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Background-The measurement of late gadolinium enhanced MRI (LGE-MRI) intensity in arbitrary units (au), limits the objectivity of thresholds for focal scar detection and inter-patient comparisons of scar burden.

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Background Atrial fibrillation (AF) is associated with left atrial (LA) structural and functional changes. Cardiac magnetic resonance (CMR) late gadolinium enhancement (LGE) and feature-tracking are capable of noninvasive quantification of LA fibrosis and myocardial motion, respectively. We sought to examine the association of phasic LA function with LA enhancement in patients with AF. Methods and Results LA structure and function was measured in 90 AF patients (age 61 ± 10 years, 76% male) referred for ablation and 14 healthy volunteers. Peak global longitudinal LA strain (PLAS), LA systolic strain rate (SR-s), and early (SR-ed) and late diastolic (SR-ld) strain rates were measured using cine-CMR images acquired during sinus rhythm. The degree of LGE was quantified. Compared to patients with paroxysmal AF (60% of cohort), those with persistent AF had larger maximum LA volume index (LAVImax, 56 ± 17ml/m2 versus 49 ± 13ml/m2 p=0.036), and increased LGE (27.1± 11.7% versus 36.8 ± 14.8% p<0.001). Aside from LA active emptying fraction, all LA parameters (passive emptying fraction, PLAS, SR-s, SR-ed and SR-ld) were lower in patients with persistent AF (p< 0.05 for all). Healthy volunteers had less LGE and higher LA functional parameters compared to AF patients (p<0.05 for all). In multivariable analysis, increased LGE was associated with lower LA passive emptying fraction, PLAS, SR-s, SR-ed, and SR-ld (p<0.05 for all). Conclusions Increased LA enhancement is associated with decreased LA reservoir, conduit, and booster pump functions. Phasic measurement of LA function using feature-tracking CMR may add important information regarding the physiological importance of LA fibrosis.

Objectives We sought to a) use a novel method of late gadolinium enhancement (LGE) quantification that utilizes normalized intensity measures to confirm the association between LGE extent and atrial fibrillation (AF) recurrence following ablation, and b) examine the presence of interaction and effect modification between LGE and AF persistence. Background Recurrent AF after catheter ablation has been reported to associate with the baseline extent of left atrial (LA) LGE on cardiac magnetic resonance (CMR). Traditional methods for measurement of intensity lack an objective threshold for quantification and interpatient comparisons of LGE. Methods The cohort included 165 participants (60.0±10.2 years, 77% men, 57% persistent AF) that underwent initial AF ablation. The association of baseline LGE extent with AF recurrence was examined using multivariable Cox proportional hazard models. Multiplicative and additive interaction between AF type and LGE extent were examined. Results During 10.2±5.7 months of follow-up, 63 (38.2%) patients experienced AF recurrence. Baseline LGE extent was independently associated with AF recurrence after adjusting for confounders [hazard ratio (HR) 1.5 per 10% increased LGE, P<0.001]. The HR for AF recurrence progressively increased as a function of LGE. The magnitude of association between LGE >35% and AF recurrence was greater among patients with persistent AF (HR 6.5, P=0.001 versus HR 3.6, P=0.001); however, there was no evidence for statistical interaction. Conclusions Regardless of AF persistence at baseline, participants with LGE ≤ 35% have a favorable outcome, whereas those with LGE > 35% have a higher rate of AF recurrence in the first year after ablation. These findings suggest a role for a) patient selection for AF ablation using LGE extent, and b) substrate modification in addition to pulmonary vein isolation in patients with LGE extent exceeding 35% of LA myocardium.

Background-Atrial fibrillation (AF) is associated with significant abnormalities of left atrial (LA) systolic and diastolic function. This study describes a novel measure, LA stiffness index, that estimates LA diastolic function and its association with clinical outcomes of catheter ablation. Methods and Results-A total of 219 AF patients referred for ablation (59% paroxysmal, mean CHA 2 DS 2 VASc score 1.7±1.4) were enrolled. Atrial pressure and volume loops were prepared from invasive pressure measures and cardiac magnetic resonance imaging volumetric data during sinus rhythm for all patients. An LA stiffness index was created, defined by the ratio of change in LA pressure to volume during passive filling of LA (ΔP/ΔV). Patients were followed prospectively. Mean LA stiffness index for AF patients was 0.6±0.5 mm Hg/mL (paroxysmal AF 0.51±0.4 and persistent AF 0.73±0.6; P<0.001). Linear regression analysis showed a rise in the stiffness index with age, increasing at a rate of 0.02 mm Hg/mL per year (P<0.001). The LA stiffness index was higher in patients with previous LA ablation(s) for AF (0.51±0.35 versus 0.83±0.70; P<0.001). Forty of 160 patients had recurrence after AF ablation with a mean follow-up of 10.4±7.6 months. Patients with recurrence had higher stiffness index than those without recurrence (0.83±0.46 versus 0.40±0.22; P<0.001). Conclusions-LA stiffness index, a novel measure to assess LA diastolic function, increases with age and is higher in persistent AF and in the setting of repeat AF ablation. Greater LA stiffness index was independently associated with recurrence of AF after LA ablation. (Circ Arrhythm Electrophysiol. 2016;9:e003163.

Background Prior studies have demonstrated regional left atrial late gadolinium enhancement (LGE) heterogeneity on magnetic resonance imaging. Heterogeneity in regional conduction velocities is a critical substrate for functional reentry. We sought to examine the association between left atrial conduction velocity and LGE in patients with atrial fibrillation (AF). Methods and Results LGE imaging and left atrial activation mapping were performed during sinus rhythm in 22 patients prior to pulmonary vein isolation. The locations of 1468 electroanatomic map points were registered to the corresponding anatomic sites on 469 axial LGE image planes. The local conduction velocity at each point was calculated using previously established methods. The myocardial wall thickness and image intensity ratio (IIR) defined as left atrial myocardial LGE signal intensity divided by the mean left atrial blood pool intensity was calculated for each mapping site. The local conduction velocity and IIR in the left atrium (mean ± standard deviation) were 0.98±0.46 m/sec and 0.95±0.26, respectively. In multivariable regression analysis, clustered by patient, and adjusting for left atrial wall thickness, conduction velocity was associated with the local IIR (0.20 m/sec decrease in conduction velocity per increase in unit IIR, P<0.001). Conclusions In this clinical in vivo study we demonstrate that left atrial myocardium with increased gadolinium uptake has lower local conduction velocity. Identification of such regions may facilitate the targeting of the substrate for reentrant arrhythmias.

Background--Recent evidence suggests that left atrial (LA) dysfunction may be mechanistically contributing to cerebrovascular events in patients with atrial fibrillation (AF). We investigated the association between regional LA function and a prior history of stroke during sinus rhythm in patients referred for catheter ablation of AF.