Anatomic characteristics of the left atrial isthmus in patients with atrial fibrillation: lessons from computed tomographic images

Introduction: Left atrial (LA) isthmus ablation was reported to improve the success rate of catheter ablation of paroxysmal atrial fibrillation (AF). LA isthmus ablation could also cure a subset of LA flutter. Therefore, understanding the anatomy of the LA isthmus is important for performing the ablation effectively.
Methods and Results: Group I included 45 patients (40 male, mean age = 50 ± 13 years) with paroxysmal AF who underwent catheter ablation. Group II included 45 patients (37 male, mean age = 54 ± 10 years) without a history of AF. They underwent a 16-slice multidetector computed tomography (MDCT) scan to delineate the LA structures before the ablation procedure. The average length of the LA isthmus was longer in group I than in group II (lateral isthmus: 3.30 ± 0.68 vs 2.71 ± 0.60 cm, P < 0.001; medial isthmus: 5.12 ± 0.94 vs 4.45 ± 0.63 cm, P < 0.001), and morphological patterns of lateral and medial isthmus were similar between groups. In addition, the average depth of lateral isthmus was similar between groups (0.62 ± 0.32 vs 0.55 ± 0.33 cm, P = 0.41), but the average depth of medial isthmus was larger in group I than in group II (0.60 ± 0.32 vs 0.44 ± 0.25 cm, P = 0.01). The medial isthmus had more ridges, as compared to the lateral isthmus (13% vs 0%, P = 0.026). Furthermore, the distances between esophagus and lateral isthmus were longer in group I than in group II (at the middle of isthmus and mitral annulus level: 21.0 ± 4.8 vs 18.4 ± 6.0 mm, P < 0.001; and 37.1 ± 5.7 vs 29.6 ± 8.1 mm, P < 0.001, respectively).
Conclusion: The LA isthmus was longer in the AF patients. The morphology of the isthmus was variable. Compared with the lateral isthmus, the medial isthmus was longer and had more ridges. A peculiar configuration of the isthmus provided by CT images could influence the ablation strategy.     

Morphological changes of the left atrial appendage after catheter ablation of atrial fibrillation

Introduction: The left atrial appendage (LAA) has been proven to be the most important site of thrombus formation in patients with atrial fibrillation (AF). However, the information regarding the morphometric alteration of the LAA related to the outcome of AF ablation is still lacking. Thus, we evaluated the long-term changes of the LAA morphology in patients undergoing catheter ablation of AF using magnetic resonance angiography (MRA).
Methods and Results: Group 1 included 15 controls without any AF history. Group 2 included 40 patients with drug-refractory paroxysmal AF. They were divided into two subgroups: group 2a included 30 patients without AF recurrence after pulmonary vein (PV) ablation. Group 2b included 10 patients with late recurrence of AF. The LAA morphology before and after (20 ± 11 months) ablation was evaluated by three-dimensional MRA. The group 2 patients had a larger baseline LAA size (including the LAA orifice, neck, and length) and less eccentric LAA orifice and neck. After the AF ablation, there was a significant reduction in the LAA size in the group 2a patients, and the morphology of the LAA neck became more eccentric during the follow-up period. In group 2b, the LAA size increased and no significant change in the eccentricity of the orifice and neck could be noted.
Conclusions: The morphometric remodeling of the LAA in the AF patients could be reversed after a successful ablation of the AF. Progressive dilation of the LAA was noted in the patients with AF recurrence. These structural changes in the LAA may play a role in reducing the potential risk of cerebrovascular accidents.     

Characterization of conduction recovery across left atrial linear lesions in patients with paroxysmal and persistent atrial fibrillation

Background: Left atrial (LA) linear lesions are effective in substrate modification for atrial fibrillation (AF). However, achievement of complete conduction block remains challenging and conduction recovery is commonly observed. The aim of the study was to investigate the localization of gap sites of recovered LA linear lesions.
Methods and Results: Forty-eight patients with paroxysmal (n = 26) and persistent/permanent (n = 22) AF underwent repeat ablation after pulmonary vein (PV) isolation and LA linear ablation at the LA roof and/or mitral isthmus due to recurrences of AF or flutter. In 35 patients, conduction through the mitral isthmus line (ML) had recovered whereas roof-line recovery was observed in 30 patients. The gaps within the ML were distributed to the junction between left inferior PV and left atrial appendage in 66%, the middle part of the ML in 20%, and in 8% to the endocardial aspect of the ML while only 6% of lines showed an epicardial site of recovery. The RL predominantly recovered close to the right superior PV (54%) and less frequently in the mid roof or close to the left PV (both 23%). Reablation of lines required significantly shorter RF durations (ML: 7.24 ± 5.55 minutes vs 24.08 ± 9.38 minutes, RL: 4.24 ± 2.34 minutes vs 11.54 ± 6.49 minutes; P = 0.0001). Patients with persistent/permanent AF demonstrated a significantly longer conduction delay circumventing the complete lines than patients with paroxysmal AF (228 ± 77 ms vs 164 ± 36 ms, P = 0.001).
Conclusions: Gaps in recovered LA lines were predominantly located close to the PVs where catheter stability is often difficult to achieve. Shorter RF durations are required for reablation of recovered linear lesions. Conduction times around complete LA lines are significantly longer in patients with persistent/permanent AF as compared to patients with paroxysmal AF.     

Prospective study of atrial fibrillation termination during ablation guided by automated detection of fractionated electrograms

Introduction: Complex fractionated atrial electrograms (CFAE) may identify critical sites for perpetuation of atrial fibrillation (AF) and provide useful targets for ablation. Current assessment of CFAE is subjective; automated detection algorithms may improve reproducibility, but their utility in guiding ablation has not been tested.
Methods and Results: In 67 patients presenting for initial AF ablation (42 paroxysmal, 25 persistent), LA and CS mapping were performed during induced or spontaneous AF. CFAE were identified by an online automated computer algorithm and displayed on electroanatomical maps. A mean of 28 ± 18 sites/patient were identified (20 ± 13% of mapped sites), and were more frequent during persistent AF. CFAE occurred most commonly within the CS, on the atrial septum, and around the pulmonary veins. Ablation initially targeting CFAE terminated AF in 88% of paroxysmal AF, but only 20% of persistent AF (P < 0.001). Subsequently, additional ablation was performed in all patients (PV isolation for paroxysmal AF, PV isolation + mitral and roof lines for persistent AF). Minimum follow-up was 1 year. One-year freedom from recurrent atrial arrhythmias without antiarrhythmic drug therapy after a single procedure was 90% for paroxysmal AF, and 68% for persistent AF.
Conclusions: Ablation guided by automated detection of CFAE proved feasible, and was associated with a high AF termination rate in paroxysmal, but not persistent AF. As an adjunct to conventional techniques, it was associated with excellent long-term single procedure outcomes in both groups. Criteria for identifying optimal CFAE sites for ablation, and selection of patients most likely to benefit, require additional study.     

Mechanisms of recurrent atrial fibrillation: comparisons between segmental ostial versus circumferential pulmonary vein isolation

Background: Electrical isolation of pulmonary veins (PVs) is an effective therapy for atrial fibrillation (AF). Both segmental ostial PV ablation and circumferential ablation with PV–left atrial (LA) block have been implicated to eliminate AF. However, the mechanism of the recurrent AF after undergoing either strategy remains unclear.
Methods and Results: Of the 73 consecutive patients with symptomatic AF that underwent PV isolation and had recurrences of AF, Group 1 consisted of 46 patients (age 56 ± 13 years old, 35 males) who underwent PV isolation by segmental ostial PV ablation and Group 2 consisted of 27 patients (age 51 ± 11 years old, 24 males) who underwent circumferential ablation with PV–LA block. In Group 1, the earliest ectopic beat or ostial PV potentials were targeted. In Group 2, circumferential ablation with PV–LA block was performed by encircling the extraostial regions around the left and right PVs. During the first procedure, all patients had PV–AF. There was no difference in the non-PV ectopy between Group 1 and Group 2. During the second procedure, the incidence of an LA posterior wall ectopy initiating AF was significantly lower (20% vs. 0%, P = 0.01) in Group 2. There was no difference in the PV ectopy initiating AF during the second procedure.
Conclusion: Circumferential ablation of AF with PV–LA block may eliminate the LA posterior wall ectopy and decrease the incidence of LA posterior wall ectopy initiating AF during the second procedure.     

Hybrid epicardial and endocardial ablation of persistent or permanent atrial fibrillation: a new approach for difficult cases

Background : Although percutaneous epicardial catheter ablation (PECA) has been used for the management of epicardial ventricular tachycardia, the use of PECA for atrial fibrillation (AF) has not yet been reported.
Objective: To evaluate the efficacy and feasibility of a hybrid PECA and endocardial ablation for AF.
Methods: We performed PECA for AF in five patients (48.6 ± 8.1 years old, all male, four redo ablation procedures of persistent AF with a risk of pulmonary vein (PV) stenosis, one de novo ablation of permanent [AF]) after an endocardial AF ablation guided by PV potentials and 3D mapping (NavX). Utilizing an open irrigation tip catheter, a left atrial (LA) linear ablation from the roof to the perimitral isthmus or localized ablation at the junction between the LA appendage and left-sided PVs or ligament of Marshall (LOM) was performed.
Results: PECA of AF was successful in all patients with an ablation time of <15 minutes. The left-sided PV potentials were eliminated by PECA in all patients. Bidirectional block of the perimitral line was achieved in two of two patients and a left inferior PV tachycardia with conduction block to the LA was observed during the ablation in the area of the LOM in one patient. A hemopericardium developed in one patient, but was controlled successfully. During 8.0 ± 6.3 months of follow-up, all patients have remained in sinus rhythm (four patients without antiarrhythmic drugs).
Conclusion: A hybrid PECA of AF is feasible and effective in patients with redo-AF ablation procedures and at risk for left-sided PV stenosis or who are resistant to endocardial linear ablation.     

The impact of CT image integration into an electroanatomic mapping system on clinical outcomes of catheter ablation of atrial fibrillation

Background: A detailed appreciation of left atrial/pulmonary vein (LA/PV) anatomy may be important in improving the safety and success of catheter ablation (CA) for atrial fibrillation (AF).
Objectives: The aim of this nonrandomized study was to determine the impact of computerized tomography (CT) image integration into a 3-dimensional (3D) mapping system on the clinical outcome of patients undergoing CA for AF.
Methods: Ninety-four patients (age: 56 ± 10 years) with AF (paroxysmal 46, persistent 48) underwent wide encirclement of ipsilateral PV pairs using irrigated radiofrequency ablation with the endpoint of electrical isolation. Ablation was guided by 3D mapping alone (electroanatomic 24, noncontact 23) in 47 (3DM group) patients and by CT image integration (Cartomerge®) in 47 (CT group). In persistent AF, a combination of linear ablation and targeted ablation of complex fractionated electrograms was also performed.
Results: Successful PV electrical isolation did not differ between the two groups. A significant reduction in fluoroscopy times was demonstrated in the CT group (49 ± 27 minutes vs 3DM group 62 ± 26 minutes, P = 0.03). Arrhythmia recurrence was reduced in the CT group (32% vs 51% in the 3DM group, P < 0.01). In 30 symptomatic patients (12 CT and 18 3DM), repeat procedures for AF (13 in 3DM and 5 CT, P ≤ 0.10) and AT (5 in 3DM and 7 CT, P = NS) were performed. Overall success on 7-day monitor off antiarrhythmic drugs was achieved in 60% in the 3DM group when compared with 83% in the CT group (P < 0.05) at a follow-up of 25 ± 5 weeks.
Conclusion: CA for AF guided by CT integration was associated with reduced fluoroscopy times, arrhythmia recurrence, and increased restoration of sinus rhythm. Improved visualization of complex LA geometries might improve the safety and success of CA for AF.     

Evaluation of an individualized strategy of cavotricuspid isthmus ablation as an adjunct to atrial fibrillation ablation

Objectives: To evaluate supplementary cavotricuspid isthmus (CTI) ablation as an adjunct to atrial fibrillation (AF) ablation in selected patients.
Background: It is unclear whether routine CTI ablation is beneficial in all patients undergoing AF ablation.
Methods and Results: In patients undergoing AF ablation, additional CTI block was created only for those with typical atrial flutter (Afl) before or during the ablation. Out of 188 consecutive patients (108 male, 56 ± 9 years), 75 underwent CTI ablation (Group CTI+) and left atrial (LA) ablation (circular mapping-guided extensive pulmonary vein isolation in all and linear LA ablation when required), while 113 underwent LA ablation alone (Group CTI−). Group CTI+ patients had smaller LA and less frequently persistent/permanent AF and linear LA ablation. Over a follow-up of 30 ± 10 months, complications (4% vs 5%, P = NS), typical Afl occurrence (1.3% and 2.6%, P = NS) and AF recurrence (25% and 28%, P = NS) were similar. Atypical Afl was more common in Group CTI− (4 vs 14%, P = 0.026). Eighty-two percent and 79% of patients in Groups CTI+ and CTI−, respectively, remained arrhythmia free in stable sinus rhythm without antiarrhythmic drug treatment (P = NS).
Conclusions: Avoiding supplementary CTI ablation in AF ablation patients without evidence of typical flutter does not result in a higher incidence of typical Afl. Despite more persistent/permanent AF and larger LA in patients without evidence of typical flutter, a strategy of selective supplementary ablation resulted in similar and low AF recurrence rates in the group without CTI ablation compared with the group with CTI ablation.     

Dilated left atrium and pulmonary veins in patients with calcified coronary artery: a potential contributor to the genesis of atrial fibrillation

Introduction: Coronary artery disease (CAD) is an important etiology of atrial fibrillation (AF). Coronary artery calcification is a marker of coronary atherosclerosis and coronary events. The purpose of this study was to investigate whether larger left atrium (LA) and pulmonary veins (PVs) were seen by multidetector computed tomography (MDCT) scans in those patients with higher coronary calcium scores.
Methods and Results: A total of 166 patients undergoing MDCT for general check-up (n = 128, 77%) or suspected CAD (n = 38, 23%) were enrolled and divided into a control (calcium score = 0, n = 60), medium calcium score (calcium score = 100∼400, n = 47), and high calcium score (calcium score >400, n = 59) groups. Diameters and areas of the LA, left atrial appendage (LAA), and PVs were measured by MDCT. The high calcium score group had significantly larger PVs diameters, LAA orifice area (1.9 ± 1.4 cm², 0.9 ± 0.5 cm², 0.8 ± 0.4 cm², P < 0.005), LA anterior-posterior distance (32.2 ± 6.8 mm, 30.4 ± 6.5 mm, 27.3 ± 6.0 mm, P < 0.05), and transverse distance (52.6 ± 7.3 mm, 50.2 ± 9 mm, 49.5 ± 4.6 mm, P < 0.05) than the medium calcium score and control groups. Six (3.6%) patients with paroxysmal AF had higher calcium scores and larger diameters of LA, LAA, and PVs than those (96.4%) without paroxysmal AF. Two patients in the high calcium score group had calcified PVs localized to the right upper and left upper PVs. The incidence of calcified PVs was 1.2% for the total patients and 3.3% for the high calcium score patients.
Conclusion: In the presence of high calcium scores in this patient population, the LA, LAA, and PVs were enlarged.     

Does Left Atrial Volume and Pulmonary Venous Anatomy Predict the Outcome of Catheter Ablation of Atrial Fibrillation?

Introduction: Preprocedural factors may be helpful in selecting patients with atrial fibrillation (AF) for treatment with catheter ablation and in making an assumption regarding their prognosis. The aims of this study were to investigate whether left atrial (LA) volume and pulmonary venous (PV) anatomy, evaluated by computed tomography (CT) prior to ablation, will predict AF recurrence following catheter ablation.
Methods and Results: We included 146 patients (mean age 57 ± 11 years, 83% male) with symptomatic AF (55% paroxysmal, 18% persistent, 27% long-standing persistent). All patients underwent CT scanning prior to catheter ablation to evaluate LA volume and PV anatomy. Circumferential PV isolation was performed guided by Cartomerge electroanatomical mapping. The outcome was defined as complete success, improvement, or failure.
After a mean follow-up of 19 ±7 months, complete success was achieved in 59 patients (40%), and 38 patients (26%) demonstrated improvement. LA volume was found to be an independent predictor of AF recurrence with an adjusted OR of 1.14 for every 10-mL increase in volume (95% CI 1.00–1.29, P = 0.047). PV variations were equally distributed among the different outcomes of the ablation procedure, and therefore univariate analysis did not identify PV anatomy as a predictor of outcome.
Conclusion: LA volume is an independent predictor of AF recurrence after catheter ablation. Additionally, PV anatomy did not have any effect on the outcome. These findings suggest that an assessment of LA volume may be incorporated into the preprocedural evaluation of patients being considered for AF ablation.     

Effect of left atrial circumferential ablation for atrial fibrillation on left atrial transport function

BACKGROUND: The effects of left atrial (LA) circumferential ablation on LA function in patients with atrial fibrillation (AF) have not been well described. OBJECTIVES: The purpose of this study was to determine the effect of LA circumferential ablation on LA function. METHODS: Gated, multiphase, dynamic contrast-enhanced computed tomographic (CT) scans of the chest with three-dimensional reconstructions of the heart were used to calculate the LA ejection fraction (EF) in 36 patients with paroxysmal (n = 27) or chronic (n = 9) AF (mean age 55 +/- 11 years) and in 10 control subjects with no history of AF. Because CT scans had to be acquired during sinus rhythm, a CT scan was available both before and after (mean 5 +/- 1 months) LA circumferential ablation (LACA) in only 10 patients. A single CT scan was acquired in 8 patients before and in 18 patients after LACA ablation. Radiofrequency catheter ablation was performed using an 8-mm-tip catheter to encircle the pulmonary veins, with additional lines along the mitral isthmus and the roof. RESULTS: In patients with paroxysmal AF, LA EF was lower after than before LACA (21% +/- 8% vs 32 +/- 13%, P = .003). LA EF after LA catheter ablation was similar among patients with paroxysmal AF and those with chronic AF (21% +/- 8% vs 23 +/- 13%, P = .7). However, LA EF after LA catheter ablation was lower in all patients with AF than in control subjects (21% +/- 10% vs 47% +/- 5%, P < .001). CONCLUSION: During medium-term follow-up, restoration of sinus rhythm by LACA results in partial return of LA function in patients with chronic AF. However, in patients with paroxysmal AF, LA catheter ablation results in decreased LA function. Whether the impairment in LA function is severe enough to predispose to LA thrombi despite elimination of AF remains to be determined.     

A new approach for complete isolation of the posterior left atrium including pulmonary veins for atrial fibrillation

Introduction: Esophageal injury is a potential complication after catheter ablation of the posterior left atrium (LA). Therefore, we describe a new approach for complete isolation of the posterior LA including all pulmonary veins (PVs) without vertical lesions along the esophageal aspect of the posterior LA, namely Box isolation .
Methods and Results: Ninety-one patients with paroxysmal atrial fibrillation (AF) underwent Box isolation. Continuous lesions at the anterior portions of the ipsilateral PVs were initially created and then linear ablation of LA roof and bottom was performed to isolate the posterior LA. Continuous vertical lesions at the posterior portions of PVs along the esophageal aspect of the posterior LA were not created. Ablation was performed with an 8-mm-tip catheter. The endpoint was the absence of electrical activity and the inability to pace the posterior LA and all PVs in sinus rhythm. Complete isolation of the posterior LA was achieved in 82 patients (90%). Ablation resulted in the termination of AF in 65%, and subsequent noninducibility of AF in 71% of the patients. A repeat ablation was performed in six of nine patients with recurrence of arrhythmia. At 13 ± 3 months of follow-up, 86 patients (95%) were arrhythmia-free without antiarrhythmic drugs.
Conclusion: This study shows that it is possible to achieve complete isolation of the posterior LA including all PVs without posterior vertical lesions. Box isolation is associated with a high clinical success rate.     

Randomized comparison of encircling and nonencircling left atrial ablation for chronic atrial fibrillation

BACKGROUND: Left atrial (LA) circumferential ablation has been reported to eliminate atrial fibrillation (AF). Whether an ablation without encirclement of the pulmonary veins (PVs) is as effective as LA circumferential ablation is not clear. OBJECTIVES: The purpose of this study was to compare the efficacy of LA circumferential ablation and nonencircling linear ablation in patients with chronic AF. METHODS: Eighty patients with chronic AF were randomized to undergo LA circumferential ablation (n = 40) or nonencircling linear ablation (n = 40). In LA circumferential ablation, the PVs were encircled, with additional lines made in the mitral isthmus and posterior wall or roof. In nonencircling linear ablation, 4 +/- 1 ablation lines were created through areas of complex electrograms, with lines in the roof (38), anterior wall (36), septum (40), mitral isthmus (32), and posterior annulus (6). The endpoint of LA circumferential ablation and nonencircling linear ablation was voltage abatement. RESULTS: LA flutter occurred in 15% after LA circumferential ablation and in 18% after nonencircling linear ablation (P = .8). A repeat ablation procedure was performed for recurrent AF in 7 and 11 patients or for atrial flutter in 6 and 4 patients after LA circumferential ablation and nonencircling linear ablation, respectively (P = .8). At 9 +/- 4 months, the prevalence of AF was 28% in the LA circumferential ablation and 25% in the nonencircling linear ablation group (P = .8). Sixty-eight percent and 60% of patients were in sinus rhythm and free of AF and atrial flutter in the absence of antiarrhythmic drug therapy after LA circumferential ablation and nonencircling linear ablation, respectively (P = .5). There were no complications. CONCLUSION: Nonencircling linear ablation and LA circumferential ablation are equally efficacious in eliminating chronic AF. However, the advantage of nonencircling linear ablation is that it eliminates the need for ablation along the posterior wall of the LA. Therefore, nonencircling linear ablation may avoid the small but real risk of atrioesophageal fistula formation associated with LA circumferential ablation.     

Left atrial contractility is preserved after successful circumferential pulmonary vein ablation in patients with atrial fibrillation

Introduction: Circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF) consists of creating extensive lesions in the left atrium (LA). The aim of the study was to evaluate changes in LA contractility after ablation and their relationship with procedure outcome.
Methods and Results: A series of 90 consecutive patients underwent cardiac magnetic resonance imaging (MRI) before and 4–6 months after CPVA. Only patients in sinus rhythm during both imaging acquisitions were included in the study to measure LA end-diastolic (LAmax) and LA end-systolic (LAmin) volumes. Fifty-five patients were finally analyzed (41 men, 52 ± 11 years, 74% paroxysmal AF). During a mean follow-up of 12 ± 7 months and after 1.2 ± 0.3 ablation procedures, 38 patients (69%) were arrhythmia-free (group I), and the remaining 17 patients had recurrences (group II). There was a significant decrease in mean LAmax volume in both groups, whereas mean LAmin volume only decreased in group I. Mean LA ejection fraction (EF) was preserved after CPVA in group I (40 ± 11% vs 38 ± 10%; P = 0.27) but decreased in patients with arrhythmia recurrences (37 ± 10% vs 27 ± 10%; P < 0.001). In fact, LA EF remained stable or increased in 68% of patients without arrhythmia recurrences.
Conclusions: LAmax volume reduction following CPVA occurs regardless of the clinical efficacy of the procedure, whereas mean LAmin volume only decreased in patients without recurrences. LA EF was preserved or even increased in most patients with successful CPVA.     

Radiofrequency ablation of complex fractionated atrial electrograms (CFAE): preferential sites of acute termination and regularization in paroxysmal and persistent atrial fibrillation

Introduction: Complex fractionated atrial electrograms (CFAE) have been described as a new target for ablation of atrial fibrillation (AF). This prospective study evaluates the acute effects of CFAE ablation in patients with paroxysmal or persistent AF and analyzes the preferential anatomic sites where these effects occur.
Methods and Results: Ablation of CFAE was performed in 66 symptomatic patients (mean age of 58 ± 12 years) with paroxysmal (n = 36) or persistent AF (n = 30). Termination or regularization of AF during ablation of CFAE was achieved in 56 of 66 patients (84%), with termination in 28 of 66 patients (42%) and regularization of AF in 28 of 66 patients (42%). Ablation of CFAE showed no effect in 10 of 66 patients (16%). Termination of AF occurred at 53 sites and AF regularization at 81 sites. The preferential sites of AF termination or regularization were found around the pulmonary veins (termination n = 15; regularization n = 22), at the anterior wall (termination n = 14; regularization n = 19) and at the interatrial septum (termination n = 8; regularization n = 17).
Conclusion: Termination or regularization of AF was achieved acutely in 84% of patients by ablation of CFAE. The preferential sites of AF termination or regularization were found around the pulmonary veins, at the anterior wall of the LA and at the interatrial septum. These findings may have implications for future ablation concepts.     

Left atrial posterior wall thickness in patients with and without atrial fibrillation: data from 298 consecutive autopsies

Introduction: Radiofrequency ablation of atrial fibrillation (AF) is associated with energy delivery on the posterior left atrial (LA) wall with small but significant risk of life-threatening complications. Anatomy of LA walls has been described, but wall thickness in patients with AF has not been studied systematically. The aim of the present study was to describe LA posterior wall thickness in patients with and without history of AF.
Methods and Results: Heart mass and LA wall thickness was measured during 298 consecutive autopsies (142 male, age 61 ± 17 years). LA posterior wall was measured at three levels: between the superior pulmonary veins (SPV), in the center of the posterior LA wall (CPV), and between the inferior pulmonary veins (IPV). Information about AF history was obtained from medical records. Fifty-nine subjects (20%) had documented AF. They were older than subjects without AF (74 ± 10 years vs 58 ± 17 years, P < 0.0001) and had greater heart mass (522 ± 114 g vs 389 ± 99 g, P < 0.0001). LA posterior wall thickness increased from the most superior to the most inferior measured level (2.3 ± 0.9 mm vs 2.5 ± 1.0 mm vs 2.9 ± 1.3 mm for SPV, CPV, and IPV, respectively; P < 0.001). Subjects with AF history had thinner LA posterior wall at CPV and IPV compared with those without AF.
Conclusions: LA posterior wall thickness is described on a large series of consecutive autopsies. LA posterior wall is found to be generally thinner in patients with history of AF. Study results have clinical implications for understanding complication risk and improvement of safety of AF ablation procedures.     

Computed tomography-fluoroscopy image integration-guided catheter ablation of atrial fibrillation

Introduction: This study examines the feasibility of atrial fibrillation (AF) ablation using registered three-dimensional computed tomography (CT) images of the left atrium with fluoroscopy.
Methods and Results: A total of 50 consecutive patients with symptomatic AF refractory to medical therapy (32 paroxysmal, 18 persistent, age 55 ± 10 years) were randomized to undergo a catheter-based AF ablation procedure with or without the CT-fluoroscopy guidance system. All patients underwent preprocedural contrast-enhanced CT imaging and segmentation of the left atrium. For the CT-fluoroscopy group, circumferential lesions encompassing the pulmonary vein (PV) antrum and linear lesions along the roof of the left atrium between the superior PVs and the mitral isthmus were created on the CT image, which was registered with real-time fluoroscopy. The registered images were then used to navigate the ablation catheters to the sites of planned ablation. After the ablation sites were completed, any remaining PV potentials were isolated with electrophysiological guidance. In the control patients, the same technique was performed without using the CT-fluoro guidance system. CT scans were accurately registered to fluoroscopic images with minimal manual correction. Operators could navigate catheters on the registered images to preplanned, extraostial sites for ablation. CT-fluoroscopy guidance decreased procedure duration and fluoro times (P < 0.05). At a mean follow-up of 9 ± 2 months, 21 patients (84%) in the CT-fluoro guidance group and 16 patients (64%) in the control group have had no recurrence of AF.
Conclusion: CT-fluoroscopic-guided left atrial ablation is feasible and allows appropriate catheter manipulation in the left atrium.     

Low incidence of left atrial or left atrial appendage thrombus in patients with paroxysmal atrial fibrillation and normal EF who present for pulmonary vein antrum isolation procedure

Introduction: The incidence of left atrial appendage (LAA) thrombus in patients with paroxysmal atrial fibrillation (PAF) who present for pulmonary vein antrum isolation procedure (PVAI) is unknown.
Methods and Results: All consecutive patients from January 2000 to June 2004 who underwent a PVAI received a computed tomography (CT) to evaluate LAA thrombus before the procedure and 3 months post-PVAI. All patients were followed prospectively. One thousand two hundred twenty-one patients received a PVAI during the study dates. All patients received a CT pre-PVAI at 3 months, and 601 (49%) received a transesophageal echocardiography (TEE) pre-PVAI. Per protocol, all patients who had CT scans that were positive for LAA thrombus received a TEE. There were 9 patients who had LAA thrombus on CT scan, but only 3 had LAA thrombus on TEE. Using TEE as the gold standard, only 3 patients had an LAA thrombus before PVAI; of these patients, 2 had chronic AF with average ejection fraction (EF) of 48% and 1 patient had PAF with EF 25%. No patients with PAF and normal EF had LAA thrombus. Patients with LAA thrombus pre-PVAI had lower EF than patients without LAA thrombus (40% vs. 53%, P = 0.007) but had similar LA size (5.0 vs. 4.5 cm, P = 0.77). No other differences in baseline characteristics were noted.
Conclusions: In this registry of 1,221 patients, we did not observe LA thrombus in PAF patients with normal EF who present for PVAI. Prescreening CT alone is likely to be sufficient in paroxysmal AF patients with normal EF, and the use of TEE may not be needed.     

Electroanatomic remodeling of the left atrium in patients undergoing repeat pulmonary vein ablation: mechanistic insights and implications for ablation

Introduction: There is limited information describing late changes in the electroanatomic characteristics of the left atrium (LA) associated with recurrence after an anatomical circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF).
Methods and Results: Forty-seven patients (57 ± 8 years) undergoing a repeat ablation after CPVA were included. Using an electroanatomic mapping system, we measured the bipolar voltage by averaging points in the pulmonary vein (PV)-LA junction and four other LA sites. Conduction velocity and AF cycle length (AFCL) were also measured and the results are compared with the first procedure. After an initial decrease observed at the end of the first procedure, voltage and conduction velocity returned to intermediate values in all LA sites, with lower voltage at the LIPV antrum (P = 0.004), and lower conduction velocity across the LIPV and RSPV (P < 0.001). Conduction gaps were more prevalent at the septal aspect of the right PV encircling lines (85%), between the left atrial appendage (LAA) and the LSPV (70%) and lines at the posterior wall (71%). There was a nonsignificant increase in AFCL, with a more widespread distribution of organized electrograms (32.4% vs 46.6%).
Conclusion: Recurrence after CPVA is associated with a reverse process of voltage and conduction velocity increase across ablated areas, especially the PV-LA junction, and is related to the presence of conduction gaps, which are distributed mostly at the septal aspect of the lines encircling the right PVs and at the LAA-LSPV area. Organization of atrial electrograms seen during AF ablation is maintained at a repeat procedure.     

The efficacy of inducibility and circumferential ablation with pulmonary vein isolation in patients with paroxysmal atrial fibrillation

Introduction: Some conflicting results of the efficacy of the inducibility test used in the catheter ablation of atrial fibrillation (AF) have been reported. The aim of this study was to investigate the inducibility and efficacy of circumferential ablation with pulmonary vein isolation (PVI) in patients with paroxysmal AF and its relationship to the atrial substrate.
Methods and Results: This study consisted of 88 patients with paroxysmal AF who underwent catheter ablation. Electroanatomic mapping using a NavX system was performed and the biatrial voltage was obtained during sinus rhythm. After successful circumferential ablation with PVI, an inducibility test was performed to determine the requirement for creating left atrial (LA) ablation line. After procedure, patients with inducible AF had a higher recurrence rate than did those with noninducibility of AF (55% vs 18%, P = 0.02). The patients with inducible AF after the PVI had a lower biatrial voltage than did those with negative inducibility. The patients with inducible AF after the final procedure who had a recurrence had a lower LA voltage (1.3 ± 0.4 vs 1.8 ± 0.4 mV, P = 0.02) and longer LA total activation time (99 ± 18 vs 88 ± 13 msec, P = 0.02) than did those with noninducible AF and no recurrence. None of the patients had occurrence of LA flutter during the follow-up.
Conclusion: After a single procedure of circumferential ablation with PVI and noninducibility, 82% patients did not have recurrence of AF. The inducibility of AF was related to the recurrence of AF. The atrial substrate affected the outcome of the inducibility.