surgical interruption of an accessory atrioventricular conduction pathway is discussed.     

Ajmaline in WPW syndrome: an electrophysiologic study

Six patients including three females with WPW syndrome (three with type A and three with type B) presenting with recurrent paroxysmal tachyarrhythmia were subject to electrophysiological studies. Apart from basal parameters, rapid atrial and ventricular pacing was done which confirmed electrophysiological characteristics of bundle of Kent operation. A single intravenous bolus of ajmaline 50 mg. was effective in blocking the bundle of Kent in all patients within 30 seconds of injection with the effect persisting for 15 minutes in one and from 25 to 60 minutes in the others. The most dramatic effect was prolongation of the HV interval with normalization of QRS complex with a marginal effect on the AH interval. The drug was also effective in breaking narrow QRS tachycardia in two patients and broad QRS tachycardia in one patient. Long-term oral therapy with ajmaline has proved effective in preventing recurrent tachyarrhythmias.We conclude that ajmaline is specifically effective and safe in the treatment of the WPW syndrome.     

不全显性预激的心电图分析

目的:评估有左侧前传旁路伴房室折返性心动过速且无器质性心脏病患者中,体表心电图无典型预激表现患者所占的比例,并分析造成预激图形不明显的原因,以在定位旁路时借鉴.方法:2007年1月至-2009年11月入院的行房室折返性心动过速导管射频消融术的左侧前传旁路的46例患者进行回顾性分析,计算术前V1导联QRS波群非主波向上者...     

Atrial fibrillation in patients with an accessory pathway: importance of the conduction properties of the accessory pathway

To investigate how the electrophysiologic properties of the accessory pathway affect the occurrence of atrial fibrillation in the Wolff-Parkinson-White syndrome, programmed stimulation data of 57 patients with overt pre-excitation and 33 patients with a concealed accessory pathway with documented circus movement tachycardia were reviewed. Atrial fibrillation had occurred spontaneously in 31 (54%) of the 57 patients with the Wolff-Parkinson-White syndrome and in 1 (3%) of the 33 with a concealed accessory pathway (p less than 0.001). Sustained atrial fibrillation was induced in 23 of 31 patients with the Wolff-Parkinson-White syndrome and spontaneous atrial fibrillation (Group A), in 7 of 26 patients with the Wolff-Parkinson-White syndrome without spontaneous atrial fibrillation (Group B) and in 5 of 33 patients with a concealed accessory pathway (Group C). The anterograde effective refractory period of the accessory pathway was shorter in Group A than in Group B (252 versus 297 ms, p less than 0.001). There were no differences among groups in PA interval, right to left atrium conduction time, cycle length of tachycardia and atrial and retrograde accessory pathway effective refractory period. Atrial fibrillation is more frequent in patients with the Wolff-Parkinson-White syndrome than in those with a concealed accessory pathway. Patients with overt pre-excitation and atrial fibrillation have a shorter anterograde accessory pathway refractory period. It seems therefore that the anterograde rather than the retrograde conduction properties of the accessory pathway are the critical determinants of atrial fibrillation in the Wolff-Parkinson-White syndrome.     

Refractory periods of the accessory pathway in the Wolff-Parkinson-White syndrome.

Antegrade (AERPAP) and retrograde (RERPAP) effective refractory periods of the accessory pathway were measured at multiple cycle lengths in 47 patients with the Wolff-Parkinson-White syndrome. In 20 patients the effect of changing cycle length on AERPAP could be determined. In 12 patients Aerpap decreased by 10-45 msec, in six it increased by 10-35 msec, and in two it was unchanged. In 13 of 15 patients in whom the effect of decreasing cycle length on RERPAP could be assessed, RERPAP decreased by 10-60 msec. In eight patients, the shortest AERPAP correlated well (r equals 0.83) with the shortest R-R interval of consecutive pre-excited beats in atrial fibrillation. However, predominantly normal conduction was observed in six of 28 patients with atrial fibrillation, probably because of concealment in the bypass. Therefore, induction of atrial fibrillation during electrophysiological evaluation may privide additional information. The RERPAP at the cycle length of the arrhythmia was shorter than the cycle length of reciprocating tachycardia in all but one of 21 patients. At the same or comparable cycle lengths, AERPAP was usually greater than RERPAP.     

Latent functional duality in an accessory pathway

Accessory atrioventricular pathways classically possess neither decremental conduction nor functional duality. This report details an accessory pathway in which functional longitudinal dissociation, with decremental ventriculoatrial conduction in each component, was observed after, but not before, administration of the antiarrhythmic drug recainam.     

Pacing site and bradycardia dependent retrograde conduction block over an atrioventricular accessory pathway.

Intermittent retrograde conduction over an accessory pathway (AP) is an uncommon phenomenon. We report a case of Wolff-Parkinson-White syndrome in which retrograde conduction of the bypass tract was present only during right ventricular (RV) outflow tract and left ventricular pacing or during RV inflow tract pacing with a fast pacing rate (pacing site and bradycardia dependent conduction block). The interaction between different branches/fibres of the bypass tract might explain the mechanism of this phenomenon. The AP was successfully ablated at the lateral aspect of mitral valve annulus. It is suggested that careful evaluation by decremental ventricular stimulation should be applied from multiple sites both during baseline study and after apparent AP ablation in order to detect such uncommon cases of intermittent conduction.     

Enhancement of conduction in an accessory pathway by local noncaptured stimuli

Subthreshold stimuli have been reported to prolong the refractory period of myocardial tissue. This report presents the first case of reproducible acceleration of a reentrant tachycardia by apparently subthreshold stimuli delivered to the os of the coronary sinus during the atrial refractory period in a child with incessant orthodromic tachycardia utilizing a posteroseptal pathway. Mechanisms by which these stimuli could influence the tachycardia circuit are proposed, and the potential usefulness of this finding for mapping tachyarrhythmias is discussed.     

Brugada syndrome in a patient with accessory pathway.

Brugada syndrome in a patient with Wolff-Parkinson-White syndrome. We report a 32-year-old man with orthodromic atrioventricular (AV) reciprocating tachycardia using a right posterior accessory pathway. However, his ECG showed ST segment elevation in leads V1 to V3. After successful radiofrequency ablation of his accessory pathway a cardioverter defibrillator was implanted.     

"Atypical" posteroseptal accessory pathway in Wolff-Parkinson-White syndrome

The posteroseptal accessory pathway in the Wolff-Parkinson-White syndrome is associated with a delta wave that is negative in the inferior electrocardiographic (ECG) leads and the occurrence of the earliest retrograde atrial activation near the orifice of the coronary sinus during atrioventricular (AV) reentrant tachycardia. Seventy-two patients with a posteroseptal accessory pathway underwent epicardial mapping before operative ablation. The earliest epicardial activation occurred at the posterosuperior process of the left ventricle in all patients. Dissection of the posteroseptal region (right atrial-left ventricular sulcus) resulted in permanent loss of preexcitation in 69 patients and failure to abolish preexcitation permanently in 3. At reoperation in two patients, preexcitation was abolished by discrete cryoablation of the left side of the interatrial septum near the AV node approached through the atrial septum in the normothermic beating heart. At reoperation, one patient had extensive AV node dissection. All patients have had permanent loss of preexcitation. The vast majority of posteroseptal accessory pathways ("typical") are epicardial and ablated by dissection of the posteroseptal region. Rarely, posteroseptal accessory pathways are "atypical" in that they are intraseptally located near the AV node on the left atrial endocardial surface.     

Electrophysiologic effects of lorcainide on the accessory pathway in the Wolff-Parkinson-White syndrome

The electrophysiologic effects of lorcainide, a class I antiarrhythmic agent with local anesthetic properties, were studied in 20 patients with the Wolff-Parkinson-White syndrome. After intravenous administration of lorcainide (2 mg/kg), the sinus cycle length decreased in all patients from 705 ± 117 to 636 ± 94 ms (p < 0.001). The atrioventricular conduction time lengthened from 84 ± 22 to 94 ± 22 ms (p < 3.01) and the QRS duration increased from 92 ± 19 to 120 ± 29 ms (p < 0.001). The effective refractory period of the atrium increased from 230 ± 27 to 243 ± 35 ms (p < 0.05), whereas the ventricular refractoriness was unaffected. Retrograde conduction over the accessory pathway was blocked in 5 of 18 patients after lorcainide; in the remaining 13 patients a prolongation from 107 ± 32 to 162 ± 57 ms (p < 0.001) was found. Anterograde conduction over the accessory pathway was blocked in 6 patients, and in all other patients it increased considerably. Circus movement tachycardia could be induced in 14 patients before and in 10 patients after the drug. The shortest R-R interval during tachycardia lengthened from 326 ± 40 to 364 ± 67 ms (p < 0.05). The tachycardia zone was unaffected by lorcainide. In 15 patients atrial fibrillation was induced. After lorcainide anterograde conduction during atrial fibrillation was blocked (n = 5). The shortest R-R interval over the accessory pathway during induced atrial fibrillation increased from 228 ± 35 to 304 ± 103 ms (p < 0.05). Intravenous administration of lorcainide produced a pronounced negative dromotropic effect on the conduction properties of the accessory pathway. Lorcainide appears to be a promising new antiarrhythmic agent in patients with the Wolff-Parkinson-White syndrome.     

Reversal of electrophysiologic effects of flecainide on the accessory pathway by isoproterenol in the Wolff-Parkinson-White syndrome

To determine the reversibility of the effects of flecainide on accessory pathways, electrophysiologic studies were performed in the drug-free control state, after flecainide loading and with isoproterenol infusion during flecainide treatment in 12 patients with symptomatic preexcitation syndrome. After the baseline drug-free evaluation, oral flecainide was given in dosages of 50 to 200 mg twice daily (mean daily dose 282 +/- 75) for at least 4 days before the repeat electrophysiologic study. Isoproterenol infusion was given in dosages of 1 to 4 micrograms/min to increase the heart rate at rest by 50%. Anterograde block in the accessory pathway was observed in 3 patients with flecainide therapy, whereas in the other patients the anterograde refractory period increased from 243 +/- 20 to 315 +/- 23 ms (p less than 0.05). The shortest preexcited RR interval during atrial fibrillation lengthened from 234 +/- 27 ms before flecainide to 313 +/- 38 ms (p less than 0.05). Retrograde block occurred in 2 patients after flecainide, whereas the retrograde refractory period of the accessory pathway increased from 247 +/- 26 to 337 +/- 45 ms in the other patients. Orthodromic atrioventricular reciprocating tachycardia, inducible in 10 patients before therapy, became noninducible in 3 patients. Its rate was significantly slowed in the other 7 patients (from 346 +/- 50 to 471 +/- 81 ms). In 2 patients the tachycardia was nonsustained during flecainide treatment. Atrial fibrillation, inducible in all patients at baseline, was rendered nonsustained and more difficult to induce in 7 patients with flecainide. When isoproterenol was infused during flecainide treatment, complete anterograde (3 patients) or retrograde block (2 patients) persisted in the accessory pathway.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atrial fibrillation and continuous hypotension induced by sildenafil in an intermittent WPW syndrome patient

A 55-year-old Japanese man was hospitalized for palpitations and severe chest oppression one hour after he ingested about 1500 ml of beer and sildenafil (Viagra) 50 mg. At 43 years of age, he had been diagnosed with intermittent WPW syndrome following a paroxysmal supraventricular tachycardia (PSVT) attack. He took a 1 mg tablet of doxazosin daily for mild hypertension. On admission, his blood pressure was 90/54 mmHg and his heart beat was weak and irregular with a rate of about 220/min. Since atrial fibrillation (Af) was diagnosed on an electrocardiogram (minimum RR interval; 0.22 seconds), direct current shock was performed with 100 joules and 150 joules but conversion to sinus rhythm failed. Sinus rhythm returned spontaneously from Af four hours after taking sildenafil. Since blood pressure was 50/17 mmHg despite the return to sinus rhythm, blood pressure was maintained by dopamine for twelve hours after sinus rhythm returned. The patient underwent catheter ablation for curative therapy and thereafter has not had any further episodes of tachycardia.