The objective of this work was to investigate if central cardiac pressures are obtainable noninvasively using the subharmonic aided pressure estimation (SHAPE) technique with Definity (Lantheus Medical Imaging Inc, N Billerica, MA, USA) or Sonazoid (GE Healthcare, Oslo, Norway) microbubbles. Patients scheduled for a left and/or right heart catheterization procedure and providing written informed consent were included in IRB approved clinical trials (NCT03243942 for Definity; NCT03245255 for Sonazoid). A standard-of-care catheterization procedure was performed advancing clinically used pressure catheter into the left and/or right ventricles and/or the aorta. After pressure catheter placement, patients received an infusion of either Definity (56 patients; 2 vials in 50 mL of saline; infusion rate: 4-10 mL/min) or Sonazoid (60 patients; rate (mL/hour) = 0.18 mL/hour/kg x weight in kg co-infused with saline at 120 mL/hour). A customized interface on a SonixTablet scanner (BK Ultrasound, Peabody, MA, USA) was used to acquire SHAPE data synchronously with the pressure catheter data. Linear correlation between the SHAPE and pressure catheter data were computed using MATLAB (Mathworks, Natick, MA, USA). Central aortic pressures were estimated using cuff-based brachial pressure measurements with a SphygmoCor device (AtCor Medical Pty Ltd, West Ryde, NSW, Australia). Central aortic pressures and SHAPE data from the aorta were used to calculate a conversion factor (in mmHg/dB) for each patient to estimate pressures and determine errors associated with the SHAPE technique. Two adverse events were observed during Definity infusion; both were resolved. Errors between the pressure catheter and SHAPE derived mean diastolic pressures were less than 5 mmHg when using Definity microbubbles and greater than 5 mmHg when using Sonazoid microbubbles. These results indicate that SHAPE is a useful technique to noninvasively obtain central cardiac pressures.
Polymer composition, the ratio of lactic acid (LA) to glycolic acid (GA), was evaluated for its contribution to the acoustic enhancement of a poly (co-lactic-glycolic) acid (PLGA) ultrasound contrast agent. Contrast agents were prepared from four different polymer compositions (LA:GA): 100:0, 85:15, 75:25, 50:50 and tested in vivo. The results indicate that all contrast agents perform well in vivo but the 50:50, which had the shortest usable life-time. The performance of the contrast agents was dependent on the ratio of LA to GA and should be considered in the design of polymeric contrast agents.
