title: Subharmonic microbubble emissions for noninvasively tracking right ventricular pressures.
abstract: Right heart catheterization is often required to monitor intra-cardiac pressures in a number of disease states. Ultrasound contrast agents can produce pressure modulated subharmonic emissions that may be used to estimate right ventricular (RV) pressures. A technique based on subharmonic acoustic emissions from ultrasound contrast agents to track RV pressures noninvasively has been developed and its clinical potential evaluated. The subharmonic signals were obtained from the aorta, RV, and right atrium (RA) of five anesthetized closed-chest mongrel dogs using a SonixRP ultrasound scanner and PA4-2 phased array. Simultaneous pressure measurements were obtained using a 5-French solid state micromanometer tipped catheter. Initially, aortic subharmonic signals and systemic blood pressures were used to obtain a calibration factor in units of millimeters of mercury per decibel. This factor was combined with RA pressures (that can be obtained noninvasively) and the acoustic data from the RV to obtain RV pressure values. The individual calibration factors ranged from -2.0 to -4.0 mmHg/dB. The subharmonic signals tracked transient changes in the RV pressures within an error of 0.6 mmHg. Relative to the catheter pressures, the mean errors in estimating RV peak systolic and minimum diastolic pressures, and RV relaxation [isovolumic negative derivative of change in pressure over time (-dP/dt)] by use of the subharmonic signals, were -2.3 mmHg, -0.8 mmHg, and 2.9 mmHg/s, respectively. Overall, acoustic estimates of RV peak systolic and minimum diastolic pressures and RV relaxation were within 3.4 mmHg, 1.8 mmHg, and 5.9 mmHg/s, respectively, of the measured pressures. This pilot study demonstrates that subharmonic emissions from ultrasound contrast agents have the potential to noninvasively track in vivo RV pressures with errors below 3.5 mmHg.
authors.affiliation: Department of Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Jaydev K
authors.initials: JK
authors.lastname: Dave
authors.forename: Valgerdur G
authors.initials: VG
authors.lastname: Halldorsdottir
authors.forename: John R
authors.initials: JR
authors.lastname: Eisenbrey
authors.forename: Joel S
authors.initials: JS
authors.lastname: Raichlen
authors.forename: Ji-Bin
authors.initials: JB
authors.lastname: Liu
authors.forename: Maureen E
authors.initials: ME
authors.lastname: McDonald
authors.forename: Kris
authors.initials: K
authors.lastname: Dickie
authors.forename: Shumin
authors.initials: S
authors.lastname: Wang
authors.forename: Corina
authors.initials: C
authors.lastname: Leung
authors.forename: Flemming
authors.initials: F
authors.lastname: Forsberg
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology; D001795:Blood Pressure Determination / Q000295:instrumentation*; D002138:Calibration; D006328:Cardiac Catheterization; D003287:Contrast Media; D003627:Data Interpretation, Statistical; D004285:Dogs; D004452:Echocardiography / Q000295:instrumentation / Q000379:methods; D008365:Manometry / Q000295:instrumentation; D045423:Microbubbles; D010865:Pilot Projects; D014160:Transducers, Pressure; D016278:Ventricular Function, Right / Q000502:physiology*; D017725:Ventricular Pressure
chemical_list: D003287:Contrast Media