Case No.: C-010

Diagnosis: Organizing thrombi associated with atrial fibrillation

Organ: Heart, atrium

Last Updated: 11/21/2011

 

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Hematoxylin & eosin

Area 1: These images are obtained at the edge of the thrombus where many foamy macrophages are present.

Hematoxylin & eosin

Area 2: These images are obtained at the deep part of the thrombus where many fibroblasts admixed with foamy macrophages are present. The fibroblasts appears spindly.
Area 2: Note that in the deepest part of the thrombus (black arrow), the endocardium cannot be well distinguished from either the myocardium or the thrombus. In a location slightly peripheral (white arrow), remnants of the fibrous component of the endocardium can still be recognized.

Hematoxylin & eosin

Area 3: Note that his area probably corresponds to the earliest phase of organizaztion of the throumbus featured by a small amount of fibroblasts and foamy macrophages.

Hematoxylin & eosin

Area 4: A thin layer of polymorphonuclear leukocytes are present in the endocardium. This is most likely acute reactive change due to the procedure but not genuine endocarditis.

History: The specimen was obtained from the cardiac atrium of a 67 year-old woman who has been treated with radiofrequency ablation before for atrial fibrillation (AF).

 

Histologic Highlights of this Case:

  • The overall shape of the specimen is consistent with that of a cardiac atrium and there is a large organizing thrombus (t) that lines the tip of the atrium. This thrombus is outlined by the arrows from the myocardium (m) and the endocardium (e).

  • The thrombus has a zonal architecture. At the most superficial part is the blood clot. The underlying area is composed of foamy macrophages and fibroblasts. The entire thrombus is attached to the endocardium. At the tip of the thrombus, the endocardium has disappeared and the thrombus is directly attached to the endocardium.

Comment:

  • Atrial fibrillation (AF) is a very common. It is caused by chaotic and unorganized electrical activity of the atria leading to reduced pumping function of the atria. The stagnation of blood set up the stage for thrombus formation. While this condition can be treated with medication, some patients are candidates for radio frequency ablation.

  • One of the two major complications of AF is stroke which is often resulted from a dislodged thrombus. The other major complication is heart failure. The current specimen is a perfect example for stroke associated with these cases. The surface of the thrombus is not lined by endothelial cells. More thrombus can form and will increase the risk of stroke due to dislodged thromboemboli.

Original slide is contributed by Dr. Kar-Ming Fung, University of Oklahoma Health Sciences Center, Oklahoma, U.S.A.

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