Diagnosing Thrombosis in Atrial Fibrillation
Diagnosing a thrombus in the atria
In atrial fibrillation (AF), thrombi tend to form in the left atrium far more often than in the right atrium; clots forming in the left atrium pose a risk of cerebral or systemic emboli.22, 49 Identifying those AF patients at increased risk of developing an embolism and further cardiovascular problems is important in order to optimise diagnosis efforts and treatment decisions.181
Transesophageal echocardiography
Transesophageal echocardiography (TEE) is a more sensitive test than transthoracic electrocardiography for detecting thrombi within the atria. For this reason, TEE is generally recommended to visualise the heart before any treatment intended to restore normal sinus rhythm (eg, electric cardioversion). TEE involves placing an ultrasound transducer into the oesophagus directly behind the heart.
Other findings from TEE often associated with thromboembolism are reduced left atrial flow velocity and spontaneous echo contrast, which is thought to be caused by fibrinogen-mediated red blood cell aggregation.50
Thrombus in left atrium
D-dimer testing
D-dimer is a fibrin degradation product produced by blood clot degradation. It is formed when plasmin dissolves the fibrin strands that hold the thrombus together, and is considered a marker of fibrin turnover and thrombogenesis.43, 199 Measurement of D-dimer has been used as a surrogate biomarker when testing new antithrombotic regimes 229, 210 or new oral anticoagulants. 192, 281 Measurement of D-dimer has been used to detect a possible thrombus in patients with AF, as an elevated level has high sensitivity for indicating the presence of an atrial thrombus. A high D-dimer level also helps predict subsequent thrombotic events in patients with nonvalvular AF.181, 237, 257, 277 More data are needed to clarify the utility of D-dimer testing for clinical stroke risk assessment in AF.
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Yahoo! My Web- 22 - Fuster V, Rydén LE, Cannom DS, et al. ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(7):e257-e354.
- 49 - Agmon Y, Khandheria BK, Gentile F, Seward JB. Echocardiographic assessment of the left atrial appendage. J Am Coll Cardiol. 1999;34(7):1867-1877.
- 181 - Dougu N, Takashima S, Sasahara E, et al. Differential diagnosis of cerebral infarction using an algorithm combining atrial fibrillation and D-dimer level. Eur J Neurol. 2008;15(3):295-300.
- 50 - Rastegar R, Harnick DJ, Weidemann P, et al. Spontaneous echo contrast videodensity is flow-related and is dependent on the relative concentrations of fibrinogen and red blood cells. J Am Coll Cardiol. 2003;41(4):603-610.
- 43 - Kearon C, Hirsh J. Cardiovascular medicine: XVIII. Venous thromboembolism. In: Dale DC, ed. ACP Medicine. New York, NY: WebMD, Inc; 2007:1-15. http://www.acpmedicine.com/acp_home.htm. Accessed February 12, 2008.
- 199 - Goldhaber SZ. Cardiovascular medicine: XVIII. Venous thromboembolism. In: Dale DC, ed. ACP Medicine. New York, NY: WebMD, Inc; 2010:1-15.
- 229 - Lip GY, Lowe GD. Fibrin D-dimer: a useful clinical marker of thombogenesis? Clin Sci (Lond). 1995;89(3):205-214.
- 210 - Kamath S, Blann AD, Chin BS, Lip GY. A prospective randomized trial of aspirin-clopidogrel combination therapy and dose-adjusted warfarin on indices of thrombogenesis and platelet activation in atrial fibrillation. J Am Coll Cardiol. 2002;40(3):484-490.
- 192 - Ezekowitz MD, Reilly PA, Nehimz G, et al. Dabigatran with or without concomitant aspirin compared with warfarin alone in patients with nonvalvular atrial fibrillation (PETRO Study). Am J Cardiol. 2007;100(9):1419-1426.
- 281 - Weitz JI, Connolly SJ, Patel I, et al. Randomised, parallel-group, multicentre, multinational phase 2 study comparing edoxaban, an oral factor Xa inhibitor, with warfarin for stroke prevention in patients with atrial fibrillation. Thromb Haemost. 2010;104(3):633-641.
- 237 - Mahé I, Drouet L, Simoneau G, Minh-Muzeaux S, Caulin C, Bergmann JF. D-dimer can predict survival in patients with chronic atrial fibrillation. Blood Coagul Fibrinolysis. 2004;15(5):413-417.
- 257 - Sadanaga T, Sadanaga M, Ogawa S. Evidence that D-dimer levels predict subsequent thromboembolic and cardiovascular events in patients with atrial fibrillation during oral anticoagulant therapy. J Am Coll Cardiol. 2010;55(20):2225-2231.
- 277 - Vene N, Mavri A, Kosmelj K, Stegnar M. High D-dimer levels predict cardiovascular events in patients with chronic atrial fibrillation during oral anticoagulant therapy. Thromb Haemost. 2003;90(6):1163-1172.
- Fibrin
- The primary end product of the coagulation cascade. Fibrin links itself into strands to form a net. This net traps blood cells and tightens itself through cross-linkages, resulting in a dense blood clot.
- Plasmin
- A component (enzyme) of the fibrinolytic system that breaks fibrin into small pieces.
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