Musotto Giulio, Monteleone Alessandra, Vella Danila, Di Leonardo Sofia, Viola Alessia, Pitarresi Giuseppe, Zuccarello Bernardo, Pantano Antonio, Cook Andrew, Bosi Giorgia M, Burriesci Gaetano
Bioengineering Unit, Ri.MED Foundation, Palermo, Italy.
Department of Engineering, University of Palermo, Palermo, Italy.
Front Cardiovasc Med. 2022 Jul 14;9:894187. doi: 10.3389/fcvm.2022.894187. eCollection 2022.
A large majority of thrombi causing ischemic complications under atrial fibrillation (AF) originate in the left atrial appendage (LAA), an anatomical structure departing from the left atrium, characterized by a large morphological variability between individuals. This work analyses the hemodynamics simulated for different patient-specific models of LAA by means of computational fluid-structure interaction studies, modeling the effect of the changes in contractility and shape resulting from AF.
Three operating conditions were analyzed: sinus rhythm, acute atrial fibrillation, and chronic atrial fibrillation. These were simulated on four patient-specific LAA morphologies, each associated with one of the main morphological variants identified from the common classification: chicken wing, cactus, windsock, and cauliflower. Active contractility of the wall muscle was calibrated on the basis of clinical evaluations of the filling and emptying volumes, and boundary conditions were imposed on the fluid to replicate physiological and pathological atrial pressures, typical of the various operating conditions.
The LAA volume and shear strain rates were analyzed over time and space for the different models. Globally, under AF conditions, all models were well aligned in terms of shear strain rate values and predicted levels of risk. Regions of low shear rate, typically associated with a higher risk of a clot, appeared to be promoted by sudden bends and focused at the trabecule and the lobes. These become substantially more pronounced and extended with AF, especially under acute conditions.
This work clarifies the role of active and passive contraction on the healthy hemodynamics in the LAA, analyzing the hemodynamic effect of AF that promotes clot formation. The study indicates that local LAA topological features are more directly associated with a thromboembolic risk than the global shape of the appendage, suggesting that more effective classification criteria should be identified.
导致心房颤动（AF）缺血性并发症的血栓绝大多数起源于左心耳（LAA），这是一个从左心房分出的解剖结构，其形态在个体间差异很大。这项工作通过计算流体-结构相互作用研究，分析了针对不同患者特异性LAA模型模拟的血流动力学，模拟了AF导致的收缩性和形状变化的影响。
分析了三种操作条件：窦性心律、急性心房颤动和慢性心房颤动。在四种患者特异性LAA形态上进行了模拟，每种形态与从常见分类中识别出的主要形态变体之一相关：鸡翅型、仙人掌型、风袋型和花椰菜型。根据充盈和排空容积的临床评估校准壁肌的主动收缩性，并对流体施加边界条件以复制各种操作条件下典型的生理和病理性心房压力。
对不同模型在时间和空间上分析了LAA容积和剪切应变率。总体而言，在AF条件下，所有模型在剪切应变率值和预测风险水平方面都很好地一致。低剪切率区域通常与较高的血栓形成风险相关，似乎因突然弯曲而加剧，并集中在小梁和叶处。这些在AF时变得更加明显和广泛，尤其是在急性情况下。
这项工作阐明了主动和被动收缩对LAA健康血流动力学的作用，分析了促进血栓形成的AF的血流动力学效应。该研究表明，局部LAA拓扑特征比心耳的整体形状更直接地与血栓栓塞风险相关，这表明应确定更有效的分类标准。
