Cardiac thrombotic stability determined by contrast-enhanced echocardiography: investigative protocol and preliminary results

OBJECTIVE: This study’s intent was to test a new system for scoring cardiac thrombotic stability, based on contrast-enhanced ultrasound (CEUS). METHODS: We used human whole blood for an in vitro thrombotic model involving 1-h (T(1h)) and 7-day (T(7d)) subsets. The T(1h) group was monitored for 1 h continuously to observe for the formation of a new thrombus on the original thrombus base. Changes in thrombotic CEUS images, histologic features, and shear wave elastography were recorded over time. We also studied 28 patients diagnosed with cardiac thrombi, each examined by transthoracic echocardiography and CEUS.Thrombi were scored for substrate (T(s)) and hardness (T(h)) based on the visualized degree of contrast penetration into the thrombi. Statistical analyses of T(s) and T(h) reflected thrombolytic time and risk of embolism to other organs. RESULTS: Histologically, the loosely constructed ends of in vitro thrombi solidified over time. In addition, the average Young’s modulus of thrombi over time indicated a progressive increase in hardness. Contrast-enhancing agents were able to penetrate fresh, loose thrombi only, not chronic, stable thrombi. As T(s) and T(h) increased, prolonged thrombolytic time and greater risk of embolism to other organs were apparent. CONCLUSIONS: Our data suggest that this new CEUS scoring system correlates well with cardiac thrombotic hardness and the quality of its underlying substrate, serving to quantify thrombotic stability.