LGE-MRI for diagnosis of left atrial cardiomyopathy as identified in high-definition endocardial voltage and conduction velocity mapping

Abstract

Background: Electro-anatomical voltage, conduction velocity (CV) mapping and late gadolinium enhancement magnetic resonance imaging (LGE-MRI) are different diagnostic modalities for atrial cardiomyopathy (ACM). However, discordances remain in the location and extent of detected ACM. Objectives: (1) Comparison of ACM extent and location between current modalities. (2) Development of new estimated optimised image intensity thresholds (EOIIT) for LGE-MRI identifying patients with ACM. Methods: Thirty-six ablation-naive persistent AF patients underwent LGE-MRI and high-definition electro-anatomical mapping in sinus rhythm. Significant ACM was defined as low voltage substrate (LVS) extent ≥ 5% of the left atrium (LA) surface at < 0.5mV. LGE areas were classified using the Utah, image intensity ratio (IIR > 1.20) and new EOIIT method for comparison to LVS and slow conduction areas < 0.2m/s. ROC analysis determined the LGE-extent enabling accurate diagnosis of ACM. Results: The degree and distribution of detected pathological substrate varied significantly (p < 0.001) across the mapping modalities: 3% (IQR 0-12%) of the LA displayed LVS < 0.5mV vs. 14% (3-25%) slow conduction areas < 0.2m/s vs. 16% (6-32%) LGE with Utah method vs. 17%(11-24%) using IIR > 1.20, with enhanced discrepancies on posterior LA. A linear correlation was found between the OIIT and each patients mean blood pool intensity (R2=0.89, p < 0.001). LGEMRI-based ACM diagnosis improved with the novel EOIIT (83% sensitivity, 88% specificity, AUC:0.94) in comparison to the Utah method (60% sensitivity, 75% specificity, AUC:0.76), and IIR > 1.20 (58% sensitivity, 75% specificity, AUC:0.71). Conclusion: Important discordances in distribution of pathological substrate exist between LA-LVS, CV and LGE-MRI, irrespective of the LGE-detection protocol that is used. However, the new EOIIT method improves LGE-MRI based ACM diagnosis in ablation-naive AF-patients.

Atrial arrhythmogenic substrate assessment: Is seeing always knowing?

“…The findings that different LGE-MRI evaluation methods disagree confirms previous reports, 4,5 which also showed that in comparison to LGE-MRI analysis, endocardial voltage and conduction velocity mapping yield different results, particularly on the posterior wall. Left atrial activation times as a functional readout of atrial substrate hardly correlated with any LGE-MRI derived metric (all nonsignificant) but with low voltage extent.…”

“…Left atrial activation times as a functional readout of atrial substrate hardly correlated with any LGE‐MRI derived metric (all nonsignificant) but with low voltage extent 4 . Both PIH and IIR methods were similarly sensitive (58%–60%) and specific (75%) for prediction of low voltage <0.5 mV in sinus rhythm in persistent AF patients 5 . Optimized methods derived from larger cohorts may increase the agreement between LGE‐MRI and voltage‐based substrate assessment 5 .…”

“…4 Both PIH and IIR methods were similarly sensitive (58%-60%) and specific (75%) for prediction of low voltage <0.5 mV in sinus rhythm in persistent AF patients. 5 Optimized methods derived from larger cohorts may increase the agreement between LGE-MRI and voltage-based substrate assessment. 5 However, part of the discrepancy is likely inherent in fundamental differences of the assessment modalities, which is a challenge (in terms of comparability) and an opportunity (in terms of yielding complementary information) at the same time.…”

Personalized ablation vs. conventional ablation strategies to terminate atrial fibrillation and prevent recurrence

“…IIR or Utah) and the respective cut-off values are influencing the estimated fibrotic distribution. 8 , 10 Moreover, current LGE-MRI technology does not have the required resolution to well distinguish fibrosis within the thin atrial myocardial wall. Accuracy is essential in this case, as inclusion of external structures in the segmented myocardium can lead to a consideration of fat or outer tissue as scar or fibrosis, and omitting parts of the myocardium in the segmentation may hinder detection of fibrotic areas.…”

Elevated fibrosis burden as assessed by MRI predicts cryoballoon ablation failure

“…In a more recent study focused on a cohort of 37 ablation‐naïve patients, Eichenlaub et al 21 concluded that there were large discrepancies between the extent of LA fibrosis estimated by the IIR and PIH approaches, which is highly consistent with our own findings. Lastly, data presented in a preprint by Nairn et al 22 assess differences in LGE‐MRI delineation approaches in the context of intracardiac voltage mapping and characterization of left atrial conduction velocity. Their findings confirm that important discordances exist in the extent and spatial localization of identified pathological LA substrate depending on the LGE‐MRI segmentation method used.…”