Abstract
Background: Electrical cardioversion in patients with atrial fibrillation is followed by a transiently impaired atrial mechanical function, termed atrial stunning. During atrial stunning, a retained risk of left atrial thrombus formation exists, which may be attributed to abnormal left atrial blood flow patterns. 4D Flow cardiovascular magnetic resonance (CMR) enables blood flow assessment from the entire three-dimensional atrial volume throughout the cardiac cycle. We sought to investigate left atrial 4D blood flow patterns and hemostasis during left atrial stunning and after left atrial mechanical function was restored.Methods: 4D Flow and morphological CMR data as well as blood samples were collected in fourteen patients at two time-points: 2–3 h (Time-1) and 4 weeks (Time-2) following cardioversion. The volume of blood stasis and duration of blood stasis were calculated. In addition, hemostasis markers were analyzed.Results: From Time-1 to Time-2: Heart rate decreased (61 ± 7 vs. 56 ± 8 bpm, p = 0.01); Maximum change in left atrial volume increased (8 ± 4 vs. 22 ± 15%, p = 0.009); The duration of stasis (68 ± 11 vs. 57 ± 8%, p = 0.002) and the volume of stasis (14 ± 9 vs. 9 ± 7%, p = 0.04) decreased; Thrombin-antithrombin complex (TAT) decreased (5.2 ± 3.3 vs. 3.3 ± 2.2 μg/L, p = 0.008). A significant correlation was found between TAT and the volume of stasis (r2 = 0.69, p < 0.001) at Time-1 and between TAT and the duration of stasis (r2 = 0.34, p = 0.04) at Time-2.Conclusion: In this longitudinal study, left atrial multidimensional blood flow was altered and blood stasis was elevated during left atrial stunning compared to the restored left atrial mechanical function. The coagulability of blood was also elevated during atrial stunning. The association between blood stasis and hypercoagulability proposes that assessment of left atrial 4D flow can add to the pathophysiological understanding of thrombus formation during atrial fibrillation related atrial stunning.
Highlights
Atrial fibrillation (AF) is the most common sustained arrhythmia, with an increasing prevalence with age, presence of cardiovascular risk factors and cardiovascular diseases (Odutayo et al, 2016; Xu et al, 2016)
Our findings based on comprehensive assessment of time resolved multidimensional blood flow using 4D Flow cardiovascular magnetic resonance (CMR), showed increased left atrium (LA) blood stasis during LA stunning, compared to the restored LA mechanical function, indicating that a higher proportion of the LA blood volume had very low velocities, and that these low blood velocities occurred for a longer time period throughout the cardiac cycle
Thrombus formation in the LA of patients with AF has been associated with blood stasis and abnormal intra atrial blood flow (Watson et al, 2009; Iwasaki et al, 2011), we investigated the relation between advanced measures of LA flow patterns and hemostasis
Summary
Atrial fibrillation (AF) is the most common sustained arrhythmia, with an increasing prevalence with age, presence of cardiovascular risk factors and cardiovascular diseases (Odutayo et al, 2016; Xu et al, 2016). The lack of normal mechanical contraction in the left atrium (LA) and left atrial appendage (LAA) leads to stasis of blood, elevating the thromboembolic risk and the risk of stroke in AF patients (Iwasaki et al, 2011). The exact mechanism leading to atrial stunning is not entirely known, studies suggest that it is caused by changes in atrial myocardium during AF and is influenced by the duration of AF, atrial size and underlying structural heart disease (Watson et al, 2009). Electrical cardioversion in patients with atrial fibrillation is followed by a transiently impaired atrial mechanical function, termed atrial stunning. We sought to investigate left atrial 4D blood flow patterns and hemostasis during left atrial stunning and after left atrial mechanical function was restored
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