Epicardial adipocytes in the pathogenesis of atrial fibrillation: An update on basic and translational studies.

Epicardial adipose tissue (EAT) is an endocrine organ containing a host of cell types and undoubtedly serving a multitude of important physiologic functions. Aging and obesity cause hypertrophy of EAT. There is great interest in the possible connection between EAT and cardiovascular disease, in particular, atrial fibrillation (AF). Increased EAT is independently associated with AF and adverse events after AF ablation (e.g., recurrence of AF, and stroke). In general, the amount of EAT correlates with BMI or visceral adiposity. Yet on a molecular level, there are similarities and differences between epicardial and abdominal visceral adipocytes. In comparison to subcutaneous adipose tissue, both depots are enriched in inflammatory cells and chemokines, even in normal conditions. On the other hand, in comparison to visceral fat, epicardial adipocytes have an increased rate of fatty acid release, decreased size, and increased vascularity. Several studies have described an association between fibrosis of EAT and fibrosis of the underlying atrial myocardium. Others have discovered paracrine factors released from EAT that could possibly mediate this association. In addition to the adjacent atrial cardiomyocytes, EAT contains a robust stromal-vascular fraction and surrounds the ganglionic plexi of the cardiac autonomic nervous system (cANS). The importance of the cANS in the pathogenesis of atrial fibrillation is well known, and it is quite likely that there is feedback between EAT and the cANS. This complex interplay may be crucial to the maintenance of normal sinus rhythm or the development of atrial fibrillation. The extent the adipocyte is a microcosm of metabolic health in the individual patient may determine which is the predominant rhythm.

Mechanical Left Ventricular Unloading in Patients Undergoing Venoarterial Extracorporeal Membrane Oxygenation.

BACKGROUND: Venoarterial extracorporeal membrane oxygenation (VA-ECMO) increases left ventricular (LV) afterload, potentially provoking LV distention and impairing recovery. LV mechanical unloading (MU) with intra-aortic balloon pump (IABP) or percutaneous ventricular assist device (pVAD) can prevent LV distension, potentially at the risk of more complications, and net clinical benefit remains uncertain. OBJECTIVES: This study aims to determine the association between MU and outcomes for patients undergoing VA-ECMO. METHODS: The authors queried the Extracorporeal Life Support Organization registry for adults receiving peripheral VA-ECMO from 2010 to 2019 and stratified them by MU with IABP or pVAD. The primary outcome was in-hospital mortality; secondary outcomes included on-support mortality and complications during VA-ECMO. RESULTS: Among 12,734 VA-ECMO patients, 3,399 (26.7%) received MU: 2,782 (82.9%) IABP and 580 (17.1%) pVAD. MU patients were older (age 56.3 vs 52.7 years) and, before extracorporeal membrane oxygenation, more often required >2 vasopressors (41.7% vs 27.2%) and had respiratory (21.1% vs 15.9%), renal (24.6% vs 15.8%), and liver failure (4.4% vs 3.1%) (all P < 0.001). MU patients had lower in-hospital mortality (56.6% vs 59.3%, P = 0.006), which persisted in multivariable modeling (adjusted OR [aOR]: 0.84; 95% CI: 0.77-0.92; P < 0.001). MU was associated with more cannula site bleeding (aOR: 1.25; 95% CI: 1.11-1.40; P < 0.001) and hemolysis (aOR: 1.27; 95% CI: 1.03-1.57; P = 0.02). Compared to pVAD, MU patients with IABP had similar mortality (aOR: 0.80; 95% CI: 0.64-1.01; P = 0.06) and less medical bleeding (aOR: 0.45; 95% CI: 0.31-0.64; P < 0.001), cannula site bleeding (aOR: 0.72; 95% CI: 0.54-0.96; P = 0.03), and renal injury (aOR: 0.78; 95% CI: 0.62-0.98; P = 0.03). CONCLUSIONS: Among adults receiving VA-ECMO, MU was associated with lower in-hospital mortality despite increased complications including hemolysis and cannulation site bleeding. Compared to pVAD, MU with IABP was associated with similar mortality and lower complication rates.