Brief negative pressure applied to perfluorocarbon containing microbubbles prior to intravenous injection produces greater myocardial contrast with intermittent harmonic imaging and better delineation of risk area during acute myocardial ischemia

Applying negative pressure to perfluorocarbon-containing emulsions prior to intravenous injection (IVI) has improved the myocardial contrast (MC) achieved when using conventional (>30 Hertz) ultrasound frame rates. The purpose of this paper was 10 determine how negative or positive pressure applied to perfluorocarbon containing microbubbles (PCMB) affects their size (S) and concentration (Conc), and determine whether applying such pressure to PCMB prior to IVI would be clinically useful by improving the MC achieved with newer imaging techniques such as intermittent and harmonic imaging (IHI). Accordingly, we measured the MC produced from a 0.0025 to 0.005 ml/kg IVI of perfluorocarbon exposed sonicated dextrose albumin (PESDA) which was exposed to a calibrated degree of negative (-400 or -200 mm Hg) or positive (+200 or +400 mm Hg) pressure for 5 minutes prior to IVI in 10 dogs Microbubble S and Cone were measured following each exposure. Peak myocardial videointensity (PMVI) was measured following IVI of each sample. The ability of the pressurized microbubbles (MB) to define risk area was compared to regular (non-pressurized) MB (Reg PESDA) during acute left anterior descending or circumflex occlusion in four dogs.*p<0.05 compared to other groups: Sample MB size(μm) #MB<4 μm MB conc PMVI Reg PESDA 4.3±3.1 51±10 30±9 50±23 -200 PESDA 3.0±2.1*61±9*45±10*72±31*- 400 PESDA 3.5±2.8 47±18 33±15 44±26 +200 PESDA 4.0±3.3 46±8 30±7 43±33 +400 PESDA 3.9±3.0 43±11 31±4 47±22 Rtsk area was easiest to visualize during IHI with PESDA exposed to -200 mm Hg. These data indicate that(1) a small degree of negative pressure applied to PCMB prior to IVI improves the MC produced with IHI by producing smaller MB, and (2) the degree of myocardial contrast produced with IHI is further enhanced with PCMB that have a large concentration of smaller (<4 micron) microbubbles.