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目的评价硝酸甘油对局部心肌氧代谢和心肌收缩功能的影响。方法实验应用8只具有静息状态血流限制的左前降支或左回旋支近端狭窄的开胸犬。以二维超声心动图评价室壁增厚率(%WT),放射性微球定量心肌血流量(MBF),用磷猝熄法在体直接测定心肌组织氧压(tPO_2)。分别在静息和左冠脉主干内输注硝酸甘油(0.3～0.6mg·kg-1)状态下,进行二维超声检查、核素微球注射,以及tPO_2和心肌氧耗量(MVO_2,ml·min-1·100g-1)测定,MVO_2等于冠状动脉与冠状静脉氧浓度差乘以MBF,心肌氧输送能力等于冠状动脉氧浓度差乘以MBF。结果与静息状态相比,经左冠脉主干内输注硝酸甘油时,无论是正常灌注区抑或是缺血灌注区的MBF明显增加(P<0.05),同时伴有%WT明显增加(P<0.05)。正常和缺血灌注区的心肌氧输送能力明显增加(P<0.05),尽管缺血灌注区的MVO2有明显增加(P<0.05),但是缺血灌注区的tPO_2仍明显增高(P<0.05)。缺血区心肌tPO_2增加的程度明显大于MBF增加的程度。结论硝酸甘油可明显提高正常和缺血灌注区心肌氧浓度,提高缺血灌注区血氧的解离和释放,可能具有正性肌力效应。除了其直接血管效应之外,硝酸甘油还通过对心肌氧代谢和收缩功能的影响在心血管中发挥重要的调节作用。
Objective To evaluate the effect of nitroglycerin on myocardial oxygen metabolism and myocardial contractility. Methods Eight dogs with proximal stenosis of the left anterior descending branch or left circumflex branch with resting blood flow restriction were used. The ventricular wall thickening (% WT) and radioactive microspheres (MBF) were measured by two-dimensional echocardiography. The myocardial oxygen tension (tPO_2) was measured directly by phosphorus quenching method. Two-dimensional ultrasonography, microsphere injection, and tPO 2 and MVO 2, ml were performed at rest and in the left coronary artery with nitroglycerin (0.3-0.6 mg · kg -1) · Min-1 · 100g-1). MVO_2 is equal to the difference between coronary artery and coronary venous oxygen concentration multiplied by MBF. The myocardial oxygen delivery capacity is equal to the difference between coronary arterial oxygen concentration and MBF. Results Compared with the resting state, when the nitroglycerin was infused through the left coronary artery, the MBF increased significantly (P <0.05) in both normal perfusion region and ischemic perfusion region, accompanied by a significant increase in% WT <0.05). Myocardium oxygen transport capacity was significantly increased in both normal and ischemic perfusion regions (P <0.05). Although MVO2 was significantly increased in ischemic perfusion regions (P <0.05), tPO_2 was still significantly increased in ischemic perfusion regions (P <0.05) . Myocardial ischemic area tPO_2 increased significantly greater than the degree of MBF increased. Conclusion Nitroglycerin can significantly increase myocardial oxygen concentration in normal and ischemic perfusion areas and increase dissociation and release of blood oxygen in ischemic perfusion area, which may have a positive inotropic effect. In addition to its direct vascular effects, nitroglycerin also plays an important regulatory role in cardiovascular regulation by its effects on myocardial oxygen metabolism and contractile function.