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. Author manuscript; available in PMC: 2010 Mar 1.
Published in final edited form as: JACC Cardiovasc Imaging. 2009 Mar;2(3):308–316. doi: 10.1016/j.jcmg.2008.10.016

Recurrence of Atrial Fibrillation Correlates with Extent of Post-procedural Late Gadolinium Enhancement: A Pilot Study

Dana C Peters 1, John V Wylie 1, Thomas H Hauser 1, Reza Nezafat 1, Yuchi Han 1, Jeong Joo Woo 1,3, Jason Taclas 1, Kraig V Kissinger 1, Beth Goddu 1, Mark E Josephson 1, Warren J Manning 1,2
PMCID: PMC2703450  NIHMSID: NIHMS110849  PMID: 19356576

Abstract

Objectives

We sought to evaluate radiofrequency (RF) ablations lesions in atrial fibrillation (AF) patients using cardiovascular magnetic resonance (CMR), and to correlate the ablation patterns with treatment success.

Background

RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium (LA) and pulmonary veins (PV) would correlate with moderate-term procedural success.

Methods

Thirty five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bi-directional conduction block around each PV ostium. AF recurrence was documented using a 7 day event monitor at multiple intervals during the first year. High spatial resolution 3D LGE CMR was performed 46±28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1-minimal, 3-extensive and circumferential) assessed.

Results

Thirteen (37%) patients had recurrent AF during the 6.7 ± 3.6 month observation period. Paroxysmal AF was a strong predictor of non-recurrent AF (15% with recurrence vs. 68% without, p=0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior PV (RIPV) (82% vs. 31%, p=0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p=<0.05), and was a univariate predictor of recurrence using Cox regression (p=0.049, Bonferroni corrected).

Conclusions

Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and LA scarring on 3D LGE CMR. This finding was significant for RIPV scar, and may have implications for the procedural technique used in PV isolation.

Keywords: Late gadolinium enhancement, Catheter ablation, Atrial fibrillation, MRI, left atrium

Introduction

Long term success of catheter ablation for treatment of atrial fibrillation (AF) remains 60-80% {Pappone, 2000 #379; Essebag, 2006 #415; Cappato, 2005 #402; Oral, 2002 #380}. The goal of the most commonly used procedure electrically isolates the antrum of each pulmonary vein (PV) through an anatomically complete circumferential ablation. Recurrence of AF has been attributed to incomplete circumferential or transmural ablation of the PV ostia leading to reconduction {Verma, 2005 #404}, and to the existence of other triggers beyond the PVs {Gerstenfeld, 2003 #424}. Imaging can contribute to the understanding of PV isolation therapy by visualizing the lesions that are created during catheter ablation {Peters, 2007 #430; Lardo, 2000 #443; Dickfeld, 2006 #442; Okada, 2007 #445; Wylie, 2008 #476}. To exploit this capability, there are ongoing efforts to perform ablations under guidance of cardiovascular magnetic resonance (CMR) or cardiac CT {Razavi, 2003 #447; Reddy, 2004 #449}.

Not all PVs are equal as sources of AF or as targets for therapy. The upper PVs have the greatest proportion of AF triggers {Kurotobi, 2006 #462; Haissaguerre, 1998 #299} and the greatest proportion of reconnected veins on follow-up {Gerstenfeld, 2003 #424}. This reconnection may be caused by less well ablated PVs during the procedure. There are fewer triggers in the left inferior PV (LIPV) {Kurotobi, 2006 #462; Haissaguerre, 1998 #299}, but a lower rate of reconnection is found {Gerstenfeld, 2003 #424} during a repeat catheter ablation procedure. The right inferior PV (RIPV) has the lowest proportion of initial AF triggers, but the highest proportion of new triggers on repeat study among patients with recurrent AF {Gerstenfeld, 2003 #424}. The RIPV also stands out technically as the most difficult vein to ablate, due to poor catheter access {Katritsis, 2004 #425; Macle, 2002 #461; Oral, 2002 #380}.

High spatial resolution three-dimensional (3D) late gadolinium enhancement (LGE) CMR{Kim, 1999 #82; Simonetti, 2001 #232} allows for non-invasive detection of left atrial (LA) ablation sites in patients with AF{Peters, 2007 #417}. The scar is observed as an accumulation of gadolinium contrast. We hypothesized that a greater volume of scar, and more circumferentially distributed scar, would lead to greater clinical success. Therefore we studied the relationship of the volume and the distribution of LGE surrounding each vein to treatment success.

Methods

Patients

Between April 2005, and May 2007, we scanned 59 consecutive patients after their first RF ablation for AF. From these, we excluded patients with suboptimal image quality (N=24) (41%). The remaining 35 consecutive patients were enrolled into our imaging study (Table 1). The study was approved by the hospital committee on clinical investigations.

Table 1. Subject characteristics.

All Subjects AF Recurrence No AF Recurrence
(n = 35) (n=13) (n=22)
Age (years) 56± 13 55 ± 13 57± 13
Male gender (%) 31 (88%) 12 (92%) 19 (86%)
Paroxysmal AF*(%) 17(49%) 2 (15%) 15 (68%)
Persistent AF (%) 10 (28%) 6 (46%) 4 (18%)
Permanent AF (%) 8 (23%) 5 (38%) 3 (14%)
Heart-rate (bpm) / % in SR 62 / 89% 69 / 69% 57 / 100%
LA volume (ml/m2) 63± 17 65± 22 61± 12
Valvular heart disease (%) 2 (6%) 1 (8%) 1 (5%)
Any mitral regurgitation (%) 19 (54%) 7 (54%) 12 (54%)
Hypertension† 15 (43%) 9 (69%) 6 (27%)
LV Ejection fraction 0.57 ± 0.08 0.56 ± 0.08 0.58 ± 0.09
Tot. RF Ablation Time (s) 3600±1000 3500±1000 3600±1000
RF Ablation # by CARTO† 145±47 166±45 129±42
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*

p = 0.002,

†

p=0.015,

†

p=.04, all others p = NS.

PV Isolation Procedure and Documentation of Recurrence

The circumferential PV isolation procedure has been described elsewhere {Essebag, 2005 #414}. Briefly, an 8mm (N=29) standard tip or a 3.5mm (N=6) externally irrigated tip ablation catheter was used for ablation, advanced through a Mullins sheath into the LA. A circumferential catheter, advanced through a second Mullins sheath, was placed at each PV ostium to guide ablation and to confirm PV entrance and exit block {Essebag, 2006 #439}. The RF ablations were placed 5-10 mm outside of each PV ostium until electrical PV isolation was achieved. For the 8mm catheter, the maximum temperature setting was 52°, and maximum power output was 50 Watts; for the 3.5mm catheter, power was limited to 30 Watts. Ablation was performed for 30-120 seconds at each site, based on changes in local electrograms. All PVs were routinely isolated in all patients, without routine addition of empiric ablation lines in the LA. As part of our standard method of stepwise ablation, in eight patients with inducible atrial tachyarrhythmias, one or more additional ablation lines were made. In six patients ablation was performed from the LIPV inferiorly and anteriorly to the mitral annulus (the “mitral isthmus”) for left atrial flutter; in two patients, ablation was created along the LA “roof”, from the left superior pulmonary vein to the RSPV. In three patients, ablation was created at the superior vena cava-right atrium junction for persistently inducible AF after LA ablation had been completed. Catheter manipulation was guided by fluoroscopy, intra-cardiac ultrasound, and 3D electroanatomic mapping systems (CARTO, Biosense Webster, Diamond Bar, CA, USA, and/or NAVx, Endocardial Solutions, St. Paul, MN, USA). A single highly experienced operator (MEJ) performed 33/35 (94%) of the RF ablation procedures. Post-procedure, patients were monitored for recurrence of AF using an event monitor for 2 weeks post-procedure; and they were scheduled to undergo mobile outpatient cardiac telemetry monitoring for 7 days at 1, 6, and 12 months post-procedure.

Recurrent AF was defined as any symptomatic or asymptomatic episode lasting longer than 10 seconds, occurring more than 30 days after the ablation procedure. The dates of recurrence or dates of most recent follow-up were used to construct survival curves.

CMR Imaging of RF ablation sites

CMR was performed 30-60 days after the PV isolation procedure, using a Philips 1.5T CMR scanner (Achieva, Philips Healthcare, Best, NL), 20-25 minutes following administration of 0.2 mmol/kg Gd-DTPA (Magnevist, Berlex Laboratories, Wayne, NJ), using a 3D LGE CMR sequence, as previously described {Peters, 2007 #417; Saranathan, 2004 #283; Stuber, 1999 #238}. Technical scan parameters included: 3D inversion recovery gradient echo sequence, 1 RR interval between inversions, repetition time (TR)/echo time (TE)/flip angle (θ) = 5.3ms/2.1ms/25°, 32×32×12.5 cm field-of-view, 250 Hz/pixel receiver bandwidth, matrix 224×224×23-32 Nz, average inversion time (TI) = 280 ms, 1.4×1.4×4-5 mm spatial resolution reconstructed to 0.6×0.6×2-2.5 mm spatial resolution. ECG-triggering (∼150 ms end-diastolic window), navigator-gating and fat suppression were employed during the 4-8 minutes scan time.

Data analysis

Analyses of the extent of scarring of the PVs and LA were performed using two metrics: a quantitative measure of scar volume in each PV region; and a qualitative visual measure of scar circumferentiality. These measurements were compared to the clinical outcome of AF recurrence on follow-up.

Quantitative Scar Volume Measurement

Image processing was performed in Matlab 7.1 (Mathworks, Natick, MA, USA), by a blinded observer (DCP). To regionally quantify scar for each slice in the 3D volume (Figure 1), the pixels containing hyperenhanced regions were identified using thresholding. A patient specific threshold was chosen by visually comparing the results of multiple thresholding values to the scarred region in the original image. The minimum threshold which eliminated most left atrial blood pool pixels was chosen. Following thresholding, isolated high signal intensity voxels were removed. Within the LA, each pixel was classified as belonging to one (or more) of 5 areas: LIPV, left superior PV (LSPV), RIPV, right superior PVs (RSPV), and LA posterior wall. The classification of scarred voxels was made by drawing regions of interest (ROIs) in each slice encompassing each area of the LA (Figure 1). The total volume of scar in each region, and in each slice was measured by summation over all slices. Because the inferior/superior PVs often share a common branch point, the ROIs for ipsilateral inferior/superior PV ostia often overlapped (see Figure 2B, LIPV and LSPV, arrow). The ROIs for the posterior wall and inferior PVs also overlap. The drawing of ROIs and choice of thresholds adds an element of subjectivity to the scar volume measurement. Nevertheless, at our center, the inter- and intra-observer variability for total scar volume measurement, including choice of threshold and ROIs, have been measured. For intra-observer variability, the coefficient of linear regression was R=0.89 with a mean bias ± standard deviation of 0.33±1.69 mls; for inter-observer variability, R=0.88 with a bias of -0.96±1.87 mls {Wylie, 2008 #476}.

Figure 1. Methodology for measuring scar volumes.

Figure 1

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(A) original LGEimages of scar, with hyperenhanced scar. (B) Scar is highlighted (in red) using signal thresholding, separating scar from normal tissues. (C) ROIs are used to identify scar on each slice as belonging to the LIPV, RIPV, LSPV, RSPV, and posterior wall. (D) Each slice is analyzed using thresholding ands ROIs to identify scarred pixels in each region. (E) Total scar is summed over all slices.

Figure 2. 3D LGE images in three patients, with a volume-rendered view.

Figure 2

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Three patients, two without recurrence of AF (A,B) and one with recurrence of AF (C). Top panels show an LGE slice from the 3D volume. Bottom panels show planar reformats across PV ostia. The orientation is shown in bottom panel B. The reformats provide examples of qualitative gradings for the RIPV of (Fig. 2A) 3 – complete; (Fig. 2B) 2–partial; and (Fig. 2C) 1 –no scar. D) A 3D volume-rendering of the scar for Patient B. A mitral isthmus line is observed (arrow).

Movie Legend (associated with Figure 2D): 3D visualization showing RF ablation scar fused with the MR angiogram, in another patient, providing evaluation of the scar in the context of the pulmonary vein anatomy.

Visual display

For visual display of the scar, the 3D LGE (Figure 1, 2) were registered to contrast-enhanced MR angiographic images {Hauser, 2004 #437} of the same patient, using scaling of voxel sizes, and translation in the x, y and z directions. The rigid registration was performed using landmarks and recorded image coordinates. The registered scar images, after thresholding and masking to include only scarred pixels, were combined with the MR angiogram, and the resulting images were surface rendered to visualize the scar in 3D.

Qualitative Assessment

An experienced reader with greater than 1.5 years clinical CMR/LGE experience, blinded to outcome, graded the circumferentiality of scar around each PV using a pre-established grading system, on a scale of 1 (no LGE or only one quadrant of a PV ostium with LGE) to 3 (extensive scarring and ≥3 quadrants with LGE) using the source 3D data sets and a public domain image viewer (ImageJ 1.37v, NIH). A second experienced reader independently analyzed the data to provide a measure of inter-observer variability. Due to the known technical difficulty in ablating the RIPV, the inferior portion of the RIPV ostia was analyzed as to the presence or absence of scar. Finally, the visibility of additional ablation lines on the LGE images was also assessed, in an unblinded fashion.

Pre-ablation LA volumes were measured at end-systole, by planimetering MR functional images of the LA in the 2-chamber, and 4 chamber view {Wylie, 2008 #476; Ujino, 2006 #472}, with indexing to body surface area.

Statistics

Continuous measurements are presented as mean ± standard deviation, and were compared using the Wilcoxon rank-sum test. Categorical variables are expressed as numbers and percentages and were compared using Fisher's exact test. Where appropriate, Bonferroni correction was used to correct for multiple testing. Estimated AF-free survival was calculated using the product-limit method (Kaplan-Meier analysis) with comparison of strata using the log-rank test. The relationship of RIPV scar with the recurrence of AF was further assessed using proportional hazards regression. The natural log transformation of RIPV scar was used in this analysis because the data were not normal. A two-sided P<0.05 was considered significant. Statistical analyses were performed using SAS for Windows (v9.1, Cary, NC, USA) or Stata IC 10, StataCorp (College Station, Texas USA).

Results

Subjects were followed for 6.7 ±3.6 months post RF ablation. Clinical recurrence of AF was noted in 13 (37%) patients, with an average time to recurrence of 109±75 days. Eight of the 13 (62%) patients with AF recurrence had symptomatic improvement, defined as greater than 90% reduction in symptoms. Twelve of the 35 patients (34%) were treated with anti-arrhythmic medications, after the RF ablation. Patients with and without recurrence were similar in age, gender, LA volume, LV ejection fraction and total RF ablation times (Table 1). Hypertension (p=0.015), non-paroxysmal vs. paroxysmal AF (p=0.002) and a greater number of ablations as recorded by the CARTO system (p=0.04), were all associated with recurrent AF {Berruezo, 2007 #458; Vasamreddy, 2004 #459}.

Study of post-ablation late gadolinium enhancement

Figure 2 shows images from three patients, including a source image and a planar reformat. The reformats show examples of complete (Figure 2A), partial (Figure 2B) and minimal (Figure 2C) ablations of the RIPV. Figure 2D presents a 3D volume rendering of the MR angiogram, overlaid with segmented scar, for one patient. This 3D method of visual display is useful for appreciating the scar circumferentiality. A 3D movie of scar fused with the MR angiogram is provided as a supplement. (Video 1)

Table 2 compares the quantitative results for scar volume. In all regions, excepting the LIPV, there was less scar among the group of patients with AF recurrence, with a significant difference found for the RIPV. AF-free survival was significantly associated with RIPV scar (p=0.03, Figure 3).

Table 2. Left atrial scar volumes as predictors of AF recurrence.

Region All Subjects
(N = 35)		 Recurrent
(N = 13)		 Non Recurrent
(N = 22)		 P-value
(recurrence vs. no recurrence)		 P-value
(Bonferroni corrected)
LGE volume (mls)
Total* 7.4±4.4 6.8±4.1 7.8±2.6 0.247 NS
LIPV 2.3±1.4 2.4±1.3 2.2±0.8 0.746 NS
LSPV 1.1±0.8 1.0±0.7 1.1± 0.7 0.746 NS
RIPV 2.1±1.2 1.6±1.0 2.4±0.8 0.008 p<0.05
RSPV 1.6±1.2 1.5±1.4 1.7±0.9 0.195 NS
PW 2.2±1.7 2.1±2.3 2.2±1.3 0.282 NS
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LIPV= left inferior pulmonary vein; RIPV=right inferior pulmonary vein; LSPV = left superior pulmonary vein, RSPV = right superior pulmonary vein; PW = posterior wall.

*

Note that, since regions overlap, total scar is less than sum of scar in each region.

Figure 3. Kaplan-Meier AF free survival curve stratified by RIPV scar.

Figure 3

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Kaplan-Meier survival curve showing AF free survival time for patients using median scar volume cutoffs (1.98 mls), for patients with greater and lesser RIPV scar volume measurement. More extensive scarring was associated with longer AF-free survival (p = 0.029).

The qualitative results are shown in Table 3. RIPV scar was lower in the recurrent vs. non-recurrent patient groups. The LIPV was more fully scarred in non-recurrent patients, and this trended towards significance. The interobserver qualitative agreement was 66%, with a kappa value of 0.46, showing moderately good agreement.

Table 3. Qualitative gradings (1 = minimal scar, 3 = circumferential scar) of the extent of left atrial scar, separated by region, as predictors of AF recurrence.

Region All Subjects
(N = 35)		 Recurrence
(N = 13)		 No recurrence
(N = 22)		 P-value P-value
(Bonferroni corrected)
LIPV 2.7 2.4 2.8 0.056 0.22
LSPV 2.1 1.9 2.2 0.389 NS
RIPV 2.3 1.9 2.5 0.032 0.13
RSPV 2.0 1.8 2.2 0.142 NS
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All six (100%) mitral isthmus ablation lines were visualized. Both (100%) of ablation lines across the LA roof were visualized. Two of three (66%) lines extending around the superior vena cava were observed in the images. Figure 2D shows a mitral isthmus line in one patient (arrow).

Using a qualitative score of 3 to indicate a fully circumferential ablation, we found that 2.2 (55% assuming 4 PVs) of veins in patients without AF recurrence, and 1.4 (35%) of veins in patients with AF recurrence were fully ablated (Table 4). Ablation in the inferior portion of the RIPV ostia was a significant predictor of recurrence (p=0.025).

Table 4. Number of veins with fully circumferential ablation, determined by a qualitative grading (grade 3).

Region All Subjects
(N = 35)		 Recurrent
(N = 13)		 Non Recurrent
(N = 22)		 P-value
(recurrence vs. no recurrence)		 P-value
(Bonferroni corrected)
LIPV 68% (21/31) 45%(5/11) 80%(16/20) 0.106 NS
LSPV 31 % (9/29) 20%(2/10) 37%(7/19) NS NS
RIPV 52% (18/35) 31%(4/13) 64%(14/22) 0.086 NS
Inferior RIPV* 22/35 (63%) 4/13 (31%) 18/22 (82%) .004 0.025
RSPV 32% (11/34) 23% (3/13) 38% (8/21) NS NS
Pts with > 2 fully ablated PVs 63%(22/35) 31%(4/13) 79% (15/22) 0.043 0.255
# of fully ablated PVs † 1.9 (48%) 1.4 (35%) 2.2 (55%) NS NS
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*

Indicating the number of patients with an ablation on the inferior portion of the RIPV.

†

also expressed as % assuming 4 PVs.

The multivariate analysis of significant univariate predictors of recurrence (paroxysmal AF, and RIPV scar volume) by Cox regression is shown in Table 5.

Table 5. Univariate and Multivariate predictors of time to AF recurrence using Cox regression.

Predictor Univariate Hazard ratio P-value (Bonferroni corrected) Multivariable Hazard ratio P-value (Bonferroni corrected)
(log) RIPV scar vol. 0.29 0.049 0.39 0.220
Paroxysmal AF 0.19 0.017 0.21 0.045
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Discussion

In this study of 35 AF patients undergoing their first RF ablation, our data demonstrate that the extent of LA scar, especially RIPV scar, assessed qualitatively and quantitatively by LGE CMR, predicts AF recurrence after catheter ablation for AF. Overall, the LIPV displayed the most circumferential LGE, followed by the RIPV, the LSPV, and the RSPV. The results are consistent with other studies showing that AF recurrence is associated with electrical reconnection in one or more PVs, since incomplete scarring may be the cause of electrical reconnection. Yamada et al. {Yamada, 2006 #475} studied patients undergoing a 2nd ablation, where only 40% of PVs were still electrically isolated using mapping, including 36% of LSPVs, 36% of RSPVs, 50% of LIPVs, and 50% of RIPVs, in good agreement with our data on PV scar in patients with recurrent AF. Verma et al found, in patients having a repeat EP study, that the number of reconnected veins was 2.0 (on average) for patients with recurrence, and only 0.2 for patients without recurrence {Verma, 2005 #404}; the culprit veins were not identified. In comparison, our study found that the number of non-circumferentially ablated veins was 2.6 (on average) for patients with recurrence, but only 1.8 for patients without recurrence.

Early recurrence, while strongly predictive, is not always followed by later recurrence {Richter, 2008 #478; Lellouche, 2008 #479}, suggesting that healing occurs after RF ablation. Furthermore, at the time of ablation, local tissue edema and incomplete myocyte damage may contribute to the appearance of acute conduction block in patients who may later develop recurrent conduction after myocardial healing {Richter, 2006 #469; Sauer, 2006 #470}. The 3D LGE method is unique and complementary to electrophysiology studies, because it can assess the circumferentiality of PV scar at any time point–early or late--and provide information non-invasively for patients with and without recurrence.

Most operators place more emphasis on primary isolation of the superior veins, however upon recurrence, the superior PVs are most likely to be reconnected {Yamada, 2006 #475; Rajappan, 2008 #480}. In our study, overall, the superior PVs were less circumferentially ablated than the inferior PVs (Table 3) in qualitative grading and also were surrounded by a lower volume of scar (Table 2). However, the greater volume of scar in the lower PVs might reflect inclusion of some adjacent posterior wall scar in the measurements or the challenges of imaging the upper PVs.

Importance of the RIPV

Both the quantitative and qualitative analyses identified that RIPV scar as the “lynch pin”, i.e. most highly correlated of all PV measurements to clinical success. This may be due to the unique technical difficulty of completely isolating the RIPV{Katritsis, 2004 #425; Macle, 2002 #461; Oral, 2002 #380} resulting in greater variability of scar in that region. Notably, Gerstenfeld et al. showed that upon recurrence, the majority of new triggers arose from the RIPV{Gerstenfeld, 2003 #424}. In a study of late recurrence (> 12 months), Mainigi and colleagues showed that the recurrences were correlated with a reconnected or initially unisolated RIPV {Mainigi, 2007 #465}. Another study of patients with late recurrence, the RIPV was the most commonly re-ablated during a repeat ablation, followed closely by the left common vein {Shah, 2008 #473}. A recent case report by Reddy et al {Reddy, 2008 #474}, using 3D LGE to image LA scar after PV isolation, found scar discontinuity in the inferior RIPV ostia, which terminated AF when ablated in a follow-up procedure. Very recently, a study of patients during repeat procedures for recurrent AF showed that sites of chronic PV reconnection were located predominantly—and in roughly equal proportion--around the LSPV, RSPV, and RIPV, especially the inferior-posterior portion of the RIPV{Rajappan, 2008 #480}. This is remarkably similar to our findings that the LIPV is well ablated in all patients alike, and that recurrence is highly correlated to lack of scarring in the inferior portion of the RIPV (31% vs. 82%). This may be due to the difficulty in accessing this portion of the RIPV. Previous findings, along with the results of our study, suggest that better RF ablation catheters and trans-septal sheaths, improving access to right PVs and permitting more complete ablation of the RIPV, may reduce recurrence rates of AF. Newer assist devices such as steerable sheaths and remote magnetic navigation system {Pappone, 2006 #467; Di Biase, 2007 #468} may allow effective creation of LA ablations.

Limitations

The sample size (35 patients) was small. A larger study will help to better define the RF ablation patterns that result in freedom from AF. This pilot study studied the relationship of many factors with recurrence, and significance of each predictor was more difficult to establish after Bonferroni correction. The conclusions of this study are based on procedures performed from 2005-2007, during which time RF ablation techniques had been—and still are--evolving. While animal studies have shown excellent correlation of LGE CMR with areas of scar for myocardial infarction {Kim, 1999 #82; Dickfeld, 2006 #442}, such validation for detecting scar in the much thinner LA wall is lacking. There may be scar which is below the threshold of detection by CMR, and detection of small scars may depend on overall image quality.

In conclusion, among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and LA scarring on 3D LGE CMR. This finding was significant for RIPV scar, and may have implications for the procedural technique used in PV isolation.

Acknowledgments

Funding Sources: This work was supported by a grant from the American Heart Association (AHA SDG 0530061N) and the NIH (NIBIB K01 EB004434-01A1).

Abbreviations

AF

Atrial fibrillation

CMR

Cardiovascular magnetic resonance

PV

pulmonary vein

LA

left atrium

LGE

late gadolinium enhancement

RIPV

right inferior PV

LIPV

left inferior PV

LSPV

left superior PV

ROI

region of interest

Footnotes

Potential conflicts of interest: Dr. Warren Manning receives research support from Philips Medical Systems; Dr. Mark Josephson receives consulting fees from Biosense Webster. Dr. Wylie has served as a speaker for Medtronic, Inc. There are no other disclosures relevant to this article.

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