Evaluating the Atrial Myopathy Underlying Atrial Fibrillation

Abstract

Atrial disease or myopathy forms the substrate for atrial fibrillation (AF) and underlies the potential for atrial thrombus formation and subsequent stroke. Current diagnostic approaches in patients with AF focus on identifying clinical predictors with evaluation of left atrial size by echocardiography serving as the sole measure specifically evaluating the atrium. Although the atrial substrate underlying AF is likely developing for years prior to the onset of AF, there is no current evaluation to identify the pre-clinical atrial myopathy. Atrial fibrosis is one component of the atrial substrate that has garnered recent attention based on newer MRI techniques that have been applied to visualize atrial fibrosis in humans with prognostic implications regarding success of treatment. Advanced ECG signal processing, echocardiographic techniques, and MRI imaging of fibrosis and flow provide up-to-date approaches to evaluate the atrial myopathy underlying AF. While thromboembolic risk is currently defined by clinical scores, their predictive value is mediocre. Evaluation of stasis via imaging and biomarkers associated with thrombogenesis may provide enhanced approaches to assess risk for stroke in patients with AF. Better delineation of the atrial myopathy that serves as the substrate for AF and thromboembolic complications might improve treatment outcomes. Furthermore, better delineation of the pathophysiologic mechanisms underlying the development of the atrial substrate for AF, particularly in its earlier stages, could help identify blood and imaging biomarkers that could be useful to assess risk for developing new onset AF and suggest specific pathways that could be targeted for prevention.

Atrial Fibrillation Is Associated With a Worse 90-Day Outcome Than Other Cardioembolic Stroke Subtypes

“…9 Proposed underlying mechanisms could relate to a reduced cardiac output, cardiac remodeling, or underdeveloped cerebral collateral circulation. 9,24,25 Although our results are in line with prior observations that AF carries an excess risk for poor outcome independent of underlying heart disease; 26 our study design did not enable us to conduct detailed electro- and echocardiographic investigations to clarify this issue. Further, studies on the robustness of cerebral collateral circulation among patients with large artery infarction did not demonstrate a significant difference between patients with vs. without AF.…”

Left Atrial and Left Atrial Appendage 4D Blood Flow Dynamics in Atrial Fibrillation

“…This likely reflects the underlying atrial myopathy responsible for the AF. 29 While the LAA is the most common site for thrombus formation in AF, the underlying pathophysiology for this has not been elucidated. Moreover, only a minority of patients with AF, even without anticoagulation, develop LA thrombi, suggesting that there are patient-specific factors that promote thrombus formation.…”

Intermittent vs. Continuous Anticoagulation theRapy in patiEnts with Atrial Fibrillation (iCARE-AF): a randomized pilot study

“…Although the association between AF and stroke has been established in multiple epidemiological studies, the exact mechanism of stroke remains poorly understood [11]. Multiple studies have shown a correlation between thromboembolic risk and asymptomatic AF episodes of variable duration detected through implantable devices [26-29], even though a temporal association of an incident stroke with an antecedent AF episode was frequently absent in the aforementioned studies [30, 31].…”

“…Thrombus formation in the left atrium is thought to represent the main source of thromboembolic events in patients with AF [11]. Consistent with recent evidence suggesting that paroxysmal AF may be associated with a lower incidence of stroke compared to persistent AF [12-15], we hypothesized that in a selected group of patients with paroxysmal AF and a low risk of stroke, maintaining therapeutic anticoagulation only during episodes of AF (either symptomatic or asymptomatic) may provide the benefits of continuous anticoagulation in terms of stroke prevention, while decreasing the risk of bleeding complications.…”