Catheter Ablation for Patients with Cardiac Arrhythmias

Catheter ablative techniques have recently been introduced as therapy for patients with drug-resistant cardiac arrhythmias. These techniques include delivery of high-energy direct-current shocks in order to electrocoagulate the atrioventricular junction for those with supraventricular arrhythmias. This technique, if successful, results in arrhythmia control but induces chronic pacemaker dependency. The evidence, to date, suggests that 90% of these patients are improved after attempted atrioventricular junctional ablation. Catheter ablative procedures have been used for attempted ablation of accessory pathways and has been shown to be especially effective for those with posteroseptal accessory pathways. More recently, techniques for ablation of ventricular tachycardia foci have been introduced but experience with this procedure is too limited to allow for definitive recommendations.     

Catheter Ablation for Control of Ventricular Tachycardia: A Report of the Percutaneous Cardiac Mapping and Ablation Registry

Catheter ablation of ventricular tachycardia is a procedure of last resort in critically ill patients. The Percutaneous Cardiac Mapping and Ablation Registry was able to collect data on 88 patients undergoing ablation of ventricular tachycardia foci. The mean following interval for the group was 10 ± 8 months. Results were divided into three categories: Group I patients remained asymptomatic and were on no antiarrhythmic medications (33%); Group II remained asymptomatic and took antiarrhythmic agents (38%): Group III patients were considered unsuccessful and consisted of 29 percent of the total. More than one-third of patients received two shocks; the remainder received from one to five shocks. Overall mortality included four procedure-related deaths and total follow-up mortality was 25 percent. Catheter ablation for ventricular tachycardia should he undertaken only in highly specialized centers with an expert and experienced electrophysiologist with immediate surgical back-up available.     

Entrapment of an Ablation Catheter in the Cardiac Venous System: A Case Report

Cannulation of the coronary sinus is a common procedure with infrequent complications. We report an unusual case of a steerable "dumb-bell" catheter passed through the ostium of the coronary sinus prior to an intended radiofrequency ablation procedure becoming stuck and requiring general anesthesia for extraction. We caution against the use of such catheters with a "waist" for the cannulation of the coronary sinus.     

Randomized Comparison of Efficacy of Cooled Tip Catheter Ablation of Atrial Flutter: Anatomic Versus Electrophysiological Complete Isthmus Block

There is a subset of patients with failed ablation of the cavotricuspid isthmus (CTI) using standard catheters and with 10% of the patients having recurrences. The purpose of this study was to compare the cooled and standard ablation with regard to acute successful electrophysiological achievement of bidirectional isthmus block and the subacute anatomic characteristics of the lesions. This randomized, experimental study compares the effects of ablation on the isthmus using a cooled catheter with those of a standard ablation catheter in 16 pigs. In 12 animals, CTI block was achieved after ablation (8/8 cooled and 4/8 standard). In two animals, it was not possible to achieve complete isthmus block and two had persistent slow conduction (all four using the standard catheter). After 1 week, the animals were slaughtered. The size of the lesion was greater with the irrigated tip catheters. Transmural lesions were found in 14 animals. A complete line of anatomic isthmus block was not documented after thefirst line in six animals, four with the standard and two with the cooled catheter. A conduction block was never present across gaps > or = 5 mm. In conclusion cooled catheters achieved a complete line of electrophysiological and anatomical block in a significantly higher percentage than the standard catheters.     

Catheter Ablation for Paroxysmal Atrial Fibrillation: A Randomized Comparison between Multielectrode Catheter and Point‐by‐Point Ablation

Introduction: Catheter ablation for paroxysmal atrial fibrillation is widely used for patients with drug‐refractory paroxysms of arrhythmia. Recently, novel technologies have been introduced to the market that aim to simplify and shorten the procedure. Aim: To compare the clinical outcome of pulmonary vein (PV) isolation using a multipolar circular ablation catheter (PVAC group), with point‐by‐point PV isolation using an irrigated‐tip ablation catheter and the CARTO mapping system (CARTO group; CARTO, Biosense Webster, Diamond Bar, CA, USA). Methods: Patients with documented PAF were randomized to undergo PV isolation using PVAC or CARTO. Atrial fibrillation (AF) recurrences were documented by serial 7‐day Holter monitoring. Results: One hundred and two patients (mean age 58 ± 11 years, 68 men) were included in the study. The patients had comparable baseline clinical characteristics, including left atrial dimensions and left ventricular ejection fraction, in both study arms (PVAC: n = 51 and CARTO: n = 51). Total procedural and fluoroscopic times were significantly shorter in the PVAC group (107 ± 31 minutes vs 208 ± 46 minutes, P < 0.0001 and 16 ± 5 minutes vs 28 ± 8 minutes, P < 0.0001, respectively). The AF recurrence was documented in 23% and 29% of patients in the PVAC and CARTO groups, respectively (P = 0.8), during the mean follow‐up of 200 ± 13 days. No serious complications were noted in both study groups. Conclusions: Clinical success rates of PV isolation are similar when using multipolar circular PV ablation catheter and point‐by‐point ablation with a three‐dimensional (3D) navigation system in patients with PAF, and results in shorter procedural and fluoroscopic times with a comparable safety profile. (PACE 2010; 33:1039–1046)     

Iatrogenic Pneumohemomediastinum Mimicking Cardiac Tamponade: A Complication of Catheter Ablation Procedure

We describe a patient who developed cardiac tamponade during electrophysiological mapping aimed at ablating an atrioventricular accessory pathway. Transesophageal echocardiography showed compression of the left pulmonary veins due to pneumohemomediastinum secondary to left subclavian vein cannulation.     

The Effects of Percutaneous Catheter Ablation on Preexisting Permanent Pacemakers

VANERIO, G., ET AL.: The Effects of Percutaneous Catheter Ablation on Preexisting Permanent Pacemakers. Study Objective: Determine the effect of percutaneous catheter ablation (CAI on permanent pacemakers. Measurements and Results: Twenty-three patients who underwent CA at The Cleveland Clinic Foundation from September 1983 to January 1990, and had a previously implanted pacemaker were studied. Electrocardiographic data during the CA procedure and clinic data including pacemaker evaluations were analyzed. Fifty-two percent (12/23) of the pacemakers malfunctioned: five developed transient ventricular loss of capture; two undersensing; one oversensing; three could not be interrogated or programmed, and one did not respond to the magnet test. Four patients developed syncopal episodes and two severe dizziness after the procedure. All had their pacemakers replaced. In total, seven were explanted. Destructive analysis by the individual manufacturer identified pacemaker circuitry failure in five. Unipolar pacemakers and anodal ablation procedures had more frequent and severe malfunctions, but the difference was not statistically significant. Conclusions: Pacemaker malfunction is frequent during CA. It may be prevented by programming the pacemaker, when possible, to the nonfunctioning mode (000 mode). Temporarily disconnecting the pacemaker during ablation requires further evaluation as an alternative approach. Close follow-up can detect pacemaker malfunction and prevent complications.     

Clinical, Electrophysiological Characteristics, and Radiofrequency Catheter Ablation of Atrial Tachycardia Near the Apex of Koch's Triangle

Atrial tachycardia, with its focus near the apex of Koch's triangle, may carry a potential risk of atrioventricular block during radiofrequency catheter ablation. The efficacy and safety of this procedure have never been addressed. The characteristics and catheter ablation results are reported for six patients with atrial tachycardia near the apex of Koch's triangle. All six patients were female aged 49.6 ± 9.3 years (range 39–63). Organic heart disease was present in 3 (50%) of the 6 patients. The P wave in surface ECG had a mean axis of − 28° (range − 90°–+ 30°) in the frontal plane. The catheter ablation was guided by activation sequence mapping. The energy was titrated from low power level. Atrial overdrive pacing was used to monitor the atrioventricular conduction should accelerated functional rhythm occur. At the final successful ablation site, the local atrial activation was 41.8 ± 9.1 ms before the P wave and His-bundle potential was present in 5 of the 6 patients. All patients had their atrial tachycardia eliminated without recurrence or heart block during a follow-up period of 17.7 ± 8.5 months (range 6–30). In conclusion, atrial tachycardia near the apex of Koch's triangle has distinct clinical and electrophysiological features, Radiofrequency catheter ablation can be performed effectively. However, extreme care must be taken to prevent inadvertent atrioventricular block. Titrated energy application and continuous monitoring of atrioventricular conduction are mandatory.     

Catheter Ablation of Idiopathic Left Ventricular Tachycardia

ZARDINI, M., etal .: Catheter Ablation of Idiopathic Left Ventricular Tachycardia . Idiopathic left ventricular tachycardia (ILVT) characterized by right bundle branch block, left axis morphology, response to verapamil and inducibility from the atrium in patients without structural heart disease may represent a distinct clinical entity. We report our experience with catheter ablation of this uncommon arrhythmia using radiofrequency energy (RF) and/or direct current (DC) shocks. Six men and 2 women, aged 16–50 years (mean ± SD, 32 ± 13), had recurrent VT for 16 ± 16 years with a mean frequency of 4 ± 3 episodes/ year. Three patients had syncope during VT. None had identifiable structural heart disease. Catheter ablation was guided by earliest endocardial activation, presence of a high frequency presystolic potential and/or pacemapping of the left ventricle. The left ventricle was accessed via a retrograde aortic approach in 6 patients, a transeptal approach in 1 patient, and a combined approach in the remaining patient. All patients had inducible right bundle branch block morphology, left axis VT with a mean cycle length (CL) of 361 ± 61 ms. A presystolic potential preceding ventricular activation and the His potential during VT was identified in 4 patients. All ablation sites were identified in a relatively uniform location, in the inferoapical left ventricle. Noninducibility of VT was obtained with RF in 3 patients and with DC in 5 patients. In 1 patient, DC delivery after unsuccessful RF prevented further inducibility. Similarly, RF was successful in 1 patient in whom an initial DC attempt was ineffective. Mean total procedure time was 282 ± 51 minutes and mean total fluoroscopy time was 40 ± 15 minutes. There were no complications. One patient treated with DC shock had recurrence of VT during treadmill test the day after ablation and refused repeat ablation. During a mean follow-up of 17 ± 13 months, no VT recurrences or other cardiovascular events occurred. In conclusion, catheter ablation in the inferoapical left ventricle is an effective treatment for this type of ILVT. RF energy can be safely complemented by low energy DC shocks when the former is ineffective.     

Catheter Ablation of Canine Myocardium with Radiofrequency Energy

High energy direct-current shocks delivered via an electrode catheter have been used to ablate the atrioventricular junction since 1981.¹ This technique has also been adapted for ablation of other cardiac tissues including the atrium, posterior interatrial septum and ventricular myocardium. The limitations of this technique include inadequate control of the energy source, poor understanding of the mechanisms of myocardial injury, and untoward complications possibly related to barotraumatic injury. Radiofrequency energy has been shown to create ablative injury when delivered lo the myocardium via standard electrode catheters. This report will review our experience with radiofrequency catheter ablation of the canine myocardium with specific emphasis on the biophysical aspects of lesion formation.     

Radiofrequency Catheter Ablation Using Cooled Electrodes: Impact of Irrigation Flow Rate and Catheter Contact Pressure on Lesion Dimensions

WEISS, C., et al. : Radiofrequency Catheter Ablation Using Cooled Electrodes: Impact of Irrigation Flow Rate and Catheter Contact Pressure on Lesion Dimensions. Irrigation of radiofrequency current (RF) ablation reduces the risk of thrombus formation. The aim of this study was to investigate the impact of different irrigation catheter flow rates and contact pressures from the catheter on the development of lesion dimension and thrombus formation. A thigh muscle preparation was achieved in six sheep to create a cradle that was filled and perfused with heparinized blood (250 mL/min, 37C°). RF ablation (30 s, 30 W) was initially performed with three different irrigation flow rates (5 mL/min, 10mL/min, and 20 mL/min) and a perpendicular position (0.1 N contact pressure) of the irrigated ablation catheter (“Sprinklr,” Medtronic, Inc., Minneapolis, MN, USA). The next lesions were induced with constant contact pressure of 0.05 Newton (N); 0.1 N; 0.3 and 0.5 N and a parallel or perpendicular orientation of the catheter, respectively. A constant irrigation flow of 10 mL/min was maintained during these RF applications. Cross sections of the lesions were investigated with regard to maximal depth and maximal diameter at and below the surface. During high flow irrigation (20 mL/min) the surface diameter was significantly smaller (0.63 ± 0.1 cm ) compared to irrigation flow rates of 5 mL/min (0.88 ± 0.2 cm ) and 10 mL/min (1 ± 0.1 cm ). Thrombus formation was not observed during any RF application. Only in perpendicular catheter orientations with a contact pressure of 0.5 N were significantly deeper lesions (0.85 ± 0.12 cm ) induced compared to 0.05 N (0.55 ± 0.02 cm ), 0.1 N (0.7 ± 0.01 cm ) and 0.3 N (0.67 ± 0.01 cm ) contact pressure. There was no significant difference in lesion depth with different flow rates. Irrigated RF ablation even with low flow rates and high catheter contact pressure prevented thrombus formation at the electrode. Smaller lesion diameters have been created with high irrigation flow rates. The deeper lesion created with high catheter contact pressure might be caused by a greater power transmission to the tissue.     

Myocardial Temperature Response During Radiofrequency Catheter Ablation

During radiofrequency catheter ablation, steady-state electrode-tissue interface temperatures are reached within 5 seconds. Within the myocardium, however, a much slower temperature rise has been observed in vitro with stabilization after approximately 2 minutes. This discrepancy suggests that tissue temperature rise time depends on distance from the ablation electrode and, thus, that temperature rise measured at the electrode-tissue interface does not correspond with temperature rise within the myocardium. In five beagles, closed-chest radiofrequency catheter ablation was performed in the vicinity of intramural thermocouples. Sequences of 60 seconds, 10- and 25-watt pulses were delivered in the unipolar mode via the 4-mm distal electrode of a 7 French steerable catheter. At all distances > 3 mm from the ablation electrode, the rate of myocardial temperature rise was low: relative rise after 5, 10, 20, and 30 seconds was 22%, 32%, 48%, and 63% of that achieved at 60 seconds, and even then steady-state temperatures had not yet been reached. Temperature rise was faster at sites closer to the ablation electrode. There was no difference in rate of rise between first and second pulses at the same site. A 6% higher myocardial temperature was reached with a second identical pulse at the same site. Tissue temperatures achieved with 25 watts were 2.4 times higher than with a preceding 10-watt pulse at the same ablation site.     

Mapping Guided Laser Catheter Ablation of the Atrioventricular Conduction in Dogs

Safety and efficacy of mapping guided laser catheter ablation of the AV junction was tested in a canine model. A total of 43 laser pulses (continuous wave, Nd:YAG, 1,064 nm, 30 W, irradiated spot diameter 2.0–2.5 mm) were delivered in 15 dogs (2–5 per dog) via a novel laser catheter system. Pulses were selectively aimed at: (1) the AV node: (2) the His bundle; and (3) the bundle branches. Laser pulses of 9.7 ± 1.1 seconds (n = 31) produced reversible conduction disturbances in the targeted segment of the AV conduction system, while pulses of 28.6 ± 7.9 seconds (n = 9) resulted in chronic block. The dogs survived the procedure without complications. Follow-up was 6.5–10.5 months. Histopathologically, lesions showed clear-cut oval-shaped areas of fibrosis of 0.5–18.0 mm in diameter and 0.5–3.5 mm (transmural) in depth, depending on the irradiation time. Pervenous mapping guided laser catheter irradiation of the AV junction can produce AV block consistently and selectively in the targeted segment of the right ventricular conduction system in dogs. The method is safe and can be performed in a controllable manner by using the catheter system presented.     

Clinical Utility of Routine Transthoracic Echocardiographic Studies After Uncomplicated Radiofrequency Catheter Ablation: A Prospective Multicenter Study

Unsuspected cardiac complications have been occasionally identified on postablation echocardiographic studies; however, the clinical utility of route echocardiographic studies following uncomplicated radiofrequency catheter ablation procedures has not been established. Two-dimensional/Doppler echocardiographic studies obtained preablation (within 3 months of the procedure) in 355 consecutive patients (180 males and 175 females, mean age 37 ± 21 years) were compared to postablation (within 24 hours of the procedure) studies obtained after a total of 387 uncomplicated RF catheter ablation procedures for AV node slow pathway (n = 120), accessory AV pathways (n = 214), and complete AV junction (n = 39). Postablation studies identified 6 new cases (1.5%) of new wall motion abnormalities, and 3 additional patients had septal wall motion abnormalities during ventricular pacing. LVEF remained unchanged from baseline (62 ± 10 vs 62 ± 11). A small pericardial effusion was detected after 11 procedures (2.8%), and there were 9 (2.3%), 21 (5.4%), and 20 (5.2%) new findings of mild (1 +) aortic, mitral, and tricuspid regurgitation, respectively; and no cases of significant valvular dysfunction in any patient. There were no new cases of cavity thrombus. There was no clear relationship between postablation echocardiographic findings and the type and approach to ablation, and no patient had any clinical sequelae possibly related to any of the new echocardiographic findings during a mean follow-up of 15 ± 6.0 months (range 1–26 months). Routine transthoracic echocardiographic studies after uncomplicated RF catheter ablation procedures identify occasional minor abnormalities that (1) may or may not be procedure related, (2) are of no apparent clinical consequence, and (3) thus appear to be of limited value.     

Radiofrequency Catheter Ablation of Refractory Ventricular Tachycardia

Transcatheter radiofrequency ablation of the arrhythmia focus was attempted in a 68-year-old patient with recurrent ventricular tachycardia, both spontaneous and inducible by programmed ventricular stimulation despite treatment with multiple antiarrhythmic drugs. The procedure was performed under local anesthetic without complication. The arrhythmia was not inducible immediately following ablation or 5 days later, and during 5 months follow-up there has been no spontaneous recurrence.     

Management of Patients After Catheter Ablation of Ventricular Tachycardia

The management of patients after catheter ablation of ventricular tachycardia is not well defined. In this article we summarize recently published results and report our own experience. Factors influencing the clinical outcome of these patients and methods to identify patients with an increased risk of recurrence of ventricular tachycardia are discussed. Furthermore, a review is given on current concomitant therapeutic tools including antiarrhythmic drugs and the implantation of an automatic cardioverter defibrillator.     

Idiopathic Left Ventricular Tachycardia: New Insights, into Electrophysiological Characteristics and Radiofrequency Catheter Ablation

KOTTKAMP, H., et.al .: Idiopathic Left Ventricular Tachycardia: New Insights into Electrophysiological Characteristics and Radiofrequency Catheter Ablation . Objectives: This study was performed to investigate the electrophysiological characteristics of idiopathic left ventricular tachycardia and to determine the feasibility of radiofrequency catheter ablation for nonpharmacological cure. Background: The underlying electrophysiological mechanism of idiopathic left ventricular tachycardia with right bundle branch block morphology and left-axis deviation is presently not known. Additionally, only limited data describing the results of radiofrequency catheter ablation for treatment of idiopathic left ventricular tachycardia so far exist. Methods: Electrophysiological studies and radiofrequency catheter ablation were performed in 5 patients (3 male and 2 female, mean age 31 ± 10 years) with idiopathic left ventricular tachycardia (cycle length 376 ± 72 msec). The patients had a history of recurrent palpitations of 4 ± 1 years and had been treated unsuccessfully with 2 ± 1 antiarrhythmic drugs. Sustained ventricular tachycardia with right bundle branch block morphology and left- or right-axis deviation was documented in all patients. Results: Inducibility with critically timed ventricular extrastimuli, inverse relationships of the coupling interval of the initiating extrastimulus and the interval to the first beat of the tachycardia, continuous diastolic or mid-diastolic electrical activity during ventricular tachycardia, and fragmented late potentials during sinus rhythm suggested reentrant activation as the underlying mechanism in three patients. On the other hand, induction dependent on isoproterenol infusion and rapid ventricular pacing and exercise inducibility indicated different electrophysiological characteristics in the remaining two patients. During electrophysiological study, intravenous verapamil terminated ventricular tachycardia in all patients, whereas ventricular tachycardia did not respond to intravenous adenosine, autonomic maneuvers, or intravenous β-blocking agent esmolol. Catheter mapping revealed earliest endocardial activation during ventricular tachycardia in different areas of the left ventricular septum being distributed from the base to the midapical portion of the septum in all patients. In 4 of 5 patients, radiofrequency catheter ablation (median number of pulses 4, range 1–9) resulted in complete abolition of idiopathic left ventricular tachycardia during a follow-up of 4–43 months (median 10) without antiarrhythmic drugs. Successful target sites for catheter ablation included continuous diastolic or mid-diastolic electrical activity during ventricular tachycardia and late potentials during sinus rhythm (2 patients), polyphasic fragmented presystolic potentials during ventricular tachycardia (1 patient), and pace mapping with identical QRS morphology compared to the ventricular tachycardia and “earliest” detectable activity during tachycardia (1 patient). No procedure related complications occurred. Conclusions: Two different patterns of electrophysiological properties of idiopathic left ventricular tachycardia were observed, indicating that this arrhythmia entity does not represent a homogeneous group. The “origin” of the tachycardias as identified by successful radiofrequency catheter ablation was located in different areas of the left ventricular septum and was distributed from the base to the mid-apical region. Radiofrequency catheter ablation was an effective and safe treatment modality in most of these patients. Distinct target site characteristics for successful catheter ablation including polyphasic diastolic activity during tachycardia and fragmented late potentials during sinus rhythm could be identified.