Accuracy of left atrial fibrosis detection with cardiac magnetic resonance: correlation of late gadolinium enhancement with endocardial voltage and conduction velocity

AIMS

Myocardial fibrosis is a hallmark of atrial fibrillation (AF) and its characterization could be used to guide ablation procedures. Late gadolinium enhanced-magnetic resonance imaging (LGE-MRI) detects areas of atrial fibrosis. However, its accuracy remains controversial. We aimed to analyse the accuracy of LGE-MRI to identify left atrial (LA) arrhythmogenic substrate by analysing voltage and conduction velocity at the areas of LGE.

METHODS AND RESULTS

Late gadolinium enhanced-magnetic resonance imaging was performed before ablation in 16 patients. Atrial wall intensity was normalized to blood pool and classified as healthy, interstitial fibrosis, and dense scar tissue depending of the resulting image intensity ratio. Bipolar voltage and local conduction velocity were measured in LA with high-density electroanatomic maps recorded in sinus rhythm and subsequently projected into the LGE-MRI. A semi-automatic, point-by-point correlation was made between LGE-MRI and electroanatomical mapping. Mean bipolar voltage and local velocity progressively decreased from healthy to interstitial fibrosis to scar. There was a significant negative correlation between LGE with voltage (r = -0.39, P < 0.001) and conduction velocity (r = -0.25, P < 0.001). In patients showing dilated atria (LA diameter ≥45 mm) the conduction velocity predictive capacity of LGE-MRI was weaker (r = -0.40 ± 0.09 vs. -0.20 ± 0.13, P = 0.02).

CONCLUSIONS

Areas with higher LGE show lower voltage and slower conduction in sinus rhythm. The enhancement intensity correlates with bipolar voltage and conduction velocity in a point-by-point analysis. The performance of LGE-MRI in assessing local velocity might be reduced in patients with dilated atria (LA diameter ≥45).

Magnetic Resonance Imaging-Guided Fibrosis Ablation for the Treatment of Atrial Fibrillation

Background:

Myocardial fibrosis is key for atrial fibrillation maintenance. We aimed to test the efficacy of ablating cardiac magnetic resonance (CMR)-detected atrial fibrosis plus pulmonary vein isolation (PVI).

Methods:

This was an open-label, parallel-group, randomized, controlled trial. Patients with symptomatic drug-refractory atrial fibrillation (paroxysmal and persistent) undergoing first or repeat ablation were randomized in a 1:1 basis to receive PVI plus CMR-guided fibrosis ablation (CMR group) or PVI alone (PVI-alone group). The primary end point was the rate of recurrence (>30 seconds) at 12 months of follow-up using a 12-lead ECG and Holter monitoring at 3, 6, and 12 months. The analysis was conducted by intention-to-treat.

Results:

In total, 155 patients (71% male, age 59±10, CHA 2 DS 2 -VASc 1.3±1.1, 54% paroxysmal atrial fibrillation) were allocated to the PVI-alone group (N=76) or CMR group (N=79). First ablation was performed in 80% and 71% of patients in the PVI-alone and CMR groups, respectively. The mean atrial fibrosis burden was 12% (only ≈50% of patients had fibrosis outside the pulmonary vein area). One hundred percent and 99% of patients received the assigned intervention in the PVI-alone and CMR group, respectively. The primary outcome was achieved in 21 patients (27.6%) in the PVI-alone group and 22 patients (27.8%) in the CMR group (odds ratio: 1.01 [95% CI, 0.50–2.04]; P =0.976). There were no differences in the rate of adverse events (3 in the CMR group and 2 in the PVI-alone group; P =0.68).

Conclusions:

A pragmatic ablation approach targeting CMR-detected atrial fibrosis plus PVI was not more effective than PVI alone in an unselected population undergoing atrial fibrillation ablation with low fibrosis burden.

Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02698631.

P402Analysis of right atrium remodeling by cardiac magnetic resonance in patients with atrial fibrillation and its association with left atrium

Funding Acknowledgements

none

Background

Atrial fibrillation (AF) causes changes in atrial anatomy and this remodeling leads to the arrhythmogenic substrate. Most studies with cardiac magnetic resonance-late gadolinium enhancement (CMR-LGE) have focused on the left atrium (LA); The role of the right atrium (RA) in AF is unknown.

Purpose

To evaluate RA remodeling parameters and its comparison with LA in patients with AF.

Methods

Observational study. We included 109 patients: 9 healthy volunteers, 55 paroxysmal AF, 45 persistent AF. All of them had a CMR-RTG 3.0 T. Image post-processed with segmentation of both atria. Comparison of mean parameters of RA and LA (T test), correlation between them (R Pearson). Multivariate analysis (Cox regression) to study predictive factors.

Results

AF patients had a mean age of 58.5 ± 10.5 years, 70(70%) were men, without structural heart disease 80(80%), and associated atrial flutter 11(11%). The RA parameters were compared by subgroups. We found differences in (healthy/paroxAF/persistAF): area(cm2) 94.0 ± 15.9 /125.3 ± 20.8/ 152.8 ± 24.4 (p &lt;0.0001); volume (ml) 76.7 ± 19.6/ 107.0 ± 25.6/ 150.9 ± 37.6 (p &lt;0.0001); and total fibrosis (%) 3.7 ± 4.3/ 16.5 ± 14.1/ 19.4 ± 15.9 (p 0.014).

RA was higher than LA in all subgroups. There was more fibrosis in RA in paroxysmal/persistent AF. Both types of AF had at least a moderate correlation for area, volume and fibrosis (table).

Finally, RA sphericity was the only predictor factor of AF recurrence after ablation among RA remodeling parameters (HR 1.1 95%CI [1.0 -1.3], p = 0.049).

Conclusions

Area, volume and fibrosis progressively increased from healthy to paroxysmal AF, and then to persistent AF. RA was higher than LA and it also had more fibrosis in patients with AF. The size and fibrosis between both atria had at least moderate correlation. The RA sphericity was a predictor of post-ablation AF recurrences.

COMPARISON/CORRELATION RA LA p R PEARSON(RA/LA) p HEALTHY VOLUNTEERS Volume (ml) 76.7 ± 19.6 37.0 ± 9.4 &lt;0.0001 0.457 0.254 Total Fibrosis (%) 3.7 ± 4.3 5.0 ± 6.1 0.278 0.837 0.005 PAROXYSMAL AF Volume (ml) 107.0 ± 25.6 69.5 ± 26.5 &lt;0.0001 0.422 0.001 Total Fibrosis (%) 16.5 ± 14.1 8.0 ± 8.6 &lt;0.0001 0.485 &lt;0.0001 PERSISTENT AF Volume (ml) 150.9 ± 37.6 103.2 ± 28.5 &lt;0.0001 0.582 &lt;0.0001 Total Fibrosis (%) 19.4 ± 15.9 10.5 ± 11.7 &lt;0.0001 0.571 &lt;0.0001

Abstract Figure. Correlation of area and fibrosis RA/LA

Delayed Gadolinium Enhancement Magnetic Resonance Imaging Detected Anatomic Gap Length in Wide Circumferential Pulmonary Vein Ablation Lesions Is Associated With Recurrence of Atrial Fibrillation

BACKGROUND

There is limited knowledge about the impact of anatomic gaps as assessed by delayed gadolinium enhancement cardiac magnetic resonance on atrial fibrillation (AF) recurrence after first pulmonary vein (PV) isolation.

METHODS

Consecutive patients underwent delayed gadolinium enhancement cardiac magnetic resonance 3 months after radiofrequency circumferential PV isolation. Delayed gadolinium enhancement cardiac magnetic resonance images were assessed from 360 PV resulting in 2880 segments in the 2×8-segment model from 94 patients (52±11 years, 62% paroxysmal AF). Left atria were segmented using dedicated software. Anatomic gap was defined as discontinuation of the ablation line by ≥3 mm. Relative gap length was calculated as absolute gap length divided by the total length of the ablation line. AF recurrence was assessed after a mean follow-up duration of 15±10 months Results: Mean number of anatomic gaps was 5.4 per patient. Recurrence within the first year of ablation was observed in 21 patients with paroxysmal AF (36%) and 19 patients with persistent AF (53%). In the univariate analysis, CHA₂DS₂-VASc score, AF type, and relative gap length were predictive of recurrence. In the multivariate analysis, only relative gap length was significantly associated with recurrence (hazard ratio, 1.16 [1.02-1.31] per each 10% of gap).

CONCLUSIONS

The total relative gap length but not the number of anatomic gaps in the PV ablation line as assessed by delayed gadolinium enhancement cardiac magnetic resonance was associated with AF recurrence 1 year after first PV isolation. An increase of 10% relative gap length increased the likelihood of AF recurrence by 16%.