Structure and Function of the Left Atrium and Left Atrial Appendage: AF and Stroke Implications

Victoria Delgado, MD, PHD; Luigi Di Biase, MD, PHD; Melissa Leung, MBBS, BSC(MED), MBIOSTAT, PHD; Jorge Romero, MD; Laurens F. Tops, MD, PHD; Barbara Casadei, MD, PHD; Nassir Marrouche, MD, PHD; Jeroen J. Bax, MD, PHD

Disclosures

J Am Coll Cardiol. 2017;70(25):3157-3172. 

In This Article

Conclusions

Significant evidence indicates that assessment of LA and LAA anatomy and function has important prognostic implications in new onset and perpetuation of AF and risk of stroke. Selection of patients for anticoagulation treatment or AF ablation does not routinely include imaging-based parameters that characterize the LA substrate. Anticoagulation therapies are very efficacious in reducing the risk of stroke of AF patients, and LA imaging may not further improve this efficacy in patients at high risk of stroke. Conversely, in patients with low risk of stroke, LA and LAA imaging may further refine the risk and identify patients who may benefit from anticoagulation (enabling "precision medicine"). Importantly, in patients with contraindications for anticoagulation who are referred for transcatheter closure of the LAA, CT and echocardiography play a central role. When selecting patients with AF who may benefit from catheter ablation techniques, imaging techniques to evaluate LA size, function, and myocardial fibrosis have shown to be important. The ongoing DECAAF-II (Efficacy of DE-MRI-Guided Ablation vs. Conventional Catheter Ablation of Atrial Fibrillation II) trial will help to establish the role of LGE CMR to guide ablation procedures and improve the efficacy of the ablation technique. Finally, to understand the LA remodeling process, LV structural and functional changes need to be considered because they are closely interrelated (Central Illustration).

Central Illustration.

Association Between LA Remodeling, AF, and Stroke
Left atrial (LA) and left atrial appendage (LAA) remodeling are common to the pathophysiology of atrial fibrillation (AF) and stroke. Increased LA volume, increased LA fibrosis, and impaired LA function are the main hallmarks of LA remodeling. Although an increase in LA volume can be assessed with any imaging modality (preferably with 3-dimensional techniques), increased LA fibrosis is evaluated with cardiovascular magnetic resonance (CMR) techniques (arrows), and LA function is better assessed with imaging techniques that directly evaluate the myocardial deformation (e.g., speckle tracking echocardiography). Specific imaging parameters related to AF include LA conduction delay, assessed with echocardiographic tissue Doppler imaging (PA-TDI) and increased LA adipose tissue evaluated with computed tomography (CT). Imaging parameters indicating the risk of stroke include blood flow, blood stagnation, and thrombus formation, assessed with transesophageal echocardiography or 4-dimensional flow CMR, and the morphology of the LAA, better assessed with CT. Evaluation of the LA remodeling process underlying the increased risk of atrial fibrillation and stroke should also integrate the influence of the left ventricle (LV), including assessment of LV fibrosis, LV function (strain imaging), microvascular dysfunction (nuclear imaging), and myocardial energetics with magnetic resonance spectroscopy. ↑= increased;↓ = reduced.

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