title: Noninvasive assessment of coronary vasodilation using magnetic resonance angiography.
abstract: OBJECTIVE
  The purpose of this study was to investigate the use of coronary magnetic resonance angiography (MRA) for assessing human epicardial coronary artery vasodilation.
  
  
  BACKGROUND
  Coronary vasodilation plays a vital role in the human coronary circulation. Previous studies of epicardial coronary vasodilation have used invasive coronary angiography. Coronary MRA may provide an alternative noninvasive method to directly assess changes in coronary size.
  
  
  METHODS
  Thirty-two subjects were studied: 12 patients (age 55 +/- 18 years) and 20 healthy subjects (age 34 +/- 4 years). High-resolution multi-slice spiral coronary MRA (in-plane resolution of 0.52 to 0.75 mm) was performed before and after sublingual nitroglycerin (NTG). Quantitative analysis of coronary vasodilation was performed on cross-sectional images of the right coronary artery (RCA). A time-course analysis of coronary vasodilation was performed in a subset of eight subjects for 30 min after NTG. Signal-to-noise ratio was also measured on the in-plane RCA images.
  
  
  RESULTS
  Coronary MRA demonstrated a 23% increase in cross-sectional area after NTG (16.9 +/- 7.8 mm2 to 20.8 +/- 8.9 mm2, p <0.0001), with significant vasodilation between 3 and 15 min after NTG on time-course analysis. The MRA measurements had low interobserver variability (< or =5%) and good correlation with X-ray angiography (r=0.98). The magnitude of vasodilation correlated with baseline cross-sectional area (r=0.52, p=0.03) and age (r=0.40, p=0.019). Post-NTG images also demonstrated a 31% improvement in coronary signal-to-noise ratio (p = 0.002).
  
  
  CONCLUSIONS
  Nitroglycerin-enhanced coronary MRA can noninvasively measure coronary artery vasodilation and is a promising noninvasive technique to study coronary vasomotor function.
authors.affiliation: Division of Cardiovascular Medicine, Stanford University, Stanford, CA 94305, USA.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Terashima
authors.forename: Craig H
authors.initials: CH
authors.lastname: Meyer
authors.forename: Brian G
authors.initials: BG
authors.lastname: Keeffe
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Putz
authors.forename: Erasmo
authors.initials: E
authors.lastname: de la Pena-Almaguer
authors.forename: Phillip C
authors.initials: PC
authors.lastname: Yang
authors.forename: Bob S
authors.initials: BS
authors.lastname: Hu
authors.forename: Dwight G
authors.initials: DG
authors.lastname: Nishimura
authors.forename: Michael V
authors.initials: MV
authors.lastname: McConnell
mesh_terms: D000328:Adult; D003326:Coronary Circulation / Q000502:physiology; D003331:Coronary Vessels / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D018810:Magnetic Resonance Angiography; D008297:Male; D005996:Nitroglycerin; D014664:Vasodilation; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D005996:Nitroglycerin