Potential pitfalls of visualization of myocardial perfusion by myocardial contrast echocardiography with harmonic gray scale B-mode and power Doppler imaging

Abstract

The present study compared the regional variation of myocardial signal intensity in visualizing myocardial perfusion by myocardial contrast echocardiography (MCE) between harmonic gray scale and power Doppler imaging. MCE was performed in 12 patients by electrocardiographic (ECG)-gated intermittent triggered MCE with harmonic gray scale and power Doppler imaging following slow intravenous injection of 0.5 ml contrast agent (Optison). The interval between the ECG triggers (pulsing interval) was increased from every heart beat (1:1) to every 2 (1:2), 4 (1:4), and 8 (1:8) cardiac cycles to allow incremental microbubble (contrast agent) replenishment. The MCE images were recorded when attenuation produced by the left ventricular cavity was minimal. The background-subtracted videointensity was measured in 7 segments in an apical 4-chamber view: 3 (apical, mid, and basal) septal segments, 3 (apical, mid, and basal) lateral segments, and 1 apex segment (apical cap). The background-subtracted videointensity for each segment was greater with the power Doppler than the gray scale imaging (p < 0.01). With the gray scale imaging, the background-subtracted videointensity in the basal septal segment demonstrated a negative value at all pulsing intervals, and the value (-9 +/- 13) was significantly lower than that (22 +/- 20) in the apical lateral segment at a pulsing interval of 1:8 (p < 0.01). With power Doppler imaging, the background-subtracted videointensity was high even in the basal septal segment (112 +/- 33), and no significant difference was observed among each segment. The findings indicate that quantitative assessment of myocardial perfusion based upon background-subtracted video-intensity may be difficult in the far field with harmonic gray scale imaging although the attenuation is not apparent by visual analysis. Harmonic power Doppler is more sensitive for detecting basilar perfusion in the far field compared with harmonic gray scale imaging.