Abstract and Introduction
Objectives. To determine the time to maximal coronary dilation following intracoronary (IC) nitroglycerin (NTG) and whether the decrease in aortic pressure (AoP) is a surrogate marker for coronary vasodilatation.
Background. Intravascular ultrasound (IVUS) facilitates assessment of coronary plaque severity and morphology and aids in stent sizing. NTG is often administered prior to IVUS to prevent catheter-induced spasm and to facilitate standardized and accurate vessel size measurements. The impact of dose, timing, and route of delivering NTG on vessel size remains undefined.
Methods. Twelve patients undergoing IVUS-guided stent placement were studied. An IVUS catheter was positioned proximal to the target lesion and the following measurements made at baseline and 30 second (sec) intervals for 180 sec following 200 mcg IC NTG: AoP, IVUS-derived lumen diameter (Ld), lumen cross-sectional area (La), external elastic membrane diameter (EEMd) and EEM area (EEMa). Lumen and EEM measurements were compared at different time intervals and the relationship between time to max Ld and nadir AoP was analyzed.
Results. All patients had a vasodilatory response to IC NTG. Increase from baseline to max Ld following IC NTG was statistically significant (mean change 0.31 ± 0.18 mm, P=.0001). Mean time to max Ld following IC NTG was 117 sec (range, 60–180 sec). No correlation between time to max Ld and AoP nadir was observed (r = 0.19).
Conclusions. Our study suggests that administration of 200 mcg IC NTG results in a significant change in lumen diameter and area with maximal vasodilation occurring on average approximately 2 minutes following IC NTG administration. There was no significant correlation between AoP change and maximal NTG-induced coronary vasodilation.
Over the last two decades, application of coronary imaging using intravascular ultrasound (IVUS) has helped improve our understanding of coronary atherosclerosis and facilitate the evolution of stent therapy. Commonly used as a clinical tool to optimize PCI, IVUS provides a detailed assessment of plaque severity and vessel remodeling, and aids optimal stent sizing. In addition, as a research tool, IVUS can quantify extent of plaque regression in response to therapy and explore mechanisms of disease, such as in-stent restenosis and stent thrombosis.
While complications are rare, coronary spasm during IVUS may be seen in approximately 3% of patients. Intracoronary (IC) nitroglycerin (NTG) is commonly administered prior to IVUS catheter placement to lower the risk of IVUS catheter-induced coronary spasm and to optimize appropriate sizing of vessel segments. NTG results in epicardial coronary artery vasodilation and reduction is systemic pressure in a time-dependent manner. However, time to IVUS-derived maximal coronary vasodilation and the relationship between time to maximal vasodilation and reduction in systemic pressure following NTG administration remains unknown.
Therefore, we conducted a study to determine the time to peak coronary vasodilatation in response to IC NTG during IVUS and whether a drop in central aortic pressure (AoP) correlates with time to peak coronary dilatation.