Patients with persistent atrial fibrillation and metabolic comorbidities have an altered inflammatory state of atrial epicardial adipose tissue, which is linked to CT-attenuation.

Patients with persistent AF had significantly more EAT neutrophils compared to those with paroxysmal AF.

• Neutrophil counts were 155[257] versus 63[106] cells/mm2 in persistent versus paroxysmal AF patients (p = 0.003).
• 113 of 134 included patients had a left atrial appendage available for (immuno)histochemistry.
• The AUC for differentiating persistent from paroxysmal AF through neutrophil count was 0.75 (p < 0.001, CI 0.63–0.87).
• Patients underwent thoracoscopic ablation for advanced AF, typically persistent with enlarged left atria and previous failed ablations.

Patients with persistent AF had significantly fewer anti-inflammatory CD163+ macrophages in EAT compared to those with paroxysmal AF.

• CD163+ macrophage counts were 126[134] versus 224[179] cells/mm2 in persistent versus paroxysmal AF patients (p = 0.03).
• CD163+ macrophages are characterized as anti-inflammatory in the paper.
• This finding indicates an altered inflammatory state in persistent AF beyond just neutrophil elevation.

CT-EAT attenuation distinguished persistent from paroxysmal AF.

• CT-EAT attenuation was -73.0 ± 4.6 HU in persistent AF versus -75.3 ± 5.3 HU in paroxysmal AF (p = 0.03).
• Higher (less negative) attenuation values corresponded to persistent AF, indicating denser EAT.
• Cardiac CT scans were performed before and 6 months after surgery.

EAT neutrophil count was independently associated with CT-EAT attenuation in multivariable analysis.

• Multivariable analysis showed expB 1.01 (CI 1.00–1.02, p = 0.04) for the relationship between neutrophil count and CT-EAT attenuation.
• This finding links histological inflammatory cell content to a non-invasive CT-based measure.
• CT-EAT attenuation (density) was used as a surrogate marker for EAT inflammation.

Patients with AF recurrence after ablation had larger adipocytes in EAT compared to those without recurrence.

• Multivariable analysis for adipocyte size and AF recurrence: ExpB 1.002 (CI 1.00–1.003, p = 0.02).
• Patients with versus without recurrence had similar inflammatory cell counts.
• Adipocyte hypertrophy rather than inflammatory cell infiltration was the distinguishing feature in AF recurrence.

Hypertensive and diabetic patients also exhibited increased EAT adipocyte size.

• Both hypertension and diabetes were associated with adipocyte hypertrophy in EAT.
• This finding parallels the adipocyte hypertrophy observed in patients with AF recurrence.
• The authors suggest this may imply a common mechanism underlying AF recurrence, hypertension, and diabetes.
• Metabolic comorbidities (metabolic syndrome) were a primary focus of the study alongside AF type.

The study enrolled 134 patients undergoing thoracoscopic ablation for advanced AF with cardiac CT imaging before and after surgery.

• 134 patients were included in total; 113 had a left atrial appendage (LAA + EAT) available for (immuno)histochemistry.
• Left atrial appendages were excised during ablation and stained for adipocytes and different inflammatory cells.
• CT-EAT atrial volume and attenuation (density) were used for analyses.
• The study population represented advanced AF, typically persistent, with enlarged left atria and previous failed ablations.