title: Coronary microvascular dysfunction is associated with baseline QTc prolongation amongst patients with chest pain and non-obstructive coronary artery disease.
abstract: BACKGROUND
  Coronary microvascular dysfunction (CMD) causes ischemia and is linked to adverse cardiovascular events. Acute transmural ischemia is associated with QT prolongation, but whether CMD affects repolarization is unknown. The aim of this study was to determine if CMD is associated with prolongation of resting heart rate corrected QT interval (QTc).
  
  
  METHODS
  In patients presenting to the catheterization laboratory with chest pain and non-obstructive coronary artery disease (CAD) at angiography, coronary flow reserve (CFR) in response to intracoronary adenosine was measured and compared to baseline to give a CFR ratio. The Bazett's-derived QTc was manually derived from patients' 12-lead ECG obtained prior to the procedure. QTc was compared between patients with normal and abnormal (CFR ratio≤2.5) coronary microvascular function.
  
  
  RESULTS
  Of the 926 patients included in this study, 281 patients (30%) had CMD (mean age 53.2 years [SD 12.7], 25% male). QTc was significantly longer in those with an abnormal CFR response to adenosine (median [Q1, Q3] ms: 420 [409, 438] vs. 416 [405, 432]; p value<0.001) and patients in the lowest quartile of CFR had a significantly longer QTc compared to those in the highest quartile (median [Q1, Q3] ms: 420 [409, 439] vs. 413 [402, 426]; p<0.001). In a linear regression model adjusting for age and sex, CMD was associated with an increase in QTc of 3.09 ms (p=0.055).
  
  
  CONCLUSIONS
  Our data suggest that CMD may be associated with an increase in baseline QTc, however the precise clinical relevance of this finding needs to be better investigated in larger clinical studies.
authors.affiliation: Division of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN, USA.
authors.forename: Jaskanwal D
authors.initials: JD
authors.lastname: Sara
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo College of Medicine, Rochester, MN, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Lennon
authors.affiliation: Division of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ackerman
authors.affiliation: Division of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Friedman
authors.affiliation: Division of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Noseworthy
authors.affiliation: Division of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN, USA. Electronic address: lerman.amir@mayo.edu.
authors.forename: Amir
authors.initials: A
authors.lastname: Lerman
mesh_terms: D015897:Comorbidity; D003324:Coronary Artery Disease / Q000175:diagnosis* / Q000453:epidemiology*; D004562:Electrocardiography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D017566:Microvascular Angina / Q000175:diagnosis* / Q000453:epidemiology*; D008875:Middle Aged; D008910:Minnesota / Q000453:epidemiology; D015995:Prevalence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity
keywords: Cardiovascular events; Coronary microvascular dysfunction; Non-obstructive coronary artery disease; QT interval prolongation; Ventricular arrhythmia