title: Endothelium-derived nitric oxide enhances the effect of intraaortic balloon pumping on diastolic coronary flow.
abstract: BACKGROUND
  High shear rate with pulsation is one of the major stimuli for the release of endothelium-derived nitric oxide leading to coronary arteriolar dilation. Intraaortic balloon pumping mechanically enhances shear rate and diastolic-to-systolic flow oscillation. We aimed to evaluate whether or not coronary blood flow augmentation during intraaortic balloon pumping is mediated by coronary arteriolar dilation through endothelium-derived nitric oxide release.
  
  
  METHODS
  Using a charge-coupled device intravital videomicroscope, we observed epicardial coronary arterioles (40 to 220 microm in diameter) in anesthetized open-chest dogs (n = 10) during 2:1 mode of intraaortic balloon pumping. Endothelium-derived nitric oxide-mediated vasodilatory effects of intraaortic balloon pumping were evaluated by comparing end-diastolic arteriolar diameters between the coupled beats of on and off intraaortic balloon pumping before and after intracoronary endothelium-derived nitric oxide synthesis inhibition with Nomega-nitro-L-arginine (L-NNA, 2 micromol/min) administration.
  
  
  RESULTS
  Intraaortic balloon pumping increased coronary arteriolar diameters and coronary blood flow by 11.4%+/-1.8% (p < 0.0001) and 33.4%+/-4.1% (p < 0.001), respectively. Vasodilation was greater in small arterioles (<110 microm; 15.4%+/-2.2%) than in large arterioles (> or =110 microm; 4.2%+/-1.2%, p < 0.0001). L-NNA attenuated the intraaortic balloon pumping-induced vasodilation and augmentation of coronary blood flow to 4.6%+/-1.0% (p < 0.001) and to 20.8%+/-2.1%, (p < 0.05), respectively. Attenuation of vasodilatory effect by L-NNA was observed mainly in small arterioles (from 15.4%+/-2.2% to 5.9%+/-1.2%).
  
  
  CONCLUSIONS
  Intraaortic balloon pumping augmented coronary blood flow by dilating coronary arterioles in diastole, more significantly in small arterioles than in large arterioles. Endothelium-derived nitric oxide inhibition markedly attenuated these effects. We conclude that, in a canine model, endothelium-derived nitric oxide contributes to mechanical enhancement of the coronary blood flow with diastolic arteriolar vasodilation during intraaortic balloon pumping.
authors.affiliation: Department of Systems Cardiology and Medical Engineering, Kawasaki Medical School, Kurashiki, Okayama, Japan. toyota@me.kawasaki-m.ac.jp
authors.forename: E
authors.initials: E
authors.lastname: Toyota
authors.forename: M
authors.initials: M
authors.lastname: Goto
authors.forename: H
authors.initials: H
authors.lastname: Nakamoto
authors.forename: J
authors.initials: J
authors.lastname: Ebata
authors.forename: H
authors.initials: H
authors.lastname: Tachibana
authors.forename: O
authors.initials: O
authors.lastname: Hiramatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Ogasawara
authors.forename: F
authors.initials: F
authors.lastname: Kajiya
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology*; D003971:Diastole; D004285:Dogs; D005260:Female; D006439:Hemodynamics; D007423:Intra-Aortic Balloon Pumping; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014665:Vasodilator Agents; D009569:Nitric Oxide; D000109:Acetylcholine