Abstract 15714: Intra-cardiac Pressure Estimation Using Subharmonic Aided Pressure Estimation (SHAPE) - A Clinical Evaluation

Introduction: Subharmonic aided pressure estimation (SHAPE) utilizes ambient pressure sensitivity of subharmonic signals from ultrasound contrast agents. The objective was to evaluate SHAPE with Definity (Lantheus Medical Imaging, Inc.) and Sonazoid (GE Healthcare) microbubbles for intra-cardiac pressure estimation. Hypothesis: Errors between SHAPE and pressures obtained during cardiac catheterization ≤ 5 mmHg. Methods: IRB approved this study. Consenting patients received an infusion of Definity (56 patients; 2 vials in 50 mL of saline; infusion rate: 4-10 mL/min) or Sonazoid (77 patients; rate (mL/hour) = 0.18 x weight in kg co-infused with saline at 120 mL/hour) during cardiac catheterization. Subharmonic data was acquired using a SonixTablet (PA 4/2 array; BK Ultrasound) synchronously with pressures from the left and right ventricles and the aorta (for left heart catheterizations only). Subharmonic data (in dB) was converted to pressure values (in mmHg) using calibration factors (mmHg/dB) based on data obtained from the aorta - utilizing pressures from the aorta either during the catheterization procedure or pressures obtained using a SphygmoCor (AtCor Medical Pty. Ltd.) device after the catheterization procedure. Clinically relevant pressures between the SHAPE technique and the pressure catheter were compared. Results: Correlation coefficient between the subharmonic and pressure data was -0.8 ± 0.1. With Definity, mean absolute errors ranged from 2.9 ± 1.5 to 5.0 ± 4.2 mmHg and from 4.4 ± 5.7 to 23.7 ± 28.3 mmHg for calibration factors utilizing aortic pressures from pressure catheter and SphygmoCor, respectively. For Sonazoid microbubbles, these errors ranged from 7.9 ± 12.0 to 10.1 ± 12.4 mmHg and from 7.2 ± 11.5 to 15.0 ± 23.2 mmHg, respectively. Two adverse events occurred during Definity infusion; these were resolved with return to baseline conditions. Conclusion: SHAPE may be useful for estimating intra-cardiac pressures noninvasively.