PATHOGENESIS AND CLINICAL SIGNIFICANCE OF CORONARY SPASM

冠状动脉痉挛发生的确切机制和冠状动脉痉挛的临床意义仍有待阐明。目前的研究表明，冠状动脉内注射乙酰胆碱，一种内皮依赖性血管扩张剂，在29岁以下的受试者中扩张心外膜冠状动脉，而在30岁以上的受试者中收缩冠状动脉。硝酸甘油，一种不依赖内皮的血管扩张剂，在年轻人和老年人中都能扩张冠状动脉。内皮细胞损伤是动脉粥样硬化发生的重要因素。因此，在大多数30岁以上的受试者中，冠状动脉内皮受损或存在冠状动脉粥样硬化。几乎所有冠状动脉痉挛的患者年龄都在30岁以上。因此，冠状动脉痉挛是在冠状动脉粥样硬化的基础上发生的。然而，冠状动脉粥样硬化本身并不能解释冠状动脉痉挛的发病机制，因为并非所有冠状动脉粥样硬化患者都有冠状动脉痉挛。45%的冠状动脉痉挛患者缺镁。因此，镁缺乏可能在某些冠状动脉痉挛患者的冠状动脉痉挛发病机制中起作用。乙酰胆碱增加冠状动脉痉挛患者以及年轻受试者的冠状动脉窦血流。因此，冠状动脉痉挛患者的冠状动脉阻力血管对乙酰胆碱或内皮依赖性松弛保持血管舒张反应。本研究还表明，冠状动脉痉挛增加血浆纤维蛋白肽A的水平，纤维蛋白肽A是纤维蛋白形成的一个指标。因此，冠状动脉痉挛可能通过激活凝血酶和纤维蛋白形成而引发冠状动脉血栓形成，从而导致急性心肌梗死。

The precise mechanisms by which coronary spasm occurs and the clinical significance of coronary spasm still remain to be elucidated. The present study shows that intracoronary injection of acetylcholine, an endothelium-dependent vasodilator, dilates the epicardial coronary arteries in the subjects less then 29 years, whereas it constricts the coronary arteries in the subjects older than 30 years. Nitroglycerin, an endothelium-independent vasodilator, dilated the coronary arteries in the younger as well as the older subjects. Injury of endothelium is essential for the pathogenesis of atherosclerosis. Thus, the endothelium of the coronary arteries are injured or coronary atherosclerosis is present in most subjects older than 30 years. Almost all of the patients with coronary spasm are older than 30 years. It is therefore concluded that coronary spasm occurs on the basis of coronary atherosclerosis. However, coronary atherosclerosis alone cannot explain the pathogenesis of coronary spasm because all patients with coronary atherosclerosis do not have coronary spasm. Mg deficiency was found in 45 % of the patients with coronary spasm. Thus, Mg deficiency may play a role in the pathogenesis of coronary spasm in some patients with coronary spasm. Acetylcholine increased coronary sinus flow in patients with coronary spasm as well as in the younger subjecjts. Thus, coronaryresistance vessels retain the vasodilatatory response to acetylcholine or endothelium-dependent relaxation in patients with coronary spasm.The present study also shows that coronary spasm in-creases plasma level of fibrinopeptide A, an indicator of fibrin formation. Thus, coronary spasm may trigger coronary thrombosis and thus lead to acute myocardial infarction by activating thrombin and fibrin formation.