Organized Left Atrial Tachyarrhythmia During Stepwise Linear Ablation for Atrial Fibrillation

Introduction: This study attempted to delineate the mechanism of organized left atrial tachyarrhythmia (AT) during stepwise linear ablation for atrial fibrillation (AF) using noncontact mapping.
Methods and Results: Eighty patients in whom organized ATs developed or induced during stepwise linear ablation for AF were enrolled. Left atrial (LA) activation during ATs was mapped using noncontact mapping. Radiofrequency (RF) energy was delivered to the earliest activation site or narrowest part of the reentrant circuit of ATs. A total of 146 ATs were mapped. Four ATs were characterized as a focal mechanism (cycle length (CL): 225 ± 49 ms). A macroreentrant mechanism was confirmed in the remaining 142 ATs. LA activation time accounted for 100% of CL (205 ± 37 ms). All 142 ATs used the conduction gaps in the basic figure-7 lesion line. There were three types of circuits classified based on the gap location. Type I (n = 68) used gaps at the ridge between left atrial appendage (LAA) and left superior pulmonary vein (LSPV). Type II (n = 50) used gaps on the LA roof. Type III (n = 24) passed through gaps in the mitral isthmus. Ablation at these gaps eliminated 130 ATs. During the follow-up period of 16.2 ± 6.7 months, 82.5% of the 80 patients were in sinus rhythm.
Conclusion: The majority of left ATs developed during stepwise linear ablation for AF are macroreentrant through conduction gaps in the figure-7 lesion line, especially at the LAA–LSPV ridge. Noncontact activation mapping can identify these gaps accurately and quickly to target effective catheter ablation.     

Electroanatomic Magnetic Mapping during Ablation of Isthmus-dependent Atrial Flutter

Introduction: Although recent studies have demonstrated that the endpoint of isthmus conduction block is superior to that of termination and subsequent inability to induce atrial flutter (AFl), the optimal method for determining isthmus conduction block has not been determined. Electroanatomic magnetic mapping during coronary sinus (CS) pacing may provide a reliable endpoint for AFl ablation. Methods and Results: Catheter mapping and ablation was performed in 42 patients with isthmus-dependent AFl. The patients were divided into two groups, based on procedural endpoint: Group I (28 patients) – isthmus conduction block was determined based on multipolar catheter recordings and electroanatomic mapping, and Group II (14 patients) – isthmus conduction block was determined by electroanatomic mapping during CS pacing alone. In Group I, ablation procedures were acutely successful in 25 of 28 patients (89±%). A 100±% concordance between the data presented by multipolar catheter recordings and electroanatomic mapping was noted in determining the presence or absence of isthmus conduction block. In Group II, ablation procedures were acutely successful in 13 of 14 patients, 13 (93±%). After a mean of 16.3±3.7 months follow up, there was 1 atrial flutter recurrence in the 38 patients (2.6±%) with demonstrated isthmus block at the end of the procedure. Conclusions: Electroanatomic magnetic mapping during CS pacing is comparable to the multipolar catheter mapping technique for assessing isthmus conduction block as an endpoint for AFl ablation procedures.     

Use of Three-Dimensional Mapping Systems in the Catheter Ablation of Atrial Fibrillation

The increasing clinical experience with remarkable advancement in the technology has enabled the catheter ablation of atrial fibrillation (AF) to become more effective and safe. Widespread utilization of three-dimensional (3D) mapping systems has facilitated the improvement in the outcomes after catheter ablation of AF. The purpose of this article is to review the current status, clinical role, and future directions of various 3D mapping systems in catheter ablation of AF.     

Prevalence of Fever in Patients Undergoing Left Atrial Ablation of Atrial Fibrillation Guided by Barium Esophagraphy

Background: Real-time esophageal imaging is critical in avoiding esophageal injury. However, the safety of esophageal imaging with barium has not been specifically explored.
Methods: Three hundred seventy consecutive patients underwent left atrial (LA) ablation of atrial fibrillation (AF) under conscious sedation. One hundred eighty-five patients (50%) underwent the ablation procedure with, and 185 patients (50%) underwent the procedure without administration of barium. Fever, as a surrogate for aspiration, was defined as a maximal temperature ≥100°F within the first 24 hours following the ablation procedure.
Results: Thirty of the 370 patients (8%) developed fever within 24 hours after LA ablation. The prevalence of fever was 9% (17/185) among patients who received barium and 7% (13/185) among those who did not receive barium (P = 0.6). Evaluation revealed the following causes of fever in 14 of the 30 patients (47%) with no difference in prevalence between the 2 groups: pericarditis, venous thromboembolism, hematoma, and infiltrate on chest radiography. Multivariate analysis failed to reveal any factors associated with development of fever. None of the patients experienced serious complications such as respiratory failure or atrioesophageal fistula.
Conclusions: Fever may occur in approximately 10% of patients undergoing LA ablation of AF. Administration of barium is not associated with fever or other complications such as aspiration pneumonia. Real-time imaging of the esophagus with barium administration in conjunction with conscious sedation appears to be safe.     

Right Atrial Mapping and Linear Ablation for Paroxysmal Atrial Fibrillation

Objective: Catheter ablation techniques to cure atrial fibrillation (AF) are under investigation. This study evaluates a mapping-based, individualized approach to right atrial (RA) linear ablation in patients with paroxysmal AF. Methods: In this prospective observational study, 29 patients with recurrent symptomatic AF refractory to medical therapy, underwent linear ablation between May 1998 and December 1999. Inclusion criteria were symptomatic paroxysmal AF, failure of at least 2 antiarrhythmic medications, and informed consent. Radiofrequency ablation was performed in the RA using a 3.3 French multielectrode catheter, ablating through sequential electrodes to establish linear lesions. Lesions were delivered during sustained AF, guided by an empiric mapping scheme, targeting arrhythmogenic areas noted during electrophysiologic testing in sinus rhythm and areas of most disorganization during AF. Reinduction of AF was attempted at the end of successful ablation. Results: The mean age was 58 years. There were 15 male and 14 female patients. Sustained AF was inducible in all patients at electrophysiology study. Acute success was achieved in 24 patients (83%). Long term success (maintaining sinus rhythm off antiarrhythmic medications) was seen in 23 (79%) over a mean follow-up of 19.7 months. Ablation lines varied from patient to patient. There were no complications. Conclusions: Individualized linear ablation in the RA using a multielectrode catheter system can produce effective suppression of paroxysmal AF. Ablation during AF, and testing to reinduce AF at the end of the procedure, make this study unique.     

Substrate Ablation in Treatment of Atrial Fibrillation

From the time catheter ablation of atrial fibrillation (AF) was first reported, of the two dominant approaches for AF ablation, only pulmonary vein (PV) isolation has been modified, while circumferential pulmonary vein ablation (CPVA) as performed by our group in Milan has remained substantially unmodified. In fact, PV isolation as initially performed by Haissaguerre et al. has undergone rapid evolution toward substrate modification with significantly higher success rates without major complications. Modification of such technique was due to modification of the substrate. It is now evident that substrate modification is indeed crucial for curing AF particularly in patients with long-lasting or permanent AF. Indeed, to achieve good outcomes, any ablation technique should simultaneously include elimination of all triggers associated with modification of both anatomic and autonomic substrate, as we started to do many years ago by performing CPVA.     

Right Atrial Remodeling is More Advanced in Patients with Atrial Flutter Than with Atrial Fibrillation

Atrial Remodeling in Atrial Flutter. Introduction: Atrial fibrillation (AF) and atrial flutter (AFL) are related arrhythmias with common triggers, yet in individual patients either AF or AFL often predominates. We performed detailed electrophysiologic (EP) and electroanatomic (EA) studies of the right atrium (RA) in patients with AF and AFL to determine substrate differences that may explain the preferential expression of AF/AFL in individual patients. Methods: Patients with AF (n = 13) were compared to patients with persistent AFL (n = 10). Detailed studies were performed, and 3‐dimensional electroanatomic mapping studies were created and the RA was divided into 4 segments for regional analysis. Global, septal, lateral, anterior, and posterior segments were compared for analysis of: bipolar voltage; proportion of low‐voltage areas and areas of electrical silence; conduction times; and proportion of abnormal signals (fractionated signals and double potentials). Results: Compared to patients with AF, patients with AFL had (1) lower bipolar voltage and an increase in the proportion of low‐voltage areas; (2) an increase in the proportion of complex signals; and (3) prolongation of activation times. Conclusions: Patients with AFL showed more advanced remodeling than patients with AF with slowed conduction, lower voltage areas with regions of electrical silence, and a greater proportion of complex signals, particularly in the posterior RA. These changes facilitate the stabilization of AFL and may explain why some patients are more likely to develop AFL as a sustained clinical arrhythmia. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1067‐1072, October 2012)     

Atrial Anatomy and Imaging in Atrial Fibrillation Ablation

Catheter ablation of atrial fibrillation (AF) can be a technically challenging procedure, requiring detailed knowledge of the anatomy of the atria and thoracic veins to achieve successful cure of AF with a low complication rate. In this article, we review the anatomy relevant to AF ablation: the intraatrial septum, the pulmonary veins and left atrial antral region, the left atrial vestibule, the right atrium and related veins, and the esophagus. We focus on normal variations of anatomy and the role of the available imaging modalities in facilitating safe and effective ablation of this common and complex arrhythmia.     

Pulmonary Vein Contraction Before and After Radiofrequency Ablation for Atrial Fibrillation

Pulmonary Vein Contraction After Ablation. Introduction: Cardiovascular magnetic resonance imaging (cMRI) may provide a noninvasive method to test for pulmonary vein (PV) isolation after ablation for atrial fibrillation (AF) by detecting changes in PV contraction. Methods: PV contraction (the maximal percentage change in PV cross‐sectional area [CSA] during the cardiac cycle) measured 1 month before and 2 months after PV isolation was compared in 63 PVs from 16 patients with medically refractory AF. Repeat cMRI imaging and invasive catheter mapping was performed prior to repeat PV ablation in 50 PVs from 14 additional patients with recurrent AF. Contraction in PVs with sustained isolation after the initial ablation was compared to contraction in PVs with electrical reconnection to adjacent atrium. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cutoff PV contraction value for prediction of PV‐atrial reconnection after ablation. The cutoff value was then prospectively tested in 40 PVs from 12 additional patients. Results: PV contraction decreased after AF ablation (22.4 ± 10% variation in CSA before ablation vs 10.1 ± 8% variation in CSA after ablation, P < 0.00001). PVs with sustained isolation on invasive mapping contracted less than PVs with electrical reconnection to adjacent atrium (13.7 ± 10.6% vs 21.4 ± 9.3%, P = 0.021). PV contraction produced a c‐index of 0.74 for prediction of PV‐atrial reconnection after ablation and >17% variation in PV CSA predicted reconnection with a sensitivity of 84.6% and specificity of 66.7%. Conclusion: PV contraction is reduced by ablation. PV contraction measurement may provide a noninvasive method to test for PV isolation after ablation procedures. (J Cardiovasc Electrophysiol, Vol. 22, pp. 169‐174, February 2011)