Flemming Forsberg PhD, Presenter: Equipment support, Toshiba Corporation Equipment support, Siemens AG Research collaboration, General Electric Company Research collaboration, Ultrasonix Medical Corporation Research collaboration, Toshiba Corporation Advisory Board, Siemens AG Advisory Board, Toshiba Corporation

Jaydev Dave, Abstract Co-Author: Nothing to Disclose

Valgerdur Halldorsdottir MSC, Abstract Co-Author: Nothing to Disclose

John Robery Eisenbrey PhD, Abstract Co-Author: Nothing to Disclose

Joel Raichlen, Abstract Co-Author: Employee, AstraZeneca PLC

Ji-Bin Liu MD, Abstract Co-Author: Research grant, Hospira, Inc

Maureen McDonald MBA, Abstract Co-Author: Nothing to Disclose

Shumin Wang MD, Abstract Co-Author: Nothing to Disclose

Corina Leung BSC, Abstract Co-Author: Employee, Ultrasonix Medical Corporation

Kris Dickie, Abstract Co-Author: Employee, Ultrasonix Medical Corporation

To investigate the use of subharmonic emissions from microbubbles to quantify left and right ventricular (LV and RV) pressures in vivo.

A commercial SonixRP ultrasound (US) scanner (Ultrasonix Medical Corp, Richmond, BC, Canada) was used in pulse inversion, grayscale mode to examine 4 closed-chest dogs (weight: 22.5 ± 1.00 kg) infused with Sonazoid (0.015 μl/kg/min; GE Healthcare, Oslo, Norway). Unprocessed RF data was obtained for 5 seconds (n = 3) with pulsed wave Doppler from the aorta, LV and RV. Simultaneous pressure measurements were obtained using a 5F solid state catheter tip Millar manometer. Subharmonic data (in dB) was extracted and processed for each of 120 acquisitions. The calibration factor (in mmHg/dB), established from the aorta, was combined with the known peak systolic pressure to estimate LV diastolic pressures and with the right atrial pressure to estimate RV pressures. Pressures obtained using the subharmonic and catheter techniques were compared.

The maximum absolute errors for mean LV diastolic, minimum LV diastolic, LV end-diastolic and mean LV pressures and the range of LV pressures were 2.50, 2.45, 8.98, 6.03 and 4.50 mmHg, respectively. For the right heart peak systolic, mean diastolic, end diastolic and minimum pressures and RV relaxation (isovolumic -dp/dt) were within 2.3, 1.3, 1.3, 0.9 mmHg and 1.5 mmHg/s, respectively, of the reference pressures from the catheter. A resolution of 0.19 to 5.48 mmHg was obtained when estimating LV pressures using the aortic calibration factor from the respective canines; but it decreased to 0.64 to 8.98 mmHg when using the mean aortic calibration factor. For the RV, a resolution of 0 to 2.3 mmHg was obtained with transient changes tractable to 0.6 mmHg.

Subharmonic emissions from US contrast agents have the potential to noninvasively monitor cardiac pressures in vivo. The ultimate applicability of this technique awaits further studies in clinical populations.

As US contrast agents are already approved in the United States for LV opacification, the application of this technique may extend their use to noninvasive cardiac pressure estimation.

Forsberg, F, Dave, J, Halldorsdottir, V, Eisenbrey, J, Raichlen, J, Liu, J, McDonald, M, Wang, S, Leung, C, Dickie, K, Noninvasive Cardiac Pressure Estimation Using Subharmonic Microbubble Signals.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034438.html