title: Prevalence and Prognosis of Nonobstructive Coronary Artery Disease in Patients Undergoing Coronary Angiography or Coronary Computed Tomography Angiography: A Meta-Analysis.
abstract: To evaluate the prevalence, clinical characteristics, and risk of cardiac events in patients with nonobstructive coronary artery disease (CAD).
  
  
  
  We searched PubMed, EMBASE, and the Cochrane Library from January 1, 1990, to November 31, 2015. Studies were included if they reported prevalence or prognosis of patients with nonobstructive CAD (≤50% stenosis) among patients with known or suspected CAD. Patients with nonobstructive CAD were further grouped as those with no angiographic CAD (0% or ≤20%) and those with mild CAD (>0% or >20% to ≤50%). Data were pooled using random effects modeling, and annualized event rates were assessed.
  
  
  
  Fifty-four studies with 1,395,190 participants were included. The prevalence of patients with nonobstructive CAD was 67% (95% CI, 63%-71%) among patients with stable angina and 13% (95% CI, 11%-16%) among patients with non-ST-segment elevation acute coronary syndrome. The prevalence varied depending on sex, clinical setting, and risk profile of the population investigated. The risk of hard cardiac events (cardiac death or myocardial infarction) in patients with mild CAD was lower than that in patients with obstructive CAD (risk ratio, 0.28; 95% CI, 0.20-0.38) but higher than that in those with no angiographic CAD (risk ratio, 1.85; 95% CI, 1.52-2.26). The annualized event rates of hard cardiac events in patients with no angiographic CAD, mild CAD, and obstructive CAD were 0.3% (95% CI, 0.1%-0.4%), 0.7% (95% CI, 0.5%-1.0%), and 2.7% (95% CI, 1.7%-3.7%), respectively, among patients with stable angina and 1.2% (95% CI, 0.02%-2.3%), 4.1% (95% CI, 3.3%-4.9%), and 17.0% (95% CI, 8.4%-25.7%) among patients with non-ST-segment elevation acute coronary syndrome. The correlation between CAD severity and prognosis is consistent regardless of clinical presentation of all-cause death, myocardial infarction, total cardiovascular events, and revascularization.
  
  
  
  Nonobstructive CAD is associated with a favorable prognosis compared with obstructive CAD, but it is not benign. The high prevalence and impaired prognosis of this population warrants further efforts to improve the risk stratification and management of patients with nonobstructive CAD.
authors.affiliation: Beijing Anzhen Hospital, Capital Medical University, Beijing Institute of Heart Lung and Blood Vessel Disease, The Key Laboratory of Remodeling-Related Cardiovascular Disease, Ministry of Education, Beijing, China.
authors.forename: Zhi Jian
authors.initials: ZJ
authors.lastname: Wang
authors.affiliation: Beijing Anzhen Hospital, Capital Medical University, Beijing Institute of Heart Lung and Blood Vessel Disease, The Key Laboratory of Remodeling-Related Cardiovascular Disease, Ministry of Education, Beijing, China.
authors.forename: Lin Lin
authors.initials: LL
authors.lastname: Zhang
authors.affiliation: Cardiology Division, Department of Medicine, Massachusetts General Hospital, Boston.
authors.forename: Sammy
authors.initials: S
authors.lastname: Elmariah
authors.affiliation: Beijing Anzhen Hospital, Capital Medical University, Beijing Institute of Heart Lung and Blood Vessel Disease, The Key Laboratory of Remodeling-Related Cardiovascular Disease, Ministry of Education, Beijing, China.
authors.forename: Hong Ya
authors.initials: HY
authors.lastname: Han
authors.affiliation: Beijing Anzhen Hospital, Capital Medical University, Beijing Institute of Heart Lung and Blood Vessel Disease, The Key Laboratory of Remodeling-Related Cardiovascular Disease, Ministry of Education, Beijing, China. Electronic address: azzyj12@163.com.
authors.forename: Yu Jie
authors.initials: YJ
authors.lastname: Zhou
mesh_terms: D054058:Acute Coronary Syndrome / Q000453:epidemiology* / Q000401:mortality; D002423:Cause of Death; D015897:Comorbidity; D003324:Coronary Artery Disease / Q000453:epidemiology* / Q000401:mortality / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000453:epidemiology* / Q000401:mortality; D015995:Prevalence; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods; D012720:Severity of Illness Index; D017678:Sex Distribution