False detection of left atrial thrombus by the angiographic sign of "neovascularity".

"Neovascularity" in the region of the left atrial appendage was demonstrated by coronary arteriography preoperatively in five patients with mitral valve disease and was attributed to the presence of thrombus in the left atrium. Subsequently, they underwent surgery, but thorough inspection of the left atrium did not reveal thrombus in any of the five patients. The presence of neovascularity without apparent thrombosis or false detection may be a result of tissue reaction and organization in an effort to resorb the thrombus.