Signal heterogeneity in contrast-enhanced echocardiographic imaging despite uniform concentration of the contrast agent

To quantify the heterogeneity of contrast enhancement inside left ventricular (LV) cavity, 10 patients were studied by harmonic intermittent power Doppler following venous echo contrast administration. Regions of interest were drawn in the LV cavity along the main axis and transversally to derive time-intensity curves. Signal intensity at plateau (A) significantly decreased along LV longitudinal axis: from apex (48±6 dB), to center (41±7) and base (31±9 dB, p<0.05), while intensity rise (b) was unaltered. A also was lower in proximity of the septum than in the center of LV cavity (p<0.05). Finally, beat-to-beat variability increased with increasing depth. Thus, LV contrast intensity varies despite a uniform concentration of the contrast agent at each time, due to ultrasound attenuation and heterogeneous beam intensity. Parameter b appears more consistent than A in deriving quantitative flow information.