Abstract 14843: Intracoronary Salbutamol is a Novel Endothelium-Dependent Coronary Vasodilator — Mechanistic Insights From an in vivo Intravascular Ultrasound (IVUS) Study
Background: The dynamic relationship between plaque burden and coronary endothelial function is poorly understood. This study aimed to investigate intracoronary (IC) salbutamol as a novel endothelium-dependent epicardial coronary vasodilator and examine this relationship with segmental plaque burden.
Methods: In 24 consecutive patients with near normal coronary angiograms, IC salbutamol was infused during IVUS and Doppler flow wire imaging. Study protocols included: (1) incremental IC salbutamol (0.15, 0.3, 0.6 μg/min) infusion (n=15 patients, 103 segments) and (2) salbutamol (0.3 μg/min) infusion before and after IC administration of NG-monomethyl-L-arginine (L-NMMA) (n=9 patients, 82 segments). Five-mm long coronary segments were studied with regard to vasomotor response [% change in segmental lumen volume (SLV)], plaque burden [segmental percent (PAV)] and coronary blood flow (CBF).
Results: IC salbutamol demonstrated a dose-response change in SLV (Fig 1A). Vasomotor response to salbutamol was greater in the low compared with high plaque volume segments (Fig 1B). There was a significant inverse relationship between IC salbutamol-induced SLV changes and segmental PAV (r= −0.54, p<0.0001). There was a significant dose-response increase in CBF from baseline (0.3 μg/min = 54±17%, p< 0.0001, 0.6 μg/min = 66±15%, p< 0.0001). L-NMMA abolished the salbutamol vasodilator response supporting a nitric oxide (NO)-dependent response in the epicardial (Fig 1C) and microvascular compartments.
Conclusions: This study confirms that IC salbutamol promotes a dose-dependent segmental vasomotor response which is NO, and thus endothelium-dependent. Segmental plaque burden and vessel remodeling are important determinants of epicardial coronary endothelial function, which also explains the heterogeneity of this response seen within the epicardial coronary vasculature.
- Endothelial function
- Intravascular ultrasound/Doppler
- Beta-adrenergic receptor agonists
- Vasodilator agents
- © 2010 by American Heart Association, Inc.