Catheter ablation techniques in patients with supraventricular tachycardia

Catheter ablation is an experimental procedure that may prove useful for patients with drug-refractory supraventricular tachycardia. Current techniques involve the use of high-energy direct-current shocks, delivered via electrode catheters. These techniques have been used most commonly for ablating the atrioventricular (AV) junction in patients with supraventricular tachycardia. Such ablation may be of value in a subset of patients with the Wolff-Parkinson-White syndrome. In addition, limited data suggest that direct catheter ablation of posteroseptal accessory pathways may prove safe and effective when shocks are applied just outside the os of the coronary sinus. Catheter ablation has also been used in small numbers of patients with ectopic atrial tachycardia. The chief limitation of catheter ablation of the AV junction is the induction of pacemaker dependency. Successful ablation of an accessory pathway or of an ectopic atrial tachycardia focus obviates the need for long-term pacing. For many reasons, catheter ablation represents an exciting approach to the management of patients with drug-refractory supraventricular tachycardia.     

Catheter Ablation for the Treatment of Paroxysmal Supraventricular Tachycardia

Catheter Ablation for PSVT. Radiofrequency catheter ablation has evolved into a front-line curative therapy for patients who have paroxysmal supraventricular tachycardia secondary to Wolff-Parkinson-White syndrome, AV nodal reentrant tachycardia, and atrial tachycardia. In patients with accessory pathways, cure rates exceed 90% in almost all anatomic locations. Equally high success rates are noted in patients with atriofascicular pathways and the permanent form of junctional reciprocating tachycardia. Complications secondary to catheter ablation of accessory pathways occur in 1% to 3% of patients and include cardiac perforation, tamponade, AV block, and stroke. In patients with AV nodal reentrant tachycardia, selective slow pathway ablation is curative in over 95% of patients with a very low risk of AV block. Atrial tachycardias originating in both the left and right atria can he successfully ablated in over 80% of patients. Given the overall effectiveness of this procedure, radiofrequency catheter ablation should be considered as front-line therapy in patients with recurrent or drug-refractory paroxysmal supraventricular tachycardia. Although an effective therapy, the risks and benefits of this procedure need to be assessed in all patients who are candidates for this procedure.     

Accessory pathway and atrioventricular node reentrant tachycardia in elderly patients: Clinical features,electrophysiologic characteristics and results of radiofrequency ablation

Objectives. This study was designed to evaluate the clinical features, electrophysiologic characteristics and results of radio-frequency ablation in elderly patients with accessory atrioventricular (AV) pathways or AV node reentrant tachycardia. Background. Radiofrequency ablation in elderly patients with paroxysmal supraventricular tachycardia has not been well described, and comparative study between elderly and younger patients is limited.Methods. Electrophysiologic studies and radiofrequency ablation were performed in 92 elderly patients (45 with an accessory pathway, 47 with AV node reentrant tachycardia).Results. The elderly patients had poorer electrophysiologic properties in accessory pathways and dual AV node pathways than those of younger patients. The success rate of radiofrequency ablation was similar in elderly and younger patients. However, elderly patients had more complications (14%) in left-sided accessory pathways.Conclusions. Radiofrequency ablation in elderly patients with supraventricular tachycardia was effective. However, it must be performed cautiously in those patients with left-sided accessory pathways.     

Experience in 1,500 patients undergoing radiofrequency ablation in the treatment of tachycardias

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular and ventricular tachycardias. This report details the results of radiofrequency catheter ablation in 1500 consecutive patients with a wide variety of supraventricular and ventricular tachycardias treated in the Instituto Nacional de Cardiología "Ignacio Chavez", between April 22, 1992 until December of 1999. Tachycardias were associated with the presence of an accessory pathway in 987 patients (65.8%). Dual accessory pathways were present in 24 patients giving a total of 1,012 accessory pathways. The mechanism of the arrhythmia was atrioventricular nodal reentrant tachycardia in 321 patients (21.4%). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 109 (7.2%) patients and a primary atrial tachycardia in 13 patients (0.8%). Atrioventricular node ablation and permanent pacemaker implantation were performed in 26 patients (1.7%). Finally we performed radiofrequency catheter ablation in 37 (2.4%) patients with ventricular tachycardia. Radiofrequency catheter ablation was successful in 908 of 1012 (89.7%) patients with accessory pathways with a complication rate of 10 (0.98%) and a recurrence rate of 92 (9%). AV nodal reentry was successfully abolished in 319 of 321 patients by selective ablation of the slow pathway in 297/321 (92.5%) patients and the fast pathway in 22/24 (92%) patients. The complication rate of this group was 8/321 (2.4%) with a recurrence rate of 34 patients (10.5%). The reentrant circuit of atrial flutter was ablated successfully in 86 of 109 (76.8%) patients with a recurrence flutter in 14 (12.8%) patients. Five of 13 (38.4%) cases of primary atrial tachycardia were successfully ablated. Complete AV block was achieved in 26 of 26 (100%) patients with atrial fibrillation or flutter treated by AV nodal ablation. The procedure was successful in 28 of 37 (75.6%) patients with fascicular ventricular tachycardia. The results of this series of patients demonstrates the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of taquicardias with high rate of success 1375 of 1500 patients (91.6%), with 142 recurrences (9.4%), 15 complications (1%), and no mortality.     

射频消融术治疗室上性心动过速80例体会

用射频消融术治疗室上性心动过速80例.其中,房室折返性心动过速64例(65条旁路),56条左侧旁路中52条(92.9%)和9条右侧旁路中7条(77.8%)被阻断.14例房室结折返性心动过速(消融慢径)及2例房性心动过速和心房纤颤(消融房室结)均成功.比较初期30例和以后34例房室旁路病人的消融,显示了射频消融术开展过程中的学习曲线.此外,本文对预激综合征体表心电图旁路定位误差的原因,作了初步探讨.     

Percutaneous radiofrequency catheter ablation for supraventricular arrhythmias in children

Nineteen procedures were performed in 17 children, aged 10 months to 17 years, using catheter radiofrequency applications for the management of malignant or drug-resistant supraventricular tachyarrhythmias. Diagnoses were junctional ectopic tachycardia in 1 patient, atrioventricular (AV) node reentrant tachycardia in 4 and accessory pathway-mediated tachycardia in 12. Accessory pathway locations were left lateral (n = 4), posteroseptal (n = 3), left posterior (n = 2), right posterolateral (n = 1), right posterior paraseptal (n = 1), right intermediate septal (n = 1) and right anterior (n = 1). Ablation of accessory pathways was performed using 20 to 40 W of energy. The catheter was passed retrograde to the left ventricle in patients with a left-sided pathway and anterograde to the right atrium in those with a right-sided or posteroseptal pathway. In the 12 patients with an accessory pathway, radiofrequency applications were successful in 11 pathways and failed in 2. There were no recurrences of accessory pathway-mediated tachycardia. Atrioventricular node reentrant tachycardia was treated by AV node modification using 15 W of energy applied until first degree AV block occurred. After radiofrequency catheter ablation, there was a prolonged AH interval, tachycardia was not inducible and tachycardia recurred in one patient. For the patient with junctional ectopic tachycardia, 15 to 18 W of energy was delivered at the site of the maximal His bundle electrogram until sinus rhythm and normal AV conduction appeared. After a recurrence, a second procedure abolished tachycardia and AV conduction. In summary, radiofrequency catheter ablation was initially successful in 17 of 19 procedures and ultimately curative in 14 (82%) of 17 patients with no serious complications. Radiofrequency catheter ablation appears to be a safe and effective method for the management of supraventricular tachyarrhythmias in children.     

Role of Radiofrequency Ablation in the Management of Supraventricular Arrhythmias:

Radiofrequency Ablation of Supraventricular Arrhythmias, Introduction: Several reports iiave demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular tachycardias. However, the efficacy, complications, risk of arrhythmia recurrence, and follou-up survival analysis have not been reported in a large series of consecutive patients with supraventricular arrhythmias with diverse electrophysiologic mechanisms. This report details the results of radiofrequency catheter ahiation in 760 consecutive patients (386 males, 374 females) with a wide variety of supraventricular tachycardias treated at one center. Methods and Results: Arrhythmias were associated with the presence of an accessory pathway i n 363 patients (384 accessory pathways), including four patients with Mahaim fibers and eight patients with the permanent form of junctional reciprocating tachycardia. The mechanism of the clinical arrhythmia was AV nodal reentrant tachycardia in 245 patients, and a primary atrial tachycardia in 20 patients (ectopic atrial tachycardia in 16 patients and sinus nodal reentry in 4 patients). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted i n 13 patients. AV node ahiation and permanent pacemaker implantation were performed in 119 patients with medically refractory atrial fihrillation or flutter. Radiofrequency catheter ahiation was successful in 346 of 363 patients (95.3%, CI 93.I%–97.5%) with accessory pathways (367 of 384 pathways, 95.6%, CI 93.5%–97.6%) with a complication rate of 1.1% and a recurrence rate of 5.5%. Successful accessory pathway ablation was achieved for 179 of the first 192 pathways treated (93.2%, CI 89.7%–96.6%) and increased to 188 of 192 pathways (97.9%, CI 95.9%–99.9%) over the second half of the series. AV nodal reentry was successfully abolished in 244 of 245 patients (99.6%, CI 98.8%–100%) by selective ablation of the slow pathway in 234 patients and the fast pathway in 10 patients. The complication rate in this group was 2.0% with a recurrence rate of 6.5%. All 20 primary atrial tachycardias were successfully ablated with no complications and a recurrence rate of 15%. The reentrant circuit of atrial flutter was ahlated successfully in 10 of 13 patients (77%) with recurrent atrial flutter in one additional patienl. Complete AV block was achieved in 117 of 119 (98.3%, CI 96.0%–100%) patients with atrial fibrillation or flutter treated hy AV nodal ablation with a complication rate of 0.8% and recurrence of AV conduction in 6%. The median duration of fluoroscopy exposure for the population was 23.4 minutes. The overall primary success rate for the entire population was 97.0% (737 of 760 patients, CI 95.8%–98.2%). Conclusion: Thus, the results of this large series of patients demonstrates the safety and efiicacy of radiofrequency ahiation for the treatment of a wide variety of supraventricular arrhythmias. It also appears that increasing experience with these procedures increases the rate of successful ahlation and decreases the risk of complications.     

Catheter Ablation with Radiofrequency Energy: Biophysical Aspects and Clinical Applications

Radiofrequency Catheter Ablation. Radiofrequency catheter ablation techniques are becoming increasingly accepted as the therapy of choice for selected patients with symptomatic arrhythmias. The ability to titrate the power output using radiofrequency current has allowed these ablative techniques to be applied safely in a variety of arrhythmias. In many institutions, radiofrequency catheter ablation has now become standard therapy for controlling medically refractory atrial arrhythmias using atrioventricular (AV) junction ablation and for curing AV nodal reentrant tachycardia and supra ventricular tachycardia due to accessory AV connections. This technology is also being used to treat some forms of ventricular tachycardia such as bundle branch reentry ventricular tachycardia, ventricular tachycardia in structurally normal hearts, and with limited success in patients with ventricular tachycardia and coronary artery disease. Advancements in catheter design and energy delivery systems may further expand the use of this form of therapy. (J Cardiovasc Electrophysiol, Vol. 3, pp. 173–186, April 1992)     

Radiofrequency catheter ablation of both atrial ventricular nodal reentrant and atrial ventricular reentrant tachycardia in a single session

Radiofrequency catheter ablation is a new therapeutic approach to treat patients with symptomatic drug-resistant paroxysmal supraventricular tachycardia. Ablation of two accessory atrioventricular pathways in a single session has been frequently described previously. However, ablation in a single session of both the fast pathway, involved in atrial ventricular nodal reentrant tachycardia, and a concealed atrioventricular accessory pathway involved in a circus movement tachycardia has rarely been reported. A 57-year-old man with a grade III aortic incompetence had the infrequent association of atrial ventricular nodal reentrant tachycardia and orthodromic circus movement tachycardia due to a concealed accessory pathway. He presented with drug-resistant reentrant supraventricular tachycardia and, in a single session, underwent a successful radiofrequency catheter ablation of the fast atrial ventricular nodal pathway and a concealed posteroseptal accessory pathway. During a 10-month follow-up he was free of palpitations without any antiarrhythmic therapy and underwent elective aortic valve replacement.     

Catheter Ablation of the Atrial Origin of a Decrementally Conducting Atriofascicular Accessory Pathway by Radiofrequency Current

Radiofrequency Ablation of Pseudo-Mahaim Fibers. Introduction: A young woman with refractory recurrent supraventricular tachycardia was referred for catheter ablation. Methods and Results: Electrophysiologic studies revealed the mechanism of tachycardia to be atrioventricular (AV) reentry, utilizing a decrementally conducting atriofascicular accessory pathway as the anterograde limb of the circuit and the normal intraventricular conducting system as the retrograde limb. Pace mapping in the right atrium during sinus rhythm suggested an atrial origin of the accessory pathway several centimeters distant from the AV node. Multiple radiofrequency lesions at the distal insertion of the accessory pathway in or near the right bundle branch failed to abolish preexcitation. In contrast, radiofrequency current applied to the ventricular side of the anterolateral tricuspid ring, adjacent to the atrial origin of the accessory pathway, was successful in abolishing preexcitation and inducible supraventricular tachycardia without affecting AV nodal conduction. Conclusion: Radiofrequency ablation can provide curative therapy for intractable supraventricular tachycardia due to decrementally-conducting atriofascicular accessory pathways. The risk of AV block in such patients as a consequence of the procedure should be quite low.     

Case Report: Clinical AV Nodal Reentrant Tachycardia in a Patient with Left Sided Accessory Pathway and Immediate Occurrence of Antidromic AV Reentrant Tachycardia after Slow Pathway Ablation

The only inducible arrhythmia in a patient with exclusive antegrade conducting left anterolateral accessory pathway, consists of slow/fast atrioventricular nodal reentrant tachycardia. After radiofrequency catheter ablation of the slow pathway, true antidromic AV reentrant tachycardia was easily induced by atrial pacing. Following ablation of the accessory pathway no arrhythmia could be induced.     

Radiofrequency catheter ablation in the treatment of supraventricular tachycardia in the elderly

Objectives. The purpose of this study was to evaluate the efficacy and safety of radiofrequency catheter ablation for the treatment of supraventricular tachycardias in an elderly (≥70 years of age) group of patients.Background. Supraventricular tachycardias are the most common form of cardiac arrhythmia and affect all age groups. Although usually well tolerated in youth, supraventricular tachycardias may be associated with disabling symptoms and have lifethreatening potential 10 the elderly. In addition, antiarrhythmic agents are less well tolerated and may be associated with a higher incidence of toxicity in the elderly.Methods. From May 1989 to March 1993, 454 patients underwent a radiofrequency catheter ablation procedure at the University of California, San Francisco, for the treatment of symptomatic supraventricular tachycardia. Sixty-seven of these patients were ≥70 years of age and constituted the study group. Patients underwent one of the following catheter ablation procedures: complete atrioventricular (AV) junctional ablation for ventricular rate control in patients with atrial fibrillation (37 patients), AV node modification for the treatment of AV node reentrant tachycardia (17 patients), accessory pathway ablation (9 patients), ablation of the “slow zone” to cure atrial flutter (4 patients) and atrial tachycardia ablation (1 patient). One patient underwent ablation for both AV node reentrant tachycardia and atrial flutter.Results. Success was achieved in 67 (98.5%) of 68 ablation procedures. There were no procedural or early deaths. The overall complication rate was 7.4%, and only one patient (1.5%) had long-term sequelze (permanent cardiac pacing for complete heart block). At a mean (±SD) follow-np of 22.1 ± 12.9 months, 63 (94%) of 67 patients were alive, with no antiarrhythmic agents for the treatment of their presenting arrhythmia.Conclusions. In this series radiofreqnency catheter ablation appears to be an effective and safe treatment option for elderly patients (≥70 yean of age) with a variety of symptomatic, drug-resistant supraventricular tachycardias. Because of the high incidence of severe symptoms associated with tachycardic episodes, the expense and the possible severe proarrhythmic problems associated with antiarrhythmic medications in this age group, catheter ablation may be considered an early rather than a “last resort” treatment option.     

Recurrence of Conduction Following Radiofrequency Catheter Ablation Procedures:

Recurrence of Conduction Following RF Catheter Ablation. Introduction : More than 1 in 10 patients may develop recurrence of conduction after undergoing a successful radiofrequency catheter ablation procedure. The physiologic basis for recurrence following successful ablation procedures remains uncertain. The purpose of this study was to evaluate the role of electrode temperature as a predictor of recurrence following radiofrequency catheter ablation procedures.
Methods and Results : The subjects of this study were 538 patients who underwent a successful attempt at radiofrequency catheter ablation of AV nodal reentrant tachycardia, an accessory pathway, and/or the AV junction. Patients were followed for a mean of 215 ± 138 days. Conduction recurred in 35 (6.5%) of the 538 patients. Recurrence of conduction occurred in 25 (9.3%) of 270 patients undergoing ablation of an accessory pathway, 7 (3.5%) of 201 patients undergoing ablation of AV nodal reentrant tachycardia, and in 3 (4.5%) of 67 patients undergoing ablation of the AV junction. The electrode temperature achieved at successful sites associated with recurrence was not different from the temperature achieved at successful sites without recurrence (61.1 ± 8.9 vs 61.6 ± 9.1; P = 0.8). The likelihood of developing a recurrence was higher following ablation of accessory pathways than following ablation of A V nodal reentrant tachycardia or the AV junction (P = 0.03). Patients experiencing a recurrence following ablation of an accessory pathway had longer procedure durations (P = 0.0001). Ablation of left free-wall pathways was associated with a lower incidence of recurrence as compared with all other locations (P = 0.008).
Conclusion : The results of this study suggest that electrode temperature at the successful ablation site cannot be used to identify patients at highest risk of recurrence.     

Cryosurgical treatment of atrioventricular node reentrant tachycardia

Paroxysmal supraventricular tachycardia most commonly arises from reentry within the atrioventricular (AV) node. Although ablation of the His bundle has gained popularity for treating patients with AV node reentrant tachycardia refractory to medical therapy, undesirable sequelae include complete heart block and the necessity for a permanent pacemaker. To obviate this limitation, we have developed a discrete cryosurgical procedure that interrupts the reentrant circuit responsible for AV node reentrant tachycardia without blocking AV conduction. After first characterizing the salutary effects of this approach in experimental animals, we performed this procedure in eight patients with AV node reentrant tachycardia. Preoperative, intraoperative, and postoperative electrophysiologic studies were performed in each patient. Under conditions of normothermic cardiopulmonary bypass and during atrial pacing at a constant rate with continuous monitoring of AV conduction, nine separate 3 mm cryolesions (-60 degrees C for 2 min) were placed at predetermined sites around the triangle of Koch in the lower right atrial septum. Postoperatively, each patient had a single AV node conduction curve. No patient had AV node reentrant tachycardia induced or has experienced AV node reentrant tachycardia clinically during a follow-up of up to 5 years. The cryosurgical procedure had no detrimental effects on the AH or HV interval or on the paced cycle length at which AV node Wenckebach occurred. Based on these results, this curative operation offers promise for patients with AV node reentrant tachycardia that is refractory to medical treatment.     

Radiofrequency Current Catheter Ablation for Control of Supraventricular Arrhythmias

Radiofrequency Catheter Ablation in SVT. With the advent of radiofrequency energy, catheter ablation techniques have become an accepted form of treatment for a variety of Supraventricular arrhythmias. The ablation of the atrioventricular (AV) node was performed first and is now widely used in patients with refractory atrial fibrillation or flutter. Ablation has also replaced surgery in patients with preexcitation syndromes, and as the complication rate in experienced centers is low, it has become the first line of treatment in these institutions. The results of catheter ablation in AV nodal reentrant tachycardia are excellent as well, although there is still debate about whether "slow" pathway ablation is superior to "fast" pathway ablation. Radiofrequency current ablation has also contributed to a better understanding of the pathophysiology of AV nodal reentrant tachycardia, as it has provided evidence for atrial participation in the reentrant circuit. Experience with atrial tachycardias and tachycardias due to Mahaim fibers remains limited. The ideal source of energy for specific arrhythmias is still unknown and improvement in catheter technology is needed.     

Dependence of electrogram duration in right posteroseptal atrium and atrium-pulmonary vein junction on pacing site: mechanism and implications regarding atrioventricular nodal reentrant tachycardia and paroxysmal atrial fibrillation

INTRODUCTION: The fractionated atrial electrogram, a signal helpful in identifying the target site for radiofrequency catheter ablation of the slow AV nodal pathway, is considered to arise from nonuniform anisotropic electrical activity. However, the effects of pacing sites and radiofrequency ablation on these electrograms are not clear. Similarly, the nature of the fractionated atrial electrogram in the atrium-pulmonary vein junction has yet to be determined. METHODS AND RESULTS: Two experiments were performed in this study. Experiment 1 evaluated the fractionated atrial electrogram at target sites before and after slow AV nodal pathway ablation during sinus rhythm or during pacing from different sites. Group 1A consisted of 16 patients with dual AV nodal pathway physiology and AV nodal reentrant tachycardia who underwent successful ablation without residual slow AV nodal pathway. Group 1B consisted of 7 patients who underwent successful elimination of AV nodal reentry but with residual dual AV nodal pathway physiology. Group 1C consisted of 6 patients who still had AV nodal reentrant tachycardia after two applications of radiofrequency energy. In group 1D, there were 16 patients with dual AV nodal pathway physiology, but without inducible AV nodal reentrant tachycardia. In group 1E, there were 15 patients without dual AV nodal pathway physiology. Experiment 2 investigated the fractionated atrial electrogram in the ostium of the left and right superior pulmonary veins in 18 patients with paroxysmal atrial fibrillation (2A) and in 8 patients without paroxysmal atrial fibrillation (2B). Before radiofrequency ablation, electrogram duration in the right posteroseptal atrium during pacing from the middle coronary sinus or the right posterolateral atrium was shorter than that during pacing from the high right atrium (HRA) in all group 1 patients. After the successful elimination of the slow AV nodal pathway conduction in group 1A, atrial electrogram duration during HRA pacing was shorter than that before ablation. In experiment 2 patients, electrogram duration during pacing from the proximal or distal coronary sinus was shorter than that during pacing from HRA or sinus rhythm. CONCLUSION: These findings suggest that the fractionated atrial electrograms in the right posteroseptal atrium and ostium of left or right superior pulmonary veins are potentially consistent with nonuniform anisotropic propagation. Alternations of electrogram characteristics after successful radiofrequency ablation of the slow AV nodal pathway may arise from the changes of nonuniform anisotropic activity in the right posteroseptal atrium.     

Radiofrequency catheter ablation of the atrioventricular junction from the left ventricle

BACKGROUND. The purpose of this study was to describe a new technique for catheter ablation of the atrioventricular junction using radiofrequency energy delivered in the left ventricle. METHODS AND RESULTS. Catheter ablation of the atrioventricular (AV) junction using a catheter positioned across the tricuspid annulus was unsuccessful in eight patients with a mean +/- SD age of 51 +/- 19 years who had AV nodal reentry tachycardia (three patients), orthodromic tachycardia using a concealed midseptal accessory pathway, atrial tachycardia, atrial flutter (two patients), or atrial fibrillation. Before attempts at catheter ablation of the AV junction, each patient had been refractory to pharmacological therapy, and four had failed attempts at either catheter modification of the AV node using radiofrequency energy or surgical and catheter ablation of the accessory pathway. Conventional right-sided catheter ablation of the AV junction using radiofrequency energy in six patients and both radiofrequency energy and direct current shocks in two patients was ineffective. The mean amplitude of the His bundle potential recorded at the tricuspid annulus at the sites of unsuccessful AV junction ablation was 0.1 +/- 0.08 mV, with a maximum His amplitude of 0.03-0.28 mV. A 7F deflectable-tip quadripolar electrode catheter with a 4-mm distal electrode was positioned against the upper left ventricular septum using a retrograde aortic approach from the femoral artery. Third-degree AV block was induced in each of the eight patients with 20-36 W applied for 15-30 seconds. The His bundle potential at the sites of successful AV junction ablation ranged from 0.06 to 0.99 mV, with a mean of 0.27 +/- 0.32 mV. There was no rise in the creatine kinase-MB fraction and no complications occurred. An intrinsic escape rhythm of 30-60 beats/min was present in seven of the eight patients. Each patient received a permanent pacemaker and has been asymptomatic during 3-13 months of follow-up. CONCLUSIONS. Catheter ablation of the AV junction can be achieved effectively and safely using radiofrequency energy delivered in the left ventricle when the conventional right-sided approach is unsuccessful.     

Radio-frequency catheter ablation of cardiac arrhythmias: appraisal of an evolving therapeutic modality

Since its introduction in 1985, there have been numerous reports of the use of radio-frequency (RF) current as an alternative energy source for catheter ablation. RF current (frequency range 150 kHz to 1 MHz), when delivered in bipolar mode, causes desiccation of tissue by creating a localized area of heat that results in discrete coagulation necrosis. An equivalent energy source such as direct current (DC) shock can be delivered at lower power (5 to 30 W) and lower voltage (30 to 80 V) for a longer pulse duration (10 to 60 seconds), thus eliminating barotraumatic effects. Because of its high frequency, RF current does not stimulate neuromuscular fibers, and general anesthesia during ablation is not needed. Studies in animals have shown that catheter-delivered RF energy can safely produce permanent complete or partial AV block, necrosis of atrial and ventricular myocardium adjacent to the mitral and tricuspid anuli potentially suitable for ablation of accessory pathways, and discrete lesions in the left and right ventricular myocardium. Recently, investigators from several centers have reported successful ablation of the AV junction (either complete or partial AV block) in patients with refractory supraventricular tachyarrhythmias, ablation of accessory pathways, and ablation of focal ventricular myocardium or a segment of a bundle branch in patients with drug-resistant ventricular tachycardia. Specific modification of AV conduction to cure AV nodal reentrant tachycardia has been successfully attempted. In all studies the application of RF current has not caused any serious complications.(ABSTRACT TRUNCATED AT 250 WORDS)     

食管心房调搏对室上性心动过速诊断的准确性评价

评价食管电生理检查对室上性心动过速诊断的准确性。方法 比较102例室上性心动过速经心内和食管电生理检查的结果。结果 102例室上性心动过速101例分型诊断一致：房室折返性心运过速（AVRT）58例,房室结折返性心运过速（AVNRT）37例,房内折返性心动过速（IART）5例,窦房结折返性心动过速（SART）1例,房性自律性心动过速（AAT）1例。6例房性心动过速（IART5例,AAT1例）起源于右房还是左房和57例房室折返性心动过速的旁路位于右侧还是左侧,两种检查结果完全一致。结论 食管心房调搏对室上性心动过速的分型诊断和初步定位诊断具有很高的准确性,这对选择射频消融术病例和简化消融术程序具有重要意义。     

Variants of Preexcitation—Specialized Atriofascicular Pathways, Nodofascicular Pathways, and Fasciculoventricuiar Pathways:

Variants of Preexcitation. introduction: In the present report, the electrophysiiologic findings in patients with different types of variants of preeexcitwtion, i.e., atriofascicualr, nodofacicular, and fasciculoventricular fibers, and the results of radiofrequency catheter ablation using different target sites are described. Methods and Results: Twelve patients (mean age 36 ± 17 years) with variants of the preexcitation syndromes underwent electrophysiologic study and radiofrequency catheter ablation. The atrial origin of atriofascicular pathways remote from the normal AV node was assessed by application of late atrial extrastimuli that advanced (“reset”) the timing of the next QRS complex without anterograde penetration into the AV node. In patients with atriofacicular pathways, ablation of the accessory pathway or the retrograde fast AV node pathway was attempted. Ablation of the atriofascicular pathways was guided by a stimulus-delta wave interval mapping in the first live patients and by recording of atriofascicular pathway activation potentials in the next five patients. A nodofascicular pathway was suggested if VA dissociation occurred during tachycardia and if atrial extrastimuli failed to reset the tachycardia without anterograde penetration into the AV node. A fasciculoventricular connection was suggested if the proximal insertion of the accessory pathway was found to arise from the His bundle or bundle branches. The PR interval was expected within normal limits during sinus rhythm and the QRS complex to he slightly prolonged with a discrete slurring of the R wave, suggesting a small delta wave. Ten of the 12 patients had evidence for atriofascicular pathways and one patient each for a nodofascicular and fasciculoventricular pathway. In six patients, the atriofascicular pathways were successfully ablated, and in two patients, the retrograde fast AV node pathway. In one patient, a concealed right posteroseptal accessory AV pathway served as the retrograde limb and was successfully ablated. The nodofascicular pathway was shown to he a bystander during AV node reentrant tachycardia. After successful fast AV node pathway ablation resulting in marked PR prolongation, no preexcitation was present during sinus rhythm because of the proximal insertion of the nodofascicular pathway distal to the delay producing parts of the AV node. The proximal insertion of the fasciculoventricular pathway was suggested to arise distal to the AV node at the site of the penetrating AV bundle. The earliest ventricular activation at the His-bundle recording site indicated the ventricular insertion of this accessory connection into the ventricular summit. The fasciculoventricular connection gave rise to a fixed ventricular preexcitation and served as a bystander during orthodromic AV reentrant tachycardia incorporating a left-sided accessory AV pathway.