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Radiofrequency Catheter Ablation for Cardiac Tachyarrhythmias
- Antonis S. Manolis, MD;
- Paul J. Wang, MD; and
- N. A. Mark Estes, MD
- From New England Medical Center and Tufts University School of Medicine, Boston, Massachusetts. Requests for Reprints: Antonis S. Manolis, MD, Division of Cardiology, Tufts/New England Medical Center, Box 868, 750 Washington Street, Boston, MA 02111.
Abstract
Purpose: To review the radiofrequency ablation method, describe the technique, and discuss the indications, results, and limitations of its use in patients with cardiac tachyarrhythmias.
Data Sources: Peer-reviewed reports in the literature by clinical investigators who use radiofrequency catheter ablation as identified by a MEDLINE search and our own experience with this intervention in 214 patients with cardiac tachyarrhythmias.
Study Selection: All articles reporting results of radiofrequency ablation for cardiac tachyarrhythmias and articles describing the ablation technique or comparing it with direct-current or surgical methods.
Results of Data Synthesis: Percutaneous catheter ablation of cardiac arrhythmias using high-voltage, direct current was limited by a high complication rate and a need for general anesthesia. This method was recently replaced by a new safe and efficacious technique using low-voltage, high-frequency (radiofrequency) alternating current. Nonsurgical cure of many supraventricular arrhythmias is now feasible with radiofrequency ablation, especially in patients with accessory pathways or atrioventricular nodal reentrant tachycardia. For these arrhythmias, success rates are greater than 90%. The indications for ablation include preexcitation syndromes, atrioventricular nodal reentrant tachycardia, and other selected atrial and ventricular tachyarrhythmias refractory to antiarrhythmic drug therapy. The efficacy and safety profile of this technique has made it feasible for children as well as adults.
Conclusions: Percutaneous radiofrequency catheter ablation has evolved as a safe and effective method for managing and curing the two most common forms of supraventricular tachycardia: those associated with preexcitation syndromes and atrioventricular nodal reentrant tachycardia. Further studies are needed to determine the efficacy of this method or to evaluate alternative transcatheter techniques in patients with atrial tachycardias and, more importantly, in the large population of patients with ischemic ventricular tachycardia.
Current therapeutic options for symptomatic supraventricular and ventricular arrhythmias include antiarrhythmic drugs, mapping-guided techniques, devices, and catheter ablation. Of these, only surgery and ablative techniques are curative. Although effective, surgery for supraventricular [1] or ventricular arrhythmias is associated with substantial cost, morbidity, and, rarely, death. Concerns about the efficacy and toxicity of antiarrhythmic drugs prompted reevaluation of their role in managing all arrhythmias. Devices such as antitachycardia pacemakers for supraventricular arrhythmias and implantable defibrillators for ventricular arrhythmias are palliative, are costly, and often require concomitant drug therapy. Catheter ablation techniques were first introduced in 1982 using direct-current shocks for ablation of the atrioventricular junction in patients with refractory atrial tachyarrhythmias [2-4]. Although direct-current shocks have since been used to treat various tachyarrhythmias, this technique has substantial risks, has only modest efficacy, and requires general anesthesia [2-5]. Given these limitations of other therapies, radiofrequency has evolved as an alternative energy source for catheter ablation [6-12]. Radiofrequency ablation is an effective and low-risk curative treatment for supraventricular arrhythmias caused by atrioventricular nodal reentry or accessory pathways, the most common mechanisms of supraventricular tachycardia. Experience with radiofrequency ablation of other atrial and ventricular tachycardias is increasing. Nearly 10 000 radiofrequency ablative procedures were done in 1991, representing a fivefold increase from 1990 [7].
Radiofrequency Energy and Current
Radiofrequency energy is a form of electrical energy, generated from low-power (15 to 60 V), high-frequency (30 KHz to 300 MHz) alternating current. Equipment generating radiofrequency energy, called the Bovie device, has been used for electrosurgical cutting since 1929 [13]. Modulation of the wave form and control of the impedance and voltage of these devices have allowed routine use of radiofrequency current for electrical cutting in various specialties [8]. Its applications recently were extended to cardiology to treat cardiac arrhythmias with catheter techniques [14]. It is also being evaluated for thermal coronary angioplasty [8]. Modulated radiofrequency current is used for electrosurgical cutting, whereas the unmodulated current, creating biological tissue desiccation with formation of coagulation necrosis, is used for catheter ablation of cardiac tissue [12]. Cardiac lesions are produced primarily through resistive heating. Multiple factors govern the effects of radiofrequency energy on cardiac tissue, including the current density, the surface area of the active electrode, the duration of current application, the impedance of the tissue, tissue contact, and the degree of tissue heating [12].
Radiofrequency Catheter Ablation Technique
The radiofrequency current is delivered to cardiac tissue through a transvenous, steerable electrode catheter with a tip that is 4 mm long. In the unipolar mode, the current passes through the active electrode that is in contact with the tissue and returns to the generator through a larger passive patch electrode located externally on the chest. In the bipolar mode, the current flows between two adjacent intracardiac electrodes usually mounted on the same catheter. A bipolar electrode configuration with two catheters has also been used [15]. In either case, good tissue contact of the active electrode is of paramount importance for effective ablation.
The radiofrequency energy used (20 to 50 W) is generated from a 300- to 750-KHz electrosurgical unit and is delivered for 10 to 60 seconds. During the ablation procedure, energy delivery and the coagulation process can be controlled by concurrent monitoring of voltage, current, power, and impedance or catheter tip temperature or both to avoid overheating and to minimize the risk for cardiac perforation [16, 17]. Impedance or temperature increase is typically associated with blood coagulum on the catheter tip. Because thermal coagulation necessitates removal of the catheter and cleaning of the electrode tip before reinsertion, monitoring catheter tip temperature with an incorporated thermistor provides valuable information about tissue effects and helps in gauging lesion size [17]. A small initial decrease in impedance and a fast temperature increase at the catheter tip may indicate good tissue contact, whereas a slow increase suggests poor contact and ineffective coagulation. Effective desiccation of the myocardium usually occurs at temperatures of 60 Carbon-o or higher. Maintaining catheter tip temperature at less than 100 Carbon-o may prevent the sudden increase in electrical impedance and prevent carbonization of tissue with its attendant risk for myocardial perforation [16]. Most commercially available radiofrequency generators and ablation catheters, however, cannot monitor temperature, and thus impedance is monitored instead.
Delivery of radiofrequency energy to cardiac tissue has several advantages compared with direct-current shocks [18] (Table 1). Although general anesthesia is not needed, it is common to use deep sedation for patient comfort, particularly when anticipating a long procedure. The absence of barotraumatic complications has made it possible also to use this technique safely to treat drug-refractory supraventricular tachyarrhythmias in children [19, 20].
Indications and Clinical Results
Radiofrequency catheter ablation has been applied to the atrioventricular junction, accessory pathways, atrioventricular nodal pathways, and atrial and ventricular myocardium in patients with various symptomatic supraventricular and ventricular tachycardias (Tables 2 and 3). In addition to reports from the literature, the results of radiofrequency ablation in 214 patients at our institution are also included (Tables 2 and 3).
Modification of the Atrioventricular Node
Atrioventricular nodal reentrant tachycardia is the most common cause of paroxysmal supraventricular tachycardia originating from reentry in two atrioventricular nodal pathways, a slow anterograde conducting (α) pathway, and a fast retrograde conducting (β) pathway (typical or slow-fast form) (Figure 1A) [21, 22]. There is also an atypical form of atrioventricular nodal tachycardia that is characterized by anterograde fast-retrograde slow pathway conduction. An entirely intranodal location of the reentry circuit of atrioventricular nodal tachycardia was recently challenged by seminal surgical work and observations [23, 24]. This tachycardia is curable with surgical modification of the atrioventricular node that abolishes the tachycardia by dissection or cryoablation of atrial perinodal tissue without disrupting atrioventricular conduction [23, 24]. These surgical procedures have laid the groundwork for development of percutaneous methods of atrioventricular nodal modification. Radiofrequency catheter ablation is the method preferred to surgery or direct-current shocks because of its superior efficacy and lower complication rates [25-34] (Table 2).
Selective ablation of either the slow or the fast pathway can be achieved using radiofrequency energy. Slow pathway ablation is preferable, and it is usually considered as the initial, most efficacious (90% to 100%) approach, minimizing the risk for atrioventricular block [26]. The site for successful slow pathway ablation is along the tricuspid annulus, either anterior to (80%), caudal to (13%), or within (7%) the coronary sinus ostium [27]. In most patients, the slow pathway is located posteriorly and inferiorly, whereas the fast pathway is found anteriorly or superiorly to the compact atrioventricular node (Figure 1A) [35]. Recording of discrete slow, low-amplitude potentials has been used to direct slow pathway ablation [28]. However, slow pathway ablation is possible without registration of these potentials [29, 31, 36]. Occurrence of nonsustained junctional tachycardia with 1:1 atrial activation during radiofrequency application is considered a marker of efficacy [36]. The end point of ablation is noninducibility of atrioventricular nodal tachycardia. Complete elimination of slow pathway conduction, with no detectable jump in the atrioventricular conduction time or inducible nodal echo beats, is not necessary for long-term success [30, 32], although other investigators have argued otherwise [37]. In selected patients in whom slow pathway ablation is unsuccessful, fast pathway ablation can be attempted with radiofrequency lesions placed just caudad to the His bundle area [38], with a higher potential risk for complete heart block (8% to 21%) [25, 26]. After fast pathway ablation for common atrioventricular nodal tachycardia, some patients have uncommon atrioventricular nodal tachycardia [39], which may then require slow pathway ablation. Inappropriate sinus tachycardia may develop in some patients and may require β-blocker therapy [40]. Apparently, ablation in the low interatrial septum in patients having atrioventricular nodal modification (with either slow or fast pathway ablation) or posteroseptal accessory pathway ablation may disrupt parasympathetic fibers innervating the sinus node, which may be one mechanism for inappropriate sinus tachycardia in these patients [41]. This is suggested by increased heart rate variability found after radiofrequency ablation in such patients.
Radiofrequency catheter modification of the atrioventricular node offers an excellent chance for permanent cure, drastically curtailing medical expenses in patients with symptomatic atrioventricular nodal reentrant tachycardia [42]. Patients having slow pathway ablation may be discharged from the hospital after approximately 24 hours. A longer period (48 to 72 hours) of in-patient monitoring is recommended for patients having fast pathway ablation because of the potential risk for heart block, which can occur within the first 48 hours after the procedure. The recurrence rate after successful atrioventricular node modification is approximately 7%, and repeated radiofrequency ablation is often very successful. In our institution, 56 patients with atrioventricular nodal reentrant tachycardia had radiofrequency ablation, which was successful in all patients (Table 2). Selective ablation of the slow pathway was performed in all but one, in whom the fast pathway was ablated. Except for transient atrioventricular block in one patient, there were no other complications. During a mean of 13 ± 8 months, tachycardia recurrence was noted in seven patients, and six of them had successful repeated slow pathway ablation.
Ablation of Accessory Pathways
In patients with either manifest or concealed preexcitation syndrome, the most common tachycardia is the orthodromic atrioventricular reciprocating tachycardia, which is characterized by macro-reentry with anterograde conduction through the atrioventricular node-His bundle and retrograde conduction over an accessory pathway (Figure 1B) [21]. Other tachyarrhythmias in these patients include atrial flutter or fibrillation with variable degrees of preexcited (wide) QRS complexes due to fast anterograde conduction over an accessory pathway, presenting a potentially serious risk because it sometimes degenerates into ventricular fibrillation. Less commonly, the accessory pathway participates in a wide-complex tachycardia called antidromic tachycardia, with anterograde conduction occurring through the accessory pathway and retrograde conduction over the His bundle-atrioventricular node or a second accessory pathway. Until recently, in patients with preexcitation syndromes, antiarrhythmic drugs were the mainstay of therapy, whereas cure could essentially be obtained only with surgery [1, 43-45].
Radiofrequency ablation of accessory pathways has ushered in a new era in the management of these patients. Remarkable success rates (as high as 99%) have been reported with this technique, whereas the complication rate has remained very low (< 3% to 5%) [14, 46-49]. Such pioneering work and reports have spawned great enthusiasm for this nonsurgical method of permanent cure. Many electrophysiology laboratories in the United States and Europe equipped for radiofrequency ablation are now offering this approach as a first-line option for patients with symptoms, performing both the diagnostic study and the ablative procedure in a single session [47-49]. Nevertheless, as with every new technique, there is always a learning curve, and success rates have been reported as starting at 52% and swiftly increasing to 80% to 99% [46, 50-56]. Various factors influence the success of the procedure, including the precise localization of the accessory pathway, the type of the ablation catheter used, the approach taken, and the operator's experience and skill [51, 54, 55].
Application of radiofrequency current to cardiac tissue produces very small lesions (5 mm or smaller in diameter). Optimal mapping and precise localization of the accessory pathway therefore are critical for the success of the procedure. Manifest accessory pathways, capable of anterograde (commonly bidirectional) conduction, are primarily mapped during sinus rhythm, atrial or ventricular pacing, or orthodromic tachycardia, whereas concealed pathways, capable of only retrograde conduction, are mapped during orthodromic tachycardia or ventricular pacing. For preliminary localization of an accessory pathway, the preexcitation pattern is analyzed on the 12-lead electrocardiogram during sinus rhythm [57] or more easily during atrial pacing or after adenosine administration, causing maximal preexcitation. Further localization is achieved using multipolar catheters, positioned and maneuvered inside the coronary sinus or at the tricuspid or mitral annuli. Finally, precise localization with mapping and radiofrequency ablation are performed using a steerable electrode catheter.
Right-sided (free-wall, midseptal, and anteroseptal) and many posteroseptal pathways, constituting about one third of all accessory pathways, can be approached from the right heart, with access obtained from the femoral, subclavian, or internal jugular veins. The ablation catheter is positioned either at the atrial or ventricular aspect of the tricuspid annulus [58]. Left-sided pathways, comprising about two thirds of all pathways, can be ablated from either the ventricular or the atrial side of the mitral annulus, which can be approached retrogradely through the aortic route or through the transseptal approach [51, 53, 55, 59]. The ablation catheter is positioned against the mitral annulus just opposite the pole of the coronary sinus catheter already bracketing the location of the accessory pathway in the atrioventricular groove. Application of radiofrequency current through the coronary sinus has been reported in a few patients with left lateral accessory pathways with an epicardial insertion [60, 61].
Criteria used to identify appropriate target sites for ablation include early ventricular activation relative to the delta wave onset or shortest atrioventricular interval for manifest pathways, earliest atrial activation during tachycardia or ventricular pacing for concealed pathways, or the presence of an accessory pathway potential for either manifest or concealed pathways [62-66]. The presence of an accessory pathway potential is not an essential requirement for successful ablation, nor does its presence guarantee success [49, 65, 67]. Once an optimal target site has been identified, radiofrequency energy (20 to 50 W) is delivered through the ablation catheter. Loss of preexcitation or interruption of the tachycardia is expected within 1 to 15 seconds of a successful radiofrequency application (Figure 2), which is usually continued for 30 to 60 seconds and frequently followed by an additional lesion. The earlier the block in the accessory pathway conduction is observed during radiofrequency current application (5 or fewer seconds), the more likely that the effect will be permanent rather than transient [68]. Delayed loss of preexcitation may occur [69] but is usually transient [68, 69]. Approximately one half hour after ablation, electrophysiologic evaluation is repeated, during which the efficacy of ablation is tested with programmed stimulation and infusion of isoproterenol, adenosine, or both [70]. The patient is monitored in the hospital for about 24 hours before discharge. Recurrences may be observed in 4% to 12% of patients and are more common for pathways ablated from the tricuspid annulus and for concealed pathways, but they are amenable to repeated radiofrequency ablation with equally high success rates [71, 72]. Nonischemic, postablation T-wave abnormalities are common in patients who had manifest preexcitation, but they gradually resolve within 1 to 3 months [73].
Table 2 summarizes the results and complication rates of radiofrequency ablation of accessory pathways in recently reported series [9, 14, 46-56, 74]. Ablation can be successful in all accessory pathway locations. However, the anteroseptal region has a higher-than-usual risk for complete heart block (approximately 5%) [49]. This nonsurgical technique offers patients a curative option with only few minor complications and thus eliminates the need for open-heart surgery or lifelong pharmacotherapy [52]. Furthermore, radiofrequency ablation is very cost-effective [75], with substantial cost savings, shorter hospital stays, and quicker return to work compared with its standard surgical counterpart [76]. Initial concerns about the long duration of the procedure and extended fluoroscopy time and radiation exposure have been raised [77], and new abbreviated approaches have been proposed [49, 78]. During a period of 2.5 years, 122 patients have had radiofrequency ablation of accessory pathways at our institution (Table 2, Figure 2). Mapping disclosed 128 pathways (106 manifest and 22 concealed); 71 were left free-wall, 55 were septal, and 2 were right free-wall pathways. Left-sided pathways were approached with the retrograde transaortic technique except in the last 33 patients, in whom a transseptal approach was used. Ablation was successful in 111 (91%) patients. Complications included one complete heart block, one cardiac tamponade, and four minor local vessel injuries. During a mean period of 15 ± 9 months, accessory pathway conduction recurred in 9 patients, 7 of whom had successful repeated ablation. Three patients in whom ablation was unsuccessful had successful surgical division of the accessory pathway.
Ablation of Permanent Junctional Reciprocating Tachycardia
The permanent form of junctional reciprocating tachycardia is an unusual type of tachycardia that manifests as a recurring or incessant tachycardia in children or young adults, is commonly refractory to medical therapy, and not infrequently is responsible for tachycardia-induced cardiomyopathy [79]. The mechanism for this tachycardia commonly is an orthodromic atrioventricular reciprocating tachycardia involving retrograde conduction over an accessory pathway with decremental or atrioventricular nodal-like properties, which many call an extra atrioventricular nodal pathway, located in the posteroseptal area close to the coronary sinus ostium [79, 80] or sometimes in other locations [81]. Until recently, surgery was the mainstay of management for such patients because most do not respond to drug therapy [82]. With the advent of radiofrequency ablation, however, these patients can be cured by this catheter ablation technique [81] (Figure 2B). Gradual improvement of ventricular function is expected after successful ablation of the accessory pathway in those patients with tachycardia-induced depression of ejection fraction [79, 81, 82].
Ablation of the Atrioventricular Junction
Catheter ablation of the atrioventricular junction [83-88] is preferred to surgery to treat drug-refractory atrial tachyarrhythmias because of its equal efficacy, better patient convenience, and lower cost and morbidity and mortality rates compared with surgery [83, 84]. Radiofrequency ablation of the atrioventricular junction is preferred to direct-current shocks because of its lower complication rate.
The ablation is accomplished through an intracardiac catheter placed across the tricuspid valve and against its septal leaflet to record a large His potential. For patients who cannot be ablated with the right-sided approach, a left-heart catheterization technique has been proposed, whereby the ablation catheter is advanced retrogradely through the aortic valve and positioned underneath the noncoronary cusp of the valve [86-88]. The immediate success rate for induction of complete heart block has been reported, ranging from 80% to 100% [83-88] (91% among 11 patients in our center), with subsequent long-term persistence of the block observed in 80% to 100% of patients. Although substantial improvement in systolic ventricular function after control of rapid atrial tachyarrhythmias by radiofrequency ablation of the atrioventricular junction was reported [85], the absence of effective atrial contraction and the need for anticoagulation in patients with atrial fibrillation persist. Thus, in the long run, causing complete heart block and creating a need for permanent pacemaker implantation is not a desirable therapeutic approach. Such a method therefore should be reserved for drug-resistant cases of atrial tachyarrhythmias, including atrial fibrillation, atrial flutter, and atrial tachycardias with a rapid ventricular response that is difficult to control medically, or in cases where the latter two arrhythmias are not amenable to radiofrequency ablation.
Catheter Ablation of Atrial Foci
Compared with the large experience with and the high success rates of radiofrequency ablation of atrioventricular nodal reentry and accessory pathways (Table 2), catheter ablation of arrhythmogenic foci in the thin-walled atria is limited and has lower efficacy and higher recurrence rates [89-97]. Direct-current ablation had only modest efficacy and caused serious complications such as atrial wall rupture. Radiofrequency ablation, which is devoid of barotraumatic effects, is an attractive alternative technique for atrial tachycardias (automatic and reentrant) and atrial flutter [89-96]. Macro-reentry within the right atrium is considered the mechanism of atrial flutter [97]. Using transient entrainment techniques (pacing the atrium faster during flutter and noting a change in F-wave morphology) and recording fractionated (continuous low amplitude) atrial electrograms, slow conduction areas are identified in the triangle of Koch and around the coronary sinus os, which constitute a critical zone for ablation [93, 94, 97]. In selected patients with atrial flutter, success rates of 83% to 100% have been achieved but with recurrence rates as high as 40%. Efficacy rates of 50% to 100% with recurrence rates as high as 30% have been reported for catheter ablation of atrial foci of automatic or reentrant atrial tachycardias. In our center, ablation has been successful in four of five patients with atrial flutter and in five of eight patients with atrial tachycardia.
Catheter Ablation of Ventricular Tachycardia Foci
Catheter ablation techniques to eliminate ventricular tachycardia foci thus far have been of limited utility, particularly in patients with coronary artery disease [98-106]. Use of direct current has been very disappointing, with a low success rate and serious complications [2, 3]. A major limitation of the radiofrequency technique is the small size of the lesions that it produces; use of catheters with larger tips or two large, closely spaced electrodes may be more helpful [107]. Relatively few patients with sustained ventricular tachycardia have small, single, isolated areas of scar suited to these ablative techniques [99, 101, 102]. Furthermore, extensive mapping is required to identify the tachycardia focus or foci before applying radiofrequency current. This can be accomplished only in patients with well-tolerated tachycardias, thus excluding those with unstable tachycardias. In contrast to ischemic ventricular tachycardia [101, 102], some specific types of ventricular tachycardia should be recognized because they appear to be more favorably amenable to radiofrequency ablation and thus are nonsurgically curable (Table 3). In particular, patients with bundle-branch reentrant ventricular tachycardia can be treated with radiofrequency ablation of the right bundle branch; and patients with idiopathic ventricular tachycardia (no structural heart disease) and foci often localized to the right ventricular outflow tract (Figure 2C), or sometimes in the septum of the right or left ventricle, have been treated successfully with radiofrequency ablation (Table 3) [98, 100, 103-106].
Complications of Radiofrequency Catheter Ablation
Complications occur during ablation in 3% to 5% of procedures. Compared with direct-current ablation, radiofrequency current delivery is associated with fewer and less serious complications (see Table 1), but sometimes serious adverse events may occur with radiofrequency ablation as well. Table 4 lists the various complications reported from different groups [14, 25, 26, 46, 47, 49, 51, 52, 59, 100].
To avoid thromboemboli, intravenous heparin is used when entering the left heart during ablation, and many physicians prescribe aspirin, less often warfarin, for about 3 months afterward. No consensus yet exists about the need for short-term anticoagulation after ablation. During postablation monitoring, we usually obtain 12-lead electrocardiograms to identify recurring preexcitation in patients who had accessory pathway ablation or the development of heart block in patients having atrioventricular node modification (particularly fast pathway ablation). Creatine kinase levels are determined to estimate the myocardial damage incurred during the ablation, although radiofrequency ablation may inactivate creatine kinase, and thus serum levels may underestimate the degree of myocardial injury [108]. Echocardiography is used to identify pericardial effusion, intracardiac thrombus, or valve disruption and to assess left ventricular function for development of any new wall motion abnormalities.
Limitations and Future Perspectives
Results of the radiofrequency ablation studies we reviewed are promising and indicate a bright future for this curative nonsurgical method. However, despite a dramatic expansion in the field of interventional electrophysiology and the emergence of this percutaneous technique that might accomplish what only cardiac surgery could previously attain, we must also acknowledge its limitations. The design and structure of electrode catheters need improvement to further facilitate mapping and ablation with the development of more steerable and versatile systems. With better electrode design, such as larger (8-mm) distal electrodes with thermistor control [109] or electrodes with orthogonal configuration [110], or invention of other ways, for example, newer power sources such as microwave energy [111] to produce larger and deeper cardiac lesions, we might overcome the current limited applicability of this technique to the large population of patients with ventricular tachycardia. The procedure requires extended fluoroscopy time (0.5 to 2.5 hours), and the long-term effects of such an exposure on either the physician or patient remain to be seen [46, 77]. To curtail this radiation exposure, abbreviated procedures have been proposed and seem more practical for the future [49, 78]. Recently it has also been possible to perform radiofrequency ablation of accessory or slow pathways on an outpatient basis [112, 113].
Clinical follow-up of patients having radiofrequency ablation has not yet been long enough to determine the effects and late consequences of the multiple cardiac lesions that are usually created during the procedure. Concern regarding the arrhythmogenic potential of such lesions in the ventricular myocardium recently prompted us and others to adopt the transseptal approach as the preferred technique for ablation of left-sided accessory pathways from the atrial side of the mitral annulus [20, 51, 53, 59]. Furthermore, this approach may provide easier manipulation and more stable positioning of the ablation catheter with better tissue contact.
Finally, selection of patients still should be guided by the frequency and severity of symptoms [75]. Radiofrequency ablation has definite risks and substantial costs. Data comparing radiofrequency ablation with drug therapy are still sparse [42, 75]. As this technique spreads from referral centers, it is essential that published guidelines for training, staffing, and equipment are followed, with monitoring of efficacy and complication rates [114].
- Copyright ©2004 by the American College of Physicians
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