title: Improved cardiac risk assessment with noninvasive measures of coronary flow reserve.
abstract: BACKGROUND
  Impaired vasodilator function is an early manifestation of coronary artery disease and may precede angiographic stenosis. It is unknown whether noninvasive assessment of coronary vasodilator function in patients with suspected or known coronary artery disease carries incremental prognostic significance.
  
  
  RESULTS
  A total of 2783 consecutive patients referred for rest/stress positron emission tomography were followed up for a median of 1.4 years (interquartile range, 0.7-3.2 years). The extent and severity of perfusion abnormalities were quantified by visual evaluation of myocardial perfusion images. Rest and stress myocardial blood flows were calculated with factor analysis and a 2-compartment kinetic model and were used to compute coronary flow reserve (coronary flow reserve equals stress divided by rest myocardial blood flow). The primary end point was cardiac death. Overall 3-year cardiac mortality was 8.0%. The lowest tertile of coronary flow reserve (<1.5) was associated with a 5.6-fold increase in the risk of cardiac death (95% confidence interval, 2.5-12.4; P<0.0001) compared with the highest tertile. Incorporation of coronary flow reserve into cardiac death risk assessment models resulted in an increase in the c index from 0.82 (95% confidence interval, 0.78-0.86) to 0.84 (95% confidence interval, 0.80-0.87; P=0.02) and in a net reclassification improvement of 0.098 (95% confidence interval, 0.025-0.180). Addition of coronary flow reserve resulted in correct reclassification of 34.8% of intermediate-risk patients (net reclassification improvement=0.487; 95% confidence interval, 0.262-0.731). Corresponding improvements in risk assessment for mortality from any cause were also demonstrated.
  
  
  CONCLUSIONS
  Noninvasive quantitative assessment of coronary vasodilator function with positron emission tomography is a powerful, independent predictor of cardiac mortality in patients with known or suspected coronary artery disease and provides meaningful incremental risk stratification over clinical and gated myocardial perfusion imaging variables.
authors: Division of Cardiovascular Medicine, Department of Medicine, Brigham & Women's Hospital, Boston, MA 02115, USA.
authors: Venkatesh L
authors: VL
authors: Murthy
authors: Masanao
authors: M
authors: Naya
authors: Courtney R
authors: CR
authors: Foster
authors: Jon
authors: J
authors: Hainer
authors: Mariya
authors: M
authors: Gaber
authors: Gilda
authors: G
authors: Di Carli
authors: Ron
authors: R
authors: Blankstein
authors: Sharmila
authors: S
authors: Dorbala
authors: Arkadiusz
authors: A
authors: Sitek
authors: Michael J
authors: MJ
authors: Pencina
authors: Marcelo F
authors: MF
authors: Di Carli
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001783:Blood Flow Velocity / Q000502:physiology; D002318:Cardiovascular Diseases / Q000000981:diagnostic imaging* / Q000401:mortality / Q000503:physiopathology*; D003326:Coronary Circulation / Q000502:physiology*; D003643:Death; D005080:Exercise Test / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D018570:Risk Assessment