title: Effect of increases in heart rate and arterial pressure on coronary flow reserve in humans.
abstract: OBJECTIVE
  The objective of this study was to determine the effect of increases in heart rate and arterial pressure on maximal pharmacologic coronary blood flow reserve.
  
  
  BACKGROUND
  Coronary flow reserve measurements are useful in assessment of the physiologic significance of coronary lesions. However, animal studies suggest that alterations in hemodynamic status may influence coronary flow reserve independent of coronary stenosis.
  
  
  METHODS
  Coronary flow reserve was measured during cardiac catheterization with the use of a 3F coronary Doppler catheter and intracoronary papaverine. Flow reserve was measured under control conditions and during increases in heart rate produced by atrial pacing (18 patients) or during elevation of arterial pressure by intravenous phenylephrine infusion (9 patients) with intracoronary alpha-adrenergic blockade by phentolamine.
  
  
  RESULTS
  Coronary flow reserve progressively decreased from 3.7 +/- 0.9 (mean +/- SD) at the rate of 71 +/- 8 beats/min at rest to 3.0 +/- 0.6 during pacing at 100 beats/min and to 2.6 +/- 0.5 during pacing at 120 beats/min. Flow reserve decreased because of a progressive increase in rest coronary flow velocity during pacing (122 +/- 16% of control value at 100 beats/min, 139 +/- 16% of control value at 120 beats/min), whereas papaverine hyperemia peak velocity remained unchanged. Flow reserve decreased with pacing tachycardia whether the initial flow reserve was normal or depressed. Mean arterial pressure increased from 95 +/- 12 mm Hg to 130 +/- 8 mm Hg during intravenous phenylephrine infusion and to 123 +/- 10 mm Hg during combined intravenous phenylephrine and intracoronary phentolamine infusions. Coronary flow reserve was not affected by the blood pressure increases (control value 4.3 +/- 1.0, phenylephrine 4.4 +/- 1.5, phenylephrine and phentolamine 4.4 +/- 2.0).
  
  
  CONCLUSIONS
  Sudden increases in heart rate but not mean arterial pressure lead to a substantial reduction in maximal coronary blood flow reserve. These data suggest that the diagnostic utility of all flow reserve measurement techniques might be improved by standardization of heart rate during measurement or extrapolation of the measured flow reserve to that expected at a reference heart rate.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.
authors.forename: J D
authors.initials: JD
authors.lastname: Rossen
authors.forename: M D
authors.initials: MD
authors.lastname: Winniford
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D006328:Cardiac Catheterization; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010208:Papaverine; D010646:Phentolamine; D010656:Phenylephrine; D014465:Ultrasonics
chemical_list: D010656:Phenylephrine; D010208:Papaverine; D010646:Phentolamine