Leong-Poi Howard, Swales James, Jayaweera Ananda R, Bin Jian-Ping, Kaul Sanjiv, Lindner Jonathan R
Cardiovascular Imaging Center, Cardiovascular Division, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Echocardiography. 2005 Jul;22(6):503-9. doi: 10.1111/j.1540-8175.2005.40001.x.
The purpose of this study was to determine whether acoustic disruption of microbubbles in the left ventricular (LV) cavity prior to entry in the coronary circulation or their gradual destruction in the myocardium during myocardial contrast echocardiography (MCE) affects quantitative parameters of myocardial perfusion.
MCE was performed in 12 open chest dogs with both intermittent high-power imaging (IHPI) and real-time low-power imaging (RLPI). To assess the affects of microbubble destruction in the LV cavity, MCE parameters of myocardial perfusion were compared for imaging planes that included versus avoided the LV cavity. To assess the effects of gradual disruption of microbubbles in the microcirculation during RLPI, MCE parameters from frames acquired continuously were compared to that from acquiring only end-systolic frames.
Destruction of microbubbles in the LV cavity did not alter perfusion data for either form of imaging unless RLPI was performed using long (6-frame) destructive pulse sequences. With RLPI, a gradual decay in microbubble signal occurred during their myocardial transit, the degree of which was related to the acoustic power. Signal decay during microbubble transit resulted in an overestimation of the microvascular blood velocity (beta-value) and an underestimation of the microvascular blood volume (A-value).
MCE parameters of perfusion at low power can be significantly altered by microbubble destruction in the LV cavity and in the myocardial microcirculation during RLPI. Short microbubble destruction pulse sequences and imaging only at end-systole can reduce these effects.
本研究的目的是确定在进入冠状动脉循环之前左心室（LV）腔内微泡的声学破坏或在心肌对比超声心动图（MCE）期间微泡在心肌中的逐渐破坏是否会影响心肌灌注的定量参数。
对12只开胸犬进行MCE，采用间歇性高功率成像（IHPI）和实时低功率成像（RLPI）。为了评估LV腔内微泡破坏的影响，比较了包含和避开LV腔的成像平面的心肌灌注MCE参数。为了评估RLPI期间微循环中微泡逐渐破坏的影响，将连续采集的帧的MCE参数与仅采集收缩末期帧的MCE参数进行比较。
LV腔内微泡的破坏不会改变任何一种成像形式的灌注数据，除非使用长（6帧）破坏脉冲序列进行RLPI。使用RLPI时，微泡在心肌传输过程中信号逐渐衰减，其程度与声功率有关。微泡传输过程中的信号衰减导致微血管血流速度（β值）高估和微血管血容量（A值）低估。
在RLPI期间，LV腔和心肌微循环中的微泡破坏可显著改变低功率下的灌注MCE参数。短微泡破坏脉冲序列和仅在收缩末期成像可减少这些影响。
