Refractory Period Of Accessory Pathway Research Articles

Analysis of clinical and electrophysiological characteristics of children with Wolff-Parkinson-White syndrome or ventricular pre-excitation

Objective To summarize the clinical and electrophysiological characteristics of children with Wolff-Parkinson-White syndrome or ventricular pre-excitation. Methods One hundred and seventy-nine consecutive children with Wolff-Parkinson-White syndrome or ventricular pre-excitation who were hospitalized at Beijing Anzhen Hospital Affiliated to Capital Medical University and planned to accept radiofrequency ablations were selected.Electrocardiogram and echocardiography were completed and detailed clinical data were collected before ablations.Anterograde refractory period of accessory pathways (ERPAPA) and retrograde ventriculoatrial conduction were measured during electrophysiology studies.The clinical and electrophysiological characteristics of these children were analyzed. Results The ratio of left-sided to right-sided accessory pathways was 1.001.93(61 cases vs.118 cases). Six out of 61 patients with left-sided accessory pathways were verified by electrophysiology study.There was no statistical difference of P-R interval and QRS duration between patients with right-sided and left-sided accessory pathways(all P>0.05). Twelve patients were combined with congenital heart diseases.Fourteen patients with right-sided accessory pathways were of ventricular pre-excitation induced dilated cardiomyopathy.ERPAPA was measured successfully in 110 patients, ERPAPA less than 250 ms accounted for 32.7%(36/110 cases). Six children with two pathways were recognized.Antidromic atrioventricular reentrant tachycardia was induced in 3 children.One child had slow conduction pathway localized in right-sided septum. Conclusions Right-sided overt accessory pathways are more common in children with Wolff-Parkinson-White syndrome or ventricular pre-excitation.Organic heart diseases are not uncommon.Besides congenital heart disease, a small proportion of patients with right overt accessory pathways may develop ventricular pre-excitatory induced dilated cardiomyopathy resulting from ventricular wall dyskinesia.Most of the decremental retrograde ventriculoatrial conduction is the characteristic of ventricular muscles rather than the accessory pathways in nature.Two pathways are not uncommon in children with Wolff-Parkinson-White syndrome or ventricular pre-excitation.Before finishing radiofrequency ablation, the anterograde and retrograde function of the accessory pathway should be evaluated in detail again because it is easy to neglect the existence of another accessory pathway. Key words: Wolff-Parkinson-White syndrome; Electrophysiology; Atrioventricular reentrant tachycardia; Anterograde refractory period of accessory pathways

Transesophageal and invasive electrophysiologic evaluation in children with Wolff-Parkinson-White pattern.

Risk stratification for Wolff-Parkinson-White (WPW) pattern either by noninvasive or invasive tests is important to determine whether an ablation is necessary or not. The aim was to compare noninvasive tests and invasive studies in a pediatric WPW population. A total of 71 WPW patients (median age 14 years [interquartile range, 11-16 years]; 43 male) underwent Holter monitoring, exercise stress test (EST), and transesophageal electrophysiological study (TEEPS). In the case of a ≤270-ms effective refractory period of accessory pathway or induction of supraventricular tachycardia using TEEPS, patients were classified as high risk and underwent invasive electrophysiological study (EPS). Nine of 23 patients with low risk by Holter and eight of 26 patients with low risk by EST had high risk in TEEPS. Risky TEEPS results were detected in 42 of 71 patients and those patients underwent EPS. High-risk characteristic in EPS was detected in seven of nine patients with low risk by Holter and in seven of eight with low risk by EST. Both tests yielded moderate specificity (52-69%) and negative predictive value (61-69%) according to TEEPS. Holter and EST have low predictive value in WPW risk stratification. However, TEEPS and EPS are extremely valuable in WPW risk stratification. TEEPS may reveal important and useful results for WPW risk determination, especially in small children not having undergone EPS in order to avoid its complications.

Supernormal and alternating conduction in intermittent bundle branch block and intermittent or concealed ventricular preexcitation. Electrophysiological study, mechanisms and clinical considerations

Supernormal and alternating conduction are not rare in clinical arrhythmology, detectable at various levels of the conduction system in different pathophysiological conditions, and often associated, so as to justify the search for a possible link between them. In order to define a possible relationship between supernormal and alternating conduction, the electrophysiological data of two patient groups were analyzed. Group 1 included 9 patients with intermittent bundle branch block in the presence of supernormal conduction through the pathological branch. Group 2 included 16 patients with ventricular preexcitation, intermittent or concealed, in the presence of supernormal conduction through the atrioventricular accessory pathway. In group 1, 8 patients had a phase 3 and 1 patient a phase 3 and phase 4 bundle branch block. In all 9 patients, the area of phase 3 block was interrupted by a window of unexpected conductivity detectable by atrial premature stimulation. In 7/9 cases, by modulating the atrial rate, alternating conduction through the branch was observed, and the cardiac cycle of occurrence of the phenomenon was in the range of supernormal conduction in 6/7 cases. In group 2, 11 patients showed conduction through the accessory pathway only for a narrow range of cardiac cycles, during atrial premature stimulation. One patient had a prolonged accessory pathway refractory period (phase 3 block), but a window of unexpected supernormal conduction within the refractory zone was observed at atrial premature stimulation. Another patient presented a tachycardia and bradycardia-dependent block along the accessory pathway (phase 3 and phase 4 block) and the phase 3 block area was interrupted by a window of supernormal conduction. In the other three cases, supernormal conduction was manifested as unexpected resumption of conductivity through the accessory pathway for atrial cycles more precocious than the actual duration of its effective refractoriness. By modulating the atrial rate, alternating conduction through the accessory pathway was observed in 13/16 cases, and the cardiac cycle at which this phenomenon appeared falling in the range of supernormal conduction in 11/13 cases. It can be hypothesized that supernormal conduction is in relation with the presence of a phase of supernormal excitability experimentally demonstrated in the late phase of repolarization of cardiac cells, and that supernormal and alternating conduction are related phenomena, so that the evidence on ECG of alternating conduction through a pathological branch or an atrioventricular accessory pathway can be considered as a marker of the presence of supernormal conduction through the structure.

0272: Why accessory pathway refractory period can be shorter at esophageal electrophysiological study than at intracardiac study?

Preexcitation syndrome (PS) is a potential cause of sudden cardiac death; its prognostic assessment is a major issue. The aim was to assess the contribution of esophageal electrophysiological study (EPS) compared to intracardiac EPS for the prognostic evaluation in patients with PS. We conducted a prospective single-centre study between November 1 st , 2008 and December 1 st , 2014, in patients who underwent both esophageal and intracardiac EPS for a PS. Accessory pathway effective refractory period (APERP) and induction of sustained supraventricular tachyarrhythmias (SVT) were noted for both methods. 69 patients were included. 45 (65%) were males and mean age was 36±16 years. There were no significant differences in the induction of SVT between both methods. APERPs were significantly shorter at esophageal EPS compared to intracardiac EPS in control state (>40 ms) in 51% of patients, but APERPs did not decrease significantly after isoproterenol: in these patients with shorter APERP at esophageal EPS, age and gender was similar to other patients; APERPs in basal state were shorter than in patients with similar APERPs at both studies (255±43 vs 281±61)(p0.032), but APERPs after isoproterenol were similar (226±33 vs 231±45)(0.55); the shortening of APERP after infusion of isoproterenol was significantly less than in patients with similar APERPs at esophageal and intracardiac EPS (30±31ms vs 49±45 ms)(p<0.05). The sensitivity of esophageal EPS in prognostic assessment was 88% in control state, 100% during isoproterenol infusion. The area under ROC curve of transesophageal EPS in prognostic assessment based on APERP measurement was 0.74. Esophageal EPS was a reliable and sensitive method of prognostic assessment in patients with PS. APERP was shorter in 51% of patients but did not decrease significantly after isoproterenol at esophageal EPS compared to intracardiac EPS, indicating esophageal EPS-related stress.

0048: A long accessory pathway refractory period measured by oesophageal atrial stimulation is always associated with a benign form of preexcitation syndrome

Measurement of accessory pathway (AP) refractory period (RP) is required for the evaluation of preexcitation syndrome (PS). The purpose of study was to evaluate the measurement of AP-RP by transesophageal electrophysiological study (EPS) and intracardiac EPS. EPS was performed in 51 patients aged from 13 to 50 years (mean 30±16) for a PS. Atrial stimulation was performed in control state (CS) at a cycle length of 400ms and coupling was decereased until AP6RP or atrial RP. Measurement was repeated after isoproterenol when AP-RP≥250ms in CS. Measurement was performed by transesophageal route and then by intracardiac route, with a delay not >3 months. AP-RP’s were 267±50ms in CS, 233±49ms after isoproterenol at transesophageal EPS, 309±72ms in CS, 280±64ms after isoproterenol at intracardiac EPS (p<0.002). Among 31 patients with initially AP-RP ≥250ms at transesophageal EPS, AP-RP was ≤220ms after isoproterenol in 12 patients. All, but one had an AP-RP≥250ms in CS at intracardiac EPS; one patient with AP-RP of 270ms at esophageal EPS had a value of 240ms at intracardiac EPS in CS but value was 250ms after isoproterenol. Three patients with transesophageal AP-RP in CS and after isoproterenol ≥280ms had lost their anterograde conduction. At transesophageal EPS, AP-RP was <250ms in 20 patients of which only 8 had a short AP-RP at intracardiac EPS and 3 had a short AP-RP after isoproterenol. There was no significant difference for the induction of orthodromic tachycardia at transesophageal and intracardiac EPS (72%) and there was a similar induction of atrial fibrillation at transesophageal EPS (32%) and intracardiac EPS (28%). A long AP refractory period measured at transesophageal EPS excluded the presence of an AP with a short refractory period at intracardiac study even after isoproterenol. There was an adrenergic factor during transesophageal EPS and isoproterenol produced a significant shortening of AP refractory periods in only 39% of patients with AP-RP ≥250ms. When AP-RP is ≥280ms at transesophageal EPS, the loss of anterograde conduction in AP can be expected in the following weeks (15%).

0035: Unpredictable long-term follow-up of untreated preexcitation syndrome

Accessory pathway (AP) ablation is currently performed in patients with a preexcitation syndrome (PS); natural follow-up is based on old studies. The purpose of the study was to report data of untreated patients with PS, studied 2 times at least one year of interval. 2 baseline electrophysiological study (EPS) were performed within 1 to 25 years of one another (mean 9.5±7) in 104 patients, 58 males, 46 females, aged initially from 4 to 67 y (30±16), with overt PS. First EPS was indicated for syncope (n=10), atrioventricular reentrant tachycardias (AVRT)(n=51), atrial fibrillation (AF)(n=6), spontaneous malignant form (AF conducted at very high rates over AP)(n=4) or for asymptomatic PS (n= 33). The protocol was similar, performed in control state (CS) and after isoproterenol. At 2 nd EPS, among patients studied for syncope at EPS1, 2 have still syncope, 3 have AVRT, 1 has AF, 3 are asymptomatic. Among patients with AVRT at EPS1, 38 (74.5%) have AVRT, 8 are asymptomatic, 3 had syncope, 3 has AF. Among patients with AF, 2 present with a malignant form, 2 had AVRT, 1 is asymptomatic. Among asymptomatic patients, 3 present with a malignant form, 17 (53%) remain asymptomatic, 7 have AVRT, 4 have syncope, 1 has AF.All AVRT or AF but 1 occurred in patients with inducible AVRT or AF at EPS1.The higher rate conducted by AP was lower in CS and after isoproterenol at EPS2 (166±80bpm, 191±90) than at EPS1 (191±67, 243±67)(p<0.01). AP refractory periods increased from 268±73ms to 283±62 in CS (p<0.03) and from 202±46 to 244±54ms after isoproterenol (p<0.03). AP has lost anterograde conduction properties in 28 patients. AVRT was induced in 5 of 27 asymptomatic PS with initially negative EPS. Two patients with initially poor anterograde conduction over AP have a very rapid conduction over AP several years later. We generally report an improvement of electrophysiological data with the time; however AVRT induction remains present in 74.5% of cases; unexpected changes may occur in 2% of patients considered initially at low risk who developed a dramatic shortening of AP refractory period several years after initial measurement.

Is the Measurement of Accessory Pathway Refractory Period Reproducible?

IntroductionShort accessory pathway (AP) effective refractory period (ERP) is one of the risk factors in Wolff-Parkinson-White syndrome (WPW). The purpose of study was to evaluate the reproducibility of APERP measurement during a same electrophysiological study (EPS). MethodsEPS consisted of 2 APERP measurements performed prospectively in 77 patients for a WPW in control state (CS) at a cycle length of 400ms (n=76) and after isoproterenol (n=56). ResultsIn CS, 18 patients (24 %) had the same APERP at both measurements; 41 (54.6 %) had differences from 10 to 40ms, 17 (22.4 %) had differences >40ms. Among 45 patients with initial APERP>240ms, 7 had an APERP≤240ms at 2nd study. Among 31 patients with initial APERP≤240ms, 5 had an APERP>240ms at 2nd study. Pearson’s productmoment correlation was 0.75. After isoproterenol, 5 patients (9 %) had the same APERPs; 37 (66 %) had differences from 10 to 40ms and 14 had differences >40ms. Among 38 patients with initial APERP>200ms, 12 had an AP ERP≤200ms at 2nd study. Among 18 patients with initial APERP≤200ms, 10 had still APERP≤200ms at 2nd study. Pearson’s productmoment correlation was 0.54. ConclusionsThere are important variations of APERPs during EPS mainly after isoproterenol infusion. Therefore the values of APERPs should be interpreted cautiously.

182 Is the measurement of accessory pathway refractory period reproducible?

Short accessory pathway (AP) refractory period (RP), atrial fibrillation (AF), were reported as risk factors of sudden death in Wolff-Parkinson White syndrome (WPW). A short AP RP is defined as 240 ms in control state (CS) and 200 ms after isoproterenol (iso). The purpose of study was to evaluate the reproducibility of the measurement of AP RP during a same electrophysiological study (EPS). 76 patients (pts) aged from 8 to 68 years (mean 30 ± 16.5) were studied prospectively for a preexcitation syndrome. EPS consisted of programmed atrial stimulation in CS at a basic cycle length of 400 ms with the introduction of one extrastimulus and the decrease of coupling until the effective AP RP or atrial RP. The measurement was repeated twice. Then, iso (0.02 to 1 μg.min −1 ) was infused to increase the sinus rate to at least 130 beats/min and the programmed atrial stimulation was repeated twice in 56 pts. We noted important variations of AP RPs with generally a shortening at the second measurement. Mean variations were 34 ± 51 ms in CS and 32 ± 24 after iso. The mean values in CS were 280 ± 50 ms and then 253.5 ± 59 ms (p<0.003). The mean values after iso were 239 ± 45 ms and then 209 ± 39 ms (p<0.0001). In CS 55 pts had initially an AP RP > 240 ms (mean 304 ± 36); at other study, mean values were 278 ± 44; 14 of them had an AP RP < 240 ms at the other measurement. Most of changes (n = 9) occurred in pts with AP RP <280 ms. 21 pts had a short AP RP (<250 ms) (mean 220 ± 18). All of them had still a short AP RP at other measurement (mean 204 ± 24). After iso 49 pts had an AP RP longer than 190 ms (mean 248 ± 41). At the other study mean value was 215 ± 35 ms; 15 pts had an AP RP < 200 ms at the other study; all of them had an initial value < 250 ms. Among 7 pts with initial AP RP < 200 ms all of them but one had an AP RP < 200 ms. There are important variations of AP refractory periods during electrophysiological study except in patients with very short AP refractory periods. Therefore the values of AP RP's should be interpreted carefully in association with the other data of electrophysiological study as the induction of tachycardias.

G007 Actual data of patients with Wolff-Parkinson-White syndrome and with spontaneous life-threatening arrhythmia

Serious events were reported in Wolff-Parkinson-White syndrome (WPW). Male sex, young age, sport, septal accessory pathway (AP), short AP refractory period, atrial fibrillation (AF) were reported as risk factors of sudden death (SD). The purpose of the study was to look for the predictors of adverse events in WPW. Adverse event occurred in 54 of 602 patients with a WPW (9 %) (group I). Other patients (group II) had syncope (61), tachycardias (285) or were asymptomatic (205). Clinical and electrophysiological data were collected. WPW was considered at risk of SD when AF had shortest RR interval < 250 ms in control state (CS), < 200 ms with isoproterenol. In group I, event was resuscitated SD (5), syncopal AF requiring urgent treatment. Facilitating factors were heart disease (4), sport (4), stress (2), calcium inhibitors (3), post operative period (2), hyperthyroidism (1). Age was higher in group I (39 ± 18) than II (34 ± 16)**. Sex male was as frequent in groups I and II (65 %, 59 %). AP left lateral location was more frequent in group I (70 %) than II (37 %)***, posteroseptal location less frequent in group I than II (20 % vs 48 %)***. Re-entrant tachycardia was more frequent in group I (30 %) than in asymptomatic patients (12.5 %)**, but less frequent than in group II patients with tachycardia (80 %)***. AF was more frequent in group I (98 %) than in asymptomatic patients (23 %) or with tachycardia (16 %)***. Maximal rate conducted by AP was higher in group I than II in CS (264 ± 43 b/min vs 186 ± 58) or after isoproterenol (324 ± 26 vs 238 ± 66)**. Malignant form was more frequent in group I (92.5 %) than II (10 %)***. risk factors of adverse event as the first manifestation of WPW have changed during the last years. Sport activity was rare but factors as drugs, post surgery were noted. Posteroseptal location was rare and left lateral location was the most frequent location. Age was relatively high and the women had risks similar to those of men.

The Natural History of Asymptomatic Ventricular Pre-Excitation: A Long-Term Prospective Follow-Up Study of 184 Asymptomatic Children

The aim of this study was to describe the natural history of asymptomatic ventricular pre-excitation in children and to determine predictors of potentially life-threatening arrhythmic events. Sudden death can be the first clinical manifestation in asymptomatic children with ventricular pre-excitation, but reduction of its incidence by prophylactic ablation requires the identification of subjects at high risk. Between 1995 and 2005 we prospectively collected clinical and electrophysiologic data from 184 children (66% male; median age 10 years; range 8 to 12 years) with asymptomatic ventricular pre-excitation on the electrocardiogram. After electrophysiologic testing, subjects were followed as outpatients taking no medications. The primary end point of the study was the occurrence of arrhythmic events. Predictors of potentially life-threatening arrhythmias were analyzed. Over a median follow-up of 57 months (min/max 32/90 months) after electrophysiologic testing, 133 children (mean age 10 years; range 8 to 12 years) did not experience arrhythmic events, remaining totally asymptomatic, while 51 children had within 20 months (min/max 8/60 months) a first arrhythmic event, which was potentially life-threatening in 19 of them (mean age 10 years; range 10 to 14 years). Life-threatening tachyarrhythmias resulted in cardiac arrest (3 patients), syncope (3 patients), atypical symptoms (8 patients), or minimal symptoms (5 patients). Univariate analysis identified tachyarrhythmia inducibility (p < 0.001), anterograde refractory period of accessory pathways (APERP) </=240 ms (p < 0.001), and multiple accessory pathways (p < 0.001) as risk factors for potentially life-threatening arrhythmic events. Independent predictors by multivariate analysis were APERP (p = 0.001) and multiple accessory pathway (p = 0.001). These findings are potentially relevant in terms of early identification of high-risk asymptomatic children with ventricular pre-excitation. Subjects with short APERPs and multiple pathways are at higher risk of developing life-threatening arrhythmic events and are the best candidates for prophylactic ablation.

Étude électrophysiologique par voie transœsophagienne chez des enfants de moins de 11 ans, non sédatés, ayant un syndrome de Wolff-Parkinson-White

The electrophysiological evaluation of Wolff–Parkinson–White syndrome (WPW) is recommended in children aged more than five years to detect a risk of life-threatening arrhythmia. The purposes of the study were to determine the feasibility of transesophageal EPS in a child between six and 10 years in out-patient clinic. Methods Electrophysiological study (EPS) was indicated in 22 children, aged six to 10 years, with a manifest WPW either for no documented tachycardia ( n = 7), unexplained dizziness ( n = 2) or for a sportive authorization in 10 asymptomatic children. Two of the last children had a history of permanent tachycardia after the birth but were asymptomatic since the age of one year without drugs. Results EPS was performed in all children. The main difficulty lied in passing the catheter through the mouth. Programmed stimulation at cycle length of 380 ms was performed in all children to avoid high rates of pacing when the conduction through the accessory pathway (AP) and normal AV system was evaluated. Isoproterenol was not required in five children, because they developed a catecholaminergic sinus tachycardia. The AP refractory period was determined in all children between 200 and 270 ms. Orthodromic reentrant tachycardia (RT) was induced in 11 children, three asymptomatic children (27%), seven complaining of tachycardia and one with syncope. Rapid antidromic tachycardia was induced in this last child with dizziness. Atrial fibrillation was never induced. Conclusions Esophageal EPS can be performed without sedation in a young child six to 10-year-old with a shortened protocol of stimulation, which was capable to clearly evaluate the WPW-related risks.

Sudden Death and Ventricular Preexcitation: Is it Necessary to Treat the Asymptomatic Patients?

Currently, asymptomatic ventricular preexcitation, which has been put at rest for many decades, remains a clinical challenge as there are no predictors of sudden death, which can be the first clinical presentation of the syndrome. Identification of risk factors for sudden death is important, considering the availability of a definitive treatment. Now, as radiofrequency catheter ablation of accessory pathways has reported success rates approaching 100 percent without major complications in many centers worldwide, it becomes unacceptable that even one asymptomatic individual with WPW will die or will experience life-threatening arrhythmic events. In our extensive experience a short anterograde refractory period of accessory pathways, inducibility of sustained tachyarrhythmias and the presence of multiple accessory pathways are the strongest predictors of life-threatening arrhythmias and sudden death. Therefore, it is not yet justified that, after an incidental diagnosis of WPW syndrome has been made, no risk stratification by invasive testing is done. Subjects at high risk, particularly if young or adolescent, should be identified and then ablated in the same session as they can develop lethal arrhythmic events within a few years and this is our current practice. Recently, we sent a questionnaire to investigate clinical practices over a large number of centers around the world about asymptomatic ventricular preexcitation. A total of 100 replies were received and the results demonstrate that there is worldwide agreement in performing invasive electrophysiologic testing and prophylactic ablation in selected subjects. These findings provide strong evidence to revisit current guidelines, which appropriately in the absence of evidence had been conservative.

The relation between atrial fibrillation wavefront characteristics and accessory pathway conduction.

Although the source-sink relationship for impulse propagation in cardiac tissues has been demonstrated in vitro, there has been no verification of this hypothesis in humans. Accordingly, eight patients undergoing surgical division of their accessory pathways were studied. A 56-channel (7 x 8) bipolar plaque electrode array was placed over the atrioventricular groove on the accessory pathway and atrial fibrillation electrically induced. 10 episodes of QRS transition from consecutively preexcited to nonpreexcited complexes were analyzed. This showed that consecutively preexcited QRS complexes were always associated with uniform large atrial wavefronts. Immediately prior to QRS transition, four general types of changes were observed: (a) premature invasion by secondary wavefronts creating local conduction block (n = 5); (b) wavefront collision leading to wavefront curvature (n = 2); (c) transition from a uniform large atrial wavefront to multiple fractionated small wavefronts (n = 1); and (d) uniform atrial wavefronts "marching" into the accessory pathway refractory period (n = 2). We conclude that local atrial wavefront characteristics are important factors influencing impulse propagation through the accessory pathway. The findings that local wavefront collision, curvature, or fractionation often precede loss of accessory pathway conduction support the notion that source-sink relationship is an important determinant of the safety factor for impulse propagation in the human heart.

Limitations of adenosine in assessing the efficacy of radiofrequency catheter ablation of accessory pathways

Adenosine has been shown to reliably confirm the success of accessory pathway catheter ablation by producing transient atrioventricular (AV) block during atrial and ventricular pacing. This is due to the insensitivity of accessory pathway conduction to adenosine (with the rare exception of accessory pathways with decremental conduction properties). However, 4 of 204 consecutive patients who underwent successful accessory pathway ablation (as shown by adenosine-induced transient AV block) had recurrent AV reciprocating tachycardia involving a second, previously nonmanifest accessory pathway. In each case, the second accessory pathway was localized to a site disparate from the original pathway. No pathway showed decremental anterograde or retrograde conduction properties. In 2 patients, adenosine initially did not show the presence of the second concealed accessory pathway, because the refractory period of the accessory pathway was longer than the pacing cycle length used to assess ventriculoatrial conduction. Only when the refractory period of this second accessory pathway was shortened by infusion of isoproterenol did adenosine reveal the presence of the pathway during follow-up electrophysiologic study. In another patient, a non-decremental accessory pathway was shown to be sensitive to adenosine. In the remaining patient, the second accessory pathway may have been transiently injured during the initial study, thereby simulating adenosine sensitivity. Therefore, it is concluded that (1) adenosine is a highly, but not completely, effective method for immediately assessing the efficacy of accessory pathway catheter ablation; (2) concomitant infusion of isoproterenol during adenosine administration is necessary to recognize the presence of accessory pathways with prolonged refractory periods; and (3) assessment of the presence of accessory pathway conduction with adenosine after ablation should preferably be performed at the longest possible, paced cycle length.

Effects of postural changes versus exercise on the electrophysiologic parameters of the accessory pathway

The electrophysiologic profile of the accessory pathway was studied in 17 patients (mean age ± standard deviation 32 ± 14 years) with Wolff-Parkinson-White (WPW) syndrome who were either lying down in a supine position, standing, or undergoing isometric or dynamic treadmill exercise. There were significant decreases in the PP interval after isometric exercise, standing and dynamic exercise (supine 764 ± 224, standing 638 ± 146, isometric 60S ± 170, treadmill 455 ± 86 ms; p <O.O5). Both anterograde and retrograde accessory pathway refractory periods were measured after a constant drive of 400 ms during lying down supine, standing and isometric and treadmill exercise (Bruce protocol stage II). There was no significant decrease in the anterograde accessory pathway refractory period during isometric exercise (lying down 26S ± 22 to isometric exercise 256 ± 13 ms, p <O.OS), but there were significant decreases (p <O.OS) during standing (246 ± 24 ms) and treadmill exercise (235 ± 17 ms). The retrograde accessory pathway refractory period also showed a significant decrease (supine 272 ± 16, isometric 267 ± 23, standing 249 ± 15, treadmill 237 ± 17 ms; p <O.O5). The relative change in refractory periods was greater when patients changed from lying down to standing than when they changed from standing to treadmill exercise, despite obvious higher adrenergic neuronal activities during exercise. These findings suggest that testing the accessory pathway during free standing can give a reliable indication of the sensitivity of the accessory pathway to sympathetic stimulation. Further increase in sympathetic stimulation, as judged by increases in the sinus rate, does not cause proportional reduction in the refractoriness of the accessory pathways.

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.

Ｐｉｒｍｅｎｏｌ単回経口投与の電気生理学的効果と心血行動態に及ぼす影響

The electrophysiologic and hemodynamic effects and the pharmacokinetics of a single oral administration of pirmenol were evaluated in 20 patients with supraventricular tachycardia (SVT). Pirmenol, at 1hr after administration, significantly shortened sinus cycle length and sinoatrial conduction time. HV interval (46±10msec to 54±11msec, P<0.01), refractory period of the right atrium and the right ventricle were significantly prolonged. Furthermore, anterograde refractory period of accessory pathway and retrograde refractory period of AV node and accessory pathway were prolonged. Hemodynamic study revealed increased systemic and pulmonary vascular resistance and decreased stroke volume index. Induction of SVT was suppressed in 11 out of 16 patients. Among 5 patients who were not suppressed at 1hr, 2 patients resulted in noninducible at 2hr after administration. Plasma concentration of pirmenol at 1hr after administration was 1.0±0.4μg/ml in effective cases and was 0.4±0.5μg/ml in failed cases (P<0.05). Pharmacokinetics of single oral pirmenol were, tmax of 2.9hr, Cmax of 1.4μg/ml, t1/2 of 6.8hr and AUC of 18.7μg·hr/ml. In conclusion, a single oral administration of pirmenol was highly effective in suppression of induction of SVT with sufficient hemodynamic tolerance.

Linking: A Mechanism of Intermittent Preexcitation in the Wolff‐Parkinson‐White Syndrome

Intermittent preexcitation in the Wolff-Parkinson-White syndrome has been equated with a long accessory pathway refractory period and long R-R interval between preexcited beats in atrial fibrillation and therefore a low risk for sudden death. A case of Wolff-Parkinson-White syndrome in which preexcitation became intermittent following procainamide infusion, with only moderate prolongation of the accessory pathway refractory period but marked prolongation of the shortest preexcited R-R interval in atrial fibrillation, is described. Programmed ventricular and atrial stimulation demonstrated that intermittent preexcitation was caused by concealed conduction producing a linking phenomenon, facilitated by the antiarrhythmic drug. Linking due to concealed retrograde penetration of a propagated impulse into the accessory pathway may contribute to the disparity between accessory pathway refractory period and shortest preexcited R-R interval in atrial fibrillation in some patients and may be a confounding factor in the interpretation of noninvasive tests of accessory pathway conduction.

Prognostic value of electrophysiology testing in asymptomatic patients with Wolff-Parkinson-White pattern.

The prognostic value of electrophysiology testing was studied in 75 asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. All patients underwent electrophysiology testing at entry to the study and were followed up annually for a total of 348 patient-years (median, 4.3 years). There were 44 male and 31 female patients, and age at enrollment ranged from 7 to 77 years (mean, 34 +/- 14 years). The median effective refractory period of the accessory pathway was 293 msec (interquartile range, 280-310 msec), and the median shortest RR interval between preexcited beats during atrial fibrillation (SRR) [corrected] was 274 msec (240-320 msec). Twenty-three patients had an SRR of 250 msec or less and eight patients had a median shortest SRR interval of 200 msec or less. Twelve patients had inducible sustained reciprocating tachycardia, 10 patients had inducible nonsustained reciprocating tachycardia, and 23 patients had inducible sustained atrial fibrillation. Twenty patients (27%) lacked retrograde conduction over the accessory pathway. No patient died suddenly during a median follow-up of 4.3 years. Six patients (8%) became symptomatic with documented supraventricular tachycardia, of whom two underwent operative ablation of their accessory pathways. No patient with absent retrograde accessory pathway conduction during the electrophysiology study became symptomatic. Inducible sustained or nonsustained reciprocating tachycardia at electrophysiology study did not predict the development of subsequent symptomatic supraventricular tachycardia. Nine patients lost preexcitation during follow-up. Age at enrollment (relative risk/decade, 1.4; 95% confidence interval, 1.0-1.8) and anterograde accessory pathway refractory period (relative risk, 1.06/10 msec; 95% confidence interval, 1.0-1.12) were independent predictors of loss of preexcitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Electropharmacology of flestolol for supraventricular tachycardia without associated structural heart disease

Flestolol is an ultrashort-acting β-blocking drug with a half-life of 6.9 minutes. Its antiarrhythmic efficacy was studied in 21 patients with spontaneous and inducible supraventricular tachycardia: atrioventricular (AV) nodal tachycardia in 6 patients and orthodromic AV reciprocating tachycardia in 15. It increased the effective refractory period of the AV node in all patients with AV nodal tachycardia (fast pathway, p < 0.02; slow pathway, p < 0.01), but did not alter the anterograde (n = 8) or retrograde (n = 9) refractory periods of accessory pathways. Flestolol prevented initiation of tachycardia by causing block in anterograde AV nodal conduction. It was more effective in patients with AV nodal tachycardia (5 of 6) than in those with AV reciprocating tachycardia (4 of 15, p < 0.03). In patients in whom it was ineffective, the mean tachycardia cycle length increased by 54 ms because of an increase in AH interval (p < 0.0001, n = 11). The cycle length of tachycardia induced 30 minutes after infusion was similar to the cycle length in the control state (354 vs 355 ms, n = 16). Flestolol's kinetics permitted clinically indicated electropharmacologic testing of a second antiarrhythmic drug in 8 patients and control of ventricular rate until arrhythmia surgery in 1 patient with incessant tachycardia. No hypotension or toxicity occurred. Our findings indicate that flestolol's principal antiarrhythmic effects are on the AV node, similar to the effects of other β-blocking drugs. Its ultrashort duration of action is an advantage during electropharmacologic testing.