title: Increased hyperaemic coronary microvascular resistance adds to the presence of myocardial ischaemia.
abstract: OBJECTIVE
  It has been argued that hyperaemic microvascular resistance (HMR), defined as the ratio of mean distal coronary pressure to flow velocity, is overestimated in the presence of a coronary stenosis compared to actual microvascular resistance (MR), due to neglecting collateral flow. We aimed to test the hypothesis that HMR allows accurate identification of microvascular functional abnormalities by evaluating the association between high or low HMR and the presence of myocardial ischaemia on non-invasive stress testing.
  
  
  RESULTS
  Myocardial perfusion scintigraphy was performed in 228 patients, with 299 lesions to identify reversible myocardial ischaemia. Intracoronary distal pressure and flow velocity were assessed during adenosine-induced hyperaemia (20-40 µg, intracoronary) to determine hyperaemic stenosis resistance (HSR) and HMR. HMR >1.9 mmHg/cm/s was defined as high. The diagnostic odds ratio (OR) for myocardial ischaemia for lesions associated with high compared to low HMR was 2.6 (95% confidence interval [CI]: 1.5-4.4; p<0.001) overall, 3.3 (95% CI: 1.2-9.0; p=0.02) for lesions with HSR >0.8 mmHg/cm/s, and 1.3 (95% CI: 0.6-2.9; p=0.52) for lesions with HSR ≤0.8 mmHg/cm/s.
  
  
  CONCLUSIONS
  The increased risk of myocardial ischaemia in the presence of high HMR, uncorrected for collateral flow, demonstrates that HMR is reflective of an increase in actual MR, identifying pertinent pathophysiological alterations in the microvasculature.
authors.affiliation: Department of Biomedical Engineering and Physics, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Froukje
authors.initials: F
authors.lastname: Nolte
authors.forename: Tim P
authors.initials: TP
authors.lastname: van de Hoef
authors.forename: Martijn
authors.initials: M
authors.lastname: Meuwissen
authors.forename: Michiel
authors.initials: M
authors.lastname: Voskuil
authors.forename: Steven A J
authors.initials: SA
authors.lastname: Chamuleau
authors.forename: José P S
authors.initials: JP
authors.lastname: Henriques
authors.forename: Hein J
authors.initials: HJ
authors.lastname: Verberne
authors.forename: Berthe L F
authors.initials: BL
authors.lastname: van Eck-Smit
authors.forename: Karel T
authors.initials: KT
authors.lastname: Koch
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: de Winter
authors.forename: Jos A E
authors.initials: JA
authors.lastname: Spaan
authors.forename: Jan G P
authors.initials: JG
authors.lastname: Tijssen
authors.forename: Maria
authors.initials: M
authors.lastname: Siebes
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Piek
mesh_terms: D000241:Adenosine; D000368:Aged; D001783:Blood Flow Velocity; D001794:Blood Pressure; D016009:Chi-Square Distribution; D003097:Collateral Circulation; D003326:Coronary Circulation; D023921:Coronary Stenosis / Q000000981:diagnostic imaging / Q000503:physiopathology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055414:Myocardial Perfusion Imaging / Q000379:methods; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012720:Severity of Illness Index; D014655:Vascular Resistance; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D000241:Adenosine