title: A simple thermodilution technique to assess coronary endothelium-dependent microvascular function in humans: validation and comparison with coronary flow reserve.
abstract: OBJECTIVE
  To validate a novel method for assessment of coronary endothelium-dependent microvascular function and compare this index with the adenosine-derived coronary flow reserve (CFR).
  
  
  RESULTS
  We validated use of intra-coronary pressure wire-derived thermodilution to assess changes in coronary flow compared to Doppler flow-wire/quantitative coronary angiography- (QCA) derived data in response to the endothelial agonist substance-P (endothelium-dependent response). There was a close correlation between Doppler/QCA- and thermodilution-derived assessment of endothelium-dependent microvascular function (r = 0.76; P < 0.001). Next, pressure wire-based thermodilution was employed to sequentially compare CFR (hyperaemia achieved with adenosine-140 microg/kg/mL) with changes in coronary flow in response to substance-P (20 pmol/min intra-coronary infusion; 2 min) in 65 unobstructed coronary arteries. There was no correlation between CFR and coronary endothelium-dependent microvascular response (r = 0.08; P = 0.50). Both indices were in turn compared with clinical markers of endothelial dysfunction, namely Framingham risk score (FRS-a marker for cardiovascular risk factor clustering, hence an indirect clinical measure of endothelial dysfunction) and presence/absence of diabetes. Patient's FRS correlated with coronary endothelium-dependent microvascular response (r = -0.48; P < 0.001), but not with CFR (r = 0.14; P = 0.25). Diabetic patients had greater endothelial dysfunction than non-diabetics (P < 0.001) whereas CFR was not influenced by diabetes (P = 0.10).
  
  
  CONCLUSIONS
  A simple pressure wire-based thermodilution technique can be used to assess coronary endothelium-dependent microvascular function. Adenosine-derived CFR does not adequately interrogate the endothelium-dependent component of coronary microvascular function.
authors.affiliation: Cardiovascular Division, King's College London School of Medicine at Guy's, King's College and St Thomas' Hospitals, London, UK.
authors.forename: Narbeh
authors.initials: N
authors.lastname: Melikian
authors.forename: Mark T
authors.initials: MT
authors.lastname: Kearney
authors.forename: Martyn R
authors.initials: MR
authors.lastname: Thomas
authors.forename: Bernard
authors.initials: B
authors.lastname: De Bruyne
authors.forename: Ajay M
authors.initials: AM
authors.lastname: Shah
authors.forename: Philip A
authors.initials: PA
authors.lastname: MacCarthy
mesh_terms: D003326:Coronary Circulation / Q000502:physiology*; D003327:Coronary Disease / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D018377:Neurotransmitter Agents; D018570:Risk Assessment; D013373:Substance P; D013815:Thermodilution / Q000379:methods
chemical_list: D018377:Neurotransmitter Agents; D013373:Substance P