Noninvasive LV pressure estimation using subharmonic emissions from microbubbles

Abstract

To develop a new noninvasive approach to quantify left ventricular (LV) pressures using subharmonic emissions from microbubbles, an ultrasound scanner was used in pulse inversion grayscale mode; unprocessed radiofrequency data were obtained with pulsed wave Doppler from the aorta and/or LV during Sonazoid infusion. Subharmonic data (in dB) were extracted and processed. Calibration factor (mm Hg/dB) from the aortic pressure was used to estimate LV pressures. Errors ranged from 0.19 to 2.50 mm Hg when estimating pressures using the aortic calibration factor, and were higher (0.64 to 8.98 mm Hg) using a mean aortic calibration factor. Subharmonic emissions from ultrasound contrast agents have the potential to noninvasively monitor LV pressures.

Figure 1

Ultrasound Data Acquisition Grayscale ultrasound image of the left ventricle without (A) and with (B) UCA. Solid arrow in panel A indicates the pressure catheter; dotted arrow in both panels indicates the pulsed wave Doppler gate used to acquire the ultrasound data.

Figure 1

Ultrasound Data Acquisition Grayscale ultrasound image of the left ventricle without (A) and with (B) UCA. Solid arrow in panel A indicates the pressure catheter; dotted arrow in both panels indicates the pulsed wave Doppler gate used to acquire the ultrasound data.

Figure 2

Ultrasound Data Processing Steps for extracting and processing the subharmonic signal. Panels A and B illustrate a typical signal from a pulsed wave Doppler gate and its frequency domain representation. Fundamental and subharmonic signals within the bandwidth of the transducer are labeled (Panel B). Panel C illustrates the processed subharmonic signal (blue) and the pressure catheter data (red) - note the inverse relationship which is in agreement with documented literature (–5)).

Figure 2

Ultrasound Data Processing Steps for extracting and processing the subharmonic signal. Panels A and B illustrate a typical signal from a pulsed wave Doppler gate and its frequency domain representation. Fundamental and subharmonic signals within the bandwidth of the transducer are labeled (Panel B). Panel C illustrates the processed subharmonic signal (blue) and the pressure catheter data (red) - note the inverse relationship which is in agreement with documented literature (–5)).

Figure 2

Ultrasound Data Processing Steps for extracting and processing the subharmonic signal. Panels A and B illustrate a typical signal from a pulsed wave Doppler gate and its frequency domain representation. Fundamental and subharmonic signals within the bandwidth of the transducer are labeled (Panel B). Panel C illustrates the processed subharmonic signal (blue) and the pressure catheter data (red) - note the inverse relationship which is in agreement with documented literature (–5)).

Figure 3

LV Pressure Tracking LV pressure waveform obtained using the manometer (red) and the corresponding subharmonic aided pressure estimation results (blue).