Estimating Central Cardiac Pressures Noninvasively in Patients Using Ultrasound Contrast Agents

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.