The minimum coronary artery diameter in which coronary spasm can be identified by synchrotron radiation coronary...

Coronary vasospasm is defined as a temporary, intense narrowing of the coronary conduit artery. It brings about ischemic chest pain and becomes one of the causes of myocardial infarction. Coronary spasms are divided into two categories. One is the coronary spasm of the conduit artery and the other is the coronary microvascular spasm. Although coronary spasms are diagnosed with the images of coronary angiography, microvascular spasms cannot be diagnosed because of the limitations of conventional angiographic systems. However, synchrotron radiation coronary angiography (SRCA) can identify coronary arteries down to 100 microm in diameter in the beating heart and 50 microm in arrested heart.

The purpose of this study was to confirm whether microvascular spasms could be identified or not using SRCA, and then down that size identification was possible.

The Langendorff perfusion system with isolated rat hearts was employed. Krebs-Henseleit solution (KH solution) was used as a perfusate. 10mM of 4-aminopyridine (4-AP: a voltage-gated potassium channel blocker; spasm inducer) was added to the KH solution and maintained for 5 min. SRCA was performed at pre-, during and 10 min after cessation of the KH solution with 4-AP. Coronary spasms were defined as a temporal 75% reduction of coronary arterial diameter.

Multiple sizes of coronary arteries showed coronary spasms. The minimum stenosed coronary artery size was 100 microm. Since coronary microvascular spasms are seen in the arterioles (50-400 microm), coronary microvascular spasms may be diagnosed with the use of synchrotron radiation coronary angiography.