In vitro identification of different degrees of mitral valve disease by online evaluation of radiofrequency ultrasound signal.

Sixty five mitral valves were studied in vitro with a 2.25 MHz transducer. Radiofrequency signals were analysed by a microprocessor system (implemented on an M-mode commercially available echocardiography) for online evaluation of ultrasonic backscatter (8 bits of amplitude resolution, 40 MHz sampling rate, 1 microsecond acquisition gate). The integrated value of the rectified signal amplitude was expressed as the integrated backscatter index (in db). The highest value recorded with ultrasonic scanning of each sample was taken as representative of that specimen. Calcification of mitral valves was assessed by radiography (24 mitral valves). Non-calcified mitral calves underwent pathological examination, and fibrotic valves (22 mitral valves) were differentiated from normal valves (19 mitral valves). A statistically significant (p less than 0.005) difference was recorded among the three groups for the index maximal value: calcific -7.4(3.1) db (mean(SD)), fibrotic -18.9(4.9) db, and normal -37.9(7.6) db. In conclusion, a microprocessor based system for online evaluation of radiofrequency ultrasonic signals, which may also be feasible for in vivo studies, provided a clear differentiation in vitro of calcific, fibrotic, and normal mitral valves.