Accessory Atrioventricular Pathway Research Articles

Two decades of SVT ablation in Denmark: a trend towards higher age, more comorbidity, and less prior use of antiarrhythmic and rate-limiting pharmacotherapy—a nationwide registry-based Danish study

Abstract Background and aims Trends in patient selection and use of pharmacotherapy prior to catheter ablation (CA) for supraventricular tachycardia (SVT) are not well described. This study examined temporal trends in patients undergoing first-time CA for regular SVT, including atrioventricular nodal re-entry tachycardia (AVNRT), accessory pathways (APs), and ectopic atrial tachycardia (EAT) on a nationwide scale in Denmark in the period 2001–2018. Methods and results Using Danish Nationwide registers, 9959 patients treated with first-time CA for SVT between 2001 and 2018 were identified, of which 6023 (61%) received CA for AVNRT, 2829 (28%) for AP, and 1107 (11%) for EAT. Median age was 55, 42, and 55 in the AVNRT, APs, and EAT group, respectively. The number of patients receiving CA increased from 1195 between 2001 and 2003 to 1914 between 2016 and 2018. The percentage of patients with a CHA2DS2-VASc score ≥ 2 increased in all patient groups. The number of patients who underwent CA with no prior use of antiarrhythmic- or rate limiting medicine increased significantly, though prior use of beta-blockers increased for AVNRT patients. Use of verapamil decreased in all three SVT groups (P < 0.05). Use of amiodarone and class 1C antiarrhythmics remained low, with the highest usage among EAT patients. Conclusion Between 2001 and 2018, CA was increasingly performed in patients with SVT, primarily AVNRT- and EAT patients. The burden of comorbidities increased. Patients undergoing CA without prior antiarrhythmic- or rate-limiting drug therapy increased significantly. Use of beta-blockers increased and remained the most widely used drug. Graphical Abstract

Hypertrophic Cardiomyopathy and Ventricular Preexcitation in the Young: Cause and Accessory Pathway Characteristics.

The cause of hypertrophic cardiomyopathy (HCM) in the young is highly varied. Ventricular preexcitation (preexcitation) is well recognized, yet little is known about the specificity for any cause and the characteristics of the responsible accessory pathways (AP). Retrospective cohort study of patients <21 years of age with HCM/preexcitation from 2000 to 2022. The cause of HCM was defined as isolated HCM, storage disorder, metabolic disease, or genetic syndrome. Atrioventricular AP (true AP) were distinguished from fasciculoventricular fibers (FVF) using standard invasive electrophysiology study criteria. AP were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in atrial fibrillation, shortest paced preexcited cycle length, or anterograde AP effective refractory period. We identified 345 patients with HCM and 28 (8%) had preexcitation (isolated HCM, 10/220; storage disorder, 8/17; metabolic disease, 5/19; and genetic syndrome, 5/89). Six (21%) patients had clinical atrial fibrillation (1 with shortest preexcited RR interval <250 ms). Twenty-two patients underwent electrophysiology study which identified 23 true AP and 16 FVF. Preexcitation was exclusively FVF mediated in 8 (36%) patients. Five (23%) patients had AP with high-risk conduction properties (including ≥1 patient in each etiologic group). Multiple AP were seen in 8 (36%) and AP plus FVF in 10 (45%) patients. Ablation was acutely successful in 13 of 14 patients with recurrence in 3. One procedure was complicated by complete heart block after ablation of a high-risk midseptal AP. There were significant differences in QRS amplitude and delta wave amplitude between groups. There were no surface ECG features that differentiated AP from FVF. Young patients with HCM and preexcitation have a high likelihood of underlying storage disease or metabolic disease. Nonisolated HCM should be suspected in young patients with large QRS and delta wave amplitudes. Surface ECG is not adequate to discriminate preexcitation from a benign FVF from that secondary to potentially life-threatening AP.

Long-term results of catheter ablation for AV nodal reentry tachycardias and accessory pathways

Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia in patients with accessory pathways (AP) are common supraventricular tachycardias. High long-term efficacy of about 97% (AVNRT) and 92% (AP) has been observed in children and adults. The risk of occurring atrioventricular block is low (0.4-0.8% during AVNRT, 0.1-0.2% for AP). Catheter ablation shows alower efficacy of 87-93% and elevated atrioventricular block risk up to 10% in patient groups with complex congenital heart disease. Nonsynchronized ventricular activation during preexcitation or permanent reentrant tachycardias can induce heart failure, and remission of left ventricular function can be expected in > 90% after successful catheter ablation. Therefore, catheter ablation is the long-term therapy of choice for AVNRT and AP with high efficacy and safety for most patient populations.

Landiolol, an intravenous β1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node.

During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site. We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation. We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020. Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence. Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

Retroflexed catheter course reduces the risk of right free wall accessory pathway recurrence.

Accessory atrioventricular pathways (APs) may mediate atrioventricular reciprocating tachycardia and, in some cases, have the potential to conduct atrial tachycardia rapidly, which can be life threatening. While catheter ablation can be curative, ablation of right free wall APs is associated with a high rate of recurrence, likely secondary to reduced catheter stability along the right free wall atrioventricular groove. We sought to identify characteristics associated with a lower rate of recurrence and hypothesized ablation lesions placed on the ventricular side of the atrioventricular groove using a retroflexed catheter approach would decrease rates of recurrence. Retrospective chart review of patients who underwent catheter ablation of a right free wall AP from January 1, 2008 through June 1, 2021 with >2 months follow up. Cox proportional hazards regression was used to identify relationships between predictor variables and AP recurrence. We identified 95 patients who underwent ablation of 98 right free wall APs. Median age was 13.1 years and median weight at ablation was 52.3 kg. Overall, 23/98 (23%) APs recurred. Use of a retroflexed catheter course approaching the atrioventricular groove from the ventricular aspect was associated with reduced risk of AP recurrence with (univariable hazard ratio of 0.10 [95% confidence interval: 0.01-0.78]), which remained significant in multiple two variable Cox proportional hazards models. Use of a retroflexed catheter course is associated with a reduced likelihood of AP recurrence. This approach results in improved catheter stability and should be considered for ablation of right free wall APs.

PRKAG2 and PRKAG3 genes in patients with Wolff-Parkinson-White syndrome: a literature review

Wolff-Parkinson-White syndrome (WPW) is a syndrome with early ventricular excitation due to the abnormal electrical conduction through an accessory atrioventricular pathway, and is usually accompanied by supraventricular tachycardia. There is a proven genetic component in the development of this syndrome. This review presents current literature data on the association of nucleotide sequence variants of the PRKAG2 and PRKAG3 genes in patients with WPW.

Corrected transposition of the great arteries with complete atrioventricular block and accessory pathway

Clinical data of a 39-year-old patient with corrected transposition of the great arteries, combined with complete atrioventricular block and conduction along an accessory pathway, are presented. The features of changes in the structure of the conduction system, rhythm and conduction characteristic of this rare congenital heart disease are discussed.

Ventricular pre-excitation in young patients: long term follow-up and natural history in a contemporary cohort

Abstract Funding Acknowledgements Type of funding sources: None. Background Ventricular preexcitation (VPE) due to atrio-ventricular accessory pathways (AP) has been associated to a higher incidence of sudden cardiac death (1,2). The incidence of major arrhythmic events (MAE) may be higher in children (1,3), but most of the past studies recruited a high proportion of patients with congenital heart disease (CHD), treated with outdated pharmacological therapy (1). Transcatheter ablation (TCA) of the AP is a safe and effective therapy and it is nowadays the standard of care (1,2). However, it may be less effective and more dangerous in smaller and younger children (1,3). It is described that patients may spontaneously lose VPE during childhood (1), but the natural history of VPE is not well understood yet. Purpose To study the natural history of VPE. We focused especially on the likelihood of spontaneous resolution of VPE during growth, the possible associated factors, and the incidence of MAE during a long follow up in a contemporary paediatric cohort. Methods We retrospectively recruited patients diagnosed with VPE at age 0 to 12, referred from 1993 to 2021 to two tertiary care hospitals. Significant CHD and double AP were excluded. The primary outcome was the spontaneous resolution of VPE, defined by the loss of short PR and delta wave seen in at least two consecutive ECG and/or on 24-hour Holter monitoring. The follow up stopped when the patients reached 16 years of age, met the primary outcome or effective TCA was performed. Given the time-to-event dependency of the condition, the survival analysis of VPE considered the left truncation resulted from the recruitment of patients after the first days of life. Results We recruited 153 patients with a median age of diagnosis of 4.9 (0.2 – 8.4). The median follow-up time was 4.9 (1.6 – 8) years. During follow-up, 42 (28%) patients spontaneously loss VPE. The left truncated Kaplan-Meier survival curve of VPE is shown in Picture 1. It estimates that VPE would persist in 53% (40.1-70.2) and 33.8% (23.7-48.4) of patients at the age of 1 and 16, respectively. Symptoms and intermittent preexcitation were the only variables significantly associated with lower (OR 0.2) and higher probability (OR 3.45) of SR of VPE. The vast majority of patients with symptoms was treated with drug therapy before the age of 8, and TCA was safely delayed thereafter. None of the patients experienced a MAE during follow up. Conclusion According to our data, a large proportion of paediatric patients are likely to spontaneously lose VPE within the first year of life, and a spontaneous resolution may occur later during childhood in a non-negligible number of cases. The absence of symptoms and/or intermittent preexcitation are significant predictors of loss of VPE. The results of our study are of the utmost clinical relevance, since they support a wait-and-see strategy, especially in very young children with VPE.

PO-03-125 VENTRICULAR PREEXCITATION AND PEDIATRIC HYPERTROPHIC CARDIOMYOPATHY: ETIOLOGY AND ACCESSORY PATHWAY CHARACTERISTICS

The etiology of pediatric hypertrophic cardiomyopathy (HCM) is varied. Ventricular preexcitation (VPe) is well recognized, yet little is known regarding the specific etiology, and accessory pathways (AP) characteristics. Define the etiology of HCM in patients with VPe and the characteristics of the responsible APs. Retrospective cohort study of patients <21 years of age with HCM/VPe from 2000-22. The etiology was defined as sarcomeric/non-sarcomeric (isolated HCM), storage disorder, metabolic disease, or genetic syndrome. AP were designated as atrioventricular (AV) or fasciculoventricular fibers (FVF) using standard invasive EP study criteria when available. AV APs were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in AF, shortest paced preexcited cycle length, or APERP. ECG characteristics were compared in patients with VPe exclusively secondary to an FVF to those with anteroseptal AP-mediated VPe. From a total of 345 patients with HCM, 28 (8%) had VPe and proportion with VPe varied significantly between etiologic groups: isolated HCM 10/220 (5%), storage 8/17 (47%), metabolic 5/19 (26%), genetic syndrome 5/89 (6%), p < 0.001. Six (21%) had clinical AF (1 with SPPRI <250 ms, 4 with storage disease). Invasive EP study was performed in 22, identifying 39 APs (23 AV AP, 16 FVF; fig 1). VPe resulted exclusively from an FVF in 8 (36%) patients. Multiple AV APs were seen in 8 (36%) and AV AP plus FVF in 10 (45%). Five (23%) patients had AV APs with high-risk conduction properties (≥1 in each etiologic group). Ablation was acutely successful in 13/14 patients with recurrence in 3. The only complication was a single case of heart block after ablation of a high-risk midseptal AP. Patients with storage disease had larger QRS amplitudes (median 42.3 v. 23.0 mm, p < 0.01). The delta wave amplitude did not discriminate between anteroseptal AP and FVF (median 4.3 v. 4.1 mm, p = 0.92). VPe and high risk or multiple AP may be associated with any etiology of childhood HCM. This is most common in storage disorders associated with high QRS amplitudes and clinical AF, with important implications for prognosis and management.

Accessory pathways in monozygotic twins with different clinical phenotypes: a case report

BackgroundThe atrioventricular reentrant tachycardia (AVRT) is the most common tachycardia associated with accessory pathways (APs). Although sporadic Wolff-Parkinson-White (WPW) syndrome has been well-described, AP occurrence in identical twins with WPW syndrome remains rarely reported.Case presentationWe report a case of 14-year-old monozygotic twin brothers referred for an electrophysiology (EP) study. Twin A presented with recurrent symptomatic narrow complex tachycardia after exercise, noted for 3 years. His 12-lead surface electrocardiogram (ECG) did not show ventricular pre-excitation. However, an orthodromic AVRT utilizing a concealed right posteroseptal AP was found and successfully ablated. AVRT did not recur 12 months after the procedure. Twin B was asymptomatic. During his medical examination for firefighter volunteerism, his 12-lead ECG showed a spontaneous ventricular pre-excitation. EP study revealed a short anterograde right midseptal AP, which was then successfully eliminated by catheter ablation. His 12-lead ECG showed no ventricular pre-excitation recurrence 12 months after the procedure.ConclusionsThese identical twin brothers had a right-side AP in almost the same place but showed completely different phenotypes. This case clearly illustrates the difficulty in understanding genetic contribution in the origin of atrioventricular APs. Environmental exposure could play a role in their clinical presentations and AP electrophysiological properties.

Catheter ablation of coronary sinus accessory pathways in the young

Accessory atrioventricular pathways (APs) are the most common tachycardia substrate for supraventricular tachycardia (SVT) in the young. Endocardial catheter ablation of AP may be unsuccessful in up to 5% of patients because of a coronary sinus location. The purpose of this study was to obtain data on ablation of accessory pathways within the coronary venous system (CVS) in the young. Analysis of feasibility, outcome, and safety in patients ≤18 years with coronary sinus accessory pathways (CS-APs) and catheter ablation via CVS in a tertiary pediatric electrophysiological referral center (May 2003 to December 2021) was performed. The control group adjusted for age, weight, and pathway location was established from patients of the prospective European Multicenter Pediatric Ablation Registry who all had undergone endocardial AP ablation. Twenty-four individuals underwent mapping and intended AP ablation within the CVS (age 2.7-17.3 years; body weight 15.0-72.0 kg). Because of proximity to the coronary artery, ablation was withheld in 2 of the patients. Overall procedural success was achieved in 20 of 22 study patients (90.9%) and in 46 of 48 controls (95.8%). Coronary artery injury after radiofrequency ablation was noted in 2 of 22 study patients (9%) and in 1 of 48 controls (2%). In CVS patients, repeat SVT occurred in 5 of 22 patients (23%) during median follow-up of 8.5 years, and 4 of the 5 underwent reablation, resulting in 94.4% overall success. Controls were free from SVT during follow-up of 12 months as defined by the registry protocol. Success of CS-AP ablation in the young was comparable to that of endocardial AP ablation. Substantial risk of coronary artery injury should be considered when CS-AP ablation is performed in the young.

Dual-chamber open-window mapping with a novel multispline mapping catheter for a left posterolateral atrioventricular accessory pathway

The conventional mapping approach for atrioventricular accessory pathways (APs) involves point-by-point mapping to identify the connection sites of the AP to the atria or ventricle, or the site where the AP potential is recorded. However, this approach requires an accurate interpretation of local electrograms. Some earlier reports have shown the efficacy of open-window mapping (OWM) for localizing the AP.1,2 The accuracy of the OWM may be enhanced by a novel multispline mapping catheter (Octaray, Biosense–Webster, Inc., Diamond Bar, CA).

PS-R02-9: A PATIENT HAS THE ONLY CONNECTION BETWEEN THE ATRIUM AND VENTRICLE IS AN ACCESSORY PATHWAY

Case report: A 62-year-old woman without cardiovascular risk factors such as hypertension, diabetes, smoking and hyperlipidemia was admitted to our cardiology outpatient clinic with palpitations and syncope history. Her electrocardiography showed preexcitation possible posteroseptal accessory pathway. We performed electrophysiological study and found posteroseptal accessory pathway. Tachycardia was not induced in inductions. ERP detected below 240 msn. The area where the shortest V-A interval was detected. His signal was not detected in this region. We determined that it was anatomically far from the AV node. We started radiofrequency ablation and in the 5. second of ablation, we saw that the patient entered 3. degree AV block. Ablation was immediately stopped then sinus rhythm restored in patients qucikly. We search his signal with ablation catheter in right atrium but could not find the signal. We detected that the AV block and accessory pathway were found together in the patient. Since the patient had a history of syncope and ERP &lt; 250 ms was detected, we planned ablation after pacemaker implantation in the patient. We implant DDDR pacemaker and 2 weeks later we make successfully accessory pathway ablation. Discussion: In these patients, atrioventricular conduction is done only, and entirely, via the accessory route. A complete block, nodal or sub-Hissian, underlying, will only be visible on the ECG if there is concomitant blockage of the atrioventricular conduction through the accessory pathway. The appearance of atrioventricular conductive disorders after radiofrequency ablation of an accessory pathway, located at a distance from the atrioventricular junction, is not considered by some authors to be a real complication of this procedure. It would rather be a prior conductive disorder having been unmasked following the blockage of the accessory pathway thanks to ablation. It is therefore logical to review the indication for the removal of the accessory pathway in these cases, especially in asymptomatic patients who have never reported a history of palpitation attacks. The only possible tachycardia remains atrial fibrillation on WPW. Only the study of anterograde refractory periods makes it possible to specify the correct indication for ablative treatment. The indication for the implantation of a pacemaker is still appropriate given the risk of progressive and subsequent degeneration of the accessory pathway. In addition, conduction via the accessory pathway, whether continuous or intermittent, would help prolong the longevity of the pacemaker by inhibiting ventricular pacing in the event of atrioventricular conduction through the accessory pathway.

Not Just a One-Way: Mahaim Accessory Pathway Concomitantly Supporting Orthodromic Atrioventricular Re-Entrant Tachycardia

We report the case of a 41-year-old female with documented narrow QRS tachycardia. During electrophysiological study, both orthodromic and antidromic atrioventricular reentry tachycardia (AVRT) were demonstrated as well as short episodes of pre-excited atrial fibrillation. Programmed atrial stimulation resulted in decremental anterograde conduction on the AP, thus confirming an unexpected Mahaim accessory pathway (AP) diagnosis. Limited 3D activation maps of the right atrium during orthoAVRT, respectively, and the right ventricle (RV) during antiAVRT were constructed and helped accurately describe the atrial and ventricular insertion points, which were superposed on the tricuspid ring, confirming the existence of a single short atrio-ventricular right free wall AP. Short atrioventricular APs with anterograde Mahaim-type conduction concomitantly sustaining orthodromic AVRT are extremely rare. Electroanatomical 3D mapping may help both to clarify the diagnosis and increase the success rate by accurately describing the insertion points of complex accessory pathways.

804 WOLF PARKINSON WHITE SYNDROME OR ASYMPTOMATIC VENTRICULAR PRE-EXITATION IN CHILDREN: EVALUATION OF ELECTROPHYSIOLOGICAL PROPERTIES CHANGES IN TWO DIFFERENT TIMING

Abstract Background In patients with Wolf Parkinson White (WPW) syndrome or asymptomatic ventricular pre-excitation (VP), electrophysiologic study (EPS) is recommended to assess and to stratify the risk of life - threatening arrhythmias and SCD. However, little information exist on the timing of EPS study. In particular, the electrophysiological properties variations of accessory pathway (AP) in patients with asymptomatic or symptomatic VP remain to be defined. Recently, the evolution of electrophysiological data was observed in a cohort of patients by including children and adults, although a transcatheter ablation (TCA) was performed during the evaluation among the two EPS. According to our knowledge, no study exists related to the changes over time in the conductive properties of an atrioventricular accessory pathway (AP) and arrhythmic vulnerability in the pediatric - young adult population. Aims The aim of our study was to investigate the evolution of clinical and electrophysiological datas of the manifest PV (intermittent or persistent), the arrhythmic vulnerability and any modifications in the features of AP anterograde conduction in symptomatic or asymptomatic children, examined on two separate timing, at least 2 years apart from one EPS to the next. Method This is a retrospective monocentric observational study performed at Bambino Gesu` Children's Hospital, Rome, Italy. Between January 2011 and July 2022, we enrolled forty-four children and young adults (32 male, mean age 10 years± 2,42) with manifest ventricular preexcitation underwent, as our standard management, at two electrophysiolgical studies (EPS, transesophageal and/or endocavitary), both at rest and during adrenergic stress (exercise testing or isoproterenol infusion) in two different timing (T0 and T1) within a minimal interval of 2 year. No transchateter ablation was performed between two EPS. Clinical and electrophysiological data were collected and compared. Results We observed a significant modification in atrioventricular accessory pathway conductive properties from T0 to T1 in basal study. In particular, at the baseline, preAVA value and 1/1 conduction VA time were respectively 306,59±43 and 292,61±61,7 and significatively decreased on occasion of second EPS evalutation (T1) (respectively to 279,51±41 with p 0,004 and 267,13±51,6, with p 0,003). Furthermore, an ARVT were induced in 14 patients in T1 respect 9 patient in T0 (p&amp;lt;0,03) and AF in 16 patients in T1 respect 7 patients in T0 (p 0,24). This results were not confirmed on adrenergic test during EPS evaluation. We also reported a clinically but not statistically relevant reduction of SPERRI time evaluated during EPS with stress test from T0 to T1 (from 251,44±47,9 to 206,9±36,7; p= 0,18). Conclusion There were significant and clinically rilevant changes of electrophysiological datas in young patients with symptomatic and asymptomatic VP underwent two EPS in two different timing. Therefore, in our opinion, a systematic evaluation with repeated EPS should be considered in this population.

Preexcitation with Multiple Accessory Pathways as a First Presentation of Undiagnosed Late Stage Ebstein’s Anomaly in an Adult

Ebstein’s anomaly (EA) is a relatively rare congenital heart disease that has long been a challenge both to cardiac surgeons and electrophysiologists. In addition to the hemodynamic burden of the tricuspid valve defect itself, the electrocardiogram (ECG) is abnormal in most cases with a high incidence of tachyarrhythmias, that can often be imputable to accessory atrioventricular pathways mostly located along the tricuspid posterior and septal valve leaflets, and rarely, to multiple accessory pathways. We here report the case of a 19-year-old girl with no known cardiac history, in whom a late stage EA with Eisenmenger syndrome, was diagnosed following a syncopal episode attributed to preexcited atrial tachy-fibrillation with an aspect consistant with multiple accessory pathways with at least one of them being right postero-septal. The patient’s management was very challenging for the heart team considering the fixed pulmonary hypertension and the fact she was reluctant to catheter ablation. This case report underlines the importance of early diagnosis and treatment of EA and its rhythmic complications and explores the anatomic peculiarities of this disease with attention to features that could be important to both arrhythmogenesis and ablation therapy in this unique population.

Anatomy for ablation of atrioventricular nodal reentry tachycardia and accessory pathways.

The atrioventricular (AV) valve plane and the central septum are of particular importance for electrophysiological diagnosis and interventional therapy of supraventricular tachycardias because accessory electrical connections of various types may be present in addition to the specific conduction system. Although modern 3D electroanatomic reconstruction systems including high-density mapping can be of great assistance, detailed knowledge of the anatomic structures involved, their complex three-dimensional arrangement, and their electrical properties in conjunction with electrophysiological features of supraventricular arrhythmias is essential for safe and efficient electrophysiological treatment. The aim of this article is to present current anatomical, topographical, and electrophysiological findings against the background of historical, seminal, and still indispensable literature.

P5 ACCESSORY PATHWAYS HIGH–DENSITY MAPPING IN WOLFF–PARKINSON–WHITE SYNDROME

Abstract Wolff–Parkinson–White syndrome is a common condition characterized by atrioventricular accessory pathways (AP), which can be asymptomatic or can be responsible for atrioventricular reentrant tachycardia or rapid conduction of atrial fibrillation to the ventricles: for this reason, patients are referred for catheter ablation procedures. Although success rates of ablation are &amp;gt;95%, late recurrences can occur in 2–21% of cases mainly depending on the anatomical position. Current approaches remain suboptimal, and when failures occur, they may be due to technical difficulties such as poor contact or catheter stability, inability to access the target site as well as mapping errors resulting in inaccurate location of the AP itself. High–density mapping represents an alternative approach to mapping arrhythmias since the collection of a high density of points allows pathway conduction to be mapped more efficiently. The use of a new software called open–window mapping proved to be reliable in the localization of AP and therefore in the determination of the effective ablation site. A 41–year–old male patient was referred to our Centre following the ECG finding of manifest ventricular preexcitation and short–lasting paroxysmal palpitations. In the Electrophysiology Lab, the diagnostic catheters were inserted with the “fluoroless” technique using the EnSite Precision™ mapping system (Abbott): the ECG and the endocavitary electrograms were indicative of a right Parahissian accessory pathway. The mapping was performed with a multipolar catheter (Advisor™ HD Grid). Once the location of the pathway had been estimated, the roving acquisition interval (RAI) was set according to the expected position of atrial and ventricular electrogram. The RAI window was centered at this point and was opened in both directions (open window mapping) to fully include signals leading up to and traveling away from the AP. It accurately showed the location of the pathway just few millimeters from the Hissian potential. The baseline electrophysiological study revealed an effective antegrade refractory period (PREAP) of 320 msec. In isoproterenol, antegrade PREAP was reduced to 300 msec and inducibility of arrhythmias was not observed. Therefore, in consideration of the poor conductive properties and the non–inducibility of arrhythmias, as well as the anatomical site near the conduction system, it was decided not to proceed with the ablation due to the significant risk of atrio–ventricular block.

Open-window mapping and the extended early-meets-late algorithm for the Wolff-Parkinson-White syndrome.

This is the first report describing open-window mapping with the extended early-meets-late algorithm to enhance visualization of the location and width of an atrioventricular accessory pathway. This may be particularly useful when linear or cluster ablation lesion sets are required for wide pathways.

Mahaim Revisited.

The name Ivan Mahaim is well-known to electrophysiologists. However, alternative anatomical substrates can produce the abnormal rhythms initially interpreted on the basis of the pathways he first described. These facts have prompted suggestions that Mahaim should be deprived of his eponym. It is agreed that specificity is required when describing the pathways that produce the disordered cardiac conduction, and that the identified pathways should now be described in an attitudinally appropriate fashion. The authors remain to be convinced that understanding will be enhanced simply by discarding the term ‘Mahaim physiology’ from the lexicon. It is fascinating to look back at the history of accessory atrioventricular junctional conduction pathways outside the normal accessory atrioventricular conduction system, and their possible role in rhythm disturbances. It took both the anatomist and the clinical arrhythmologist quite some time to understand the complex anatomical architecture and the ensuing electrophysiological properties. Over the years, the name Mahaim was often mentioned in those discussions, although these pathways were not the ones that produced the eponym. The reason for this review, therefore, is to present relevant information about the person and what followed thereafter.