Fluid dynamics and atherosclerosis development in the human thoracic aorta: a transesophageal echocardiographic evaluation of protruding aortic plaque distribution and motion

Abstract

The pathogeneses of atherosclerosis in the thoracic aorta is heterogeneous and still incompletely elucidated. Protruding aortic plaques (PAP), reliable markers of atherosclerosis development and extension, could be easily identified by transesophageal echocardiography (TEE). A close relation between atherosclerosis development in the thoracic aorta, stroke and peripheral emboli were established. The purpose of this study was to use PAP distribution and motion on TEE to characterize atherogenesis in the human thoracic aorta. Out of 569 consecutive patients (age range 18-83 years), 108 were referred for TEE to evaluate recent embolism (Group I). The remaining 461 patients were referred for TEE for reasons unrelated to embolism (Group II). The plaque thickness was measured perpendicularly to the aortic wall. In the subgroup of patients with multiple mobile lesions, multiple vortices were suggested to be present when simultaneous rotations in different directions were found. The presence of a fixed PAP was associated with a statistically significant, albeit moderate, increase in the risk for embolism (adjusted odds ratio 4.1). The presence of mobile lesions was linked to an abrupt augmentation in this risk (adjusted odds ratio 30.1). Among the 35 patients in Group I there were 69 PAP: 8 (12%) in the ascending, 28 (41%) in the arch and 33 (48%) in the descending aorta. A total of 34 mobile lesions was detected: 1 (one patient) in the ascending aorta, 15 (10 patients) in the arch and 18 (11 patients) in the descending aorta. There was no significant difference between the arch and the descending aorta regarding the frequency of the plaques in these regions, whereas the ascending aorta presented the lowest prevalence for atheromatosis. Diastolic retrograde and rotational flows were observed in all patients. There were 16 multiple mobile PAP in 6 patients: in all these cases simultaneous rotations of mobile aortic plaques (MAP) in different directions (highly suggestive for the presence of multiple vortices and significant flow instability) were found in the arch and the descending but not the ascending aorta. Protruding aortic plaques and signs of relative aortic flow instability (presence of vortices) are mainly observed in the human arch and in the descending aorta, whereas the ascending aorta presented the lowest prevalence for atheromatosis. This issue may have significant implications in the study of atherosclerosis development in the human thoracic aorta and the pathogeneses of embolic events.