Abstract 2614: Noninvasive Assessment of the Relationship of Coronary Vasomotion to Plaque Burden
Introduction: The cold pressor test (CPT) dilates normal epicardial coronary artery segments and increases coronary blood flow, but constricts segments with angiographically visible coronary atherosclerosis. However the relationship of plaque burden to coronary vasomotion in response to CPT is unknown and tools for noninvasive assessment of coronary vasomotion are needed.
Methods: We used cardiac MRI (CMR) imaging of the left anterior descending (LAD) coronary artery before and during CPT to evaluate the relationship between plaque burden and LAD vasomotion. Nitroglycerin (NTG) induced endothelium independent vasodilation was used as a control. Clinically healthy subjects (n=31) with and without risk factors, with no history of coronary artery disease or diabetes underwent CT calcium scoring as an index of plaque burden (EBCT or Siemens 64-slice multi-detector CT). In 14 (45%) subjects CT coronary angiography was used to exclude coronary stenosis. On another day, CMR (Siemens Sonata) was performed at rest, during CPT and during NTG. After scout imaging and axial 3D breath-hold MRA, dark blood imaging (segmented turbo spin echo) was used to image the proximal LAD and cross sectional lumen area determined. Groups with low Agatston scores (LOW, <100 (n= 20)) and higher scores (HIGH ≥ 100 (n=11) were compared.
Results: Calcium score ranged from 0 –1869. A significant negative relationship was seen between calcium score and % change in LAD area (r = −0.44, p= 0.01. The LOW group had mean LAD dilation of 5.24% compared to mean vasoconstriction of −9.81 % in HIGH subjects (p= 0.02). Vasoconstriction was seen in 10/11 (90.9%) HIGH patients but only 6/20 (30%) LOW patients. There was no relationship between calcium score and LAD response to NTG.
Conclusion: CMR can evaluate LAD vasomotion non-invasively and in conjunction with cardiac CT, determine the relationship of vasomotion to plaque burden in the absence of stenosis. The inverse relationship between plaque burden and LAD vasomotion, is consistent with endothelial dysfunction and/or abnormal sympathetic coronary regulation.