ANALYSIS OF HIGH-FREQUENCY ROTATIONAL ANGIOPLASTY-INDUCED ECHO CONTRAST

During high-frequency rotational angioplasty (HFRA), myocardial contrast enhancement (echo contrast) was observed by means of two-dimensional echocardiography. In order to evaluate the echo contrast produced by HFRA, an in vitro experimental model was built using a cylinder with the HFRA catheter scanned in a water bath. The cylinder was filled with blood, mineral water, and distilled water. With a 2.5-MHz transducer, echograms were recorded and analyzed by video intensitometer, and the maximum intensity IU(max) and persistence time P were calculated. Rotation frequencies of 20,000-200,000 rpm with 2.0-mm burrs and times of 10 s were tested. In another model, hyperbaric conditions for the same media were produced. The influence of debris from arterioscleroic plaque and of hematocrit on echo contrast intensity were also analyzed. The effect of HFRA on hemolysis (LDH, free hemoglobin) within 10 s and temperature were also measured. The contrast effect was transient, depending on the rotation frequency. In blood, it appeared at 20,000 rpm (IU(max) at 200,000 rpm: 237 IU), in mineral water at 40,000 rpm (IU(max) 165 IU), and in distilled water at 80,000 rpm (IU(max) 72 IU). Persistence time was measured up to about a half-minute. Echo contrast production was reduced at 0.5 bar and fully suppressed at 2.5 bar. Debris increased contrast intensity from about 219 IU to 225 IU (at 160,000 rpm). In blood IU(max) decreased from 227 IU to 97 IU by lowering the hematocrit from 44.2% to 3.6%. Free hemoglobin increased up to 4,890 mg/L (baseline value 38 mg/L), LDH increased up to 680 U/L (baseline value 100 U/L). Temperature rose only by 1.0-degrees-C within 10 s of rotation, whereas an increase up to 7.7-degrees-C occurred within 40 s. The observed echocontrast seems to be due to microcavitation, depending on the fluid, frequency, and pressure.