硝酸甘油对心肌血流灌注直接影响的对比超声评价

Evaluation of the direct effects of nitroglycerin (NTG) on myocardial perfusion with myocardial contrast echocardiaography

目的应用心肌对比成像（MCE）评价硝酸甘油对心肌血流灌注的直接影响。方法实验应用12只具有静息状态血流限制的左前降支近端狭窄的开胸犬（其中6只结扎远处的冠脉以消除侧支循环的影响）,根据远处的冠脉是否结扎分组（非结扎犬为组1、结扎犬为组2）。分别在静息和左冠脉主干内直接输注硝酸甘油（0.3-0.6μg·kg^-1）状态下,测定全血黏滞性（WBη）和心肌血管阻力（MVR）,同步应用放射性标记微球测定心肌血流量（MBF）,MCE评估心肌血流容积（A）和心肌血流速度（β）。结果与静息状态相比,经冠脉内输注硝酸甘油时,组1和组2实验犬正常区、整个缺血区和缺血中心区的MBF均明显增加（P〈0.05）,同时伴有MVR和WBη明显减低（P〈0.05）。MCE显示正常灌注区和整个缺血区β增加的程度明显大于标准化A增加的程度（P〈0.05）;标准化A和β增加（%）与A与β的乘积（A×β）增加（%）之间均有良好的相关性。然而,无论正常灌注区和整个缺血区标准化A增加（%）与A×β增加（%）之间相关方程的斜率明显小于β增加（%）与A×β增加（%）之间的斜率（P〈0.05）。结论硝酸甘油可降低血液黏滞性和心肌血流阻力,进而增加心肌的血液供应,后者主要是源于红细胞在心肌微循环中流动的速度增快所致。MCE是全面定量评价心肌血流灌注的良好方法。

Objective To evaluate the direct effects of nitroglycerin （NTG） on myocardial blood flow perfusion with myocardial contrast echocardiaography （ MCE ）. Methods Twelve dogs （ divided into 2 equal groups ） with resting flow-reducing single-vessel stenosis were studied at rest and during intracoronary infusion of NTG （0.3 - 0.6 μg·kg^-1 ·min^-1 ） directly into the left main coronary artery. Six dogs （group 2） also had occlusion of the remote coronary artery to remove any collateral effects. At baseline and during NTG infusions, myocardial blood flow （ MBF ） （ radio-labeled microspheres ）, myocardial vascular resistance （ MVR ） and whole blood viscosity （WBη） were measured. MCE was performed to determine myocardial blood volume （A） and myocardial blood flow velocity （β）. Results As compared to baseline, MBF increased and MVR decreased significantly after NTG in normal bed, whole ischemic bed and the central 25 % of the ischemic bed （ P 〈 0.05） with an decrease in WBη（ P 〈 0.05） in all dogs. MCE demonstrated that the increases in β were significant higher than the increases in A in both normal and ischemic bed （ P 〈 0.05）. There were good relations between both A and β versus A × β in both normal and ischemic bed. However, the slopes of the equation in A versus A × β were smaller than those in β versus A × β （ P 〈 0.05）. Conclusion NTG reduces blood viscosity and myocardial vascular resistance and enhances red blood cell velocity induced an increase in MBF in the microcirculation. MCE is an excellent method for evaluating myocardial perfusion quantitatively and multi-functionally.