Structural Thickening Of Medial Layer In Coronary Artery With Spasm In Patients With Myocardial Infarction

BACKGROUND: The underlying pathophysiology of coronary artery spasm (CAS) remains unclear. We aim to determine whether coronary artery medial layer thickness is associated with CAS using optical coherence tomography.METHODS AND RESULTS: A total of 50 patients with previous myocardial infarction underwent optical coherence tomography of the left anterior descending artery: 20 with CAS and 30 without CAS. Intimal and medial layer areas were measured by planimetric analysis of optical coherence tomography images. The medial area/external elastic membrane (EEM) area was significantly greater in patients with than without CAS (0.13 +/- 0.01 versus 0.09 +/- 0.01, respectively, P<0.01), whereas the intimal area/EEM area was similar in the 2 groups. In patients without CAS, the relationship of intimal area/EEM area with medial area/EEM area and coronary diameter response to intracoronary injection of acetylcholine was characterized by an inverted U-shaped curve (y=-1.85x(2)+0.81x+0.01, R-2=0.43, P<0.001) and a U-shaped curve (y=2993.2x(2)-1359.6x+117.1, R-2=0.53, P<0.001), respectively. Thus, the medial layer became thin and the contractile response became weak in coronary arteries with greater intimal area in the non-CAS patients. In contrast, in patients with CAS, the intimal area/EEM area had no significant relationship with the medial area/EEM area in either linear correlation analysis or quadratic regression analysis. Thus, even when the intimal layer thickened, the medial layer did not thin in patients with CAS.CONCLUSIONS: The structural thickness of the coronary medial layer was increased in patients with CAS, which may provide mechanistic insight into the pathogenesis of CAS.