Baseline Electrophysiologic Study Research Articles

Frequent Premature Atrial Contractions Lead to Adverse Atrial Remodeling and Atrial Fibrillation in a Swine Model.

Frequent premature atrial complexes (PACs) are associated with future incident atrial fibrillation (AF), but whether PACs contribute to development of AF through adverse atrial remodeling has not been studied. This study aimed to explore the effect of frequent PACs from different sites on atrial remodeling in a swine model. Forty swine underwent baseline electrophysiologic studies and echocardiography followed by pacemaker implantations and paced PACs (50% burden) at 250-ms coupling intervals for 16 weeks in 4 groups: (1) lateral left atrium (LA) PACs by the coronary sinus (Lat-PAC; n=10), (2) interatrial septal PACs (Sep-PAC; n=10), (3) regular LA pacing at 130 beats/min (Reg-130; n=10), and (4) controls without PACs (n=10). At the final study, repeat studies were performed, followed by tissue histology and molecular analyses focusing on fibrotic pathways. Lat-PACs were associated with a longer P-wave duration (93.0±9.0 versus 74.2±8.2 and 58.8±7.6 ms; P<0.001) and greater echocardiographic mechanical dyssynchrony (57.5±11.6 versus 35.7±13.0 and 24.4±11.1 ms; P<0.001) compared with Sep-PACs and controls, respectively. After 16 weeks, Lat-PACs led to slower LA conduction velocity (1.1±0.2 versus 1.3±0.2 [Sep-PAC] versus 1.3±0.1 [Reg-130] versus 1.5±0.2 [controls] m/s; P<0.001) without significant change in atrial ERP. The Lat-PAC group had a significantly increased percentage of LA fibrosis and upregulated levels of extracellular matrix proteins (lysyl oxidase and collagen 1 and 8), as well as TGF-β1 (transforming growth factor-β1) signaling proteins (latent and monomer TGF-β1 and phosphorylation/total ratio of SMAD2/3; P<0.05). The Lat-PAC group had the longest inducible AF duration (terminal to baseline: 131 [interquartile range 30, 192] seconds versus 16 [6, 26] seconds [Sep-PAC] versus 22 [11, 64] seconds [Reg-130] versus -1 [-16, 7] seconds [controls]; P<0.001). In this swine model, frequent PACs resulted in adverse atrial structural remodeling with a heightened propensity to AF. PACs originating from the lateral LA produced greater atrial remodeling and longer induced AF duration than the septal-origin PACs. These data provide evidence that frequent PACs can cause adverse atrial remodeling as well as AF, and that the location of ectopic PACs may be clinically meaningful.

PO-455617-18 SHORT COUPLED PREMATURE ATRIAL COMPLEXES LEAD TO ADVERSE ATRIAL REMODELING AND ATRIAL FIBRILLATION IN A SWINE MODEL

Frequent premature atrial complexes (PACs) are associated with left atrial (LA) myopathy and atrial fibrillation (AF), however, the effect of coupling interval and irregularity on the ensuing atrial myopathy has not been tested. To explore the impact of coupling interval and regularity of atrial ectopics on the development of atrial remodeling and AF in a swine model. Thirty-five swine underwent baseline electrophysiologic study followed by pacemaker implantation and pacing from the lateral LA via the coronary sinus for 16 weeks in 4 groups: 1) controls without PACs (CTRL, n=10); 2) 50% paced PACs at a short coupling interval (CI) of 250ms (Short-PAC, n=10); 3) 50% PACs at a long CI of 400ms (Long-PAC, n=5); and 4) regular pacing at a faster mean atrial rate (130 beats/min) than during PACs (Reg-130, n=10). At the terminal study, a repeat electrophysiologic study was performed followed by sacrifice and histologic analysis. Structural changes: The Short-PAC group had the greater degree of LA dilation (terminal - baseline: Short-PAC 5.9±1.2cm2 vs. Long-PAC 3.9±0.5cm2 vs. Reg-130 3.0±1.0cm2 vs. CTRL 0.9±0.3cm2, p<0.001) and decrease in peak LA strain (terminal - baseline: Short-PAC -17.3±3.2% vs. Long-PAC -12.7±2.9% vs. Reg-130 -8.2±2.9% vs. CTRL -0.7±4.2%, p<0.001). Electrophysiologic changes: The Short-PAC group had slower LA conduction velocity than the Reg-130 and CTRL groups (Short-PAC 1.1±0.2m/s vs. Long-PAC 1.2±0.1m/s vs. Reg-130 1.3±0.1m/s vs. CTRL 1.5±0.2m/s, p<0.001); atrial effective refractory period (ERP) was only decreased in the Reg-130 group (terminal - baseline: Short-PAC -4.0±23.6ms vs. Long-PAC -8.7±17.9ms vs. Reg-130 -23.7±14.3ms vs. CTRL -3.2±23.7ms, p=0.09). Fibrosis: percent LA fibrosis was highest in the Short-PAC group followed by Long-PAC, Reg-130, and then CTRL groups (Figure, Panel A). AF induction: The Short-PAC group had the longest duration of induced AF (Panel B). In a swine model, frequent PACs can cause structural and electrical atrial remodeling with a heightened propensity for AF. PACs led to slow conduction and fibrosis without change in atrial ERP, suggesting a process distinct from tachy-pacing induced atrial remodeling. Moreover, PACs with short CIs resulted in a greater degree of LA remodeling and induced AF duration compared to PACs with long CIs. These findings suggest that frequent, short coupled PACs pose the highest risk for developing atrial remodeling and AF.

PO-01-001 SHORT COUPLED PREMATURE ATRIAL COMPLEXES LEAD TO ADVERSE ATRIAL REMODELING AND ATRIAL FIBRILLATION IN A SWINE MODEL

Frequent premature atrial complexes (PACs) are associated with left atrial (LA) myopathy and atrial fibrillation (AF), however, the effect of coupling interval and irregularity on the ensuing atrial myopathy has not been tested. To explore the impact of coupling interval and regularity of atrial ectopics on the development of atrial remodeling and AF in a swine model. Thirty-five swine underwent baseline electrophysiologic study followed by pacemaker implantation and pacing from the lateral LA via the coronary sinus for 16 weeks in 4 groups: 1) controls without PACs (CTRL, n=10); 2) 50% paced PACs at a short coupling interval (CI) of 250ms (Short-PAC, n=10); 3) 50% PACs at a long CI of 400ms (Long-PAC, n=5); and 4) regular pacing at a faster mean atrial rate (130 beats/min) than during PACs (Reg-130, n=10). At the terminal study, a repeat electrophysiologic study was performed followed by sacrifice and histologic analysis. Structural changes: The Short-PAC group had the greater degree of LA dilation (terminal - baseline: Short-PAC 5.9±1.2cm2 vs. Long-PAC 3.9±0.5cm2 vs. Reg-130 3.0±1.0cm2 vs. CTRL 0.9±0.3cm2, p<0.001) and decrease in peak LA strain (terminal - baseline: Short-PAC -17.3±3.2% vs. Long-PAC -12.7±2.9% vs. Reg-130 -8.2±2.9% vs. CTRL -0.7±4.2%, p<0.001). Electrophysiologic changes: The Short-PAC group had slower LA conduction velocity than the Reg-130 and CTRL groups (Short-PAC 1.1±0.2m/s vs. Long-PAC 1.2±0.1m/s vs. Reg-130 1.3±0.1m/s vs. CTRL 1.5±0.2m/s, p<0.001); atrial effective refractory period (ERP) was only decreased in the Reg-130 group (terminal - baseline: Short-PAC -4.0±23.6ms vs. Long-PAC -8.7±17.9ms vs. Reg-130 -23.7±14.3ms vs. CTRL -3.2±23.7ms, p=0.09). Fibrosis: percent LA fibrosis was highest in the Short-PAC group followed by Long-PAC, Reg-130, and then CTRL groups (Figure, Panel A). AF induction: The Short-PAC group had the longest duration of induced AF (Panel B). In a swine model, frequent PACs can cause structural and electrical atrial remodeling with a heightened propensity for AF. PACs led to slow conduction and fibrosis without change in atrial ERP, suggesting a process distinct from tachy-pacing induced atrial remodeling. Moreover, PACs with short CIs resulted in a greater degree of LA remodeling and induced AF duration compared to PACs with long CIs. These findings suggest that frequent, short coupled PACs pose the highest risk for developing atrial remodeling and AF.

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.

Advantages and disadvantages of drug challenge during electrophysiological study in patients with new left bundle branch block after transaortic valve implantation.

AimsElectrophysiological study (EPS) is recommended in case of new-onset persistent left bundle branch block (NOP-LBBB) after transaortic valve implantation (TAVI) to identify patients at high risk of delayed atrioventricular block (D-AVB). We evaluated the added value of drug challenge, after normal baseline EPS, to predict D-AVB in such patients.MethodsWe conducted a comparative single-centre study of two successive periods, during which we used baseline EPS alone (first period) or drug challenge in case of normal baseline EPS (second period), for patients with NOP-LBBB after TAVI. The primary endpoint was a composite of pacemaker use, documented D-AVB, cardiac syncope, sudden death, or delayed pacemaker implantation.ResultsAmong 736 patients with TAVI implantation between January 2016 and September 2019, 64 with NOP-LBBB were included. During the first period, 4/22 (18.2%) presented with a positive baseline EPS. After a mean (standard deviation [SD]) of 15.6 (8.3) months, 7/22 (31.8%) reached the primary endpoint. During the second period, 19/42 (45.2%) presented with a positive EPS. After a mean (SD) of 12.8 (3.5) months, 8/42 (19.0%) reached the primary endpoint. There was a tendency to increased sensitivity (42.9–87.5%; P = 0.12) and negative predictive value (77.8–95.7%; P = 0.15) of the EPS, respectively during the first to the second period. However, the specificity decreased (93.3–64.7%; P = 0.04).ConclusionDiagnostic yield improved with drug challenge in case of normal baseline EPS. However, the decrease in specificity led to a high rate of unnecessary pacemaker implantation.

Optimising Large Animal Models of Sustained Atrial Fibrillation: Relevance of the Critical Mass Hypothesis.

BackgroundLarge animal models play an important role in our understanding of the pathophysiology of atrial fibrillation (AF). Our aim was to determine whether prospectively collected baseline variables could predict the development of sustained AF in sheep, thereby reducing the number of animals required in future studies. Our hypothesis was that the relationship between atrial dimensions, refractory periods and conduction velocity (otherwise known as the critical mass hypothesis) could be used for the first time to predict the development of sustained AF.MethodsHealthy adult Welsh mountain sheep underwent a baseline electrophysiology study followed by implantation of a neurostimulator connected via an endocardial pacing lead to the right atrial appendage. The device was programmed to deliver intermittent 50 Hz bursts of 30 s duration over an 8-week period whilst sheep were monitored for AF.ResultsEighteen sheep completed the protocol, of which 28% developed sustained AF. Logistic regression analysis showed only fibrillation number (calculated using the critical mass hypothesis as the left atrial diameter divided by the product of atrial conduction velocity and effective refractory period) was associated with an increased likelihood of developing sustained AF (Ln Odds Ratio 26.1 [95% confidence intervals 0.2–52.0] p = 0.048). A receiver-operator characteristic curve showed this could be used to predict which sheep developed sustained AF (C-statistic 0.82 [95% confidence intervals 0.59–1.04] p = 0.04).ConclusionThe critical mass hypothesis can be used to predict sustained AF in a tachypaced ovine model. These findings can be used to optimise the design of future studies involving large animals.

An intriguing case of regular RR and QRS alternans during idiopathic left posterior fascicle ventricular tachycardia

This study represents a case of idiopathic left posterior fascicle ventricular tachycardia (LPF-VT), which is intriguing due to regular alternation of short-long RR intervals and QRS morphology. Transthoracic echocardiogram analysis did not detect any structural heart disease. A baseline electrophysiological study was performed. Intracardiac recording during tachycardia showed V-A dissociation, confirming the final diagnosis of idiopathic LPF-VT. No regularity in the monomorphic VT was recorded. Previous relevant studies suggested that a single focus with two exits in distal branches of the left posterior fascicle or two different foci localized in the Purkinje-myocardial network of the left posterior fascicle can clarify the mechanisms. Our team proposed an additional explanation that combines the physiological refractory period with the Ashman phenomenon in individual reentrant LPF-VT circuit.

Predictors of Appropriate Shocks and Ventricular Arrhythmia in Indonesian with Brugada Syndrome

Background :&#x0D; Brugada syndrome is an inherited disease characterized by an increased risk of sudden cardiac death owing to ventricular arrhythmias in the absence of structural heart disease. It has been reported that this syndrome is more prevalent in South-East Asia than in Western countries. Furthermore, genetic studies showed important contributions of several gene mutations to the phenotype of BrS. These suggest that ethnic difference play significant roles in the pathogenesis of BrS. In addition, ICD implantation remains the cornerstone management with a low rate of appropriate shocked. Therefore, it is important to investigate patients’ characteristics for risk stratification. Our objective to investigate the clinical, electrocardiography (ECG) and electrophysiological characteristics that can be used as predictor of appropriate shock due to ventricular arrhythmia (VA) in Indonesian patients with BrS.&#x0D; Methods : We analyse data from Brugada syndrome registry at National Cardiovascular Centre Harapan Kita since January 2013. Total 22 patients were included. Characteristics of BrS that we analysed were baseline characteristics (age and sex), Clinical finding (syncope, cardiac arrest), ECG finding (spontaneous type 1 or drug induced) and Electrophysiology study result (inducible VA and RV ERP). We also added some new ECG characteristic (S wave in lead 1, S wave duration in V1, Fragmented QRS, Junction ST elevation and early repolarization pattern in infero-lateral) to be analysed. Our end point are appropriate shock during ICD interrogation for those who have been implanted an ICD, and documented VA for those who didn’t receive ICD.&#x0D; Result : We found high incidence of appropriate ICD’s shock in our population (50% in our study vs 5-11.5% in real world). Predictors of appropriate shock and documented VA are history of syncope (p = 0.045; OR 2.57 [1.44-4.59]), spontaneous type-1 ECG (p = 0.005) and right ventricular effective refractory period (RV ERP) of &lt;200 ms (p=0.018). Other parameters that have been reported to correlate with the occurrence of VA (S Wave in lead 1 (p = 0.530), early repolarization pattern (p = 0.578), fragmented QRS (p = 0.601), S Wave duration (p = 0.365) and J Point STE (p = 0.800) were found to be not correlated to appropriate shock in our populations.&#x0D; Conclusion : History of syncope, spontaneous type-1 Brugada ECG and RV ERP of &lt;200 ms have predictive values for risk stratification of Indonesian patients with Brugada syndrome. &#x0D; Keywords : Brugada Syndrome, Ventricular arrhythmia, ICD shock

Flecainide Versus Procainamide in Electrophysiological Study in Patients With Syncope and Wide QRS Duration.

This study sought to compare the differences between procainamide and flecainide to stress the His-Purkinje system during electrophysiological study (EPS) in patients with syncope and bundle branch block (BBB). Patients with syncope and BBB are at risk of developing atrioventricular block. EPS is recommended including class I drug challenge to unmask His-Purkinje disease in cases with baseline normal His-ventricular interval. There is little data on differences between different class I drugs. This was a prospective study of all consecutive patients undergoing EPS for syncope and BBB at a single center (January 1, 2012 to June 30, 2017). Of those patients with negative baseline EPS, 2 cohorts were compared: groupA (historical cohort: procainamide) and group B (flecainide). During the study, 271 patients (age 73.9 ± 12.1 years, 64.9% male, QRS duration: 139.4 ± 13.9 ms) underwent EPS. In 166, baseline EPS was negative and class I drug challenge was performed (90 procainamide, 76 flecainide). The final value and percentage increase in the His-ventricular interval (76 ± 16 ms vs. 64 ± 10 ms and 22.5 ± 6.2% vs. 11.8 ± 5.3%; p< 0.001) and diagnostic yield (14.5% vs. 7.8%, p= 0.04) were higher with flecainide. No differences were found in baseline characteristics. During follow-up (25.8 ± 6.3 months), 39 patients (24.8%) with negative EPS (19.2% with flecainide vs. 30.1% with procainamide: relative risk: 5.1; 95% confidence interval: 2.6 to 10.2; p< 0. 001) received a pacemaker. Flecainide has a higher diagnostic yield than does procainamide in patients with BBB, syncope, and negative baseline EPS due to a greater increase of the His-ventricular interval. Additionally, there is a lesser need for pacemaker implantation in patients in whom the class I drug test using flecainide was negative.

Paradoxical Effects of Sodium-Calcium Exchanger Inhibition on Torsade de Pointes and Early Afterdepolarization in a Heart Failure Rabbit Model.

Calcium homeostasis plays an important role in development of early afterdepolarizations (EADs) and torsade de pointes (TdP). The role of sodium-calcium exchanger (NCX) inhibition in genesis of secondary Ca rise and EAD-TdP is still debated. Dual voltage and intracellular Ca optical mapping were conducted in 6 control and 9 failing rabbit hearts. After baseline electrophysiological and optical mapping studies, E4031 was given to simulate long QT syndrome. ORM-10103 was then administrated to examine the electrophysiological effects on EAD-TdP development. E4031 enhanced secondary Ca rise, EADs development, and TdP inducibility in both control and failing hearts. The results showed that ORM-10103 reduced premature ventricular beats but was unable to suppress the inducibility of TdP or EADs. The electrophysiological effects of ORM-10103 included prolongation of action potential duration (APD) and increased APD heterogeneity in failing hearts. ORM-10103 had a neutral effect on the amplitude of secondary Cai rise in control and heart failure groups. In this model, most EADs generated from long-short APD junction area. In conclusion, highly selective NCX inhibition with ORM-10103 reduced premature ventricular beat burden but was unable to suppress secondary Ca rise, EADs development, or inducibility of TdP. The possible electrophysiological mechanisms include APD prolongation and increased APD heterogeneity.

Long‐Term Outcome of Patients With Idiopathic Ventricular Fibrillation: A Meta‐Analysis

The long-term outcome of the patients with idiopathic ventricular fibrillation (IVF) is not well known. Relevant studies published through May 21, 2014 were searched and identified in the MEDLINE, PsycINFO, Cochrane Library, CINAHL, and EMBASE databases and a hand search of article references was also performed. Random-effect models were used for pooling proportions of mortality and recurrent events. Twenty-three studies were included with a total of 639 patients (449 males) with a mean age ranging from 33 to 51 years. Eighty percent of patients had received ICD implantation. Over an average of 5.3 years follow-up, 167 patients (31%) experienced a recurrence of ventricular arrhythmic events (proportion, 0.29 [95% CI 0.21-0.38]). Moreover, 17 patients (3.1%) died among all studies (proportion, 0.01 [95% CI 0.00-0.04]). No association was found between the induction of sustained ventricular tachycardia or ventricular fibrillation at baseline electrophysiological study and risk of recurrent ventricular arrhythmias (risk difference: 0.12 [95% CI, 0.08-0.32]). In patients with IVF, this meta-analysis revealed an estimated recurrent event rate of 31% and a pooled mortality rate of 3.1% during an average of 5 years follow-up. The results of baseline electrophysiological studies are not predictive of future ventricular arrhythmias.

Utility of Exercise Testing and Adenosine Response for Risk Assessment in Children with Wolff-Parkinson-White Syndrome.

We aimed to determine the correlation between noninvasive testing (exercise stress testing [EST] and adenosine responsiveness of accessory pathway [AP] ) and invasive electrophysiology study (EPS) for assessment antegrade conduction of the AP in Wolff-Parkinson-White syndrome. This prospective, observational study enrolled 40 children (58% male children, median age of 13 years, and median weight of 47.5 kg) with Wolff-Parkinson-White syndrome. Conduction through the AP to a cycle length of ≤250 ms was considered rapid or high-risk; otherwise, patients were nonrapid or low-risk. The sudden disappearance of the delta-wave was seen in 10 cases (25%) during EST. Accessory pathway was found to be high-risk in 13 cases (13/40, 32.5%) while the accessory path was identified as low-risk in 27 cases; however, six patients (15%) had blocked AP conduction with adenosine during EPS. Low-risk classification by EST alone to identify patients with nonrapid conduction in baseline EPS had a specificity of 93% and a positive predictive value of 90% (accuracy 54%). Blocked AP conduction with adenosine as a marker of nonrapid baseline AP conduction had a specificity of 93% and a positive predictive value of 84%. Finally, AP was adenosine nonresponsive in the majority of patients (28/30, 93%) with persistent delta-waves, 40% of those who had a sudden disappearance of delta-waves had an adenosine-responsive AP (P value: .028). Abrupt loss of preexcitation during EST and blocked AP conduction with adenosine had high specificity and positive predictive value for nonrapid and low-risk antegrade conduction during baseline invasive EPS. Successful risk stratification of pediatric patients with Wolff-Parkinson-White is possible through the use of EST and the adenosine responsiveness of AP.

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.

0164: Evolution of preexcitation syndrome in children

Previous studies reported a spontaneous disappearance of preexcitation syndrome (PS) in patients with a long accessory pathway (AP) effective refractory period (ERP) and in children <12 years (y), but stability in children >12 y with inducible SVT and short AP-ERP. The purpose of the study was to collect the data of untreated children with a PS, studied 2 times at least one year of interval. 2 baseline electrophysiological studies (EPS) were performed within 1 to 25 years of one another (mean 6±years) in 39 children and teenagers, 17 boys, 22 girls, aged initially from 1 to 19 years (12.5±4), with overt PS. First EPS (EPS1) was indicated for syncope (n=4), atrioventricular reentrant tachycardias (AVRT)(n=17) or for asymptomatic PS (n=18). The protocol was similar, performed in control state (CS) and after isoproterenol. At EPS2, among patients studied for syncope at EPS1, 1 has still syncope, 2 have AVRT, 1 is asymptomatic. Among patients with AVRT at EPS1, 14 (82%) have still AVRT, 3 are asymptomatic. Among asymptomatic patients, 13 (72%) remain asymptomatic, 2 have AVRT, 3 have syncope. AVRT in children presenting initially with syncope or initially asymptomatic children occurred in 2/4 with inducible AVRT at EPS1. The higher rate conducted by AP was similar in CS and after isoproterenol at EPS2 (178±72bpm, 203±81) and at EPS1 (188±62, 237±83)(p<0.01). AP-ERP’s were similar in CS at EPS2 (283±68ms) and 1 (281±91.5) and tended to increase from 211±72 at ESP1 to 234±58ms at EPS2 (p<0.07) after isoproterenol. AP has lost anterograde conduction in 6 children with initially long APERP but all 5 children with initially inducible AVRT had still inducible AVRT. Two children with initially a long AP-ERP had shorter AP-ERP at EPS2. AVRT was induced at EPS2 in asymptomatic PS with initially negative EPS in 3 children. Contrary to previous studies, we did not find significant changes of clinical and electrophysiological data in children after a mean follow-up of 6±5 years. Most of children with spontaneous or inducible AVRT’s at the first evaluation have still inducible AVRT’s at the second evaluation. AP-ERP did not increase significantly.

Intra-cardiac echocardiography guided catheter ablation of a right posterior accessory pathway in a patient with Ebstein׳s anomaly

We report a case of Ebstein׳s anomaly in which radiofrequency catheter ablation of an accessory pathway was successfully performed under intra-cardiac echocardiography. A 50-year-old woman was referred to our hospital for radiofrequency catheter ablation of a paroxysmal supraventricular tachycardia. A 12-lead surface electrocardiogram revealed ventricular pre-excitation associated with type B Wolff–Parkinson–White syndrome. In the baseline electrophysiological study, an orthodromic atrioventricular reciprocating tachycardia with a right posterior accessory pathway was induced. A phased-array intra-cardiac echo probe was positioned in the right atrium to visualize the atrioventricular junction. The key structures for catheter ablation, such as the atrialized right ventricle, atrioventricular junction, and tricuspid valve, were clearly visualized on intra-cardiac echocardiography. Radiofrequency current was successfully delivered at the atrioventricular junction, where a Kent potential was recorded. During a 6-month follow-up period, the patient was free from arrhythmias. The findings in this case suggest that phased-array intra-cardiac echocardiography is useful for ablation of right-sided accessory pathways in patients with Ebstein׳s anomaly.

Wolff‐Parkinson‐White Syndrome and Adenosine Response in Pediatric Patients

Adenosine administration to patients with Wolff-Parkinson-White (WPW) usually increases preexcitation and therefore may be diagnostic for WPW syndrome when the electrocardiogram (ECG) is questionable. We aimed to determine the adenosine response in pediatric patients with WPW pattern on ECG and whether blocked accessory pathway (AP) conduction with adenosine correlated with nonrapid AP conduction measured by invasive electrophysiology study (EPS). All patients with WPW ≤ 18 years of age who underwent EPS over a 5-year period were identified. The adenosine response during atrial pacing was characterized as blocked or continued AP conduction. Invasive data were obtained during atrial pacing and atrial fibrillation. Conduction through the AP to a cycle length ≤ 250 ms was considered rapid; otherwise patients were nonrapid. The sensitivity, specificity, and positive (PPV) and negative predictive value were calculated for blocked AP conduction to identify nonrapid baseline AP conduction during EPS. There were 59 patients included and nine (15%) had blocked AP conduction with adenosine. Five of these nine had WPW syndrome and four had fasciculoventricular APs. All nine patients had nonrapid conduction on baseline EPS. Blocked AP conduction with adenosine as a marker of nonrapid baseline AP conduction had a specificity of 100%, a PPV of 100%. In these pediatric patients with WPW pattern on ECG, a significant minority blocked AP conduction with adenosine and this finding had 100% specificity and PPV for nonrapid baseline antegrade AP conduction. The finding of blocked AP conduction with adenosine may aid in risk stratification.

Is isoproterenol really required during electrophysiological study in patients with Wolff-Parkinson-White syndrome?

We have studied the results of electrophysiological study (EPS) in patients with Wolff-Parkinson-White syndrome (WPW) and spontaneous adverse clinical presentation and determined whether isoproterenol added incremental value. MethodsEPS was performed in 63 patients with WPW and adverse clinical presentation at baseline. EPS was repeated after infusion of isoproterenol in 37 patients, including 25 without criteria for a malignant form at baseline. ResultsAtrioventricular orthodromic tachycardia was induced 44%, antidromic tachycardia in 11%, atrial fibrillation (AF) in 68% at baseline. At baseline EPS, criteria for a malignant form (AF induction and shortest CL <250ms) were noted in 60%; tachycardia was not inducible in 16%. All the patients met the criteria for a malignant form after isoproterenol. ConclusionsEPS at baseline missed 16% of patients at risk of life-threatening arrhythmias who had no inducible tachyarrhythmia and 40% without classical criteria for malignant form.

Risk Stratification in Wolff‐Parkinson‐White Syndrome: The Correlation Between Noninvasive and Invasive Testing in Pediatric Patients

In Wolff-Parkinson-White (WPW) syndrome, rapid antegrade conduction of atrial tachyarrhythmias can result in ventricular fibrillation and sudden death. Antegrade conduction can be assessed through noninvasive testing or invasive electrophysiology study (EPS). We aimed to determine the correlation between noninvasive testing and EPS in a pediatric WPW population. All WPW patients <21 years who underwent EPS over a 10-year period were identified. Noninvasive testing reviewed included electrocardiogram, Holter, and exercise stress test (EST). Patients were classified as low-risk if preexcitation was lost during any test. EPS data reviewed included antegrade conduction during atrial pacing and atrial fibrillation. Conduction through the accessory pathway (AP) to a cycle length ≤ 250 ms was considered rapid, otherwise patients were nonrapid. Sensitivity, specificity, positive (PPV), and negative predictive value (NPV) of noninvasive testing to correctly identify nonrapid conduction was calculated. There were 135 EPS. Twenty-four patients (18%) were classified low-risk noninvasively. Two of the 24 (8%) had rapid conduction at baseline EPS. The sensitivity, specificity, PPV, and NPV of low-risk noninvasive testing to predict nonrapid conduction was 22%, 94%, 92%, and 31%, respectively. Sixteen of the 24 had low-risk EST and none had rapid conduction at baseline EPS. The specificity and PPV of low-risk EST were 100%. Loss of preexcitation during noninvasive testing had high specificity and PPV for nonrapid antegrade conduction during baseline EPS. Abrupt loss of preexcitation during EST was a highly reliable noninvasive marker of nonrapid AP conduction at baseline in our pediatric WPW patients.

Noncontact Mapping Guided Ablation of Atrioventricular Nodal Reentrant Tachycardia in a Patient with Persistent Left Superior Vena Cava

We described a successful slow-pathway (SP) ablation in a 30-year-old woman with persistent left superior vena cava (PLSVC) guided by 3-dimensional noncontact-mapping (NCM) system. She presented with frequent episodes of poorly tolerated paroxysmal supraventricular tachycardia. The course of the CS catheter was unusual, and the presence of PLSVC with right superior vena cava atresia was documented by venography. The baseline electrophysiologic study indicated the presence of common type AV nodal reentrant tachycardia (AVNRT). By anatomical approach, SP ablation was initially performed in the posteroinferior region of Koch triangle near the CS ostium, but AVNRT was still inducible. In order to avoid extensive ablation and the risk of AV node injury, we introduced a multielectrode array catheter for a NCM approach. We determined the earliest atrial activation area of the retrograde conduction using ventricular extrastimulation. To locate the SP, a right ventricle extrastimulus pacing with S1S1 interval 500 ms, and S1S2 interval started from 450 ms with a 10 ms decrement. In this way, the retrograde slow and fast pathway can be identified from the earliest atrial activation with a rS pattern on the virtual electrograms. Successful ablation was achieved at the site of retrograde SP with an accelerated junctional rhythm observed during RF application. After slow pathway ablation, dual AV nodal physiology disappeared, and AVNRT became non-inducible.

215 Is it necessary to indicate another electrophysiological study in patients previously studied for a preexcitation syndrome?

Accessory pathway (AP) refractory period (RP) increases from the youth to the elderly. The large indications of AP ablation have changed the natural follow-up. The purpose of the study was to report the clinical and electrophysiological data of pts with a Wolff-Parkinson White syndrome (WPW), studied within 1 to 20 years of one another to evaluate the changes of these data. 2 baseline EPS were performed within 1 to 20 years (y) of one another (mean 9 y ± 4) in 61 pts, 37 males and 24 females, aged initially from 10 to 67 y (30 ± 14), with a patent WPW. First electrophysiological study (EPS) was indicated for syncope (n = 6), atrioventricular reentrant tachycardias (AVRT) (n = 34), atrial fibrillation (AF) (n = 5) or for asymptomatic preexcitation (n = 16). The protocol was similar: the higher rate conducted through AP was measured and programmed atrial stimulation with 1 and 2 ES performed in control state (CS) and after isoproterenol. At 2 nd study, among pts studied for syncope at study 1, 1 has still syncope, 2 have AVRT, 1 has rapid AF, and 2 are asymptomatic. Among pts with AVRT at study 1, 25 have AVRT, 7 are asymptomatic and 2 have AF. Among pts with AF, 4 have still AF and 1 is asymptomatic. Among asymptomatic pts 3 have a spontaneous malignant form, 7 remain asymptomatic, 3 have AVRT, 1 has syncope and 1 has AF. All AVRT or AF occurred in pts with inducible AVRT or AF at EPS 1. The higher rate conducted by AP was significantly lower in CS and after isoproterenol at study 2 (157 ± 95 b/min, 193 ± 113) than at study 1 (199 ± 65, 257 ± 65). AP has lost anterograde conduction properties in 17 pts aged from 17 to 67 years (47 ± 15); all of them but one had initially 1/1 conduction through AP 170/min. However 8 of them had still AVRT. Among pts with initially rapid conduction through AP (250/min), all but one have a rapid conduction at EPS 2; 3 of them which were asymptomatic developed rapid AF. The study confirms that a benign form of WPW without inducible AVRT or AF remains benign. Pts with AVRT and AP and long refractory period become asymptomatic in 20% of cases. Pts with inducible rapid AF remain at high risk of events in most cases.