Subharmonic microbubble emissions for noninvasively tracking right ventricular pressures.

Area of Science:

• Cardiovascular Ultrasound
• Medical Acoustics
• Diagnostic Imaging

Background:

• Right heart catheterization is invasive and often necessary for monitoring intra-cardiac pressures.
• Ultrasound contrast agents can produce pressure-modulated subharmonic emissions.
• These emissions may offer a noninvasive method for estimating right ventricular (RV) pressures.

Purpose of the Study:

• To evaluate the clinical potential of a novel technique using subharmonic acoustic emissions from ultrasound contrast agents.
• To track right ventricular (RV) pressures noninvasively.

Main Methods:

• Subharmonic signals were recorded from the aorta, RV, and right atrium (RA) in dogs using an ultrasound scanner.
• Simultaneous pressure measurements were obtained using a micromanometer-tipped catheter.
• A calibration factor derived from aortic signals and systemic blood pressure was used with RA pressures and RV acoustic data to estimate RV pressures.

Main Results:

• Individual calibration factors ranged from -2.0 to -4.0 mmHg/dB.
• Subharmonic signals tracked transient RV pressure changes within 0.6 mmHg error.
• Acoustic estimates for RV peak systolic, minimum diastolic pressures, and relaxation were within 3.4 mmHg, 1.8 mmHg, and 5.9 mmHg/s, respectively, of measured pressures.

Conclusions:

• Subharmonic emissions from ultrasound contrast agents show potential for noninvasive RV pressure tracking.
• The developed technique achieved errors below 3.5 mmHg for RV pressure estimation.
• This pilot study suggests a promising noninvasive approach for monitoring RV pressures.