Cardiac magnetic resonance T1 mapping of left atrial myocardium.

Cardiac magnetic resonance (CMR) T1 mapping is an emerging tool for objective quantification of myocardial fibrosis. To (a) establish the feasibility of left atrial (LA) T1 measurements, (b) determine the range of LA T1 values in patients with atrial fibrillation (AF) vs healthy volunteers, and (c) validate T1 mapping vs LA intracardiac electrogram voltage amplitude measures. CMR imaging at 1.5 T was performed in 51 consecutive patients before AF ablation and in 16 healthy volunteers. T1 measurements were obtained from the posterior LA myocardium by using the modified Look-Locker inversion-recovery sequence. Given the established association of reduced electrogram amplitude with fibrosis, intracardiac point-by-point bipolar LA voltage measures were recorded for the validation of T1 measurements. The median LA T1 relaxation time was shorter in patients with AF (387 [interquartile range 364-428] ms) compared to healthy volunteers (459 [interquartile range 418-532] ms; P < .001) and was shorter in patients with AF with prior ablation compared to patients without prior ablation (P = .035). In a generalized estimating equations model, adjusting for data clusters per participant, age, rhythm during CMR, prior ablation, AF type, hypertension, and diabetes, each 100-ms increase in T1 relaxation time was associated with 0.1 mV increase in intracardiac bipolar LA voltage (P = .025). Measurement of the LA myocardium T1 relaxation time is feasible and strongly associated with invasive voltage measures. This methodology may improve the quantification of fibrotic changes in thin-walled myocardial tissues.

Beinart R ，Khurram IM ，Liu S ，Yarmohammadi H ，Halperin HR ，Bluemke DA ，Gai N ，van der Geest RJ ，Lima JA ，Calkins H ，Zimmerman SL ，Nazarian S ... -  《-》

Sinus rhythm restores ventricular function in patients with cardiomyopathy and no late gadolinium enhancement on cardiac magnetic resonance imaging who undergo catheter ablation for atrial fibrillation.

Atrial fibrillation (AF) and systolic heart failure (HF) frequently coexist. Restoration of sinus rhythm by catheter ablation may result in a variable improvement in left ventricular (LV) function. Late-gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging identifies irreversible structural change and may predict incomplete recovery of LV function. To prospectively select patients with AF and symptomatic HF but without LV LGE and report the impact of AF ablation on LV function. Patients with AF and symptomatic HF (LV ejection fraction <50%) resistant to at least 1 antiarrhythmic drug and prior electrical cardioversion underwent contrast-enhanced CMR. LGE-negative patients underwent pulmonary vein isolation and left atrial roof line with continued antiarrhythmic medications until follow-up CMR 6 months postablation. Sixteen patients (aged 52 ± 11 years; mean AF duration 37 ± 39 months; left atrial size 44 ± 13 mL/m(2)) underwent AF ablation. At 6 months, 15 of the 16 patients maintained sinus rhythm and underwent CMR. LV ejection fraction increased from 40% ± 10% at baseline to 60% ± 6% (P < .001) and LV end-systolic volume index decreased from 52 ± 12 to 36 ± 9 mL/m(2) (P < .001). Left atrial size decreased from 44 ± 13 to 36 ± 11 mL/m(2) (P < .01). In patients with AF and LV dysfunction in the absence of LGE on CMR, ventricular function normalizes following the restoration of sinus rhythm. CMR may assist in the selection of patients with combined AF and systolic HF most likely to benefit from catheter ablation.

Ling LH ，Taylor AJ ，Ellims AH ，Iles LM ，McLellan AJ ，Lee G ，Kumar S ，Lee G ，Teh A ，Medi C ，Kaye DM ，Kalman JM ，Kistler PM ... -  《-》

Myocardial extracellular volume expansion and the risk of recurrent atrial fibrillation after pulmonary vein isolation.

This study tested whether myocardial extracellular volume (ECV) is increased in patients with hypertension and atrial fibrillation (AF) undergoing pulmonary vein isolation and whether there is an association between ECV and post-procedural recurrence of AF. Hypertension is associated with myocardial fibrosis, an increase in ECV, and AF. Data linking these findings are limited. T1 measurements pre-contrast and post-contrast in a cardiac magnetic resonance (CMR) study provide a method for quantification of ECV. Consecutive patients with hypertension and recurrent AF referred for pulmonary vein isolation underwent a contrast CMR study with measurement of ECV and were followed up prospectively for a median of 18 months. The endpoint of interest was late recurrence of AF. Patients had elevated left ventricular (LV) volumes, LV mass, left atrial volumes, and increased ECV (patients with AF, 0.34 ± 0.03; healthy control patients, 0.29 ± 0.03; p < 0.001). There were positive associations between ECV and left atrial volume (r = 0.46, p < 0.01) and LV mass and a negative association between ECV and diastolic function (early mitral annular relaxation [E'], r = -0.55, p < 0.001). In the best overall multivariable model, ECV was the strongest predictor of the primary outcome of recurrent AF (hazard ratio: 1.29; 95% confidence interval: 1.15 to 1.44; p < 0.0001) and the secondary composite outcome of recurrent AF, heart failure admission, and death (hazard ratio: 1.35; 95% confidence interval: 1.21 to 1.51; p < 0.0001). Each 10% increase in ECV was associated with a 29% increased risk of recurrent AF. In patients with AF and hypertension, expansion of ECV is associated with diastolic function and left atrial remodeling and is a strong independent predictor of recurrent AF post-pulmonary vein isolation.

Neilan TG ，Mongeon FP ，Shah RV ，Coelho-Filho O ，Abbasi SA ，Dodson JA ，McMullan CJ ，Heydari B ，Michaud GF ，John RM ，Blankstein R ，Jerosch-Herold M ，Kwong RY ... -  《-》

Evaluation of quantification methods for left arial late gadolinium enhancement based on different references in patients with atrial fibrillation.

Hwang SH ，Oh YW ，Lee DI ，Shim J ，Park SW ，Kim YH ... -  《-》

Extent and spatial distribution of left atrial arrhythmogenic sites, late gadolinium enhancement at magnetic resonance imaging, and low-voltage areas in patients with persistent atrial fibrillation: comparison of imaging vs. electrical parameters of fibro

Atrial fibrosis contributes to arrhythmogenesis in atrial fibrillation and can be detected by MRI or electrophysiological mapping. The current study compares the spatial correlation between delayed enhancement (DE) areas to low-voltage areas (LVAs) and to arrhythmogenic areas with spatio-temporal dispersion (ST-Disp) or continuous activity (CA) in atrial fibrillation (AF). Sixteen patients with persistent AF (nine long-standing) underwent DE-magnetic resonance imaging (1.25 mm × 1.25 mm × 2.5 mm) prior to pulmonary vein isolation. Left atrial (LA) voltage mapping was acquired in AF and the regional activation patterns of 7680 AF wavelets were analysed. Sites with ST-Disp or CA were characterized (voltage, duration) and their spatial relationship to DE areas and LVAs <0.5 mV was assessed. Delayed enhancement areas and LVAs covered 55% and 24% (P < 0.01) of total LA surface, respectively. Delayed enhancement area was present at 61% of LVAs, whereas low voltage was present at 28% of DE areas. Most DE areas (72%) overlapped with atrial high-voltage areas (>0.5 mV). Spatio-temporal dispersion and CA more frequently co-localized with LVAs than with DE areas (78% vs. 63%, P = 0.02). Regional bipolar voltage of ST-Disp vs. CA was 0.64 ± 0.47 mV vs. 0.58 ± 0.51 mV. All 28 ST-Disp and 56 CA areas contained electrograms with prolonged duration (115 ± 14 ms) displaying low voltage (0.34 ± 0.11 mV). A small portion of DE areas and LVAs harbour the arrhythmogenic areas displaying ST-Disp or CA. Most arrhythmogenic activities co-localized with LVAs, while there was less co-localization with DE areas. There is an important mismatch between DE areas and LVAs which needs to be considered when used as target for catheter ablation.

Chen J ，Arentz T ，Cochet H ，Müller-Edenborn B ，Kim S ，Moreno-Weidmann Z ，Minners J ，Kohl P ，Lehrmann H ，Allgeier J ，Trenk D ，Hocini M ，Jais P ，Haissaguerre M ，Jadidi A ... -  《-》