Optimum trigger timing for intermittent mode in intravenous myocardial contrast echocardiography

Background Although the intermittent mode is necessary for myocardial opacification in intravenous myocardial contrast echocardiography (MCE), the effect of EGG trigger timing, on good myocardial opacification without production of artifacts, is not clear. Method MCE was performed on six closed-chest dogs by injecting FS 69 (0.1 ml) intravenously using an Acuson Sequoia 512 ultrasound system with intermittent harmonic imaging (1.75/3.5 MHz) in the short-axis view. Myocardial opacification and acoustic shadow were evaluated from a video tape recording triggered at every end-systole or end-diastole phase. Peak video intensity of four quadrant regions and extent of the acoustic shadow expressed as the incident angle viewed from the center of the left ventricular cavity were measured. Results The angle of acoustic shadow was significantly larger in the image triggered at end-diastole than in the image triggered at end-systole. However, trigger timing did not affect myocardial opacification in either region. Conclusion Trigger timing should be set at end-systole to minimize acoustic shadowing.