DYNAMIC EXPANSION OF THE CORONARY-ARTERIES - IMPLICATIONS FOR INTRAVASCULAR ULTRASOUND MEASUREMENTS

The majority of coronary artery blood flow occurs in diastole; however , systolic epicardial coronary artery expansion has been described. Wi th the advent of intravascular ultrasound, precise measurements of art erial structures with excellent spacial and temporal resolution are no w readily available. However, the effect of dynamic expansion of the c oronary arteries on routine intravascular ultrasound measurements has not been assessed. The purpose of thisstudy was to determine in vivo t he presence, timing, and extent of dynamic changes in the coronary art eries and saphenous vein grafts and to assess their implications for i ntravascular ultrasound measurements. Intravascular ultrasound images were obtained with simultaneous electrocardiographic monitoring in 202 coronary artery and 50 saphenous vein graft sites in 32 patients with varying plaque burden and morphologic features. Arterial, luminal, an d plaque area were measured at end-diastole and early, mid-, and end-s ystole. Coronary luminal diameter increased 2.1%; luminal area increas ed 8.1%; arterial area increased 3.7%; and plaque area decreased 4.9% during mid and late systole (p < 0.01). There was no detectable cyclic change in saphenous vein graft dimensions. In coronary arteries there was significant systolic expansion of the artery and lumen and systol ic thinning of the plaque. The magnitude of dynamic luminal area chang e was greater than the variability in measurement and thus warrants ga ting to the cardiac cycle. The lack of dynamic change in saphenous vei n grafts and the relatively small dynamic change in luminal diameter a nd arterial and plaque areas suggest nominal utility in gating these m easurements to the cardiac cycle.