Background: Nowadays there are many literature linking inflammation to a wide verities of cardiovascular conditions such as coronary artery disease (CAD), insulin resistance, diabetes mellitus and hypertension, in addition, there is emerging data supporting the link between inflammation and AF. Histological evidence to support the association between inflammation and AF has been derived through atrial biopsies taken from patients with AF were compared with controls has demonstrated evidence of inflammatory infiltrates and oxidative damage within the atrial tissue. The inflammatory marker that has been most frequently studied is high-sensitivity C reactive protein (hs-CRP). Levels of hs-CRP have been noted to be higher among patients with AF compared with controls in sinus rhythm. Also, persistent AF patients have higher hs-CRP levels than paroxysmal AF patients, and both have higher levels than controls. Furthermore, it is found that the longer the duration of AF is associated with higher hs-CRP levels and the larger left atrial dimensions, supporting a link among the burden of AF, inflammation, and structural remodeling. In both cross-sectional and longitudinal studies, hs-CRP has remained a consistent and a significant predictor of early AF recurrence after successful cardioversion, even after adjustment for risk factors for AF, such as hypertension and CAD. hs-CRP has also been shown to be predictive of subsequent future development of new cases of AF among a large cohort of patients in sinus rhythm. AF promotes thromboembolism through many mechanisms as mechanical dysfunction in the atria leading to impaired blood flow and stasis, endothelial dysfunction, inflammation, platelet activation, and a hypercoagulable state have also been implicated. Objective: This study aimed to determine the cut-off value of hs-CRP at which there is an increased risk of thromboembolism in patients with non-valvular atrial fibrillation. Methods: This study included 100 patients with non-valvular AF which were subjected to transesophageal echocardiography(TEE) before cardioversion or were referred to assess the left atrial appendage in NVAF with stroke patients for evaluation the presence of thromboembolic markers (LAA thrombus, LAA low flow velocity, SEC), transthoracic echocardiography(TTE) (to measure LA anteroposterior diameter, LA area, and LVEF) and hs-CRP blood level. Our patients were divided into two groups, group(A) included 26 patients with hs-CRP
4.5 mg/dl and group(B) included 74 patients with hs-CRP<4.5 mg/dl. Results: Our study showed that: Group (A) patients were significantly older (p < 0.05), had longer duration of AF (P < 0.05), had larger left atrium (LA AP diameter and LA area, P < 0.001), had lower LVEF (50.923  8.291% vs 57.054  7.828%, P < 0.05), had higher incidence of thromboembolic markers as LAA thrombus (76.9% vs 0.03%, p < 0.001), dense SEC (53.84% vs 18.92%, p < 0.001) and low LAAEV (17.085  2.109 vs 26.986  9.083, p < 0.001) and had higher CHA2DS2-VASc score (4.692  1.032 vs 1.838  1.118, p < 0.001) when compared with group (B). Also our study showed that hs-CRP had: -Highly significant positive correlation with age (r = 0.514, p < 0.001), CHA2DS2-VASc score (r = 0.603, p < 0.001), LA diameter (r = 0.628 p < 0.001), LA area (r = 0.525, p < 0.001), SEC (r = 0.603 p < 0.001), and LAA thrombus (r = 8.313, p < 0.001) -Significant positive correlation with AF duration (r = 2.877, p < 0.05) -Highly significant negative correlation with LAA emptying velocity (r =0.530, p < 0.001), and LAA filling