Case Report: Acute Thrombotic Angiopathy of Atrial Appendage Epicardial Veins: A Seemingly Innocuous Finding Portending a Fatal Outcome

Abstract

Thrombotic angiopathy is a pathologic description to describe endothelial injury, and with sufficient and sustained injury can lead to exposure of underlying tissue factor and the deposition of associated fibrin material. We present briefly a case of an 87-year-old woman with mitral valve regurgitation and atrial fibrillation undergoing mitral valve annuloplasty, Cox-maze procedure, and excision of the left atrial appendage. Pathologic examination of the excised atrial appendage revealed commonly encountered cardiomyocyte hypertrophy and endocardial fibroelastosis, however also showed a non-occlusive, acute thrombotic angiopathy involving epicardial veins. The surgical and immediate post-operative course was unremarkable; however, 3 weeks after discharge, the patient would develop a fatal pulmonary embolism. While fibrin thrombosis developing within the atrial appendage chamber is a recognized concern in the setting of atrial fibrillation, the significance of an acute thrombotic angiopathy involving epicardial veins of the atrial appendage is less clear although in the presented case was the sole potential harbinger of a subsequent fatal thrombotic event.

Keywords: acute thrombotic angiopathy; atrial appendage; atrial fibrillation; pulmonary embolism; thrombosis.

Figure 1

The excised left atrial appendage revealed few epicardial veins involved by a non-occlusive acute thrombotic angiopathy (A–C, with stars indicating veins at lower power magnification). The acute thrombotic angiopathy was characterized by eccentric intimal edema, endotheliosis (note swollen nature of endothelial cells adjacent to fibrin), and fibrin deposition (D). The vessels involved were determined to be veins based upon morphologic features including an attenuated smooth muscle layer and lined by endothelial cells that by immunoperoxidase staining expressed CD34 (E) and ERG (F) and were negative for D2-40 (G). Fibrin material associated with the endothelial injury was characteristically fuchsinophilic by Masson trichrome stain (H inset) and bright red by Russell-Movat pentachrome stain (I). The usually encountered findings of endocardial fibroelastosis (A) and cardiomyocyte hypertrophy (B,C) were also evident. Images (A–D) are from paraffin sections stained with hematoxylin and eosin. Original magnification for (A) at ×20; for (B,C), and (E–I) at ×100; for (D) at ×400; and for (H inset) at ×200.

Figure 2

A ventilation and perfusion lung scan was performed. Analysis of the perfusion images revealed multiple mismatched segmental/subsegmental defects (particularly in the right lung) and matched non-segmental defects along the periphery of both lungs (A). Analysis of the ventilation images revealed moderate heterogeneity of tracer deposition with retention of radiotracer in the central bronchi and several areas of diminished ventilation along the periphery of both lungs (B). Both images are of the anterior view.