Radiofrequency Ablation Of Accessory Pathways Research Articles

Successful catheter ablation of an inferoseptal accessory pathway within the coronary sinus in a patient with a previously unsuccessful attempt at surgical interruption: Coronary sinus ablation for Wolff-Parkinson-White syndrome

In a patient with Wolff-Parkinson-White syndrome and a right inferoseptal accessory pathway who had had a previously unsuccessful surgical attempt at accessory pathway ablation, the accessory pathway was found to be adjacent to a branch of the coronary sinus. Radiofrequency energy was delivered within this branch to ablate the pathway successfully. This demonstrates an alternative approach to the more common method of radiofrequency ablation of accessory pathways from a tricuspid or mitral annular location.

Relation between impedance and temperature during radiofrequency ablation of accessory pathways

Temperature monitoring is a useful tool for radiofrequency ablation of accessory pathways. Impedance monitoring is also helpful, and an impedance fall of 20 ohm may predict coagulum formation. Therefore the purpose of this study was to prospectively quantitate the correlation between impedance and temperature during radiofrequency ablation. Thirty-three consecutive patients underwent radiofrequency ablation with a thermistor ablation catheter with continuous temperature and impedance monitoring during each energy application. The initial and final impedance and temperature measurements for 319 applications of radiofrequency energy were 109 ± 17 ohm and 102 ± 17 ohm ( p < 0.0001), respectively, and 37 ± 1° C and 57° ± 11° C ( p < 0.0001), respectively. Among the 319 applications of radiofrequency energy, 158 were associated with ≥20° C increase in tissue temperature, and 10 were associated with coagulum formation. A ≥20° C increase in tissue temperature was observed in 84 of 104 applications associated with a 5 to 10 ohm decrease in impedance (81% positive predictive value and 93% negative predictive value). The mean change in impedance for applications associated with and without coagulum formation was −19 ± 7 ohm and −6 ± 6 ohm ( p < 0.0001), respectively, and coagulum formation never occurred with less than a 12 ohm decrease. In conclusions successful tissue heating without coagulum formation can be achieved by titrating the power to achieve a 5 to 10 ohm decrement in impedance. Impedance decrements beyond 10 ohm increase the likelihood of coagulum formation.

777-5 The Relationship Between Impedance and Temperature During Radiofrequency Ablation of Accessory Pathways

Temperature monitoring is a useful tool for radiofrequency (RF) ablation of accessory pathways (AP), but this technology is not universally available and is not suitable for some catheter designs. Impedance monitoring is also helpful and prior studies in humans have demonstrated that an impedance fall of 20 ohms is predictive of coagulum formation or a loss of AP conduction. The purpose of this study was to prospectively quantitate the correlation between impedance and temperature during RF ablation of APs. Thirty-three consecutive patients, each with a single AP, underwent RF ablation using a thermistor ablation catheter. Temperature and impedance were continually recorded during each RF application. The initial and final temperatures and impedance measurements for 319 applications of RF energy were analyzed. The initial and final impedance and temperature measurements were 109 ± 17 ohms and 102 ± 17 ohms (p &lt; 0.000t). and 37 ± 1°C and 57 ± 11°C (p &lt; 0.0001). Among the 319 applications of RF energy, 158 were associated with ≥20°C increase in tissue temperature. There were 10 applications of RF energy associated with coagulum formation. A ≥20°C increase in tissue temperature was observed in 84 of 104 applications associated with a 5–10 ohm decrease in impedance (81% positive predictive value and 93% negative predictive value). The mean change in impedance for applications associated with and without coagulum formation was–19 ± 7 ohms and –6 ± 6 ohms (p &lt; 0.0001), respectively, and was never less than 12 ohms. In conclusion, successful tissue heating without coagulum formation can be achieved by titrating the power to achieve a 5–10 ohm decrement in impedance. Impedance decrements beyond 10 ohms increase the likelihood of excessive tissue heating and coagulum formation.

1009-46 Does Reinnervation of Cardiac Sympathetic Nerves Occur in Regions Denervated by Catheter Ablation of Accessory Pathways?

Long term effects of radiofrequency (RF) ablation of accessory pathways are unknown. We hypothesized that defects in sympathetic innervation detected by 1-123 metaiodobenzylguanidine (MIBG) and myocardial perfusion detected bythallium-201 (TI) scintigraphy after RF ablation would not change in three years followup. Six pts were studied 6.8 +/-9.1 days (acute) and 3.1 +/-0.3 years (chronic) after RF. TI and MIBG images were scored: absent, decreased, or normal uptake in 13 cardiac segments. The mean numbers of segments with decreased uptake of TI and MIBG were compared for acute and chronic studies. Acute Chronic TI 0.2 ± 0.4 0.7 ± 0.8 (p = NS) MIBG 1.5 ± 1.5 2.5 ± 1.5 (p = NS) As expected, MIBG defects were larger than TI defects in 9 studies. Three studies had no MIBG defects: one of these had a TI defect. There was no difference in the number of segments with decreased TI or MIBG uptake between acute and chronic studies. No segments had absent TI uptake, and only one segment had absent MIBG uptake. Two chronic MIBG defects were smaller and four larger than the acute MIBG defects. Thus, focal MIBG defects after RF ablation of accessory pathways do not significantly change in three years follow-up, suggesting sympathetic reinnervation does not occur.

The effects of accumulated experience on radiofrequency ablation of accessory pathways.

Increasing experience in radiofrequency ablation for accessory pathways appears to reduce the procedure time, radiation time and radiofrequency pulse number, and results in a higher success rate. However, the effect of a learning curve on this procedure from the perspective of location and conduction direction of accessory pathways has not been reported before. The purpose of this study was to determine the effect of accumulated experience on the outcomes of radiofrequency ablation for accessory pathways and on the duration of the procedure parameters by analyzing the results of a dedicated ablation team. The first 512 patients with a single accessory pathway treated in this laboratory were included for analysis of the procedure parameters with respect to locations and conduction directions of accessory pathways. The results showed that the average procedure time, radiation time, and radiofrequency pulse number differed significantly among the different subgroups (left free wall, right free wall, posteroseptal and anteromidseptal location; manifest or concealed conduction). All subgroups except the anteromidseptal pathways showed a significant improvement of the procedure parameters with increased ablation experience. Although the initial rate of improvement was similar among the different subgroups, the rate of improvement in left free wall pathways nearly reached a plateau after 120 ablation procedures. Thus it was concluded that a certain number of ablation procedures was necessary before achievement of a high success rate with shorter procedure and radiation times and a lower radiofrequency pulse number.

Recurrence and Late Block of Accessory Pathway Conduction Following Radiofrequency Catheter Ablation

Many issues regarding the recurrence of accessory pathway conduction and the long-term outcome of late block of accessory pathway conduction are still unknown or controversial. Data from 217 patients who underwent an initially successful radiofrequency ablation of accessory pathways and 7 patients with late block of accessory pathway conduction following an initially unsuccessful ablation were analyzed. During a mean follow-up of 19 +/- 11 months, accessory pathway conduction resumed in 21 (10%) of 217 patients following an initially successful ablation and in 6 (86%) of 7 patients with late block of accessory pathway conduction (P < 0.01). After initially successful ablations, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. A late electrophysiologic study at 6 months uncovered recurrence in only 1 of 124 asymptomatic patients, but failed to detect the late recurrence in 2 patients in whom the accessory pathway conduction resumed after more than 6 months. Multivariate analysis revealed that independent predictors for recurrence of accessory pathway conduction were concealed accessory pathway, presence of transient effect of radiofrequency pulse, and more than 5 pulses required for initial cure. Accessory pathway location, length of the tip electrode of the ablation catheter, and repeat radiofrequency pulses ("safety pulses") after effective pulses did not predict resumption of accessory pathway conduction. After initially successful ablation, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3%, respectively. Late electrophysiologic testing had little prognostic value in asymptomatic patients following successful ablation. Application of "safety pulses" did not prevent recurrence. Late block of accessory pathway conduction did not predict long-term efficacy.

Safety of radiofrequency catheter ablation of accessory atrioventricular pathways

The acute anatomic and valvular consequences of radiofrequency catheter ablation of accessory pathways were evaluated in 62 patients by means of serial echocardiographic examinations. Semiquantitative assessment of valvular incompetence and classification into one of four grades according to the width and the extension of the jet from the valvular orifice were carried out. Segmental wall motion abnormalities were evaluated semiquantitatively with four grades of severity (normal, hypokinesia, akinesia, or dyskinesia). New echocardiographic abnormalities were observed in five patients. One thrombus on the ventricular aspect of the mitral valve, three hemodynamically insignificant pericardial effusions, and one increase in severity of tricuspid incompetence were found 1 day after radiofrequency catheter ablation. We conclude that echocardiographic changes after radiofrequency ablation of accessory pathways are rare and of minor significance. These findings confirm the safety of the procedure.

Radiofrequency catheter ablation of accessory pathways during entrainment of AV reentrant tachycardia.

Radiofrequency ablation of accessory pathways must sometimes be done during orthodromic atrioventricular reentrant tachycardia when manifest anterograde accessory pathway conduction is absent or retrograde fusion obscures accessory pathway location during ventricular pacing. Unfortunately, abrupt heart rate slowing upon radiofrequency induced termination of atrioventricular reentrant tachycardia often causes catheter dislodgment. We report our experience in circumventing this problem during radiofrequency ablation by using entrainment of atrioventricular reentrant tachycardia. The latter maintains retrograde activation pattern over the accessory pathway while preventing abrupt ventricular rate change. Eight patients (4 men and 4 women, mean age 37.3 +/- 17.9) with eleven left-sided accessory pathways were included. Ablation during entrainment was used as the first approach in three patients with concealed accessory pathways and one patient with a bidirectional accessory pathway. In another four patients, ablation during entrainment was used after technical difficulties in ablating during tachycardia. Only 1-3 radiofrequency applications were required to eliminate the accessory pathway using the entrainment technique. The catheter remained stable when accessory pathway conduction was interrupted by radiofrequency current. In conclusion, entrainment of atrioventricular reentrant tachycardia during radiofrequency application is useful for maintaining catheter position for accessory pathway ablation during atrioventricular reentrant tachycardia.

Radiofrequency ablation of accessory pathways: implications of accumulated experience and time dedicated to procedures.

Previous reports on radiofrequency ablation of accessory pathways have shown that the experience of the operator is of crucial importance in reducing fluoroscopy time and achieving higher success rates. However, a detailed analysis of this important issue has not been previously attempted. We analysed 71 consecutive ablation procedures undertaken at St George's Hospital by the same electrophysiology group and always with the same first operator. Of all procedures, 66 (91.6%) were successful, as judged by abolition of accessory pathway conduction without recurrence within the next 24 h. Failures included two out of 38 left-sided pathway procedures (5.3%), one out of 11 intermediate septal (9.1%) and four out of 22 right-sided pathway procedures (18.2%). These differences were not statistically significant. Average procedure and screening times for all procedures were 162.9 +/- 86.0 min and 56.8 +/- 48.2 min respectively, whereas the median of the number of discharges was 12, ranging from one to 51. There was no significant difference between pathway groups or between concealed and non-concealed pathways in respect to procedure and screening time or number of discharges. There was a significant tendency towards decreased procedure and screening times with accumulating experience and this was similar for all pathway groups. There was also a tendency towards improved cumulative success rates with time dedicated to procedures. We conclude that a certain amount of ablation experience is required, even by experienced electrophysiologists, before a relatively high success rate without long radiation exposure can be achieved, regardless of the location or the mode of conduction of the pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Safety and cost of outpatient radiofrequency ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia

Radiofrequency ablation of atrioventricular (AV) nodal reentrant tachycardia has been shown to be an effective and safe treatment and to have a significant cost advantage over other forms of therapy. 1 In studies reported to date, patients were hospitalized for 2 to 10 days after slow pathway ablation to monitor for possible complications or a recurrence of the tachycardia. 2,3 A previous study reported that radiofrequency ablation of accessory pathways can be performed safely on an outpatient basis, 4 but no prior studies evaluated the safety of outpatient radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia. Therefore, the purpose of this study was to evaluate the safety and cost of performing radiofrequency catheter ablation of the slow AV nodal pathway on an outpatient basis.

Curative Therapy for Supraventricular Arrhythmia with Radiofrequency Catheter Ablation—Comparison with Surgical Therapy

Radiofrequency catheter ablation is a newly introduced technique that does not require open heart surgery and is designed for curing patients with arrhythmia. We present our experience with this technique in 223 patients, with recurrent supraventricular tachycardia due to accessory pathways associated with the Wolff-Parkinson-White syndrome or AV nodal reentrant tachycardia. Of the patients, 119 underwent radiofrequency ablation of accessory pathways, while 101 underwent AV nodal modification. Two patients underwent both AV nodal modification and accessory pathway ablation during the same session. One patient had AV nodal ablation. Mean age was 39.4 ± 14.1 years (13–73 years). There were 108 males and 115 females. Except for 1 patient, all had significant symptoms. Radiofrequency ablation performed during the first session was successful in 215 patients (96.4%). With repeat ablation, 218 (97.8%) of the patients were successfully ablated. When compared with surgery, the efficacy is similar; however, radiofrequency ablation is less costly and results in less morbidity. Radiofrequency catheter ablation is highly efficacious and is the treatment of choice in patients who are at risk for sudden death or have failed drug therapy. It should also be offered as an alternative to lifelong drug therapy.

Radiofrequency ablation of accessory pathways associated with congenital heart disease including heterotaxy syndrome

Congenital heart disease complicates the management of most accessory pathway-mediated tachycardias and also increases the challenge of radiofrequency ablation. Since 1990, radiofrequency ablation of accessory atrioventricular (AV) pathways has been attempted in 10 patients (age range 3.5 months to 30 years) with congenital heart disease: Ebstein's anomaly (n = 5), heterotaxy with AV discordance (n = 3), tetralogy of Fallot (n = 1) and total anomalous pulmonary venous return (n = 1). Eight patients had manifest Wotff-Parkinson-White syndrome and 2 had concealed pathways. Five patients had multiple pathways including 4 of the 5 with Ebstein's anomaly. Of 16 pathways total, 15 were associated with the tricuspid valve including all pathways in the patients with Ebstein's anomaly and heterotaxy. The His bundle area was identified in all patients and involved an anterior AV node in 2 of 3 with heterotaxy. Ablation was performed on the atrial side of the AV ring in all cases. No instance of AV block was encountered. Complete success was achieved in 6 patients including the 3 with heterotaxy. In 2 patients, manifest preexcitation was eliminated and clinical symptoms were greatly modified. The procedure was transiently successful in 1 patient who later had surgical interruption of the accessory pathway during tetralogy of Fallot repair. Ablation was unsuccessful in 1 patient. Thus, the overall success was 80%.

Effect of preexcitation on Doppler indexes of left ventricular filling

Doppler echocardiography of mitral inflow has enhanced our understanding of left ventricular (LV) diastolic function but multiple factors contribute to these velocity recordings, In addition to LV relaxation and compliance, variables such as age, heart rate, left atrial pressure and LV systolic function all interact to comprise the mitral inflow Doppler velocities. 1 The effects of altering atrioventricular (AV) delay on Doppler indexes of LV filling have only been examined in patients with sequential AV pacemakers and although these Doppler patterns are well documented, the beneficial hemodynamic eifects of an optimal AV delay are still debated. 2–5 To date, there has been no report on the effects of preexcitation and its abolition on mitral inflow patterns. Current techniques with radiofrequency ablation of accessory pathways has a high success rate in restoring normal AV conduction with minimal adverse effects on patients 6 and thus allows us to examine this question. We hypothesize that just as is seen with AV pacing, the mitral inflow patterns associated with a short AV interval during preexcitation are altered by normalization of the AV interval after radiofrequency ablation. In addition, we hypothesize that these changes may have beneficial hemodynamic effects by increasing stroke volume.

Radiofrequency catheter ablation for paroxysmal supraventricular tachycardia: a report of 135 procedures.

Paroxysmal Supraventricular Tachycardia (PSVT) is a common condition which until recently has been treated with anti-arrhythmic drugs or surgery. Radiofrequency (RF) catheter ablation is a new mode of treatment which provides a cure of this condition. To present our early experience of RF catheter ablation for PSVT. One hundred and thirty-five procedures were performed in 117 patients. The diagnostic study and therapeutic catheter ablation were performed as a combined electrophysiological procedure in 74 patients (63%). In 58 patients (50%), PSVT was due to Atrio-ventricular junctional (nodal) re-entrant tachycardia (AVJRT). Twenty-five of the 58 patients underwent a fast pathway ablation while 33 had ablation of their slow pathway. The mean number of radiofrequency pulses delivered was ten for a mean duration of 25 seconds. Radiofrequency ablation of accessory pathways was attempted in 58 patients; pathways were left-sided in 29 patients, postero-septal in 21, midseptal in five, Mahaim connection in two, antero-septal in one and right free wall in one patient. One patient with incessant automatic atrial tachycardia also underwent a successful RF ablation. Using RF ablation cure of PSVT was achieved in 90% of patients. Cure of AVJRT was achieved in 95% (55/58) of patients using either fast or slow pathway ablation. Only one patient required permanent pacemaker implantation for Mobitz type I AV block following fast pathway ablation. The overall success rate for ablation of accessory pathways was 85%. There is an operator learning curve for this procedure suggested by the fact that the success rate for accessory pathway ablation at first attempt was 63% in the first 29 patients and 93% in the remaining 29. There was no significant morbidity or mortality during or after the procedure. In a mean follow-up of nine months in the patients with successful ablation only two patients with AVJRT had a recurrence of documented PSVT. Both these patients had successful repeat RF ablation. Catheter ablation using radiofrequency energy is an effective and safe therapeutic option for patients with symptomatic PSVT.

Editor's Note: Transseptal Left Heart Catheterization for Radiofrequency Ablation of Accessory Pathways

In summary, I think it is important to state that transseptal left heart catheterization is a safe procedure when the operator pays meticulous attention to detail. Potential complications can be avoided if the operator: (1) heparinizes the sheath prior to catheterization, (2) fully heparinizes the patient when the catheter and sheath are across the septum, and (3) remembers that the left atrium in these patients is quite small and can be perforated easily by the tapered tip of the transseptal catheter. Transesophageal cardiac ultrasound makes this latter point very clear to anyone doing this procedure.

Evaluation of possible long-term adverse consequences of radiofrequency ablation of accessory pathways

Several recent publications have demonstrated a high success rate and few serious procedure-related acute complications with radiofrequency ablation of accessory atrioventricular (AV) pathways 1–3 However, the long-term consequences have not been well characterized. This procedure usually involves making 1 or more radiofrequency lesions at the accessory pathway's ventricular insertion site at the level of the AV groove. Segments of several of the major coronary arteries lie within the AV groove and could be damaged or thrombosed inadvertently by this procedure. Furthermore, each lesion creates a small scar that could be associated with new ventricular arrhythmias. 4 Because of these theoretic concerns, this study was designed to determine prospectively whether radiofrequency ablation of accessory pathways causes the development of inducible or spontaneous ventricular tachycardia or chronic alterations of coronary arterv anatomy.

Radiofrequency ablation of accessory pathways: characteristics of transiently and permanently effective pulses.

The purpose of this study was to characterize and compare the radiofrequency current applications that produced permanent or transient accessory pathway conduction block. One hundred fifty-two radiofrequency energy applications that induced permanent (permanently effective pulses, n = 48) or transient (transiently effective pulses, n = 104) accessory pathway block in 57 patients with 60 accessory pathways were analyzed. The time from the onset of current application to disappearance of preexcitation or termination of supraventricular tachycardia by permanently effective pulses was 1-15 seconds (mean 3.6 +/- 3.8 sec) compared to 2-29 seconds (mean 11.5 +/- 7.5 sec) by transiently effective pulses (P less than 0.01). After transiently effective pulses that induced block in accessory pathway, conduction resumed within 5 minutes while induced block by permanently effective pulses persisted in 44 of 48 patients (92%) during follow-up of 11 +/- 12 months. The accessory pathway conduction returned in the remaining four patients after ablation 2 weeks to 7 months. After transiently effective pulses, 41 impulses were delivered to the same site using a higher power output (n = 32) and/or longer energy delivery duration (n = 20) without new mapping of accessory pathway location. Thirty-six of these impulses again resulted in transient accessory pathway block, four had no effect, only one impulse induced a permanent block in the accessory pathway. Pulses with higher power outputs tended to induce transient effects more frequently than pulses with lower energy.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiofrequency ablation of accessory pathways

Radiofrequency ablation of accessory pathways

Atrial endocardial radiofrequency ablation of accessory pathways

Atrial endocardial radiofrequency ablation of accessory pathways