Abstract 2286: Ultrasonographic And Pathological Measurement Of Fibrous Cap In Rupture-prone Carotid Plaques Using Advanced Ultrasound Technology

[Background and Purpose] In carotid stenosis, thin fibrous cap, as one of the characteristics of unstable plaques, have been thought to be an important risk factor for plaque rupture and acute cerebral ischemic events. A study reported there was good agreement between ultrasonographic and pathological fibrous cap thickness(FCT). The fibrous cap of ultrasound image in this study, however, was not measured at the same location in pathology. So, we precisely aligned ultrasonographic images with pathology in carotid plaques by advanced ultrasound with global position system (GPS)-like positon-sensing technology, and examined the characteristics of fibrous cap in rupture-prone plaques. [Methods and Results] 24 patients(symptomatic=18, asymptomatic=6) undergoing carotid endarterectomy for carotid stenosis between June 2010 and January 2011 were subjected in this study. We performed carotid ultrasound using a LOGIQ E9(GE Healthcare) within three days before carotid endarterectomy. Three-dimensinal images with the positonal information were obtained using an electromagnetic transmitter and sensors mounted on a linear probe. Endarterectomy specimens were cut every 3mm from carotid bifurcation in the short axis view. The three-dimensinal images alined with the specimens were extracted every 3mm of the same location in the short axis view. We measured maximal and minimal FCT in these ultrasonographic and pathological images. There was a positive relation(r=0.74) between fibrous cap thickness in pathology(maximal FCT =571μm[93 to 1062]) and ultrasound(maximal FCT =439μm[242 to 809]). Maximal FCT in pathology was significantly less in the pathologically ruptured plaques(n=16) than in the nonrupured plaques(n=8) (456μm VS 803μm, P<0.05). In contrast, maximal FCT in ultrasound had no difference in the two groups(389μm VS 497μm, P=0.09). In pathology fibrous cap was ruptured in 16 patients(67%, minimal FCT=0μm), and thin, restored and sparse though nonruptured in other 5 patients(21%, minimal FCT=177μm[50 to 339]). At the same location, the fibrous cap of ultrasound image disappeared in all these 21 patients. The other 3 patients(13%) without plaque rupture showed thick fibrous cap in pathology(minimal FCT =301μm[279 to 325]) and ultrasound(minimal FCT =283μm[250 to 300]). [Conclusions] Using advanced ultrasound with GPS-like technology, we were able to examine the pathological characteristics of fibrous cap in ultrasound in detail. It is difficult to sort out preoperatively more pathologically unstable plaques only by measuring FCT in ultrasound. Ultrasonographic disappearance of fibrous cap is more significant sign of pathologically unstable plaques.