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Objectives This study hypothesized that left atrial structural remodeling (LA-TR) correlates with exercise capacity (EC) in a cohort of patients with atrial fibrillation (AF). Background Late gadolinium-enhanced cardiac magnetic resonance (LGE-CMR) imaging provides a method of assessing LA-TR in patients with AF. Methods A total of 145 patients (32% female, mean age 63.4 ± 11.6 years of age) with AF (66 paroxysmal, 71 persistent, 8 long-standing persistent) presenting for catheter ablation were included in the study. All patients underwent LGE-CMR imaging as well as maximal exercise test using the Bruce protocol prior to catheter ablation of AF. EC was quantified by minutes of exercise and metabolic equivalent (MET) level achieved. LA-TR was quantified from LGE-CMR imaging and classified according to the Utah classification of LA structural remodeling (Utah stage I: 30%). AF recurrence was assessed at 1 year from the date of ablation. Results The average duration of exercise was 8 ± 3 min, and the mean MET achieved was 9.7 ± 3.2. METs achieved were inversely correlated with LA-TR (R 2 = 0.061; p = 0.003). The duration of exercise was also inversely correlated with LA-TR (R 2 = 0.071; p = 0.001). Both EC and LA-TR were associated with AF recurrence post ablation in univariate analysis, but only LA-TR and age were independently predictive of recurrence in multivariate analysis (p = 0.001). For every additional minute on the treadmill, subjects were 13% more likely to be free of AF 1 year post ablation (p = 0.047). Conclusions EC is inversely associated with LA-TR in patients with AF and is predictive of freedom from AF post-ablation.

Current late gadolinium enhancement (LGE) imaging of left atrial (LA) scar or fibrosis is relatively slow and requires 5-15min to acquire an undersampled (R=1.7) 3D navigated dataset. The GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) based parallel imaging method is the current clinical standard for accelerating 3D LGE imaging of the LA and permits an acceleration factor ~R=1.7. Two compressed sensing (CS) methods have been developed to achieve higher acceleration factors: a patch based collaborative filtering technique tested with acceleration factor R~3, and a technique that uses a 3D radial stack-of-stars acquisition pattern (R~1.8) with a 3D total variation constraint. The long reconstruction time of these CS methods makes them unwieldy to use, especially the patch based collaborative filtering technique. In addition, the effect of CS techniques on the quantification of percentage of scar/fibrosis is not known. We sought to develop a practical compressed sensing method for imaging the LA at high acceleration factors. In order to develop a clinically viable method with short reconstruction time, a Split Bregman (SB) reconstruction method with 3D total variation (TV) constraints was developed and implemented. The method was tested on 8 atrial fibrillation patients (4 pre-ablation and 4 post-ablation datasets). Blur metric, normalized mean squared error and peak signal to noise ratio were used as metrics to analyze the quality of the reconstructed images, Quantification of the extent of LGE was performed on the undersampled images and compared with the fully sampled images. Quantification of scar from post-ablation datasets and quantification of fibrosis from pre-ablation datasets showed that acceleration factors up to R~3.5 gave good 3D LGE images of the LA wall, using a 3D TV constraint and constrained SB methods. This corresponds to reducing the scan time by half, compared to currently used GRAPPA methods. Reconstruction of 3D LGE images using the SB method was over 20 times faster than standard gradient descent methods.

MRI Assessment of Ablation-Induced Scarring in Atrial FibrillationBackground There is limited knowledge on the extent and location of scarring that results from catheter ablation and its role in suppressing atrial fibrillation (AF). We examined the effect of atrial fibrosis and ablation-induced scarring on catheter ablation outcomes in AF. Methods We conducted a prospective multicenter study that enrolled 329 AF patients presenting for catheter ablation. Delayed enhancement magnetic resonance imaging (DE-MRI) of the left atrium was obtained preablation. Scarring was evaluated in 177 patients with a DE-MRI scan obtained 90 days postablation. We evaluated residual fibrosis, defined as preablation atrial fibrosis not covered by ablation scar. The primary outcome was freedom from recurrent atrial arrhythmia. Results In the analysis cohort of 177 patients, preablation fibrosis was 18.7 ± 8.7% of the atrial wall. Ablation aimed at pulmonary vein (PV) isolation was performed in 163 patients (92.1%). Ablation-induced scar averaged 10.6 ± 4.4% of the atrial wall. Scarring completely encircled all 4 PVs only in 12 patients (7.3%). Residual fibrosis was calculated at 15.8 ± 8.0%. At 325 days follow-up, 35% of patients experienced recurrent arrhythmia. Multivariable Cox proportional hazards models demonstrated that baseline atrial fibrosis (HR and 95% CIs) (1.09 [1.06–1.12], P < 0.001) and residual fibrosis (1.09 [1.05–1.13], P < 0.001) were associated with atrial arrhythmia recurrence, while PV encirclement and overall scar were not. Conclusions Catheter ablation of AF targeting PVs rarely achieves permanent encircling scar in the intended areas. Overall atrial fibrosis present at baseline and residual fibrosis uncovered by ablation scar are associated with recurrent arrhythmia.

Objectives Outcomes of catheter ablation of atrial fibrillation (AF) vary widely. We used late-gadolinium enhancement MRI (LGE-MRI) to examine the relationship of ablation-induced scarring in the pulmonary vein (PV) region and overall atrium to evaluate the role of PV encirclement and substrate modification in predicting outcome of catheter ablation in AF. Methods and Results LGE-MRI was performed to quantify baseline atrial fibrosis, which was classified into four stages (stage I with fibrosis 30%). Patients then underwent ablation and repeat LGE-MRI at three months to assess for ablation-induced scarring. PVs were studied to evaluate for complete encirclement with scar. Image processing was used to overlay the scar onto baseline fibrosis to assess the overlap and calculate residual fibrosis. A total of 172 patients were included with an average baseline fibrosis of 14.6 ± 8.4%. The average number of PVs encircled with scar at three months was 1.2 ± 1.3 with only 9% of patients having all four PVs completely encircled. The average residual fibrosis was 11.9 ± 7.3%. High residual fibrosis was defined as >10%. Recurrent AF was found in 60 patients (34.9%) over a follow-up of 346 ± 82 days. Baseline and high residual fibrosis were significant predictors of recurrence (hazard ratio [HR] of 2.2; P < 0.01 and HR of 3.2; P < 0.01, respectively). The number of PV encircled was not a significant predictor of recurrence. Conclusion LGE-MRI of ablation-induced scarring demonstrates that chronic PV encirclement is rarely achieved. Procedural outcomes are better predicted by baseline atrial fibrosis and ablation-induced substrate modification.

AF Ablation and eGFR Introduction Chronic kidney disease (CKD) and atrial fibrillation (AF) often coexist. We studied the association of CKD with atrial fibrosis and the effect of AF ablation on kidney function. Methods AF patients who had a pre- and postablation serum creatinine and who completed a late gadolinium enhancement cardiac magnetic resonance imaging (MRI; LGE-MRI) prior to ablation were included. Estimated glomerular filtration rate (eGFR) was calculated and CKD was staged using the National Kidney Foundation guidelines. Patients with eGFR

LV Systolic Dysfunction is Related to LA-SRM in AF Patients Background Catheter ablation significantly improves the left ventricular (LV) function in patients with atrial fibrillation (AF) and LV systolic dysfunction. In this study, we compared the degree of left atrial structural remodeling (LA-SRM) in patients with normal versus reduced LV ejection fraction (LVEF). We also studied the impact of LA-SRM on LVEF improvement in patients undergoing ablation of AF. Method and Results We categorized 384 patients into 2 groups based on their cardiac function: reduced LVEF group (LVEF ≤50%; n = 105) and normal LVEF group (LVEF > 50%; n = 279). LVEF was determined prior and mean 8 ± 3 months after catheter ablation for AF. Percentage of LA-SRM was quantified using LGE-MRI and patients were classified into 4 groups based on the amount of structural remodeling in their LA wall: minimal ≤ 5%, mild = 5–20%, moderate = 20–35%, and extensive ≥ 35%. The average preablation LA-SRM (21.5 ± 13.2% vs 15.4 ± 10.0%; P < 0.001) was significantly higher in reduced LVEF group than normal LVEF group. Among the 105 patients with reduced LVEF, while there was a modest 11.7 ± 8.4% average increase in LVEF following ablation, the greatest increase was seen in patients with less extensive LA-SRM (minimal = 19.3 ± 5.1%, n = 3, P = 0.02 and mild = 16.6 ± 9.9%, n = 48, P < 0.001). Patients with moderate and extensive fibrosis had an average EF improvement of 8.7 ± 11.1% and 2.8 ± 6.4%, respectively (n = 39, P

Background: Magnetic resonance imaging (MRI) can visualize locations of both the ablation scar on the left atrium (LA) after atrial fibrillation (AF) ablation and epicardial fat pads (FPs) containing ganglionated plexi (GP). Methods: We investigated 60 patients who underwent pulmonary vein antrum (PVA) isolation along with LA posterior wall and septal debulking for AF. FPs around the LA surface in well-known GP areas (whichwereconsidered asthesubstitutionofGPareasaroundtheLA)weresegmentedfromthedark-blood MRI. Then the FP and the ablation scar image visualized by late gadolinium enhancement (LGE)-MRI on the LA were merged together. Overlapping areas of FP and the ablation scar image were considered as the ablated FP areas containing GP. Patients underwent 24-hour Holter monitoring after ablation for the analysis of heart rate variability. Results: Ablated FP area was significantly wider in patients without AF recurrence than those in patients with recurrence (5.6 ± 3.1 cm 2 vs 4.2 ± 2.7 cm 2 ,P = 0.03). The mean values of both percentage of differences greater than 50 ms in the RR intervals (pRR > 50) and standard deviation of RR intervals over the entire analyzed period (SDNN), which were obtained from 24-hour Holter monitoring 1-day post-AF ablation, were significantly lower in patients without recurrence than those in patients with recurrence (5.8 ± 6.0% vs 14.0 ± 10.1%; P = 0.0005, 78.7 ± 32.4 ms vs 109.2 ± 43.5 ms; P = 0.005). There was a significant negative correlation between SDNN and the percentage of ablated FP area (Y =− 1.3168X + 118.96, R 2 = 0.1576, P = 0.003). Conclusion: Extensively ablating LA covering GP areas along with PVA isolation enhanced the denervation of autonomic nerve system and seemed to improve procedural outcome in patients with AF. (PACE 2013; 00:1‐10)

The aim of this study was to assess acute ablation injuries seen on late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) immediately post-ablation (IPA) and the association with permanent scar 3 months post-ablation (3moPA).Success rates for atrial fibrillation catheter ablation vary significantly, in part because of limited information about the location, extent, and permanence of ablation injury at the time of procedure. Although the amount of scar on LGE MRI months after ablation correlates with procedure outcomes, early imaging predictors of scar remain elusive.Thirty-seven patients presenting for atrial fibrillation ablation underwent high-resolution MRI with a 3-dimensional LGE sequence before ablation, IPA, and 3moPA using a 3-T scanner. The acute left atrial wall injuries on IPA scans were categorized as hyperenhancing (HE) or nonenhancing (NE) and compared with scar 3moPA.Heterogeneous injuries with HE and NE regions were identified in all patients. Dark NE regions in the left atrial wall on LGE MRI demonstrate findings similar to the "no-reflow" phenomenon. Although the left atrial wall showed similar amounts of HE, NE, and normal tissue IPA (37.7 ± 13%, 34.3 ± 14%, and 28.0 ± 11%, respectively; p = NS), registration of IPA injuries with 3moPA scarring demonstrated that 59.0 ± 19% of scar resulted from NE tissue, 30.6 ± 15% from HE tissue, and 10.4 ± 5% from tissue identified as normal. Paired t-test comparisons were all statistically significant among NE, HE, and normal tissue types (p0.001). Arrhythmia recurrence at 1-year follow-up correlated with the degree of wall enhancement 3moPA (p = 0.02).Radiofrequency ablation results in heterogeneous injury on LGE MRI with both HE and NE wall lesions. The NE lesions demonstrate no-reflow characteristics and reveal a better predictor of final scar at 3 months. Scar correlates with procedure outcomes, further highlighting the importance of early scar prediction.

BACKGROUND Lone atrial fibrillation (AF) is thought to be a benign type or an early stage of the disease. OBJECTIVE This study sought to compare the left atrium (LA) substrate using delayed-enhanced magnetic resonance imaging (DE-MRI) in patients with lone AF versus those with comorbidities. METHODS Forty of 333 included patients met criteria for lone AF. All patients underwent DE-MRI to quantify atrial fibrosis as a marker for structural remodeling (SRM) and underwent catheter ablation. Based on the degree of SRM, patients were staged into 4 groups: Utah I (5% LA wall enhancement), Utah II (5% to 20%), Utah III (20% to 35%), or Utah IV (35%). RESULTS Distribution in Utah I to IV was comparable in patients with lone AF and non‐lone AF. In both groups, a number of patients showed extensive SRM. Mean enhancement (14.08 8.94 vs. 16.94 11.37) was not significantly different between the 2 groups (P .0721). In the lone AF group, catheter ablation was successful in suppressing AF in all of Utah I, 81.82% of Utah II, 62.5% of Utah III, and none of Utah IV patients. Similar results were achieved in the non‐lone AF group. Outcome after ablation was significantly dependent on the SRM of the LA (P .001). CONCLUSION The degree of LA structural remodeling as detected using DE-MRI is independent of AF type and associated comorbidities. Selecting appropriate treatment candidates based on the quality and quantity of atrial fibrosis using DE-MRI would improve procedural outcome and avoid unnecessary intervention.

Background— Esophageal wall thermal injury after atrial fibrillation ablation is a potentially serious complication. However, no noninvasive modality has been used to describe and screen patients to examine whether esophageal wall injury has occurred. We describe a noninvasive method of using delayed-enhancement MRI to detect esophageal wall injury and subsequent recovery after atrial fibrillation ablation. Methods and Results— We analyzed the delayed-enhancement MRI scans of 41 patients before ablation and at 24 hours and 3 months after ablation to determine whether there was evidence of contrast enhancement in the esophagus after atrial fibrillation ablation. In patients with contrast enhancement, 3D segmentation of the esophagus was performed using a novel image processing method. Upper gastrointestinal endoscopy was then performed. Repeat delayed-enhancement MRI and upper gastrointestinal endoscopy was performed 1 week later to track changes in lesions. The wall thickness of the anterior and posterior wall of the esophagus was measured at 3 time points: before ablation, 24 hours after ablation, and 3 months after ablation. Evaluation of preablation MRI scans demonstrated no cases of esophageal enhancement. At 24 hours, 5 patients showed contrast enhancement. Three of these patients underwent upper gastrointestinal endoscopy, which demonstrated esophageal lesions. Repeat upper gastrointestinal endoscopy and MRI 1 week later demonstrated resolution of the lesions. All 5 patients had confirmed resolution of enhancement at 3 months. All patients with esophageal tissue enhancement demonstrated left atrial wall enhancement directly adjacent to the regions of anterior wall esophageal enhancement. Conclusions— Our preliminary results indicate delayed-enhancement MRI can assess the extent and follow progression of esophageal wall injury after catheter ablation of atrial fibrillation. It appears that acute esophageal injury recovers within 1 week of the procedure.

Background— Atrial fibrillation (AF) is associated with diffuse left atrial fibrosis and a reduction in endocardial voltage. These changes are indicators of AF severity and appear to be predictors of treatment outcome. In this study, we report the utility of delayed-enhancement magnetic resonance imaging (DE-MRI) in detecting abnormal atrial tissue before radiofrequency ablation and in predicting procedural outcome. Methods and Results— Eighty-one patients presenting for pulmonary vein antrum isolation for treatment of AF underwent 3-dimensional DE-MRI of the left atrium before the ablation. Six healthy volunteers also were scanned. DE-MRI images were manually segmented to isolate the left atrium, and custom software was implemented to quantify the spatial extent of delayed enhancement, which was then compared with the regions of low voltage from electroanatomic maps from the pulmonary vein antrum isolation procedure. Patients were assessed for AF recurrence at least 6 months after pulmonary vein antrum isolation, with an average follow-up of 9.6±3.7 months (range, 6 to 19 months). On the basis of the extent of preablation enhancement, 43 patients were classified as having minimal enhancement (average enhancement, 8.0±4.2%), 30 as having moderate enhancement (21.3±5.8%), and 8 as having extensive enhancement (50.1±15.4%). The rate of AF recurrence was 6 patients (14.0%) with minimal enhancement, 13 (43.3%) with moderate enhancement, and 6 (75%) with extensive enhancement ( P Conclusions— DE-MRI provides a noninvasive means of assessing left atrial myocardial tissue in patients suffering from AF and might provide insight into the progress of the disease. Preablation DE-MRI holds promise for predicting responders to AF ablation and may provide a metric of overall disease progression.

IMPORTANCE: Left atrial fibrosis is prominent in patients with atrial fibrillation (AF). Extensive atrial tissue fibrosis identified by delayed enhancement magnetic resonance imaging (MRI) has been associated with poor outcomes of AF catheter ablation. OBJECTIVE: To characterize the feasibility of atrial tissue fibrosis estimation by delayed enhancement MRI and its association with subsequent AF ablation outcome. DESIGN, SETTING, AND PARTICIPANTS: Multicenter, prospective, observational cohort study of patients diagnosed with paroxysmal and persistent AF (undergoing their first catheter ablation) conducted between August 2010 and August 2011 at 15 centers in the United States, Europe, and Australia. Delayed enhancement MRI images were obtained up to 30 days before ablation. MAIN OUTCOMES AND MEASURES: Fibrosis quantification was performed at a core laboratory blinded to the participating center, ablation approach, and procedure outcome. Fibrosis blinded to the treating physicians was categorized as stage 1 (

Background High-resolution late gadolinium enhancement (LGE) MRI is used to assess fibrosis of the left atrium (LA) and visualize post-ablation scar in patients with atrial fibrillation (AF). Only few centers with advanced expertise in cardiac MR (CMR) have shown successful and good quality LGE-MRI of the LA. In this work, we assess the dependence of image quality of LGE images on the number of patients imaged in the centers participating in the multi-center trial DECAAF (Delayed Enhancement - MRI determinant of successful Catheter Ablation of Atrial Fibrillation). Also, main causes of poor image quality were determined. Methods Fifteen centers with different degrees of CMR expertise and typical MRI hardware participated in DECAAF.

Background— Although catheter ablation therapy for atrial fibrillation (AF) is becoming more common, results vary widely, and patient selection criteria remain poorly defined. We hypothesized that late gadolinium enhancement MRI (LGE-MRI) can identify left atrial (LA) wall structural remodeling (SRM) and stratify patients who are likely or not to benefit from ablation therapy. Methods and Results— LGE-MRI was performed on 426 consecutive patients with AF without contraindications to MRI before undergoing their first ablation procedure and on 21 non-AF control subjects. Patients were categorized by SRM stage (I–IV) based on the percentage of LA wall enhancement for correlation with procedure outcomes. Histological validation of SRM was performed comparing LGE-MRI with surgical biopsy. A total of 386 patients (91%) with adequate LGE-MRI scans were included in the study. After ablation, 123 patients (31.9%) experienced recurrent atrial arrhythmias during the 1-year follow-up. Recurrent arrhythmias (failed ablations) occurred at higher SRM stages with 28 of 133 (21.0%) in stage I, 40 of 140 (29.3%) in stage II, 24 of 71 (33.8%) in stage III, and 30 of 42 (71.4%) in stage IV. In multivariate analysis, ablation outcome was best predicted by advanced SRM stage (hazard ratio, 4.89; P P =0.036), whereas increased LA volume and persistent AF were not significant predictors. LA wall enhancement was significantly greater in patients with AF versus non-AF controls (16.6±11.2% versus 3.1±1.9%; P Conclusions— Atrial SRM is identified on LGE-MRI, and extensive LGE (≥30% LA wall enhancement) predicts poor response to catheter ablation therapy for AF.

Results 37 patients (26 males, mean age = 63±10.12 years) were included in this study. Six patients underwent an ablation using PVAC catheter, SRF catheter was used in 14 patients, and 17 patients underwent a cryoballoon ablation. Pre-ablation LATR was comparable in all three cohorts (Figure 1). Extent of scar tissue was higher in Cryo and SRF patients compared to PVAC patients (Figure1). Overall six patients were found to have AF recurrence at 3-months follow-up. Patients with recurrence had a significantly lower amount of ablation lesions than patients in sinus rhythm (5.93% vs. 15.98%; P=0,004; Figure 2). 3-dimensional visualization allows comparison of induced lesions by different ablation catheters (Figure 3). Conclusions From our preliminary results, PVAC ablation appears to result in lesser scar formation as compared to Cryo and SRF ablation. The greater recurrence in patients with low scar post-ablation suggests the need to implement an adequate ablation strategy that results in greater scar to maximize successful outcomes. DE-MRI is an appropriate method to compare lesion formation induced by different ablations strategies.

Catheter ablation significantly improves the left ventricular (LV) function in patients with atrial fibrillation (AF) and LV systolic dysfunction. In this study, we compared the degree of left atrial structural remodeling (LA-SRM) in patients with normal versus reduced LV ejection fraction (LVEF). We also studied the impact of LA-SRM on LVEF improvement in patients undergoing ablation of AF.We categorized 384 patients into 2 groups based on their cardiac function: reduced LVEF group (LVEF ≤50%; n = 105) and normal LVEF group (LVEF50%; n = 279). LVEF was determined prior and mean 8 ± 3 months after catheter ablation for AF. Percentage of LA-SRM was quantified using LGE-MRI and patients were classified into 4 groups based on the amount of structural remodeling in their LA wall: minimal ≤ 5%, mild = 5-20%, moderate = 20-35%, and extensive ≥ 35%. The average preablation LA-SRM (21.5 ± 13.2% vs 15.4 ± 10.0%; P 0.001) was significantly higher in reduced LVEF group than normal LVEF group. Among the 105 patients with reduced LVEF, while there was a modest 11.7 ± 8.4% average increase in LVEF following ablation, the greatest increase was seen in patients with less extensive LA-SRM (minimal = 19.3 ± 5.1%, n = 3, P = 0.02 and mild = 16.6 ± 9.9%, n = 48, P 0.001). Patients with moderate and extensive fibrosis had an average EF improvement of 8.7 ± 11.1% and 2.8 ± 6.4%, respectively (n = 39, P 0.001 and n = 15, P = 0.11, respectively).Patients with LV systolic dysfunction displayed a comparatively greater LA-SRM than patients with normal LVEF. Patients with lesser LA-SRM experienced a greater improvement in LVEF after catheter ablation for AF.

Asrac Caegor 21. Imagig MRIreseaio umer 1089-167Auhors Mehmet Akkaya, Koji Higuchi, Nazem Akoum, Nathan Burgon, Kavitha Damal, Derek Chang, Eugene Kholmovski, Nassir Marrouche, University of Utah Hospital, Salt Lake City, UT, USA, CARMA Center, Salt Lake City, UT, USABackground: We correlae he relaioshi ewee lef vericular herroh (LVH) a lef arial irosis re-alaio a evaluae he imac of irosis o arial irillaio (AF) recurrece os-alaio i aies wih LVH.Method: From he AF aaase, 467 aies who uerwe a LGE-MRI a resee for caheer alaio were ieiie a iclue io he su. All aies were followe u for a oe-ear erio. Base o he egree of LA irosis eie as erceage of LA wall ehaceme o LGE-MRI, aies were sraiie io he four ah sages (ah 1= 35%). aies wih a iervericular seum hicess (IST) of >12mm were classiie io LVH (=127) grou a IST < 12 mm as o-LVH grou (=340).Results: The mea LA irosis was sigiical higher i aies wih LVH (18.8 ± 12.87%) ha i o-LVH aies (15.61 ± 9.84%; = 0.04). aies wih LVH geerall ha exesive LA irosis (ah sages 3 a 4; 37.8% of aies) ha o-LVH aies (25.3% of aies; = 0.01). Cox-regressio aalsis showe ha aies wih LVH also ha sigiical higher AF recurrece raes ha o-LVH aies (41.09% vs. 28.51%; < 0.05) urig he oe-ear follow-u erio os-alaio.Conclusion: aies wih LVH ee o have sigiical more lef arial srucural remoelig a greaer roesi o have recurre AF eisoes os caheer-alaio for AF whe comare o aies wih o-LVH

Radiofrequency ablation is a promising procedure for treating atrial fibrillation (AF) that relies on accurate lesion delivery in the left atrial (LA) wall for success. Late Gadolinium Enhancement MRI (LGE MRI) at three months post-ablation has proven effective for noninvasive assessment of the location and extent of scar formation, which are important factors for predicting patient outcome and planning of redo ablation procedures. We have developed an algorithm for automatic classification in LGE MRI of scar tissue in the LA wall and have evaluated accuracy and consistency compared to manual scar classifications by expert observers. Our approach clusters voxels based on normalized intensity and was chosen through a systematic comparison of the performance of multivariate clustering on many combinations of image texture. Algorithm performance was determined by overlap with ground truth, using multiple overlap measures, and the accuracy of the estimation of the total amount of scar in the LA. Ground truth was determined using the STAPLE algorithm, which produces a probabilistic estimate of the true scar classification from multiple expert manual segmentations. Evaluation of the ground truth data set was based on both inter- and intra-observer agreement, with variation among expert classifiers indicating the difficulty of scar classification for a given a dataset. Our proposed automatic scar classification algorithm performs well for both scar localization and estimation of scar volume: for ground truth datasets considered easy, variability from the ground truth was low; for those considered difficult, variability from ground truth was on par with the variability across experts.

Summary Identification of early post-atrial ablation MRI characteristics can help predict the development of significant chronic pulmonary stenosis. Background Pulmonary vein stenosis (PVS) is a rare complication of atrial fibrillation (AF) ablation with a rate of significant stenosis, defined as >50%, of 1.3% in a recent multicenter study. As significant morbidity is associated with PVS, detection and surveillance with non-invasive imaging is routine. In this study, we hypothesized that prediction of PVS can be determined with early MRI to identify patients at risk for this complication. Methods A single-center, retrospective, 1:1 cohort to control matched study including patients with (23) and without (23) significant PVS 3 months post-ablation (3moPA) was performed. Study groups were selected from 925 patients who underwent AF ablation and serial MRI scanning. Inclusion criteria for both groups required a full set of three MRI scans: pre-ablation (pre), 24 hours post-ablation (24hrPA), and 3moPA. MRI scanning was performed on a 1.5T or 3T Siemens magnet. Of the 925 patients, 28 were found with significant stenosis on MRA 3moPA. The final PVS study cohort included 23/ 28 patients as 5 were excluded secondary to incomplete MRI scan sets. The control group was comprised of 23 age and sex-matched patients without significant stenosis 3moPA. PV cross-sectional areas were measured at the ostial/proximal portion of the vessels by 3D MRA (Figure 1). In patients with multiple stenotic PV’s, the most stenotic vein was selected for analysis. Results Out of 925 patients, we found 3% (28/925) incidence of significant PVS 3moPA. Of the 23/28 patients in the PVS study cohort, early PV narrowings of >20% on the 24hrPA scan were found in all (23/23, 100%) compared with significantly fewer in the control group (9/23, 39%) (p 20%) on the 24hrPA MRI scan. In addition, small PV caliber on baseline imaging appears to predispose to PVS with the LIPV involved disproportionately. Overall, MRI image characteristics are useful for predicting PVS and may help determine which patients will benefit from surveillance imaging.

ObjectivesThis study tried to determine the association between left atrial (LA) fibrosis, detected using delayed-enhanced magnetic resonance imaging (DE-MRI), and the CHADS2 score (point system based on individual clinical risk factors including congestive heart failure, hypertension, age, diabetes, and prior stroke) variables, specifically stroke.BackgroundIn patients with atrial fibrillation (AF), conventional markers for the risk of stroke base their higher predictive effect on clinical features, particularly previous stroke history, and not individual LA pathophysiological properties. We aimed to determine the association between LA fibrosis, detected using DE-MRI, and the CHADS2 score variables, specifically stroke.MethodsPatients with AF who presented to the AF clinic and received a DE-MRI of the LA were evaluated. Their risk factor profiles, including a CHADS2 score, were catalogued. The degree of LA fibrosis was determined as a percentage of the LA area. Any history of previous strokes, warfarin use, or cerebrovascular disease was recorded.ResultsA total of 387 patients, having a mean age of 65 ± 12 years, 36.8% female, were included in this study. A history of previous stroke was present in 36 (9.3%) patients. Those patients with previous strokes had a significantly higher percentage of LA fibrosis (24.4 ± 12.4% vs. 16.2 ± 9.9%, p < 0.01). A larger amount of LA fibrosis was also seen in those patients with a higher CHADS2 score (≥2: 18.7 ± 11.4 vs.

Purpose: To develop and test a hybrid radial (stack of stars) acquisition and compressed sensing reconstruction for efficient late gadolinium enhancement (LGE) imaging of the left atrium. Materials and Methods: Two hybrid radial acquisition schemes, kx-ky-first and kz-first, are tested using the signal equation for an inversion recovery sequence with simulated data. Undersampled data reconstructions are then performed using a compressed sensing approach with a three-dimensional total variation constraint. The data acquisition and reconstruction framework is tested on five atrial fibrillation patients after treatment by radio-frequency ablation. The hybrid radial data are acquired with free breathing without respiratory navigation. Results: The kz-first radial acquisition gave improved image quality as compared to a kx-ky-first scheme. Compressed sensing reconstructions improved the overall quality of undersampled radial LGE images. An image quality metric that takes into account the signal, noise, artifact, and blur for the radial images was 35% (±17%) higher than the corresponding Cartesian acquisitions. Total acquisition time for 36 slices with 1.25 × 1.25 × 2.5 mm3 resolution was under 3 min for the proposed scheme. Conclusion: Hybrid radial LGE imaging of the LA with compressed sensing is a promising approach for obtaining images efficiently and offers more robust image quality than Cartesian acquisitions that were acquired without a respiratory navigator signal. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

Background— We evaluated scar lesions after initial and repeat catheter ablation of atrial fibrillation (AF) and correlated these regions to low-voltage tissue on repeat electroanatomic mapping. We also identified gaps in lesion sets that could be targeted and closed during repeat procedures. Methods and Results— One hundred forty-four patients underwent AF ablation and received a delayed-enhancement MRI at 3 months after ablation. The number of pulmonary veins (PV) with circumferential lesions were assessed and correlated with procedural outcome. Eighteen patients with AF recurrence underwent repeat ablation. MRI scar regions were compared with electroanatomic maps during the repeat procedure. Regions of incomplete scar around the PVs were then identified and targeted during repeat ablation to ensure complete circumferential lesions. After the initial procedure, complete circumferential scarring of all 4 PV antrum (PVA) was achieved in only 7% of patients, with the majority of patients (69%) having P =0.004) and percent PVA scar of 66.2±25.4 ( P =0.01) compared with patients with AF recurrence who had an average total LA wall scar 11.3%±8.1 and PVA percent scar 50.0±24.7. In patients who underwent repeat ablation, the PVA scar percentage was 56.1%±21.4 after the first procedure compared with 77.2%±19.5 after the second procedure. The average total LA scar after the first ablation was 11.0%±4.1, whereas the average total LA scar after second ablation was 21.2%±7.4. All patients had an increased number of completely scarred pulmonary vein antra after the second procedure. MRI scar after the first procedure and low-voltage regions on electroanatomic mapping obtained during repeat ablation demonstrated a positive quantitative correlation of R 2 =0.57. Conclusions— Complete circumferential PV scarring difficult to achieve but is associated with better clinical outcome. Delayed-enhancement MRI can accurately define scar lesions after AF ablation and can be used to target breaks in lesion sets during repeat ablation.

Atrial fibrosis is a hallmark of atrial structural remodeling (SRM) and leads to structural and functional impairment of left atrial (LA) and persistence of atrial fibrillation (AF). This study was conducted to assess LA reverse remodeling after catheter ablation of AF in mild and moderate-severe LA SRM.Catheter ablation was performed in 68 patients (age 62 ± 14 years, 68% males) with paroxysmal (n = 26) and persistent (n = 42) AF. The patients were divided into group 1 with mild LA SRM (10%, n = 31) and group 2 with moderate-severe LA SRM (10%, n = 37) by delayed enhancement magnetic resonance imaging (DEMRI). Two-dimensional echocardiography, LA strain, and strain rate during left ventricular systole by velocity vector imaging were performed pre and at 6 ± 3 months postablation. The long-term outcome was monitored for 12 months.Patients in group 1 were younger (57 ± 15 vs 66 ± 13 years, P = .009) with a male predominance (80% vs 57%, P.05) as compared to group 2. Postablation, group 1 had significant increase in average LA strain (Δ↑: 14% vs 4%, P.05) and strain rate (Δ↑: 0.5 vs 0.1 cm/s, P.05) as compared to group 2. There was a trend toward more patients with persistent AF in group 2 (68% vs 55%, P = .2), but it was not statistically significant. Group 2 had more AF recurrences (41% vs 16%, P = .02) at 12 months after ablation.Mild preablation LA SRM by DEMRI predicts favorable LA structural and functional reverse remodeling and long-term success after catheter ablation of AF, irrespective of the paroxysmal or persistent nature of AF.

Methods: 174 patients with AF were included in the original analysis. 25 of these patients met criteria for Lone AF as deined by absence of structural heart disease based on history, physical examination and imaging tests including chest x-ray and echocardiography, with no history of coronary artery disease, diabetes, hypertension, and hyperthyroidism. Patients underwent DE-MRI and placed in 1 of 3 categories; Stage 1 structural remodeling (SRM) ( 35%).

Background— Atrial fibrillation (AF) is a progressive condition that begins with hemodynamic and/or structural changes in the left atrium (LA) and evolves through paroxysmal and persistent stages. Because of limitations with current noninvasive imaging techniques, the relationship between LA structure and function is not well understood. Methods and Results— Sixty-five patients (age, 61.2�14.2 years; 67% men) with paroxysmal (44%) or persistent (56%) AF underwent 3D delayed-enhancement MRI. Segmentation of the LA wall was performed and degree of enhancement (fibrosis) was determined using a semiautomated quantification algorithm. Two-dimensional echocardiography and longitudinal LA strain and strain rate during ventricular systole with velocity vector imaging were obtained. Mean fibrosis was 17.8�14.5%. Log-transformed fibrosis values correlated inversely with LA midlateral strain ( r =−0.5, P =0.003) and strain rate ( r =−0.4, P P =0.04) and lower midseptal (27�14% versus 38�16%, P =0.01) and midlateral (35�16% versus 45�14% P =0.03) strains. Multivariable stepwise regression showed that midlateral strain ( r =−0.5, P =0.006) and strain rate ( r =−0.4, P =0.01) inversely predicted the extent of fibrosis independent of other echocardiographic parameters and the rhythm during imaging. Conclusions— LA wall fibrosis by delayed-enhancement MRI is inversely related to LA strain and strain rate, and these are related to the AF burden. Echocardiographic assessment of LA structural and functional remodeling is quick and feasible and may be helpful in predicting outcomes in AF.

LA Debulking for Atrial Fibrillation.Introduction: Though pulmonary vein (PV) isolation has been widely adopted for treatment of atrial fibrillation (AF), recurrence rates remain unacceptably high with persistent and longstanding AF. As evidence emerges for non-PV substrate changes in the pathogenesis of AF, more extensive ablation strategies need further study. Methods: We modified our PV antrum isolation procedure to include abatement of posterior and septal wall potentials. We also employed recently described image-processing techniques using delayed-enhancement (DE) MRI to characterize tissue injury patterns 3 months after ablation, to assess whether each PV was encircled with scar, and to assess the impact of these parameters on procedural success. Results: 118 consecutive patients underwent debulking procedure and completed follow-up, of which 86 underwent DE-MRI. The total left atrial (LA) radiofrequency delivery correlated with percent LA scarring by DE-MRI (r = 0.6, P < 0.001). Based on DE patterns, complete encirclement was seen in only 131 of 335 PVs (39.1%). As expected, Cox regression analysis showed a significant relationship between the number of veins encircled by delayed enhancement and clinical success (hazard ratio of 0.62, P = 0.015). Also, progressive quartile increases in postablation posterior and septal wall scarring reduced recurrences rates with a HR of 0.65, P = 0.022 and 0.66, P = 0.026, respectively. Conclusion: Pathologic remodeling in the septal and posterior walls of the LA helps form the pathogenic substrate for AF, and these early results suggest that more aggressive treatment of these regions appears to correlate with improved ablation outcomes. Noninvasive imaging to characterize tissue changes after ablation may prove essential to stratifying recurrence risk. (J Cardiovasc Electrophysiol, Vol. 21, pp. 126-132, February 2010)

Background. The extent of left atrial (LA) wall fibrosis detected by delayed enhancement MRI (DE-MRI) appears to be correlated with advanced atrial fibrillation (AF). However, the effect of LA fibrosis on left ventricular function (LVEF) is not well understood. We report the relationship between left atrial fibrosis and LVEF in patients with AF. Methods. Sixty-seven patients underwent DE-MRI and 2-dimensional trans-thoracic echocardiography prior to ablation for AF. Three dimensional segmentation of the LA was performed and the extent of fibrosis was quantified using a semi-automated algorithm. Patients were assigned to one of three groups based on the degree of LA fibrosis; 1) mild enhancement where the fibrosis < 15% of the LA wall, 2) moderate enhancement where fibrosis > 15% and < 35%, and extensive where fibrosis > 35% of the LA wall. LVEF was determined both prior to and 3 months following pulmonary vein antrum isolation with posterior wall and septal debulking. Results. The average pre-ablation LVEF among patients with mild fibrosis was 53.2% ± 9.9% (n = 41), 52.3% ± 7.4% (n = 19) among patients with moderate fibrosis and 42.1% ± 9.9% (n = 7) among those with extensive enhancement (p = 0.01,one way ANOVA). The difference remains significant after controlling for patient age, gender, hypertension, MI, AF type, mitral valve regurgitation, CAD and the presence of non-AF related CHF. Following ablation, all groups had an increase in the LVEF. The greatest increase occurred among patients in the extensive group. On average, this group experienced an overall improvement of 10.8% ± 14.1%. Patients in the mild enhancement group had an average improvement of 3.3% ± 11.1% and those in the moderate group had an average improvement of 3.8% ± 5.6%. The post-ablation LVEF among patients with mild fibrosis was 56.6% ± 8.3%, 56.2% ± 6.4% among patients with moderate fibrosis and 53.0% ± 15.4% among patients with extensive fibrosis. Conclusion. From our preliminary experience with DE-MRI fibrosis detection, patients with extensive LA fibrosis appear to have depressed LV function pre-ablation. This group of patients seems to experience a large improvement (~11%) in LV function post-ablation compared to patients with less LA fibrosis.

Background. A mechanism of atrial fibrillation (AF) recurrence following ablation may be incomplete pulmonary vein antrum (PVA) scarring that allows for conduction between the pulmonary veins (PV) and the left atrium (LA). We report the relationship between circumferential PV scarring detected by delayed enhancement MRI (DE-MRI) and AF recurrence following PVAI. Methods. Eighty-six patients presenting for PVAI underwent DE-MRI 3 months post ablation. Circumferential ablation with posterior wall debulking was performed in all patients. PV ostia were marked on 3D images generated from the MRI data and assessed by consensus of two independent reviewers for the extent of scarring. Complete PVA scarring was defined as a continuous ring of enhancement surrounding the PVA. For patients with incomplete scarring, the degree of scarring was estimated. Results. The figure shows two patients from the cohort, Patient 1 exhibits successful scarring of all PVA. Patient 2 shows scarring of 1 PVA. At three months post ablation, complete circumferential lesion was seen on 131/335 PVA (39.1%). Complete scarring of 4 PVA was seen in 9 patients (10.5%), scarring of 3 PVA in 11 patients (12.8%) and scarring of 2 PVA was seen in 17 patients (19.8). Twenty-nine patients (33.7%) exhibited complete scarring in 1 PVA while 20 patients (23.3%) exhibited scarring in 0 PVA. Kaplan Meier analysis (Figure [E] ), suggests that PVA isolation may be important for long-term procedural success. Conclusion: Complete pulmonary vein antrum scarring exists in a very limited number of patients, despite its apparent importance for long-term procedural success.

Objectives. Pulmonary vein antrum (PVA) isolation is a common ablation strategy to treat patients with atrial fibrillation (AF). Incomplete lesion formation around the PVA is thought to contribute to recurrence of AF. We report a new multi-step approach to ensure complete PVA scarring by using 3D delayed enhancement MRI (DE-MRI) models of the LA to show regions needing ablation during repeat procedure. Methods. Five patients who suffered AF recurrence following PVAI elected to undergo a second procedure. All 5 patients received DE-MRI scans 3 months following each procedure. 3D segmentation of the LA was performed to evaluate for complete PVA scarring. Application of a color look-up table was used to illuminate scar tissue. Regions of healthy PVA myocardium was marked following the failed ablation and targeted during repeat procedure. Results. All patients showed incomplete PVA scarring after the first ablation. All patients had increased PVA scarring following the repeat procedure. 4 (80%) patients were free of AF (determined by 8 day Holter recordings, ECG and event monitoring) at 3-month follow-up. The figure below shows lack of continuous scar (orange/white) around the left and right PVA following the failed procedure. Gap lesions of healthy myocardium (blue) were identified and targeted (yellow arrows) prior to repeat ablation. Following the successful repeat procedure, all four PVA had continuous scar lesions. Conclusion. 3D DE-MRI models of the LA may identify gaps in RF lesions following failed PVA isolation. These 3D models may assist in procedure planning for the second ablation procedure by identifying the regions necessary for re-ablation.

Background Atrial fibrillation (AF) ablation uses radiofrequency (RF) energy to induce thermal damage to the left atrium (LA) in an attempt to isolate AF circuits. This injury can be seen using delayed enhancement magnetic resonance imaging (DE-MRI). Objective The purpose of this study was to describe DE-MRI findings of the LA in the acute and chronic stages postablation. Methods Twenty-five patients were scanned at two time points postablation. The first group (n = 10) underwent DE-MRI at 24 hours and at 3 months. The second group (n = 16) was scanned at 3 months and at 6 or 9 months. One patient had three scans (24 hours, 3 months, 9 months) and was included in both groups. The location and extent of enhancement were then analyzed between both groups. Results The median change in LA wall injury between 24 hours and 3 months was −6.38% (range −11.7% to 12.58%). The median change in LA wall injury between 3 months and later follow-up was +2.0% (range −4.0% to 6.58%). There appears to be little relationship between the enhancement at 24 hours and 3 months (R 2 = 0.004). In contrast, a strong correlation is seen at 3 months and later follow-up (R 2 = 0.966). Qualitative comparison revealed a stronger qualitative relationship between MRI findings at 3 months and later follow-up than at 24 hours and 3 months. Conclusion RF-induced scar appears to have formed by 3 months postablation. At 24 hours postablation, DE-MRI enhancement appears consistent with a transient inflammatory response rather than stable LA scar formation.

Background Atrial fibrillation (AF) is the most common rhythm disturbance. Radio-frequency ablation (RFA) of the left atrium (LA) is effective for drug refractory AF patients. Outcome of RFA procedure depends on the degree of pre-ablation LA fibrosis and amount of post-ablation scar. Late gadolinium enhancement (LGE) imaging can detect fibrosis and visualize scar. However, only few centers with advanced expertise in cardiac MR (CMR) have demonstrated successful LGE of LA. Multi-center study was initiated to study reproducibility of LGE of LA.

Background Atrial fibrillation (AF) is a common sustained cardiac arrhythmia associated with increased risks of heart failure and stroke. Late gadolinium enhanced MRI (LGE-MRI) is being routinely used to assess and manage the treatment of AF. To acquire LGE images of thin left atrial (LA) wall high-resolution 3D inversion recovery prepared GRE pulse sequence with cardiac gating and respiratory navigation should be used. This makes the image quality dependent on the patient’s heart rate and respiration pattern. In this work, we study the effect of the patient respiration on image quality of LGE-MRI of LA.

Atrial fibrillation (AF) is known to result in structural remodeling and fibrosis of the atrial myocardium. Late gadolinium enhancement (LGE) MRI has been applied to determine the extent and severity of atrial fibrosis but tissue validation is lacking. In this study, we correlated LGE MRI

We are able to detect subclinical post-irradiation changes to the heart with left atrial late gadolinium enhanced magnetic resonance imaging (LGE-MRI).

The aim of this study was to evaluate left atrial (LA) volume measurements using cardiac magnetic resonance (CMR) based angiography before and after LA radio frequency (RF) ablation therapy as a treatment strategy for atrial fibrillation (AFIB).

Category: 26. Clinical Electrophysiology—Supraventricular ArrhythmiasSession-Poster Board Number: 1020-403Authors: Christian Mahnkopf, Nathan Burgon, Alexander Au, Nazem Akoum, Thomas Haslam, Gaston Vergara, Eugene Kholmovski, Rob MacLeod, Nassir Marrouche, Comprehensive Arrhythmia and Research Management (CARMA) Center, University of Utah School of Medici, Salt Lake City, UT Background: Correlation between atrial fibrillation (AF) and CRP has been established. We sought to compare the degree of left atrium (LA) disease based on the amount of fibrosis detected using delayed-enhancement MRI (DE-MRI) with C-reactive protein (CRP) levels as an indicator for reactive versus permanent fibrosis.Methods and Results: 177 patients (109 male; 68.5±0.7 years old) underwent DE-MRI to quantify left atrial structural remodeling (SRM) as a marker for atrial fibrosis. Based on the degree of SRM patients were staged into 4 groups: Utah I (≤5% LA wall enhancement), Utah II (>5% to ≤20%), Utah III (>20% to ≤35%) and Utah IV (>35%) (Figure 1). CRP was measured 5±33 days to DE-MRI examination. Highest level of CRP was found in patients with Utah II (0.61±0.71 mg/dl). Course of CRP showed a significant increase from Utah I to Utah II (0.2±0.17 mg/dl vs. 0.61±0.71 mg/dl; p=0.021) and a decrease from Utah II. To Utah III and to Utah IV (Figure 2). Levels of CRP were comparable in Utah I and Utah IV (0.2±0.17 vs. 0.43±0.53 mg/dl; p =0.338)Conclusion: From our preliminary experience inflammation process is involved in the early stages of atrial structural remodeling in patients with AF as detected using DE-MRI.

Results: Patients in group 1 were younger (57±15 vs. 66±13 years, p=0.009) with a male predominance (80% vs. 57%, p

Background: Catheter ablation with pulmonary vein isolation (PVI) of atrial fibrillation (AF) scars the left atrial (LA) wall around the pulmonary veins and its impact on LA function has been conflicting. We assessed the effect of ablation scar by LA debulking which included PVI plus ablation of posterior wall and inter-atrial septum on reverse remodeling of LA by 2-dimensional echocardiography and strain by velocity vector imaging (VVI).

Results 20 patients (13 male, age 62 ± 9 years) received CMR (Siemens Espree 1.5 T, Germany) before, during and after the PVAI procedure. Using DE-MRI, the average lesion to healthy myocardium ratio was 15.3 ± 7.2% during, and 15.7 ± 6.4% long-term after PVAI. Figure 1 shows an example of MIP of a DE scan in 2D (A-C) and 3D segmentation (D-F) in a anterior view pre (A, D), during (B, E), and long-term after PVAI (C, F). Myocardial injury is idenfrom 13th Annual SCMR Scientific Sessions Phoenix, AZ, USA. 21-24 January 2010

Pulmonary vein antrum isolation (PVAI) has become an effective therapy in patients with paroxysmal atrial fibrillation (AF). Extension and location of ablation lesions often remain unclear during the procedure.