Safety and efficacy of radiofrequency ablation of common atrial flutter in elderly patients: a single center prospective study

Little data is available concerning the invasive treatment of atrial flutter (AFL) in elderly patients. The purpose of this prospective study was to evaluate the risks, safety, and follow-up of radiofrequency (RF) catheter ablation of common AFL in patients >75 years old (n = 61) (Group I) compared to patients younger than 75 years (n = 187) (Group II). The study population consisted of 248 patients (81% men/19% women), 21 to 96 years old (mean 66.3 +/- 12 years) with AFL, referred for RF from June 1999 to June 2001. RF endpoint was the assessment of the bidirectional block. The cumulative risk of atrial fibrillation (AF) was analyzed by the Kaplan-Meier method and log-rank test. The mean follow-up was 12.4 +/- 9 months. No complication occurred. Group I (80.1 +/- 4.5 years) did not differ significantly from Group II (61 +/- 11 years) regarding: AF history before ablation (34.4% vs 39.8%), structural heart disease (54% vs 42%), LVEF (57%+/- 12% vs 58%+/- 12%), left atrial size (43.8 +/- 7 vs 42.5 +/- 7), cava-tricuspid isthmus dimension (40 +/- 10 vs 39 +/- 4 mm), bidirectional block (100% vs 96.2%), RF application (12.5 +/- 10 vs 13.5 +/- 12 minutes), AFL recurrence (3.3% vs 5.3%), antiarrhythmic agents at hospital discharge (34.4% vs 38.9%), mean follow-up (12 +/- 9 vs 13 +/- 9 months) and AF occurrence (29.5% vs 20.3%; P = 0.2). Of these, the incidence of AF in patients without prior history (n = 150) was 7 (18%) of 39 for Group I and 11 (10%) of 111 for Group II (P = 0.1) after follow-up. Catheter ablation of AFL in very elderly patients appears to be a reasonable approach regarding feasibility, effectiveness, and low procedural risk.     

A randomized clinical trial of continuous flow nitrous oxide and nalbuphine infusion for sedation of patients during radiofrequency atrial flutter ablation

BACKGROUND: In patients with common atrial flutter (CAF), radiofrequency ablation (RFA) causes discomfort. Patients undergoing RFA often feel pain which is difficult to control as the mechanisms are unclear. HYPOTHESIS: Inhaled nitrous oxide (N2O) is a potent sedative-analgesic-anxiolytic agent that may relieve anxiety and discomfort during CAF ablation. METHODS AND RESULTS: In a prospective randomized study, the effect of Inhaled N2O was compared with that of intravenous sedation with Nalbuphine during CAF ablation in 76 patients (64 +/- 13 years, 56 men). We used a 24 pole mapping catheter around the tricuspid annulus and a 8-mm tip ablation catheter for each patient. Forty-two patients (group 1) underwent radiofrequency (RF) application to the cavotricuspid isthmus 5 minutes after the beginning of inhalation of a (50% N2O/50% O2) mixture. Thirty-four patients (group 2), underwent the first RF application 15 minutes after the end of an infusion of Nalbuphine (20 mg delivered over 15 minutes). Ablation-related anxiety and discomfort were assessed using a visual analog scale (VAS) ranging from 0 to 100 mm, with 0 correlating to the statement "no pain at all" and 100 with "the worst possible pain." The VAS score was determined at the end of each application.The number of RF applications (group 1; 10 +/- 8 vs group 2; 11 +/- 6, P = NS) and procedure duration (group 1; 75 +/- 53 minutes vs group 2; 72 +/- 45 minutes, P = NS), were similar for the two groups. N(2)O sedation compared with nalbuphine infusion reduced VAS for anxiety (10 mm +/- 8 vs 58 mm +/- 22, P < 0.05) and for discomfort (18 mm +/- 9 vs 45 mm +/- 34, P < 0.01), respectively. Although there was more frequent vomiting in group 1; 7 of 42 (17%) than in group 2; 3 of 34 (9%), P < 0.05, patients were less likely to have hypotension during the procedure 1 of 42 (2.5%) versus 4 of 34 (12%), P < 0.05, respectively. CONCLUSION: Inhalation of a (50% N2O/50% O2) mixture during RF ablation for atrial flutter is a safe and efficient way to reduce anxiety and discomfort caused by RF applications.     

Initial clinical experience with a remote magnetic catheter navigation system for ablation of cavotricuspid isthmus-dependent right atrial flutter

Background: A remote magnetic navigation system (MNS) is available and has been used with a 4‐mm‐tip magnetic catheter for radiofrequency (RF) ablation of some supraventricular and ventricular arrhythmias; however, it has not been evaluated for the ablation of cavotricuspid isthmus‐dependent right atrial flutter (AFL). The present study evaluates the feasibility and efficiency of this system and the newly available 8‐mm‐tip magnetic catheter to perform RF ablation in patients with AFL. Methods: Twenty‐six consecutive patients (23 men, mean age 64.6 ± 9.6 years) underwent RF ablation using a remote MNS. RF ablation was performed with an 8‐mm‐tip magnetic catheter (70°C, maximum power 70 W, 90 seconds). The endpoint of ablation was complete bidirectional isthmus block. To assess a possible learning curve, procedural data were compared between the first 14 (group 1) and the rest (group 2) of the patients. Results: The initial rhythm during ablation was AFL in 20 (19 counterclockwise and 1 clockwise) and sinus rhythm in six patients. Due to technical issues, the ablation in the 18th patient could not be done with the MNS, and so we switched to conventional ablation. The remote magnetic navigation and ablation procedure was successful in 24 of the 25 (96%) remaining patients with AFL. In one patient (patient 2), conventional catheter was used to complete the isthmus block after termination of AFL. The procedure, preparation, ablation, and fluoroscopy times (median [range]) were 53 (30–130) minutes, 28 (10–65) minutes, 25 (12–78) minutes, and 7.5 (3.2–20.8) minutes, respectively. Patients in group 2 had shorter procedure (45 [30–70] min vs 80 [57–130] min, P = 0.0001), preparation (25 [10–30] min vs 42 [30–65] min, P = 0.0001), ablation (20 [12–40] min vs 31 [20–78] min, P = 0.002), and fluoroscopy (7.2 [3.2–12.2] min vs 11.0 [5.4–20.8] min, P = 0.014) times. No complication occurred during the procedure. Conclusion: Using a remote MNS and an 8‐mm‐tip magnetic catheter, ablation of AFL is feasible, safe, and effective. Our data suggest that there is a short learning curve for this procedure.     

Is a Cooled Tip Catheter the Solution for the Ablation of the Cavotricuspid Isthmus?

SCAVÉE, C., et al. : Is a Cooled Tip Catheter the Solution for the Ablation of the Cavotricuspid Isthmus? To test the theoretical superiority of irrigated tip catheters to achieve complete cavotricuspid isthmus block, a 4-mm cooled tip catheter was compared to a conventional 8-mm tip catheter with a double temperature sensor in the cavotricuspid isthmus (CTI) ablation. The study prospectively enrolled 60 patients (47 men, mean   65 ± 10   years) with common flutter divided in group 1   (n = 30)   assigned to an 8-mm tip catheter versus group 2   (n = 30)   , assigned to an internal circuit, irrigated tip catheter. Linear radiofrequency applications were performed in a point-by-point protocol to achieve complete CTI block. Complete CTI block was achieved in 29 patients in each group. Mean durations of procedure and fluoroscopy were 91 versus 90 and 40 versus 33 minutes in group 1 versus 2, respectively, (NS). The mean number/patient of RF pulses to interrupt atrial flutter was four in group 1 and eight in group 2   (P = 0.034)   , and 11 and 13, respectively, to interrupt CTI conduction (NS). The total energy delivered was similar in both groups (29,237 vs 23,236 W/s, NS). CTI ablation with a conventional 8-mm tip catheter versus an irrigated tip catheter was associated with similar success rates, procedure duration, and fluoroscopic exposure. The technical complexity of the cooled tip catheter renders it less competitive. (PACE 2003; 26[Pt. II]:328–331)     

Primary radiofrequency ablation for incessant idiopathic ventricular tachycardia

Fascicular VT and RVOT tachycardia are sometimes difficult to induce by programmed electrical stimulation (PES), despite pharmacologic provocation. In such instances, catheter mapping is hampered and efficacy of catheter ablation is difficult to judge. The study included nine patients who presented with incessant idiopathic VT and were directly taken to the electrophysiological laboratory for RF ablation. During the same period, elective ablation was performed on 108 patients with idiopathic VT. The success rate, procedural and fluoroscopy times number of energies, and the peak temperature were evaluated and compared. Of the nine patients, seven had incessant fascicular VT and two had RVOT tachycardia. The mean VT cycle length was 356 +/- 32 ms and the earliest endocardial activation time during VT was 23.6 +/- 6 ms relative to surface QRS complexes. A fascicular potential was not seen in three of the seven patients with fascicular VT. The mean procedural time was 71 +/- 32 minutes and 144 +/- 40 minutes (P = 0.023) while the fluoroscopy time was 14.6 +/- 4.6 minutes and 30 +/- 16 minutes (P < 0.001), respectively, in the primary ablation and elective groups. The total number of RF energies delivered was 2.0 +/- 1.3 versus 7.4 +/- 5.6 (P = 0.07), respectively. The significantly increased procedural time during elective ablation was largely due to time spent in fascicular VT induction. All patients in the primary ablation group were successfully ablated and none had a recurrence. Primary ablation is a safe and effective option in patients with incessant idiopathic VT. Moreover, in fascicular VT, it is superior to elective ablation in terms of success, fluoroscopy and procedural times.     

The results of radiofrequency catheter ablation of supraventricular tachycardia in children

BACKGROUNDS: Radiofrequency (RF) catheter ablation represents a major advance in the management of children with cardiac arrhythmias and has rapidly become the standard of care for the first-ling therapy of supraventricular tachycardias (SVTs). The purpose of this study was to investigate the results of the RF catheter ablation of SVTs in pediatric patients. METHODS: From December 1989 to August 2005, a total of 228 pediatric patients (age: 9 +/- 7 years, range: 5-18 years; male:female = 117:111) with clinically documented SVT underwent an electrophysiologic study and RF catheter ablation at our institution. RESULTS: The arrhythmias included atrioventricular reentrant tachycardia (AVRT; n = 140, 61%), atrioventricular nodal reentrant tachycardia (AVNRT; n = 66, 29%), atrial tachycardia (AT; n = 11, 5%), and atrial flutter (AFL; n = 11, 5%). The success rate of the RF catheter ablation was 92% for AVRT, 97% for AVNRT, 82% for AT, and 91% for AFL, respectively. Procedure-related complications were infrequent (8.7%; major complications: high grade AV block (2/231, 0.9%); minor complications: first degree AV block (6/231, 2.6%), reversible brachial plexus injury (2/231, 0.9%), and local hematomas or bruises (10/231, 4.3%)). The recurrence rate was 4.7% (10/212) during a follow-up period of 86 +/- 38 months (0.5-185 months). CONCLUSIONS: The RF catheter ablation was a safe and effective method to manage children with paroxysmal and incessant tachycardia. The substrates of the arrhythmias differed between the pediatric and adult patients. However, the success rate of the ablation, complications, and recurrence during childhood were similar to those of adults.     

Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil‐Sensitive Idiopathic Left Ventricular Tachycardia?

The exact reentrant circuit of the verapamil-sensitive idiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundle branch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I included 11 patients (10 men, 1 woman; mean age 25 +/- 8 years) with left anterior fascicular block (4 patients), or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men, 9 women; mean age 35 +/- 16 years) without fascicular block during sinus rhythm. Duration of QRS complex during sinus rhythm before RF catheter ablation in group I patients was significant longer than that of group II patients (104 +/- 12 vs 95 +/- 11 ms, respectively, P=0.02). Duration of QRS complex during VT was similar between group I and group II patients (141 +/- 13 vs 140 +/- 14 ms, respectively, P=0.78). Transitional zones of QRS complexes in the precordial leads during VT were similar between group I and group II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 +/- 11 vs 95 +/- 10 ms, P=0.02); fascicular block did not occur in group II patients. Duration and transitional zone of QRS complex during VT were similar between the two groups, and new fascicular block did not occur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in the antegrade limb of reentry circuit in idiopathic left VT.     

Cooled intramural needle catheter ablation creates deeper lesions than irrigated tip catheter ablation

Endocardial radiofrequency ablation of the left ventricle does not create transmural lesions reliably even with active electrode cooling. The authors developed a prototype catheter with an internally cooled needle electrode that could be advanced an adjustable distance into the myocardium. Freshly excised hearts from eight male sheep were perfused and superfused using oxygenated ovine blood. Ablations were performed for 2 minutes using the prototype catheter and a conventional endocardial 5-mm irrigated tip ablation catheter at target temperatures of 80 degrees C and 50 degrees C, respectively. The prototype catheter needle was inserted 12 mm deep for all ablations. The maximal power and irrigation rate was 50 W, 20 mL/min for the irrigated tip catheter and 20 W, 10 mL/min for the intramural needle catheter. Intramural needle lesions were significantly deeper (13.5 +/- 2.3 vs 9.1 +/- 1.3 mm, P < 0.01) but less wide (8.7 +/- 1.5 vs 12.7 +/- 1.9 mm, P < 0.01) than irrigated tip lesions. Popping occurred during 12 (37%) of the 32 irrigated tip ablations. Popping did not occur during intramural needle ablation. The cooled intramural needle ablation catheter creates lesions that are significantly deeper than irrigated tip catheters with less tissue boiling. In contrast to irrigated tip ablation, electrode temperature monitoring can be used to determine if a lesion has been created during intramural needle ablation. The cooled intramural needle ablation lesions were of a clinically useful width, addressing one of the main recognized deficiencies of intramural needle ablation.     

Catheter intramural needle radiofrequency ablation creates deeper lesions than irrigated tip catheter ablation

Radiofrequency ablation of the left ventricle using an endocardially placed electrode is unable to reliably create transmural lesions even with active electrode cooling. To produce deeper radiofrequency lesions, the authors developed and tested a prototype intramural needle ablation catheter that had a distal 1.1-mm diameter straight needle that could be advanced 12 mm into the myocardium. Freshly excised hearts from eight male sheep were perfused and superfused with oxygenated ovine blood. Ablations were performed for 60 seconds with the prototype catheter and a conventional 5-mm irrigated tip ablation catheter at target temperatures of 90 degrees C and 50 degrees C, respectively. The ablation lesions were bisected and stained with blue tetrazolium to assess lesion geometry. The irrigated tip ablation catheter required significantly more power than the intramural needle ablation catheter (37.7 +/- 7.3 vs 6.4 +/- 2.1 W, P < 0.01). Intramural needle lesions were significantly deeper (12.5 +/- 3.0 mm vs 8.3 +/- 2.1 mm, P < 0.01) but less wide (3.9 +/- 1.1 mm vs 11.5 +/- 2.0 mm, P < 0.01) than irrigated tip lesions. There was a high incidence of crater formation (74%), popping (45%), and myocardial charring (29%) during irrigated tip ablation; these phenomena were not observed during intramural needle ablation. The intramural needle ablation catheter creates significantly deeper but narrower lesions without evidence of tissue boiling. This technology may be particularly useful for ablation of ventricular tachycardia originating from regions where tissue depth is increased, like the ventricular septum.     

Cavotricuspid Isthmus Ablation with Large-Tip Gold Alloy Versus Platinum-Iridium-Tip Electrode Catheters

Background: Gold has excellent electrical conductive properties and creates deeper and wider lesions than platinum-iridium during radiofrequency (RF) ablation in vitro . We tested the maximum voltage-guided technique (MVGT) of cavotricuspid isthmus (CTI) ablation using two 8-mm tip catheters containing gold (group G) or platinum-iridium (group PI).
Methods: We enrolled 31 patients who underwent CTI ablation. In group G (n = 15) CTI ablation was performed with a gold-tip ablation catheter, while in group PI (n = 16) a platinum-iridium tip was used. Ablation was guided by CTI potentials with the highest amplitude until achievement of bidirectional block (BIB). If BIB was not achieved after 10 RF applications, RF was delivered via a 3.5-mm irrigated-tip catheter. Success rate, procedure duration, duration of fluoroscopic exposure, and number of RF applications were measured.
Results: BIB was achieved in all patients in group G, while in group PI an irrigated tip was used in four patients (0% vs 25%, P < 0.001). These four patients required a total of 21 additional RF applications (5.25 ± 2.22). Procedure time (56.4 ± 12 vs 73.1 ± 15 minutes P < 0.05) and fluoroscopic explosure (4.9 ± 2.3 vs 7.1 ± 3.8 minutes, P < 0.01) were shorter in group G than in group PI. Mean number of RF applications was lower (4.6 ± 1.9 vs 6.6 ± 3.1 P < 0.001) and total RF duration shorter (280 ± 117 vs 480 ± 310 seconds) in group G than in group PI. No difference was observed in the number of recurrences at a 6 month-follow up (1 in group G vs 1 in group PI).
Conclusion: Using the MVGT of CTI ablation, gold-tip catheters were associated with shorter procedural and fluoroscopic times, and fewer RF applications.     

Comparison of the efficacy of cooled-tip and 8-mm-tip catheters for radiofrequency catheter ablation of the cavotricuspid isthmus: a meta-analysis

BACKGROUND: Cooled-tip RFA (cRFA) and conventional 8-mm-tip catheters were found to be more effective and as safe as conventional 4-mm-tip catheters for atrial flutter (AFL) radiofrequency ablation (RFA), facilitating the rapid achievement of bi-directional isthmus block (BIB), but studies comparing cRFA and 8-mm-tip catheters are not randomized or results are discussed. Thus, we performed a meta-analysis of available randomized trials to evaluate the effectiveness in terms of primary success and procedure parameters. METHODS: Reports of trials were identified through a Medline, Embase, Current Contents, Cardline, and an extensive bibliography search. Trials that met the following criteria were included: (1) prospective, randomized, controlled, and open trials; (2) patients assigned to an 8-mm-tip or a cRFA catheter for AFL RFA; (3) endpoints events related to primary success rate (BIB achievement), and procedure parameters (number of RF applications, x-ray exposure and ablation duration). RESULTS: Seven trials met the inclusion criteria. They included 603 patients with established AFL randomized to an 8-mm-tip or cRFA catheter group. Comparing 8-mm groups with cRFA groups, the meta-analysis showed similar BIB achievement relative risk (RR) 0.96, 95% confidence interval (CI): 0.92 to 1.01, (P = 0.13); total RF application time weighted mean difference (WMD) 0.88, 95% CI: -0.36 to 2.12, (P = 0.16); duration of x-ray exposure (min) (WMD = 1.07, 95% CI: -0.81 to 0.295, (P = 0.26); ablation procedure duration (min) (WMD = 0.68, 95% CI: -3.37 to 4.73; P = 0.74). CONCLUSION: The present meta-analysis confirms that cooled-tip and large-tip catheters are equally efficient for cavotricuspid isthmus ablation with both similar primary success rates and procedure parameters.     

Remote magnetic versus manual catheter navigation for ablation of supraventricular tachycardias: a randomized, multicenter trial

Introduction: The potential benefits of remote robotic navigation for catheter ablation procedures have not been demonstrated in controlled clinical trials. The purpose of this study was to compare remote magnetic catheter navigation to manual navigation for the ablation of common supraventricular arrhythmias. Methods and Results: Patients with supraventricular arrhythmias due to atrioventricular (AV) nodal reentry, accessory pathways, or undergoing AV junctional ablation for complete heart block were randomized in a 3:1 ratio between magnetic (Niobe system and Helios II catheter, Stereotaxis, Inc., St. Louis, MO) and manual navigation for radiofrequency ablation at 13 centers. The primary endpoint of the study was total fluoroscopic time. Fifty‐six patients were randomized to magnetic navigation and 15 to manual navigation. AV nodal reentry was the most common arrhythmia in both groups. Total fluoroscopy time was reduced in the magnetic navigation group (median 17.8 minutes, interquartile (IQ) range 9.9,27.8 minutes) compared to manual navigation (27.1, IQ 19.0,48.0, P < 0.05). The acute success rates (91% for magnetic and 87% for manual navigation, P > 0.05) did not differ between groups. The number of lesions delivered was less for magnetic navigation (6, IQ 4,9 vs 10, IQ 7, 26, P < 0.05). Total procedure time (median 151, IQ 111, 221 minutes magnetic and 151, IQ 110, 221 minutes manual) and complication rates (5.4% patients magnetic and 6.7% patients manual) were similar between the groups (both P > 0.05). Conclusions: Remote magnetic catheter navigation reduces fluoroscopic time and radiofrequency lesion deliveries for the ablation of common supraventricular arrhythmias compared to manual catheter navigation.     

Comparison of the Effects of AV Nodal Ablation Versus AV Nodal Modification in Patients with Congestive Heart Failure and Uncontrolled Atrial Fibrillation

Radiofrequency (RF) catheter ablation of the atrioventricular node (AVN) and implantation of a ventricular pacemaker can improve cardiac performance in patients with congestive heart failure (CHF) and uncontrolled atrial fibrillation (AF). Alternatively. RF catheter modification of the A VN has been proposed to slow ventricular response during AF without requirement for permanent pacing. Among 44 consecutive patients (mean age 69.7 ± 10.2 years) with drug resistant chronic AF, 22 (group I) had AVN ablation with permanent ventricular pacemaker implantation, while 22 patients had attempted AVN modification. Complete AV block was obtained in all group I patients while only seven (32 %) A VN modification patients (group II) had permanent slowing of ventricular rate. Among patients in group I, mean left ventricular ejection fraction (EF) increased from 32.2%± 8.8% before ablation to 41.9%± 14.6% 4-weeks postablation (P < 0.01); exercise tolerance time (ETT) increased from 2.9 ± 2.2 minutes to 4.5 ± 2.9 minutes (P < 0.01); and quality-of-life score decreased from 66.1 ± 22.6 to 36.9 ± 17.1 (P < 0.01). By comparison, there was only a small increase in ETT in the seven successful group II patients (2.4 ± 1.8 minutes to 3.0 ± 1.9 minutes; P < 0.05) and there was no significant change in EF or quality-of-life. While AVN ablation can occasionally have transient adverse effects, it is more effective than AVN modification for improving cardiac performance in selected patients with CHF and AF.     

Tissue temperatures and lesion size during irrigated tip catheter radiofrequency ablation: an in vitro comparison of temperature-controlled irrigated tip ablation, power-controlled irrigated tip ablation, and standard temperature-controlled ablation

The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced in the power-controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature-controlled irrigated tip ablation, comparing it with standard temperature-controlled ablation and power-controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature-controlled irrigated tip ablation at target temperatures 60 degrees C, 70 degrees C, and 80 degrees C with infusion of 1 mL saline/min were compared with standard temperature-controlled ablation at 70 degrees C and power-controlled irrigated tip ablation at 40 W, and infusion of 20 mL/min. Lesion size and tissue temperatures were significantly higher during all modes of irrigated tip ablation compared with standard temperature-controlled ablation (P < 0.05). Lesion volume correlated positively with tissue temperature (r = 0.87). The maximum recorded tissue temperature was always 1 mm from the ablation electrode and was 67 +/- 4 degrees C for standard ablation and 93 +/- 6 degrees C, 99 +/- 6 degrees C, and 115 +/- 13 degrees C for temperature-controlled irrigated tip ablation at 60 degrees C, 70 degrees C, and 80 degrees C, respectively, and 112 +/- 12 degrees C for power-controlled irrigated tip ablation, which for irrigated tip ablation was significantly higher than tip temperature (P < 0.0001). Crater formation only occurred at tissue temperatures > 100 degrees C. We conclude that irrigated tip catheter ablation increases lesion size and tissue temperatures compared with standard ablation in the temperature-controlled mode at the same or higher target temperatures and in the power-controlled mode. Furthermore, tissue temperature and delivered power are the best indicators of lesion volume during temperature-controlled ablation.     

Deep myocardial ablation lesions can be created with a retractable needle-tipped catheter

RF catheter ablation of ventricular tachycardia is sometimes limited by inadequate lesion depth. This study investigated the use of a retractable needle-tipped catheter to create deep RF lesions in vivo in porcine myocardium. An 8 Fr electrode catheter with an extendable 27-gauge needle at the tip was modified for RF ablation by embedding a thermocouple and attaching a pin connector. In three swine (32-58 kg) the left ventricle was entered via the femoral artery and endocardial contact was made. The needle was advanced 10 mm and 13 RF applications were made under a controlled temperature (90 degrees C x 120 s). Nine control lesions were made using a standard 4-mm tip catheter (60 degrees C x 120 s). The lesions were fixed, serially sectioned from the endocardium, digitally imaged, and quantified. Needle ablation lesions were deeper (10.15 +/- 0.77 vs 5.67 +/- 0.37 mm, P < 0.001) and more likely to be transmural (77 vs 11%, P = 0.008) than control lesions. The volume of control lesions, however, was larger (358.4 +/- 56.2 vs 174.7 +/- 18.6 mm(3), P = 0.002) due to a significantly larger cross-sectional area at the endocardium (0.548 +/- 0.04 vs 0.151 +/- 0.01 cm(2), P < 0.001). At depths > 6 mm, the needle electrode lesions had a greater cross-sectional area (0.136 +/- 0.01 vs 0.005 +/- 0.004 cm(2), P < 0.001). Catheter-based needle ablation is feasible and allows creation of deeper lesions that can be transmural. Although deep, the lesions had a small cross-sectional area such that precise targeting would be required for success.     

Effect of radiofrequency catheter ablation on plasma B-type natriuretic peptide

The study was designed to investigate the impact of radiofrequency catheter ablation on the plasma level of B-type natriuretic peptide (BNP). In 36 patients who underwent catheter ablation of paroxysmal supraventricular tachycardia, the plasma level of BNP was analyzed before and after the ablation procedures. The plasma BNP at baseline, 30 minutes after the ablation, 3 and 24 hours after the ablation was 12.78 +/- 2.47, 18.45 +/- 4.02 (P = 0.446), 43.54 +/- 8.12 (P = 0.0001), and 17.88 +/- 4.71 (P = 0.493) pg/mL, respectively. Plasma troponin I was also increased 3 and 24 hours after the ablation (n = 10, P < 0.05). Multivariate regression analysis showed a significant correlation between the levels of BNP 3 hours after ablation and the preablation BNP and the total radiofrequency energy used for the ablation. We conclude that radiofrequency catheter ablation of supraventricular tachycardia increases the plasma level of BNP. The clinical significance of the ablation-induced increase in BNP needs to be further investigated.     

Popping Phenomena in Temperature‐Controlled Radiofrequency Ablation: When and Why Do They Occur?

During temperature-controlled radiofrequency (RF) ablation a popping sound sometimes occurs. This popping phenomenon is known to be associated with unwanted effects like blood boiling, endocardial rupture, catheter dislocation, and impedance rise. The present in vitro study determined the influence of cooling, electrode contact, and tip temperature on the occurrence of popping phenomena. Pieces of porcine ventricle were immersed in a bath of saline solution at 37 degrees C. Forty-two RF ablations were performed with different electrode-tissue contact forces (i.e., 0.0-0.44 N) in a temperature-controlled mode (70 degrees C setpoint, 30 s, 50 W maximum power output, 4-mm tip, thermocouple). Half of the 42 ablations were performed with fluid flow (0.1 m/s, group I), the other half without flow (group II). In group I, mean tip temperature and power were 55.6 +/- 8.5 degrees C and 36.2 +/- 13.8 W, resulting in a lesion volume of 121 +/- 57 mm3. In group II, the respective values were 67.3 +/- 1.5 degrees C and 9.9 +/- 5.2 W resulting in a volume of 42 +/- 18 mm3. The differences between groups were statistically significant. Overall, ten popping phenomena occurred in group I and none in group II. Pops occurred significantly more often when the contact force was < 0.1 N (8/10) and the tip temperature was < 60 degrees C (8/10). Two endocardial ruptures occurred, both were associated with a popping phenomenon. Using temperature control, the probability of pops is significantly higher when the ablation electrode and the endocardial tissue surface are exposed to fluid flow and the electrode-tissue contact is poor. Under these conditions the tissue temperature can be much higher than the temperature measured at the tip electrode and can potentially reach 100 degrees C causing intramyocardial steam formation and a popping phenomenon.     

The effect of ablation electrode length and catheter tip to endocardial orientation on radiofrequency lesion size in the canine right atrium

Although the determinants of radiofrequency lesion size have been characterized in vitro and in ventricular tissue in situ, the effects of catheter tip length and endocardial surface orientation on lesion generation in atrial tissue have not been studied. Therefore, the dimensions of radiofrequency lesions produced with 4-, 6-, 8-, 10-, and 12-mm distal electrode lengths were characterized in 26 closed-chested dogs. The impact of parallel versus perpendicular catheter tip/endocardial surface orientation, established by biplane fluoroscopy and/or intracardiac echocardiography, on lesion dimensions was also assessed. Radiofrequency voltage was titrated to maintain a steady catheter tip temperature of 75 degrees C for 60 seconds. With a perpendicular catheter tip/tissue orientation, the lesion area increased from 29 +/- 7 mm2 with a 4-mm tip to 42 +/- 12 mm2 with the 10-mm tip, but decreased to 29 +/- 8 mm2 with ablation via a 12-mm tip. With a parallel distal tip/endocardial surface orientation, lesion areas were significantly greater: 54 +/- 22 mm2 with a 4-mm tip, 96 +/- 28 mm2 with a 10-mm tip and 68 +/- 24 mm2 with a 12-mm tip (all P < 0.001 vs perpendicular orientation). Lesion lengths and apparent volumes were larger with parallel, compared to perpendicular tip/tissue orientations, although lesion depth was independent of catheter tip length with both catheter tip/tissue orientations. Electrode edge effects were not observed with any tip length. Direct visualization using intracardiac ultrasound guidance was subjectively helpful in insuring an appropriate catheter tip/tissue interface needed to maximize lesion size. Although atrial lesion size is critically dependent on catheter tip length, it is more influenced by the catheter orientation to the endocardial surface. This information may also be helpful in designing electrode arrays for the creation of continuous linear lesions for the elimination of complex atrial tachyarrhythmias.     

Impaired longitudinal conduction in crista terminalis is necessary for sustenance of experimental atrial flutter

Sustained atrial flutter (AFL) can be induced by creating a lesion between the vena cava in dogs. In previous studies on this model, the crista terminalis (CT) was often injured, and thus, role of CT in sustained reentry was not well understood. We hypothesized that impaired longitudinal conduction in CT is necessary for sustained AFL. In 16 anesthetized, open-chest dogs, linear radiofrequency ablation of the intercaval region was performed without interrupting CT. Intra-atrial conduction times (IAT) along CT were measured using a plaque electrode (25x35 mm) containing 30 bipolar electrodes before and after additional ablation of CT (group A, n=10) or the pectinate muscle (PM) region (group B, n=6). In group A, IAT along CT was 27 +/- 5 ms at baseline and was increased to 43 +/- 3 ms after ablation of CT (P<0.001). In group B, IAT along CT was 28 +/- 4 ms at baseline and 27 +/- 3 ms after ablation of PM (P=NS). Sustained AFL lasting >20 minutes was induced in 10/10 dogs in group A only after additional ablation of CT, and in 0/6 dogs in group B (P<0.001). The cycle lengths of AFL after ablation of the intercaval region and additional ablation of CT were 119 +/- 14 and 140 +/- 14 ms, respectively (P<0.01). There was a significant positive correlation between the cycle length of AFL and IAT along CT (r2=0.63, P<0.001). These results indicate that longitudinal conduction property in CT and not in PM strongly affects sustenance of AFL in this model.     

Shortcut Link Between the Fast and Slow Pathways and the Mechanism of Cure in Atrioventricular Nodal Reentrant Tachycardia by Catheter Ablation

The mechanism of cure in AV nodal reentrant tachycardia (AVNRT) by catheter ablation has not been fully clarified. We hypothesized that disruption of a shortcut link between the fast and slow pathways is responsible for the elimination of tachycardia. Results: AVNRT was eliminated in 20 patients by catheter ablation. In five patients (25%; group 1) slow pathway conduction disappeared 1 week after ablation. In six patients (30%; group II), the effective refractory period of the slow pathway was prolonged by more than 50 ms (212 ± 81 ms vs 340 ± 81 ms; P < 0.05). In the remaining nine patients (45%; group III), there was no change in the refractory period (270 ± 65 ms vs 273 ± 74 ms), although tachycardia was not inducible. A shortcut link between the fast and slow pathways was examined by comparing the A-H intervals over the slow pathway during the tachycardia and during atrial pacing at the tachycardia cycle length. Prior to ablation, a shortcut link was assumed in 1 of group I patients, 2 of group II patients, and 8 of group III patients. Of the 9 patients in whom the slow pathway was not impaired after ablation (group III), 8 patients were found to have a shortcut link, while 8 of 11 patients with impairment of the slow pathway after ablation (groups I and II) had no shortcut link between the fast and slow pathways (P < 0.05). Conclusion: In patients with a shortcut link between the fast and slow pathways, slow pathway conduction itself does not need to be impaired to eliminate the AVNRT, whereas in patients without this shortcut link, slow pathway conduction must be impaired.