Radiofrequency Ablation Of Accessory Pathways Research Articles

Dyssynchronous cardiomyopathy in patients with WPW syndrome and its reversibility after RFA of accessory pathway

Abstract Introduction In some cases accessory pathway-mediated ventricular preexcitation can be associated with electro-mechanical dyssynchrony and, consequently, with dyssynchrony-related dilated cardiomyopathy, even in the absence of supraventricular tachycardia (SVT). Sometimes rapid progression of ventricular dysfunction developed in such patients after birth. Methods and materials 8 patients with asymptomatic WPW and dyssynchronous cardiomyopathy were examined in our Institute from 2017 till 2019. Four patients of the group were observed in other clinics with dilated cardiomyopathy (DCM) and prescribed appropriate therapy without significant clinical effect. The absence of complaints of heartbeat and episodes of tachycardia at the scheduled Holter monitoring allowed eliminating incessant tachycardia as a possible cause of cardiomyopathy. After radiofrequency ablation (RFA) all patients were performed ECG to assess QRS duration, Holter monitoring, echocardiography (Echo) for assessment of heart chamber volume and left ventricle (LV) contractile function and Speckle tracking – Echo with LV longitudinal strain assessment. The average age of the patients was 9.5 years (from 2 to 14 years). 6 children had heart failure (NYHA Class II). Results According to Echo all patients had widened QRS complex. Dilatation and enlargement of LV volume were marked in 6 pts. According to Echo7 patients had decrease of LV contractile function. According to Speckle tracking – Echo all patients had intraventricular dyssynchrony, decrease of longitudinal strain indices. At intracardiac electrophysiology study right-sided accessory pathways was diagnosed in all patients, successful RFA was performed. Preexitation relapsed, and the repeated RFA was performed in 2 pts. Complications caused by RFA were not marked. After RFA all patients showed a regular normalization of QRS duration. At the 5th day after RFA Echo was performed to all patients. The patients with initially decreased LV ejection fraction had it increased. The patients with initial dilatation and LV volume enlargement had normalization of the given indices. According to Speckle tracking – Echo normalization of global and regional myocardial function, LV longitudinal strain, disappearance of intraventricular and interventricular dyssynchrony were marked in all patients. The index of longitudinal strain was 17,0±0,64% before RFA, after RFA - 23,75±0,92% (p=0,ehab724.035946). Conclusion As a result of RFA of accessory pathways electromechanical resynchronization causes LV demodeling and restoration of its contractile ability. The presented clinical examples are an additional indication for RFA of accessory pathways even in the absence of SVT in patients regardless of age. Funding Acknowledgement Type of funding sources: None.

Coronary Occlusion to Avoid Heat Convection During Radiofrequency Ablation of an Accessory Pathway.

Radiofrequency ablation (RFA) of right free wall accessory pathway can be compromised by the proximity of the right coronary artery (RCA). We report a case of with a right sided accessory pathway despite previous RFA attempts with immediate loss of pre-excitation. The accessory pathway was mapped

СЛУЧАЙ СИНДРОМА ВОЛЬФА-ПАРКИНСОНА-УАЙТА И РАННЕЙ РЕПОЛЯРИЗАЦИИ ЖЕЛУДОЧКОВ С ВЫСОКИМ РИСКОМ ВНЕЗАПНОЙ СЕРДЕЧНОЙ СМЕРТИ

The article presents a case of diagnosis and treatment of Wolff-Parkinson-White syndrome combined with early ventricular repolarization syndrome in a 19-year-old patient. The clinical presentation was characterized by a rarer variant of tachycardia involving the manifest atrioventricular accessory pathway – antidromic atrioventricular reentrant tachycardia accompanied by syncope. The risk of sudden cardiac death was estimated based on the concomitant pathology. The indications for radiofrequency ablation of accessory pathway are presented and the method of carrying out ablation in the above patient is described.

Risk factors of atrial fibrillation recurrence despite successful radiofrequency ablation of accessory pathway: At 11 years of follow-up.

Previous reports on patients with radiofrequency catheter ablation (RFCA) of accessory pathway (AP) and atrial fibrillation (AF) include only short follow-up periods. The aim of this study was to analyze predictors of recurrence of AF in patients after successful RFCA of APs over long term follow-up periods. Of the 1,007 patients who underwent non-pharmacological treatment of APs (between the years 1993-2008), data of 100 consecutive patients were retrospectively analyzed (75 men, mean age 43.6 ± 14.7), with the longest period of follow-up (mean 11.3 ± 3.5 years) after successful RFCA of AP. In Group 1, there were 72 patients (54 men, mean age 40.66 ± 13.85 years) without documented episodes of AF after RFCA of AP. Group 2 consisted of 28 patients (21 men, mean age 50.79 ± 14.49 years) with AF episodes despite successful elimination of AP. In univariate analysis, patients from Group 1 were significantly younger at the time of abla-tion than patients from Group 2 (40.66 ± 13.85 vs. 50.79 ± 14.49 years; p = 0.002), had shorter his¬tory of AF episodes (4.11 ± 4.07 vs. 8.25 ± 7.50 years; p = 0.024) and had less frequently documented atrial tachycardia (AT) prior to ablation (3.39 vs. 20.00% years; p = 0.022). In multivariate analysis, the history of AF in years (p = 0.043), was an independent risk factor for AF recurrences. Older patient age, longer history of AF and AT prior to RFCA of APs identified a sub-group of patients who required additional treatment. In the multivariate analysis, the history of AF in years (p = 0.043) was a risk factor for AF recurrence.

Radiofrequency ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome: long-term risk of mortality and coronary events.

The long-term outcomes of radiofrequency catheter ablation (RFCA) in patients with Wolff-Parkinson-White syndrome (WPW) remain unclear. We investigated the impact of RFCA on the long-term risk of coronary events and mortality in WPW patients. We conducted a prospective cohort study utilizing the Taiwan National Health Insurance Research Database. Between 2000 and 2003, WPW patients with no prior coronary artery disease (CAD) history, aged over 18 years, who underwent RFCA were identified. WPW patients without RFCA were matched with propensity-score 1:4 matching for confounding coronary risk factors. The study outcomes were total mortality and coronary events. A total of 1524 matched non-ablated WPW patients (Group 1) and 381 ablated WPW patients (Group 2) were included. After a mean follow-up of 9.6 ± 2.9 and 10.3 ± 1.9 years, respectively, ablation group demonstrated a lower incidence of mortality compared with non-ablation group (17 vs. 26/1000 person-years, P < 0.001; adjusted HR: 0.57, 95% CI: 0.44-0.7). However, ablation group had a higher incidence of coronary events compared with non-ablation group (47 vs. 82/1000 person-years, P < 0.001; adjusted HR: 1.69, 95% CI: 1.4-2.04). The ablation-treated WPW patients had lower risk of total mortality but higher risk of coronary events than non-ablated WPW patients during the long-term follow-up. Coronary artery injury produced by RFCA may account for the increased risk of coronary events. Therefore, the ablation strategies to avoid coronary artery injury should be implemented.

0340: Initial experience with ultra-high density electroanatomical mapping for arrhythmias

We report our initial experience with the newly released ultra-high density (UHD) electroanatomical mapping system (Rhythmia, Boston Scientific) for arrhythmias. All procedures using the multielectrodes catheter (Orion, Boston Scientific) in our institution, for arrhythmias mapping were analyzed. Procedure and fluoroscopy times were also assessed. 20 patients were included (67,9±13 y) for radiofrequency ablation of accessory pathway (n=2) / typical flutter (n=5) / atrial fibrillation (AF n=2) / post-AF ablation left atrial tachycardia (AT n=6) / focal AT (n=2)/ left and right ventricular ectopies (n=3). 63 maps (3,15 maps per patient) were acquired within a mean mapping time of 18±10min per map, including a mean number of 10024,3±9371 electrograms per map (Figure): RA maps (flutter=12; sinus rhythm SR=14; coronary sinus CS pacing=4); left atrial maps (during tachycardia=18; SR=3; CS pacing=4); right ventricular maps (n=4); left ventricular maps (during tachycardia=3; pacing=1). Acute success was achieved in 19/20 patients. In one patient, the ablation could not be performed in the absence of clinical ectopies. Total procedure and fluoroscopy times were respectively 232±78min and 15,9±8 min. No periprocedural complications were noticed. UHD electroanatomical endocardial mapping can be safely performed in both atria and ventricles and allows fast and accurate mapping. Abstract 0340 – Figure: Ultra high density left atrial macro reentry map

Radiofrequency ablation of accessory pathways

Radiofrequency ablation of accessory pathways

Radiofrequency ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome: the long-term mortality and risk of atrial fibrillation.

To assess the long-term mortality and occurrence of post-ablation atrial fibrillation in patients undergoing a radiofrequency ablation for the Wolff-Parkinson-White (WPW) syndrome. A retrospective cohort study of patients (N = 362) subjected to radiofrequency ablation of the WPW syndrome at Aarhus University Hospital from 1990 to 2011. A comparison cohort (N = 3619) was generated from the Danish National Board of Health Central Population Registry. We found no significant difference in all-cause mortality when comparing the WPW group with the control group [hazard ratio (HR): 0.77 and confidence interval (CI): 0.47-1.25]. After radiofrequency ablation, the WPW group had a significantly higher risk of atrial fibrillation than the control group (HR: 4.77 and CI: 3.05-7.43). Atrial fibrillation prior to ablation (HR: 4.66 and CI: 2.09-10.41) and age over 50 years (HR: 9.79 and CI: 4.29-22.36) at the time of ablation were independent risk factors for post-ablation atrial fibrillation in the WPW group. Patients with radiofrequency ablation-treated WPW syndrome have a post-ablation mortality that is similar to the background population. The risk of atrial fibrillation remains high after radiofrequency ablation of the WPW syndrome.

Электрокардиографическая и электрофизиологическая топическая диагностика синдрома Вольфа–Паркинсона– Уайта и результаты радиочастотной аблации дополнительных предсердно-желудочковых соединений у больных с аномалией Эбштейна

Электрокардиографическая и электрофизиологическая топическая диагностика синдрома Вольфа–Паркинсона– Уайта и результаты радиочастотной аблации дополнительных предсердно-желудочковых соединений у больных с аномалией Эбштейна

Incessant Tachycardia After Radiofrequency Ablation of Accessory Pathway

Incessant Tachycardia After Radiofrequency Ablation of Accessory Pathway

Ablação com RF de arritmia na infância: registro observacional em 125 crianças

Radiofrequency ablation (RFA) in children is an increasingly common practice. To evaluate, in our institution, the results of RFA in children younger than 15 years. A total of 125 children submitted to RFA between May 1991 and May 2010 were analyzed. Sixty-seven (53.6%) children were males, aged between 44 days and 15 years (mean 8.6 ± 3.3 years) with median weight of 31 kg. Heart disease was present in 21 (16.8%) patients. The RFA of accessory pathways (AP) was the most common procedure (62 children - 49.6%). The RFA of nodal reentrant tachycardia (NRT) was the second most common arrhythmia in 27 (21.6%), followed by atrial tachycardia (AT) in 16 (12.8%) and ventricular tachycardias (VT) in 8 (6.4%) children. The success criteria were achieved in 86.9%, 96.1%, 80% and 62.5% of patients undergoing RFA of AP, NRT, AT and VT, respectively. Transient AVB occurred during RFA in 4 (3.2%) and LBBB in 7 (5.6%) children. Twenty-five children underwent a new RFA due to initial failure or recurrence. During the mean follow up of 5.5 ± 3.4 years, 107 (88.4%) remained without recurrence. There was no statistical difference regarding the results and the age at which the patient underwent the procedure. No child had persistent AVB or required a permanent pacemaker. Catheter ablation is a safe and effective alternative therapy in children with recurrent tachycardias refractory to medical treatment.

Management and outcome of Ebstein's anomaly in children

To assess clinical presentation, treatment, and outcome of children with Ebstein's anomaly. Data on long-term outcome of children with Ebstein's anomaly are scarce. Retrospective analysis of all children with Ebstein's anomaly treated between February, 1979 and January, 2009 in a single tertiary institution. Primary outcomes included patient survival and need for intervention, either cardiac surgery or catheter intervention. A total of 42 patients were diagnosed with Ebstein's anomaly at a median age of 5 days ranging from 1 day to 11.7 years. Symptoms included cyanosis, heart murmur, and/or dyspnoea. Associated cardiac anomalies occurred in 90% of the patients. Average follow-up was 9.5 plus or minus 7.0 years. The overall mortality rate was 14%. Of the six patients, three died postnatally before treatment. Cardiac surgery and/or catheter-guided interventions were required in 33 patients (79%). Cardiac surgery was performed in 21 (50%) patients at a median age of 9.1 years (range 0.1-16.5 years), including biventricular repair in 13 (62%), one-and-a-half chamber repair in seven (33%), and a staged single-ventricle repair in one. Peri-operative mortality was 4%. Catheter-guided interventions consisted of device closure of an atrial septal defect in three cases and radiofrequency ablation of accessory pathways in nine patients. The estimated 10-year survival was 85.3 plus or minus 5.6%. In children, Ebstein's anomaly is usually diagnosed in the first year of age. Even though children with Ebstein's anomaly often require an intervention, their peri-operative mortality is low and long-term survival is good. Symptomatic newborns requiring an intervention may have a worse outcome.

Better is the enemy of good: Not the right approach for ablation of accessory pathways

Originally attributed to the French writer and philosopher Voltaire in 1772, the aphorism stated in the title has been quoted to generations of medical students, residents, and junior attending physicians. While the French version “Le mieux est l’ennemi la begueule de bien” sounds rather elegant, the New York version “If it ain’t broke, don’t fix it” is somewhat less refined. This viewpoint can be considered practical wisdom or conversely a rallying cry for mediocrity. During the past decade, based on available literature and curriculum at scientific sessions, it appears that this philosophy may have been adopted by cardiac electrophysiologists with respect to the catheter ablation of accessory pathways. The safety and efficacy of radiofrequency catheter ablation of accessory pathways, particularly at major centers, have been commendable since its introduction. The initial riteria for determining successful sites for accessory pathay ablation were identified during surgical cryoablation nd catheter ablation utilizing DC current, establishing the oundation for future approaches. The introduction of transcatheter radiofrequency energy for arrhythmia ablation resulted in a smaller, more defined lesion delivered to the myocardium While this decreased the morbidity associated with accessory pathway ablation, it required more precise mapping in order to achieve a successful lesion. In the early 1990s, there was significant interest in identifying electrogram criteria for successful radiofrequency ablation of accessory pathways in the adult and pediatric populations. Interest in determining additional criteria or utilizing techniques to further assess electrograms for successful ablation has waned since the initial flurry of manuscripts. More recent attention regarding accessory pathway ablation has focused on challenging anatomic locations, including utilizing right coronary electroanatomic mapping for right freewall pathways and case reports of accessory pathway ablation from an epicardial or aortic sinus location. The progress that has been made with respect to catheter ablation of atrial fibrillation has redistributed the procedural case mix seen by the majority of internal medicine trained

Radiofrequency Ablation of Accessory Pathways in Children and Congenital Heart Disease Patients: Impact of a Nonfluoroscopic Navigation System

We sought to assess the impact of routine use of a nonfluoroscopic navigation system in the procedural aspects of radiofrequency ablation of accessory pathways (APs) in pediatric and congenital heart disease (CHD) patients and the reduction of fluoroscopy in different pathway locations. This was a retrospective review of 192 patients, divided in two groups: group A (76 patients, fluoroscopic only ablation) and group B (116 patients, combined use of fluoroscopy and a nonfluoroscopic system (NavX™). Comparison of procedural aspects (procedure time, fluoroscopy time, success, complications, and recurrences) was performed. The two groups were comparable in terms of age, AP location, and presence of CHD. The mean age was 11.34 ± 4.65 years in group A versus 10.91 ± 3.68 years in group B. The procedure duration was significantly shorter in group B than in group A (177.06 ± 62.18 vs 242.45 ± 99.07) (P < 0.001). There was a significant reduction in the fluoroscopy time in group B compared to group A (8.27 ± 8.23 vs 39.77 ± 32.65 minutes) (P < 0.001). The difference between the two groups was statistically significant in all categories of APs. The success rate was 97.4% in group A and 96.6% in group B. There were no complications directly related to the use of the nonfluoroscopic system. There was no difference in the recurrence rate. The use of a nonfluoroscopic system for catheter navigation resulted in significant reduction of total procedure and fluoroscopy time during catheter ablation of APs in pediatric and CHD patients, regardless of the location of the pathway, without a compromise in safety and efficacy.

Ablation d’un faisceau accessoire chez les enfants : indications et résultats

Introduction Radiofrequency ablation of accessory pathways (AP) has become a first-line treatment, except in young children where the indications are discussed because of radiation risks and complications of catheterization . The purpose of the study was to evaluate the indications and results of radiofrequency AP ablation in children and teenagers. Methods Electrophysiological study (EPS) was performed in 145 patients aged from 5 to 18 years (13.5 ± 3) with a preexcitation syndrome (PS). Results AP ablation was indicated in 66 children (group 1); others represent the group I. Group I was older and less frequently asymptomatic. All children with a spontaneous malignant form had an ablation. Group 1 has a faster conduction through the AP than group 2. The induction of reentrant tachycardia (RT), atrial fibrillation and the presence of a malignant form is more common in group 1. Failures or reappearances of WPW after ablation were frequent (20, 26%) related to a younger age (15 ± 3 vs 17 ± 4) (< 0.05). In group 2, one 18-year-old teenager with untreated RT died before ablation. Asymptomatic children are well with disappearance of PS in two. Medically treated symptomatic children are well. Conclusion If spontaneous malignant forms, symptoms with drugs or practice of competitive sport are indications of AP ablation, it is recommended to wait for adolescence in other children.

Mitral Stenosis with WPW Syndrome

The catheter ablation of accessory pathways in patient with underlying structural heart disease is essential and it can provide permanent cure. A 32 year farmer with WPW type A with recurrent supraventricular tachycardia with severe rheumatic mitral stenosis was investigated. Firstly, PTMC (Percutaneous Trans-catheter Mitral Commissurotomy) was performed successfully in this patient improving mitral valve area from 1.1 cm2 to 2.29 cm2 with 10 mmHg dropped in invasive mean left atrial and pulmonary pressure. After PTMC, basic EP (Electrophysiology) study with 4 catheters at coronary sinus (CS), right ventricular and atrium, and His was carried out. The earliest ventricular activation at sinus rhythm and atrial activation with ventricular pacing were observed both at CS-1 position. The inducible tachycardia was consistent with AVRT (Atrio-Ventricular Reentrant Tachycardia) involving the left lateral free wall accessory pathway. Mapping was performed around the CS-1 below the mitral valve with retrograde aortic approach. Radiofrequency energy was applied where ventricular activation was earlier than delta wave in surface ECG and retrograde atrial activation was earlier than CS 1 with ventricular pacing. The delta wave was disappeared and ventriculo-atrial dissociation was observed with ventricular pacing immediately after ablation indicating the successful ablation of left lateral free wall accessory pathway. Conclusively, successful radiofrequency ablation of accessory pathway in patients with structural heart disease is valuable and PTMC is a treatment option in selected cases of mitral stenosis.

208 Reappearance of the preexcitation syndrome after ablation; significance

Accessory pathway (AP) ablation is the treatment of choice of symptomatic patients (pts) with a Wolff-Parkinson-White (WPW) syndrome or pts with a malignant form at electrophysiological study (EPS). WPW can reappear after ablation. The purpose of the study was to look for the risk factors of AP reappearance and the clinical consequences. AP ablation was performed in 327 pts aged from 8 to 77 years (37 ± 16), with a WPW. Ablation failed in 6 pts. In other pts, the anterograde and retrograde conduction disappeared after AP radiofrequency ablation. Reappearance of AP occurred in 48 pts from several hours to several years. Their data were studied. There were no significant clinical differences between pts with and without reappearance of AF, concerning the age (33 ± 16 years vs 36 ± 16), the gender (male gender 28/48 vs 166/280), the reason of ablation (spontaneous malignant form: 10/48 vs 70/280; spontaneous AV reentrant tachycardia (AVRT): 29/48 vs 176/280, asymptomatic with electrophysiological signs of malignancy: 9/48 vs 38/280), the location of AP (left lateral AP: 21/48 vs 125/280, posteroseptal AP: 22/47 vs 119/280, anteroseptal: AP 5/47 vs 27/280). During the follow up, among 9 of 45 pts asymptomatic before ablation but with only inducible rapid AF at EPS, 2 pts became symptomatic and had inducible AVRT at the control. 29 of 202 pts with spontaneous AVRT presented recurrences of AVRT, except one and a 2 nd procedure was required. Among 10 of 79 with syncope and signs of malignancy or spontaneous rapid AF, 2 pts have lost the signs of malignancy at 2 nd EPS; 2 pts who presented only with rapid AF, had an AP with long refractory period but developed incessant AVRT's; 6 pts had still signs of malignancy, requiring a second procedure. There was no significant clinical or electrophysiological cause that explains the reappearance of AP after ablation. The reappearance of conduction is generally associated with reappearance of all properties of AP associated with malignancy or AVRT, except in some cases. Pts without AVRT before ablation may become symptomatic and develop this AVRT after AP ablation.

315 Indications of radiofrequency ablation of accessory pathway in the young population

Radiofrequency (RF) ablation of accessory pathway (AP) is widely used in Wolff-Parkinson-White syndrome (WPW), but the indications remain controversial in children and teenagers. The purpose of the study was to evaluate the clinical and electrophysiological factors associated with the indications of AP ablation in the youth. 133 children and teenagers aged from 5 to 18 years (13.5±3) were admitted for a WPW and electrophysiological study (EPS) either for tachycardia, syncope or they were asymptomatic. EPS was performed in control state and after isoproterenol. Then RF ablation was proposed in case of recurrent tachycardias or induction of rapid atrial fibrillation (AF). AP ablation was indicated in 51 children (38%), several years after initial evaluation in 5 of them (group I), and was not performed in 82 children (group II). The indications did not differ significantly from the adult population (232/504, 46%). Clinical and electrophysiological data of groups I and II were compared. Group I was older than group II (15±2 vs 13±4) (p<0.001); male sex was more frequent in group I (72.5%) than in group II (56%) (p<0.05); group I was less frequently asymptomatic (27%) than group II (55%) (p< 0.01) and had more frequently spontaneous reentrant tachycardias than group II (49% vs 28%) (p< 0.05). Syncope was as frequent in group I (21.5%) as II (18%). At EPS, group I had a more rapid conduction through AP than group II, in control state (208±68 b/min vs 176±53, p< 0.001), but not after isoproterenol (245±74 vs 230±63, NS). Reentrant tachycardia was induced more frequently in group I (70.5%) than II (37.5%) (p< 0.001). AF was induced more frequently in group I 35%) than in group II (11%). Malignant forms (rapid AF) were more frequent in group I (31%) than in group II (5%) (p< 0.001). Failures of ablation were as frequent in children (8%) as in adults (2.5%) (NS). The indications of AP ablation in the young population are based on recommended data and are similar to those of adults, with a similar risk of failure; they concern symptomatic or high risk children. The boys are referred more frequently than girls for the ablation.

Is radiofrequency ablation of accessory pathways always necessary?: The case of a variant of Wolff-Parkinson-White syndrome

A 16-year-old boy was referred for radiofrequency ablation of an accessory pathway. He had not experienced palpitations, but a normal electrocardiogram was a prerequisite for enrolment in a professional soccer school. The electrocardiogram showed a PR interval of 0.10 second and wide QRS complexes suggestive of an accessory pathway. The case of a variant of Wolff-Parkinson-White syndrome is discussed.

Reentry in an accessory atrioventricular pathway as a trigger for atrial fibrillation initiation in manifest Wolff-Parkinson-White syndrome: A matter of reflection?

Patients with an accessory pathway (AP) have an increased propensity to develop atrial fibrillation (AF), but the mechanism is unknown. The purpose of this study was to identify crucial risk factors and to test the hypothesis that reflection and/or microreentry of atrial impulses propagating into the AP triggers AF. Five hundred thirty-four patients successfully treated with radiofrequency ablation of AP at two university hospitals were evaluated. Patients were separated into those with concealed vs those with manifest AP in terms of their propensity to develop AF. To investigate AF triggering mechanisms, linear and branched two-dimensional models of atrium-to-ventricle propagation across a heterogeneous 1 x 6 AP using human ionic kinetics were simulated. A history of AF was twice as common in patients with manifest AP vs concealed AP irrespective of AP location. AF was more likely to occur in older males and in patients with larger atria. There was no correlation between AF history and AP refractory measures. However, the electrophysiologic properties of APs seemed to fulfill the prerequisites for reflection and/or microreentry of atrially initiated impulses. In the linear AP model, repetitive atrial stimulation resulted in progressively larger delay of atrium-to-ventricle propagation across the passive segment. Eventually, sufficient time for repolarization of the atrial segment allowed for reflection of an impulse that activated the entire atrium and by wavefront-wavetail interaction with a new atrial stimulus AF reentry was initiated. Simulations using the branched model showed that microreentry at the ventricular insertion of the AP could also initiate AF via retrograde atrial activation as a result of unidirectional block at the AP-ventricle junction. Propensity for AF in patients with an AP is strongly related to preexcitation, larger atria, male gender, and older age. Reflection and microreentry at the AP may be important for AF initiation in patients with manifest (preexcited) Wolff-Parkinson-White syndrome. Similar mechanisms also may trigger AF in patients without an AP.