Atrial Linear Lesions Research Articles

Atrial linear lesions: Feasibility using cryoablation

Although focal ablation has become an accepted approach to treat AF it is associated with a high arrhythmia recurrence rate. Therefore, the concept of creating linear lesions in the right or left atrium is of great interest as well. However, the creation of long linear lesions using RF ablation is extremely difficult. Therefore, the aim of our study was to asses whether the creation of a long linear lesion in the right atrium is possible using cryotherapy. A right atrial septal linear lesion was performed in 6 pigs. The ablation procedure was performed with a 7 F Freezor cryocatheter (CryoCath Technologies). The non-fluoroscopic mapping system LocaLisa was used as a navigation tool. The CARTO system was used for the evaluation of the linear lesions. Furthermore, all animals were sacrificed immediately after the ablation procedure and a post-mortem examination of the lesions was performed. Additionally, an analysis of the amplitudes of the intracardiac electrograms registered via the ablation catheter was performed before and after the ablation procedure. A right atrial septal linear lesion could be performed successfully in all 6 pigs. For the performance of this ablation line, a median number of 16 (range: 15) cryoapplications was necessary. The amplitudes of the intracardiac electrograms registerd via the ablation catheter decreased significantly after the ablation. Similarly, a CARTO bipolar voltage map revealed very low potentials among the ablation line in all pigs. There was a sharply demarcated ablation line in all pigs. Further analysis of the CARTO maps revealed an incomplete conduction block in all pigs. This was mostly due to a gap in the area of the fossa ovalis. The creation of long linear lesions using cryoablation is feasible and safe. Lesion characteristics are different and more favourable in comparison to RF-lesions. However, lesion transmurality was lacking especially in the area of the fossa ovalis.

Comparison of bipolar and unipolar radiofrequency ablation in an in vivo experimental model

Linear atrial radiofrequency lesions have been used effectively for the treatment of atrial fibrillation. In most cases an endocardial approach has been suggested. A method for epicardial placement of lesions would reduce the complexity of these procedures. We compared lesions created in ovine hearts in vivo using irrigated bipolar or unipolar handheld radiofrequency ablation devices. Radiofrequency lesions were produced around a left pulmonary vein, around the left atrial appendage and in the free wall of the right ventricle in ovine hearts. All lesions were created in the beating heart. A bipolar clamping device (n = 7) or a handheld unipolar device (n = 6) was used. Measurements of local electrograms and pacing thresholds were performed before and after ablation at each site to assess the electrical integrity of lesions. Tetrazolium and digital image analysis were used to assess lesion geometry. In atrial tissue continuous transmural lesions were achieved more often with the bipolar than with the unipolar device (92.3 vs. 33.3%, P < 0.02). In atrial tissue the reduction in signal amplitude caused by the lesions was significantly larger with the bipolar than the unipolar device (87.6+/-9.4% vs. 60.6+/-23.7% reduction, P < 0.01). There was a significant relationship between loss of pacing capture and lesion transmurality (P < 0.05). The bipolar device created narrower lesions than the unipolar device (4.1+/-0.9 mm vs. 5.9+/-2.1 mm, P < 0.001). The bipolar clamping device produces narrower lesions which are more likely to be transmural and lead to electrical isolation of ablated tissue than those produced by the unipolar device. However, both devices failed to consistently produce transmural lesions using the epicardial beating heart technique studied, particularly in thicker tissues. High output pacing within the ablated tissue partially predicts lesion transmurality and be a guide to the need for further ablation. However, endocardial ablation or transmural bipolar ablation are likely to remain the techniques of choice for linear radiofrequency ablation in the atria until improved techniques are developed.

Linear Cryoablation of the Left Atrium Versus Pulmonary Vein Cryoisolation in Patients With Permanent Atrial Fibrillation and Valvular Heart Disease

The aim of this study was to clarify the role of pulmonary vein isolation (PVI) alone versus left atrial linear lesions in the treatment of permanent atrial fibrillation (AF) in patients with left atrial dilatation and valvular disease. The primary end point was to assess the persistence of sinus rhythm (SR) off antiarrhythmic drugs (AADs) at 2-year follow-up and to correlate clinical outcome with surgical results validated with electroanatomic mapping (EAM). A total of 105 patients with permanent AF undergoing valve surgery were assigned to 3 different groups: in groups "U" and "7," left atrial linear cryoablation was performed, whereas in group "PV" patients, anatomic cryoisolation of pulmonary veins only was performed. In groups U and 7, SR was achieved in 57% of patients, whereas it was achieved in 20% of PV patients during 2-year follow-up. In the first 51 patients, the ablation schemes were validated with EAM. The EAM showed that the U lesion was never obtained: in 59% of these patients, a complete 7 lesion was achieved instead; in the 7 group, a complete 7 lesion was present in 65% of patients, whereas a complete PVI was obtained in 71% of patients. Considering patients in whom a complete 7 lesion was demonstrated with the EAM, SR without AADs was achieved in 86% of patients, whereas only 25% of patients with complete PVI were in SR without AADs. In patients with permanent AF, left atrial dilatation and valvular heart disease linear lesions in the posterior region of the left atrium are more effective than PVI alone. With cryoablation, the surgical intent is fulfilled in only approximately 65% of the cases. Knowing the real anatomic and electrophysiological effects of surgical ablation is necessary to correctly interpret the clinical outcome.

Stable Secondary Arrhythmias Late After Intraoperative Radiofrequency Ablation of Atrial Fibrillation:

Intraoperative radiofrequency (RF) ablation is an effective treatment of atrial fibrillation (AF). However, secondary arrhythmias late after ablation may complicate the patient's course. We report on the incidence, mechanisms, and treatment of gap-related atrial flutter and other secondary arrhythmias during long-term follow-up. In 129 patients who underwent intraoperative RF ablation with placement of left atrial linear lesions using minimally invasive surgical techniques, secondary arrhythmias were analyzed during long-term follow-up (20 +/- 6 months). Transient atrial arrhythmias during the first 3 postoperative months were excluded. In 8 (6.2%) of 129 patients, sustained stable secondary arrhythmias were documented. Left atrial, gap-related atrial flutter was observed in 4 patients (3.1%). The flutter was treated by percutaneous RF ablation in 3 patients (2.3%) and with drugs in 1 patient (0.8%). In 2 patients (1.6%), right atrial isthmus-dependent atrial flutter occurred and was treated successfully by percutaneous RF ablation. In 2 patients (1.6%), ectopic right atrial tachycardias occurred and were treated with percutaneous RF ablation. Late after intraoperative RF ablation of atrial fibrillation, three types of stable secondary arrhythmias were observed in 6% of patients: left atrial gap-related atrial flutter, right atrial isthmus-dependent atrial flutter, and ectopic atrial tachycardia. Gaps after intraoperative RF ablation due to noncontinuous or nontransmural linear lesions may lead to stable left atrial macroreentrant tachycardias, requiring new interventional therapy.

Percutaneous catheter ablation procedures for the treatment of atrial fibrillation.

In light of the significant morbidity and mortality from atrial fibrillation (AF), there has been significant interest in the development of percutaneous catheter ablation procedures for the suppression of AF. Given the success of the surgical Maze procedure, initial catheter-based approaches involved creation of linear atrial lesions. Success rates were low and utility was limited by a high complication rate and long procedural times. The recent discovery that AF is often initiated by atrial ectopic beats has resulted in therapies designed to target the ectopic sources, particularly those within the pulmonary veins. Experience and technological advances have improved the efficacy and safety of such procedures. This article will review catheter ablation procedures for the maintenance of sinus rhythm in patients with AF.

3736 Specific left atrial linear lesions as a curative therapeutic principle for atrial fibrillation: long-term results of the IRAAF study with minimum follow-up of 2 years

3736 Specific left atrial linear lesions as a curative therapeutic principle for atrial fibrillation: long-term results of the IRAAF study with minimum follow-up of 2 years

P973 Substrate modification by left atrial linear lesions as an alternative in patients with recurrence of atrial fibrillation despite pulmonary vein isolation

P973 Substrate modification by left atrial linear lesions as an alternative in patients with recurrence of atrial fibrillation despite pulmonary vein isolation

Modification of the atrial substrate by left atrial linear lesions in symptomatic patients after pulmonary vein isolation

Modification of the atrial substrate by left atrial linear lesions in symptomatic patients after pulmonary vein isolation

Specific linear left atrial lesions in atrial fibrillation: Intraoperative radiofrequency ablation using minimally invasive surgical techniques

ObjectivesA specific left atrial (LA) linear lesion concept for treatment of paroxysmal and permanent atrial fibrillation (AF) was tested using intraoperative ablation with minimally invasive surgical techniques. BackgroundCurative treatment for patients with chronic AF is among the main challenges of interventional electrophysiology. MethodsSeventy patients (mean age 53 ± 10 years) with drug-refractory persistent (n = 28) or paroxysmal (n = 42) AF underwent intraoperative radiofrequency (RF) ablation using video-assisted minimally invasive techniques via a right anterolateral minithoracotomy. Contiguous lesion lines involving the mitral annulus and the orifices of the pulmonary veins were placed with RF energy application under direct vision to prevent anatomically defined LA re-entrant circuits. ResultsMean follow-up was 18 ± 7 months in patients with permanent AF and 18 ± 5 months in patients with paroxysmal AF. Antiarrhythmic drug treatment was instituted in patients with postoperative atrial arrhythmias to allow “reverse electrical remodeling” and was discontinued after three months. Six months following ablation, 93% of the patients were in sinus rhythm in both groups, and after 12 months, 95% and 97%, respectively. As major complications, one esophagus perforation and one circumflex coronary artery stenosis were observed. ConclusionsA pure linear lesion line concept confined to the left atrium targeting specifically at elimination of anatomically defined LA “anchor” re-entrant circuits eliminated AF in >90% of the patients treated with intraoperative ablation using minimally invasive surgical techniques over a mean follow-up of 1.5 years.

Comparison of two different approaches for catheter ablation of persistent atrial fibrillation: pulmonary vein isolation versus left atrial linear lesions

Comparison of two different approaches for catheter ablation of persistent atrial fibrillation: pulmonary vein isolation versus left atrial linear lesions

Characterization of a long linear thermolesion in rabbit atria by high density mapping.

A major problem in radiofrequency ablation is to evaluate if linear atrial lesions are transmural and continuous. Characteristics of the atrial electrograms recorded from these lesions might be useful to determine the completeness of linear atrial lesions. In seven isolated perfused rabbit atria, a long transmural linear lesion was made with a hot needle (perfused with water of 80 degrees C) (width 2 +/- 0.2 mm). The lesion extended from the orifice of the superior caval vein to the A V ring. High density mapping (240 electrodes, 7.5 x 7.5 mm) of the right atrium was performed before and after the lesion. Complete bidirectional conduction block was confirmed by pacing close at either side of the lesion. No change in conduction or electrogram characteristics occurred outside the lesion. From the center of the lesion, low amplitude double potentials were recorded. The conduction delay around the lesion and the width of the double potentials showed a high correlation (R2 = 0.99) and were both dependent of the site of pacing. From the boundaries of the lesion towards its center, the amplitude and slope of the unipolar electrograms decreased exponentially by 72 +/- 5 and 85 +/- 3%. From the decay of these electrotonic potentials a space constant (lambda of 0.79 +/- 0.04 mm) could be calculated for the lesion. Unipolar electrograms recorded from a complete and transmural linear atrial lesion are electrotonic in nature. Their characteristics could be used to evaluate the width and depth of the lesion.

"Pills and pulses": hybrid therapy for atrial fibrillation.

Nonpharmacologic techniques are being increasingly applied to the treatment of atrial fibrillation (AF). None of these techniques (other than maze surgery) begins to approach 100% efficacy for long-term elimination of arrhythmia. This review examines the evidence for "hybrid" therapy, using combinations of drug and nonpharmacologic treatments. The immediate success rate of electrical cardioversion can be increased with amiodarone or ibutilide, and a number of drugs reduce the risk of AF recurrence. Preventing or reversing electrical atrial remodeling is an attractive strategy for maintenance of sinus rhythm. However, the available evidence (relating to the use of verapamil) is limited and conflicting. Ablation of the cavotricuspid isthmus is effective when antiarrhythmic drugs given for AF give rise to typical flutter. Isthmus and other right atrial linear lesions are poor as a sole therapy for AF, but better when drugs are added. Better still is the combination of left atrial linear lesions with drugs. In patients with AF recurrence following focal ablation/pulmonary vein isolation procedures, drugs are an alternative to extensive linear ablation. Some studies indicate that pacing to prevent AF may be effective, but rarely without continued antiarrhythmic drug therapy. This may represent a specific effect or simply improved drug tolerance. Drugs also might assist pacemaker therapy by increasing the proportion of atrial arrhythmias that are highly organized and thus amenable to antitachycardia pacing. This and other forms of hybrid therapy will remain the subject of conjecture in the absence of controlled clinical trials, which are urgently needed.

Effect of radiofrequency ablation on atrial myocardium.

Successful RF ablation of atrial fibrillation supposedly requires the creation of continuous linear lesions. This study aimed to determine the potential role of functional modifications of atrial myocardium in the vicinity of anatomic RF lesions. In 10 normal beagles (group A), a multiplexer mapping system and an epicardial multi-electrode were used to reconstruct atrial activation patterns during pacing at two cycle lengths before and after attempts to induce two linear right atrial lesions with a standard ablation catheter, respectively. An intercaval "drawback" was repeated 3 times over 5 min at a set temperature of 70 degrees C, followed by a transversal "point-by-point" ablation from the interatrial septum to the right-lateral tricuspid annulus at 70 degrees C/60 s each. Induction of atrial flutter was attempted before and after each ablation. In another 6 beagles (group B), a high-resolution multi-electrode was used to study epicardial functional effects resulting from single endocardial RF lesions on the free right atrial wall. Using three energy settings (60 degrees C/30 s, 60 degrees C/60 s, 70 degrees C/60 s), activation patterns were analyzed at two cycle lengths and local effective refractory periods were measured across the lesion. The lesions induced in group A only marginally affected atrial activation patterns and total activation times. However, as shown in dogs with atrial flutter, regional slow conduction was enhanced and functional conduction blocks were facilitated at high atrial rates, resulting in a significant prolongation in the revolution time of respective reentrant circuits. Apart from inducing anatomic lesions, single endocardial RF lesions (group B) were shown to delay epicardial conduction in adjacent myocardium in an energy- and rate-dependent way. Furthermore, an energy-dependent prolongation of effective refractory periods by far exceeding the size of anatomic lesions was observed. Continuous linear atrial lesions are hard to achieve with conventional ablation techniques. However, RF lesions induce changes in conduction and refractoriness around the anatomic lesion, which are likely to contribute to the overall effect of respective therapeutic interventions.

Ablation of atrial fibrillation in the rapid pacing canine model using a multi-electrode loop catheter

OBJECTIVESThis investigation details our experience using a loop catheter to ablate atrial fibrillation (AF) in dogs.BACKGROUNDAtrial fibrillation is the most common arrhythmia and has significant morbidity. Maintenance of normal sinus rhythm (NSR) after conversion in many patients is still a challenge.METHODSA multi-electrode loop catheter was used to create linear atrial lesions to ablate AF in a rapid atrial pacing model in 29 dogs. Rhythm status was assessed over a six-month recovery period, after which tissue analysis was performed.RESULTSAcute conversion to NSR or atrial tachycardia (AT) was achieved in 90% of cases. Six of 26 conversions occurred after only left atrial (LA) lesions, and two after just right atrial lesions. Sixteen (62%) of 26 lesions that resulted in AF conversion were in the LA, and 11 of these 16 conversions occurred during a lesion connecting the mitral ring to the pulmonary veins. Acute conversion rate was similar with ring and coil electrodes, but AT was more frequent with coil electrodes (63% vs. 31%). At six months 80% of dogs were in NSR, 14% were in AT, and 7% remained in AF. There was an average reduction in P-wave amplitude of 64 ± 26% after power application. Tissue analysis revealed transmural contiguous lesions when final outcome was NSR, and nontransmural/noncontiguous lesions where AF persisted.CONCLUSIONSMulti-electrode loop catheters can create contiguous transmural lesions in either atrium to safely and effectively ablate AF and provide a stable long-term rhythm outcome in this dog model. The left atrium appears to be the dominant chamber that sustains AF. Atrial tachycardia is a frequent acute outcome with coil electrodes.

Electrophysiological characteristics of atrial fibrillation and clinical outcome after right atrial radiofrequency linear lesions

Electrophysiological characteristics of atrial fibrillation and clinical outcome after right atrial radiofrequency linear lesions

Electrophysiological characteristics of atrial fibrillation and clinical outcome after right atrial radiofrequency linear lesions

Electrophysiological characteristics of atrial fibrillation and clinical outcome after right atrial radiofrequency linear lesions

In vivo and in vitro study of radio-frequency application with a new long linear probe: Implication for the maze operation

Background: The maze operation for atrial fibrillation is effective but highly invasive. We tested, both in vitro and in vivo, a new technique for creating long linear atrial lesions with a custom-made, 25-mm long, stainless-steel, linear probe and a corresponding 500-kHz generator for assistance in the maze operation. Methods: In the in vitro study with the isolated canine atria, the power of the delivered radio-frequency energy and the saline irrigating flow rate were changed independently, and the sizes of the lesions were measured. In the in vivo study radio-frequency energy was delivered to 4 portions (ie, the smooth and trabeculated portions of the right and left atria). The sizes of the lesions were measured, and the histologic features of the lesions were examined. Electrical isolation of the right atrial appendage from the remaining right atrium was attempted by using this linear probe. Results: In the in vitro study the size of the lesion became larger as the delivered power was increased, although the lesion was limited when the flow rate was high. In the in vivo study the size of the lesion was equal at the 4 different sites. Histologic examinations demonstrated linear and transmural lesions, and electrophysiologic examinations revealed conduction block between the right atrial appendage and the remaining right atrium. Conclusions: The new original long linear probe was effective for creating transmural linear atrial lesions with the irrigation method, presenting the possibility of an intraoperative technique that mimics the maze procedure. (J Thorac Cardiovasc Surg 2000;120:164-72)

Catheter ablation approach on the right side only for paroxysmal atrial fibrillation therapy: long-term results.

We report the long-term follow-up of a right side only catheter ablation approach for paroxysmal AF. Eighteen patients with AF refractory to drugs entered the study. Ablation was attempted in the right atrium only by creating linear lesions based on a specific design including from two to four linear lesions. Induction of AF was attempted before ablation and after placement of the lesions. A septal lesion was performed in nine patients. In ten patients atrial defibrillation thresholds (ADFTs) before ablation and following creation of the linear lesions were compared. After a mean follow-up of 22 +/- 11 months, seven patients had recurrence of AF, and another nine patients experienced atrial flutter or atrial tachycardia. Five patients remained in sinus rhythm without medications and four required the use of drugs. Three patients had sporadic AF and six were in chronic AF. The recurrence rate was similar in patients with and without the septal lesion. However, a cure with right side ablation appeared to be predicted by the presence of disorganized and earlier activity in the high right atrium and crista terminalis. Linear lesions in the right atrium were associated with a lower ADFT (pre 2.6 +/- 04 J vs post 1.7 +/- 0.6 J). In conclusion, in a small number of patients, control of AF can be obtained with a right side only approach. Certain activation patterns may identify patients suitable to this approach. No specific lesion pattern appeared more effective. Right atrial linear lesions resulted in lower ADFT.

Linear atrial ablation with a diode laser and fiberoptic catheter.

The catheter maze procedure for the treatment of chronic atrial fibrillation requires the creation of transmural, continuous linear atrial lesions. Attempts to drag a conventional radiofrequency ablation catheter across the atria in clinical as well as experimental studies have resulted in discontinuous lesions. Continuous linear lesions have been most difficult to create in trabeculated atrial muscle. Lesion discontinuities or gaps have resulted in reentrant atrial tachyarrhythmias in patients after ablation. We have explored the use of a linear laser catheter for the creation of continuous atrial lesions. A linear laser system may offer a number of potential advantages over conventional radiofrequency catheter ablation: (1) the laser diffuser …

The creation of linear contiguous lesions in the atria with an expandable loop catheter

OBJECTIVESThis article describes a catheter system designed to create linear atrial lesions and identifies electrophysiologic markers that are associated with the creation of linear lesions.BACKGROUNDAtrial fibrillation (Afib) is the most common arrhythmia in humans and causes a significant morbidity. The success of surgical interventions has provided the impetus for the development of a catheter-based approach for the ablation of Afib.METHODSWe tested a catheter system with 24 4-mm ring electrodes that can create loops in the atria. The electrodes can be used to record electrical activity and deliver radiofrequency power for ablation. In 33 dogs, 82 linear lesions were generated using three power titration protocols: fixed levels, manual titration guided by local electrogram activity and temperature control. Bipolar activity was recorded from the 24 electrodes before, during and after lesion generation. Data were gathered regarding lesion contiguity, transmurality and dimensions; the changes in local electrical activity amplitude; the incidence rate of rapid impedance rises and desiccation or char formation; and rhythm outcomes.RESULTSCatheter deployment usually requires <60 s. Linear lesions (12 to 16 cm in length and 6 ± 2 mm wide) can be generated in 24 to 48 min without moving the catheter. Effective lesion formation can be predicted by a decrease of greater than 50% in the amplitude of bipolar recordings. Splitting or fragmentation of the electrogram and increasing pacing threshold (3.1 ± 3.3 mV to 7.1 ± 3.8 mV, p < 0.01) are indicative of effective lesion formation. Impedance rises and char formation occurred at 91 ± 12°C. Linear lesion creation does not result in the initiation of Afib. However, atrial flutter was recorded after the completion of the final lesion in 3/12 hearts. When using temperature control, no char was noted in the left atrium, whereas 8% of the right atrium burns had char.CONCLUSIONSThis adjustable loop catheter forces the atrial tissue to conform around the catheter and is capable of producing linear, contiguous lesions up to 16 cm long with minimal effort and radiation exposure. Pacing thresholds and electrogram amplitude and character are markers of effective lesion formation. Although Afib could not be induced after lesion set completion, sustained atrial flutter could be induced in 25% of the hearts.