Black I W
Department of Cardiology, Manly Hospital, Darley Road, Manly NSW 2095, Australia.
Echocardiography. 2000 May;17(4):373-82. doi: 10.1111/j.1540-8175.2000.tb01153.x.
Left atrial (LA) spontaneous echo contrast (SEC), or "smoke," is a frequent finding on transesophageal echocardiography (TEE), but it is rarely detected with transthoracic echocardiography. LA SEC is characterized by dynamic smoke-like echoes within the LA cavity or appendage. Most patients with LA SEC have atrial arrhythmias, mitral stenosis, or a mitral valve prosthesis, and they have an enlarged LA, conditions that are associated with LA stasis. Conversely, mitral regurgitation is protective against LA SEC. LA SEC is present in almost all patients with LA thrombus and is associated with previous embolic events in many patient populations. In patients with nonvalvular atrial fibrillation, LA SEC predicts future embolism and death. LA SEC may therefore assist in selecting patients with atrial fibrillation or with mitral stenosis and sinus rhythm who benefit the most from anticoagulation. Hematological studies have shown that LA SEC is a marker of an hypercoagulable state. LA SEC is a manifestation of red cell aggregation, arising from an interaction between red cells and plasma proteins such as fibrinogen, at low shear rates. LA SEC does not require platelets. The detection of LA SEC on ultrasound arises from the increased amplitude of backscatter from red cell aggregates rather than single cells. Patients with LA SEC should be considered for anticoagulant therapy and may require correction of underlying cardiovascular abnormalities. Future directions in LA SEC include further assessment of integrated backscatter for quantification, assessment of its prognostic role in clinically low-risk patients with nonvalvular AF, and novel pharmacological treatment.
左心房（LA）自发显影（SEC），即“烟雾”征，是经食管超声心动图（TEE）检查中常见的表现，但经胸超声心动图很少能检测到。LA SEC的特征是在LA腔或心耳内出现动态的烟雾样回声。大多数有LA SEC的患者患有房性心律失常、二尖瓣狭窄或二尖瓣人工瓣膜，且左心房增大，这些情况都与LA血流淤滞有关。相反，二尖瓣反流可预防LA SEC。几乎所有有LA血栓的患者都存在LA SEC，并且在许多患者群体中与既往栓塞事件相关。在非瓣膜性心房颤动患者中，LA SEC可预测未来的栓塞和死亡。因此，LA SEC可能有助于选择从抗凝治疗中获益最大的心房颤动或二尖瓣狭窄且为窦性心律的患者。血液学研究表明，LA SEC是高凝状态的一个标志物。LA SEC是红细胞聚集的一种表现，是在低剪切速率下红细胞与血浆蛋白（如纤维蛋白原）相互作用产生的。LA SEC不需要血小板。超声检测到LA SEC是由于红细胞聚集体而非单个细胞的反向散射振幅增加。有LA SEC的患者应考虑接受抗凝治疗，可能还需要纠正潜在的心血管异常。LA SEC未来的研究方向包括进一步评估综合背向散射以进行量化、评估其在临床低风险非瓣膜性房颤患者中的预后作用以及新型药物治疗。
