NASPE Plenary Lecture 2001. Catheter ablation: a personal perspective

Catheter ablation for control of cardiac arrhythmias was introduced 20 years ago. Since then, this technique has been applied successfully to virtually all cardiac rhythm disturbances. In this essay, some of the newer applications of ablative techniques for patients with AV nodal reentrant tachycardia, atrial flutter, and atrial fibrillation are emphasized. "AV nodal reentrant tachycardia" may involve a nodofascicular tract. A new classification of atrial flutter is proposed and various causes of atrial fibrillation are discussed.     

Radiofrequency Ablation of Concealed Left Free-Wall Accessory Pathways Without Coronary Sinus Catheterization:

Ablation of Concealed Accessory Pathways. Introduction: Feasibility of radiofrequency (RF) ablation using a two-catheter technique without coronary sinus catheterization was studied in 100 consecutive patients with a single concealed left free-wall accessory path-way.
Methods and Results: Tachycardia was induced by electrical stimulation in the right atrium/right ventricle, and the presence of a concealed left free-wall accessory pathway was suggested electrocardiographically (negative P wave in leads I and/or a VL during orthodromic tachycardia) or by earlier atrial activation in the pulmonary artery compared to the high right atrium. Mapping of the mitral annulus was performed during right ventricular pacing or orthodromic tachycardia, and RF energy was applied at the site with the earliest retrograde atrial activation. Ablation was considered effective if tachycardia could not be induced, and if VA dissociation or exclusive retrograde nodal conduction was observed. Ablation was initially successful in 98 of 100 patients. Mean number of radiofrequency pulses were 3.2 ± 2. Mean fluoroscopy time and total procedure time was 14 ± 9 and 107 ± 32 minutes, respectively. There were no complications related to the procedure. At a mean follow-up of 22 ± 13 months, two patients experienced tachycardia recurrence and required a second procedure, which was successful.
Conclusions: Our results suggest that RF catheter ablation of concealed left free-wall accessory pathways can be safely, effectively, and rapidly performed using a simplified two-catheter technique with no need for coronary sinus catheterization.     

Catheter technique for ablation of accessory atrioventricular pathway: long-term results

Catheter ablation of an accessory atrioventricular pathway wasattempted in six patients with recurrent tachy arrhythmias resistantto medication (four to five trials). Localization of the accessorypathway was performed by potential recordings with an electrodecatheter from the region of the tricuspid and mitral valve ringsduring orthodromic supraventricular tachycardia (n = 4), duringsinus rhythm (n = l), and during ventricular pacing (n = 1).Using this mapping technique, the site of earliest atrial orventricular activation through the accessory pathway was localizedin the anterior septal (n = 2), right free wall (n = 2), posteriorseptal (n = 2), or left free wall (n= 1) region of the atrioventricularvalve rings. The shortest ventriculo–atrial (VA) and atrio–ventricular(AV) intervals measured in the local electrograms ranged fromVA = 45–70 ms, and AV = 45–65 ms, respectively.The accessory pathway responsible for the arrhythmia demonstratedexclusive retrograde (n = 4) or bidirectional (n = 2) conductionproperties. A total of 13 direct current transcatheter shocks(one to three per patient) of 20–200 J each were aimedat the site of the accessory pathway. Thereby, conduction throughthe accessory pathway was abolished (n = 5) or modified (n =l) and the patients were freed from their syncope and disablingarrhythmias (follow-up: 4–6–5–9 years). Theprocedure was well tolerated without complications. Mappingguided catheter ablation of accessory pathways is an effectivetreatment of refractory supraventricular tachyarrhythmias inselected patients.     

双极食管心电图对P波的形态特征及右侧隐匿性旁道的诊断

目的探讨双极食管心电图P波的形态特征以及其对右侧隐匿性旁道的诊断价值。方法选择经心内电生理检查和射频消融术证实的32例右侧隐匿性旁道患者。消融术前经食管心房调搏诱发阵发性室上性心动过速发作,以相同的走纸速度和振幅记录发作前后体表12导联、单极食管、双极食管心电图。分别观察P波形态、极性、P波与QRS波关系,测量P波振幅、时限,以心内电生理检查结果为标准分析单极与双极心电图对右侧隐匿性旁道的诊断灵敏度。结果单极食管心电图P波无极性变化,双极食管心电图P波可根据需要调整极性。双极食管心电图和单极食管心电图的P波振幅分别为0.55±0.10mV和0.34±0.10mV(P<0.05),P波时限分别为98.4±11.2ms和101.2±12.5ms(P>0.05)。单极食管心电图和双极食管心电图对右侧隐匿性旁道的诊断灵敏度分别为68.8%和93.8%(P<0.05)。结论双极食管心电图记录的P波振幅大于单极食管心电图,并能更清晰的显示P波以及P波与QRS波之间的关系,对右侧隐匿性旁道的诊断优于单极食管心电图。     

Pace mapping of Koch's triangle reduces risk of atrioventricular block during ablation of atrioventricular nodal reentrant tachycardia

INTRODUCTION: Slow pathway (SP) ablation of AV nodal reentrant tachycardia (AVNRT) can be complicated by second- to third-degree AV block. We assessed the usefulness of pace mapping of Koch's triangle in preventing this complication. METHODS AND RESULTS: Nine hundred nine consecutive patients undergoing radiofrequency ablation of AVNRT were analyzed. Group 1 (n=487) underwent conventional slow pathway ablation. Group 2 (n=422) underwent ablation guided by pace mapping of Koch's triangle, which located the anterogradely conducting fast pathway (AFP) based on the shortest St-H interval obtained by stimulating the anteroseptal, midseptal, and posteroseptal aspects of Koch's triangle. In group 2, AFP was anteroseptal in 384 (91%), midseptal in 33 (7.8%), and posteroseptal or absent in 5 (1.2%). In 32 of 33 patients with midseptal AFP, slow pathway ablation was performed strictly in the posteroseptal area. In 4 of 5 patients with posteroseptal or no AFP, retrograde fast pathway was ablated. Two patients refused ablation. Persistent second- to third-degree AV block was induced in 7 (1.4%) of 487 group 1 patients versus 0 (0%) of 422 group 2 patients (P=0.038). Ablation was successful in all patients in whom ablation was performed. CONCLUSION: Pace mapping of Koch's triangle identifies patients in whom the AFP is absent or is abnormally close to the slow pathway. In these cases, guiding ablation helps to avoid AV block.     

Retrograde Multiple and Multifiber Accessory Pathway Conduction in the Wolff-Parkinson-White Syndrome:

Retrograde Multiple Accessory Pathway Precipitating AF. Introduction : The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff-Parkinson-White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF.
Methods and Results : Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221).
Conclusion : The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.     

Ice mapping during cryothermal ablation of accessory pathways in WPW: the role of the temperature time constant.

AIM: Cryothermal energy has the ability reversibly to demonstrate loss of function with cooling, ice mapping, at less deep temperatures. The purpose of this study was to investigate the time course of the temperature during ice mapping of accessory pathways. METHODS AND RESULTS: Thirteen patients with the Wolff-Parkinson-White (WPW) syndrome underwent cryoablation. After identification of a prospective ablation site, ice mapping was performed by cooling the tip to a minimum of -30 degrees C. Successful ice mapping was defined by loss of accessory pathway (AP) conduction. A total of 104 ice maps were analyzed. Successful ice mapping was demonstrated in 17 attempts. There was no significant difference in mapping temperature between successful and unsuccessful ice mapping (-29.4+/-3.2 degrees Celsius vs -30.4+/-1.7 degrees Celsius). The temperature time constant tau during successful ice mapping was significantly shorter compared with unsuccessful ice mapping (7.0+/-1.1 s vs 10.1+/-1.3 s; P<0.0001). The response time (RT) to mapping temperature of -30 degrees C was significantly prolonged in unsuccessful ice mapping attempts (35.8+/-4.5 s vs 53.5+/-11.0 s; P<0.0001). Significant correlations were found between successful ice mapping and the temperature time constant, and between RT and the temperature time constant (P<0.001). CONCLUSION: The ability to identify prospective ablation sites by ice mapping was demonstrated. Successful ice mapping attempts were characterized by a short temperature time constant and a short response time to mapping temperature with a sudden disappearance of pathway conduction.     

Ablation of the atrioventricular junction: technique, acute and long-term results in 115 consecutive patients.

Atrioventricular junctional ablation is an attempt to interrupt conduction from the atrium to the ventricle using radiofrequency energy. The objective is to ablate the compact atrioventricular node as high as possible, leaving a stable ventricular escape rhythm. The compact node is identified in part by its relation to His recordings and partly through the known anatomy. In our series of 115 consecutive patients, atrioventricular block was achieved from the right side in 96% of patients and the remainder had the atrioventricular node ablated from the left side. Long-term success, i.e. complete heart block, was achieved in all patients. Complications in this and other series are rare, but there remains concern about sudden death in these patients.     

High-energy catheter ablation of cardiac arrhythmias: an outmoded technique in the 1990s.

Catheter ablation has become an accepted technique for creating complete heart block in patients with drug refractory supraventricular tachycardias. However, it remains experimental for other indications, such as ablation of accessory pathway or ventricular tachycardia. The use of high energy defibrillator discharges is associated with adverse effects which greatly contribute to the limitations of the technique. Advances in technology have led to newer methods, such as radiofrequency and low energy capacitive discharge, which hold significant advantages over the conventional high energy technique, to the extent that the use of defibrillator discharges should now be considered outmoded and potentially damaging. Radiofrequency is the technique of choice for accessory pathway ablation and modification of AV conduction, and low energy capacitive discharge is the preferred method for creation of complete heart block. There are currently no acceptably safe and efficacious catheter techniques for treating ventricular tachycardia, and more research needs to be done in this area. The potential for the success of these techniques depends to an extent on the creation of new standards of practice for catheter ablation. There has been no unbiased comparative assessment of the different techniques, and consequently no consensus exists on the preferred technique and technologies which should be used. Only within the framework of these standards can the technique achieve significant clinical utility.     

左侧房室旁道左右心室起搏下室房逆传研究

目的左侧房室旁道患者,射频消融术前于左、右心室心尖部在相同刺激条件下行S1S2早搏刺激至旁道不应期,测量旁道室房传导时间及旁道不应期的相关数据,探讨旁道的逆传特性有何异同。方法选取2011年10月至2012年09月于贵州省人民医院心导管室接受射频消融术的室上性心动过速患者,入选患者经心内电生理检查为左侧房室旁道,射频消融术后心内电生理检查房室结无室房逆传功能者共44例为研究对象。结果不同性别者左、右心室起搏下旁道不应期比较,差异无统计学意义(p0.4及p0.4);不同性别者左、右心室起搏下旁道室房传导时间比较,差异无统计学意义(p0.8及p0.2)。合并显性房室旁道与单纯隐匿性房室旁道左、右心室起搏下旁道不应期比较,差异无统计学意义(p0.4及p0.3);合并显性房室旁道与单纯隐匿性房室旁道左、右心室起搏下旁道室房传导时间比较,差异无统计学意义(p0.7及p0.2)。所有患者左、右心室起搏下旁道不应期比较,差异无统计学意义(p0.5);所有患者左、右心室起搏下旁道室房传导时间比较,差异有统计学意义(p0.001),且右心室起搏旁道室房传导时间较左心室起搏明显延长。结论左侧房室旁道患者,男女性别之间,旁道不应期及旁道室房传导时间比较无明显差异;合并显性房室旁道与单纯隐匿性房室旁道之间,旁道不应期及旁道室房传导时间比较无明显差异;所有患者左、右心室起搏下旁道不应期比较无明显差异,旁道室房传导时间右心起搏较左心起搏明显延长。     

Ablation of Left Free-Wall Accessory Pathways Using Radiofrequency Energy at the Atrial Insertion Site:

Transseptal versus Transaortic Ablation. Introduction: Transcatheter ablation of the left free-wall atrioventricular accessory pathways (AP) by delivery of radiofrequency current at the ventricular insertion site has been shown to be effective. The efficacy of such a technique targeting the atrial insertion site of the AP was evaluated.
Methods and Results: One hundred consecutive patients with left free-wall APs and symptomatic supraventricular tachyarrhythmias were included. APs were manifest in 55 patients and concealed in 45. There were 55 men and 45 women with a mean age of 35 years. A total of 107 left free-wall APs were identified in these patients. In these 100 patients, successful ablation was accomplished in all by using a transseptal (45 patients) or transaortic (54 patients) technique. In one patient, ablation was accomplished from within the coronary sinus. Seven patients required a repeat ablative procedure, which was performed successfully. During 107 ablative procedures, six were associated with nonfatal complications including pericardial effusion (hemopericardium) in two patients, mild mitral regurgitation in two patients, swelling of the left arm in one patient, and staphylococcal bacteremia in one patient. Eighty-two (82%) patients underwent a repeat electrophysiologic study 6 to 8 weeks after successful ablation and were found to have no functioning AP or inducible supraventricular tachycardia. During a mean follow-up of 20 ± 8 months, none of the 100 patients had a recurrence of tachyarrhythmias.
Conclusion: These data indicate that the atrial insertion site of the AP can be successfully ablated in the majority of patients with left free-wall APs by using cither a transseptal or transaortic approach. Furthermore, both techniques are associated with minimal morbidity and no mortality.     

Anatomy,histology, and pathology of the cardiac conduction system: Part II

Normal anatomic and histologic features of the atrioventricular junction (transitional cell zone, atrioventricular node, penetrating portion of bundle) and the bifurcation of the penetrating portion into bundle branches are reviewed. Terminal ventricular Purkinje fibers are also discussed.     

Slow pathway catheter ablation of atrioventricular nodal re-entrant tachycardia guided by electroanatomical mapping: a randomized comparison to the conventional approach.

BACKGROUND: Electroanatomical mapping may be expected to improve safety, efficiency and efficacy of selective slow pathway ablation for atrioventricular nodal re-entrant tachycardia (AVNRT). The goal of this prospective randomized study was to compare the efficiency of conventional fluoroscopic and electroanatomical mapping in guiding catheter ablation of AVNRT. METHODS AND RESULTS: Following induction of typical AVNRT, 20 consecutive patients were randomized to either conventional fluoroscopic or electroanatomical (CARTO) mapping to guide slow pathway ablation using a 4mm electrode. Endpoints for ablation were non-inducibility and no more than a single AV nodal echo on aggressive retesting. Acute procedural success was 100% in both groups, with no complications. Although there were no differences in time taken for pre- and post-ablation electrophysiological evaluations, in the electroanatomical group the ablation portion of the procedure showed a substantial reduction in duration (12.6+/-6.8 vs 35.9+/-18.3 min; P< 0.001) and fluoroscopic exposure (0.7+/-0.5 vs 9.6+/-5.0 min; P< 0.001) compared with the fluoroscopic group, reflected in reduced total procedure time (83.6+/-23.6 vs 114+/-19.3 min; P=0.008) and total fluoroscopic exposure (4.2+/-1.4 vs 15.9+/-6.4 min; P< 0.001). Electroanatomical mapping was associated with a lower number (2.7+/-1.6 vs 5+/-2.8; P=0.018), duration (165.3+/-181.6 vs 341+/-177.7s; P=0.013), and total energy delivery (24.3+/-3.1 vs 28.7+/-4.5 watts; P=0.042) of RF applications. There were no acute or long-term (8.9+/-2.2 month) complications or arrhythmia recurrence in either group. CONCLUSIONS: While both conventional and non-fluoroscopic electroanatomical mapping are associated with excellent results in guiding ablation of typical AVNRT, the latter offers significantly shorter procedure and fluoroscopy times, improving the efficiency of the procedure and reducing X-ray exposure.     

Irregularity of the ventricular rhythm during atrial fibrillation: effect of slow atrioventricular nodal pathway ablation.

BACKGROUND: The contribution of dual atrioventricular (AV) nodal pathway physiology to the irregularity of the ventricular rhythm during atrial fibrillation has not been clarified. HYPOTHESIS: This study was performed to assess the effects of slow AV nodal pathway ablation on the irregularity of the ventricular rhythm during atrial fibrillation. METHODS: Irregularity of the ventricular rhythm was quantified using analysis of heart rate variability. In 20 patients with AV nodal reentrant tachycardia, absolute heart rate variability during atrial fibrillation was quantified before and after slow AV nodal pathway ablation by the standard deviation of all NN intervals (SDNN). Relative heart rate variability was determined by computing the coefficient of variation, SDNN normalized for the standard deviation of the mean ventricular cycle length (MVCL-AF). RESULTS: The slope of the regression between MVCL-AF and SDNN was significantly more gradual after slow pathway ablation (slope 0.39 vs. 0.23, p < 0.001). Coefficient of variation increased in 12 patients with heart rates > 120 beats/min at baseline (18.6 +/- 3.9 vs. 22.1 +/- 2.7% MVCL-AF, p < 0.05), but decreased in 8 patients with heart rates < 120 beats/min at baseline (25.6 +/- 3.1 vs. 22.2 +/- 2.2% MVCL-AF, p = 0.05). Furthermore, coefficient of variation correlated with MVCL-AF only at baseline (slope 0.034, r = 0.66), but no relation was found after slow pathway ablation (slope 0, r = 0). CONCLUSIONS: Slow AV nodal pathway ablation alters the relation between absolute heart rate variability and mean ventricular rate during atrial fibrillation and eliminates cycle length dependency of relative heart rate variability. These data indicate that dual AV nodal pathway physiology contributes to the irregularity of the ventricular rhythm during atrial fibrillation.     

Catheter ablation of arrhythmias in ebstein's anomaly: a multicenter study

Catheter Ablation in Ebstein's Anomaly. Introduction: In patients with Ebstein's anomaly (EA) arrhythmias are frequently encountered. Although most arrhythmias can be targeted with catheter ablation, specific issues render the procedure more challenging in EA. This study examines the mechanisms of the different arrhythmias related to EA and the outcome after catheter ablation. Methods And Results: Clinical and procedural data of catheter ablation in patients with EA in 4 European centers were analyzed. In 32 patients (mean age 24 ± 15 years), 34 accessory pathways (APs), 8 intra‐atrial reentry tachycardias (IART), 5 cavotricuspid isthmus‐dependent atrial flutter (CTI‐AFL), 2 focal atrial tachycardias, and 1 atrioventricular nodal reentry tachycardia were ablated. In 11 patients (34%), multiple ablation targets were present. Eighteen patients (56%) required multiple procedures either for repeat ablation of the same arrhythmia (n = 12), ablation of a different arrhythmia (n = 4), or both re‐ablation of the same and of a different arrhythmia (n = 2). Procedural success rate after first ablation was 80% for APs and CTI‐AFL ablation, and 100% for IART ablation. Redo procedures were necessary in 40% of the patients after ablation of an APs, and in 60% after CTI‐AFL ablation, but in none of the patient with IART ablation. Conclusion: Most arrhythmias related to EA are amenable to catheter ablation. However, ablation procedures are challenging and the need for repeat procedure is particularly high, because some patients have multiple ablation targets and because of technical issues in relation with the dysplastic tricuspid annulus. In addition, several patients develop other arrhythmia mechanisms following ablation . (J Cardiovasc Electrophysiol, Vol. 22, pp. 1391‐1396, December 2011)     

Right‐Sided Free Wall Accessory Pathway Refractory to Conventional Catheter Ablation: Lessons From 3‐Dimensional Electroanatomic Mapping

Right Free Wall Accessory Pathway Ablation . Introduction: The aim of this study was to delineate the electroanatomic substrates of right‐sided free wall (RFW) accessory pathways (APs) that were refractory to conventional catheter ablation utilizing 3‐dimensional (3‐D) mapping. Methods and Results: Eleven patients with RFW APs that failed initial conventional catheter ablation(s) by a mean of 1.9 ± 0.5 attempts were enrolled in the study. Electroanatomic mapping of the right atrium was performed during orthodromic reciprocating tachycardia in 3 patients and right ventricular pacing in 8 patients. The earliest atrial activation site, which represented the atrial insertion of the AP, was separated from the tricuspid annulus by an average of 14.3 ± 3.9 mm, and the local activation time was 27.8 ± 17.0 ms earlier than that of the corresponding annular point. One patient exhibited an AP with wide branching on the atrial side. RF ablation with an irrigated catheter successfully interrupted AP conduction in all patients without complications. Conclusions: RFW APs resistant to conventional catheter ablation might be due to unique anatomic AP features such as more epicardial course at the annulus level with atrial insertion distant from the tricuspid annulus. Electroanatomic mapping is helpful to accurately localize the atrial insertion sites of these APs and facilitates catheter ablation. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1317‐1324, December 2010)