title: Low-dose CT coronary angiography using prospective ECG-triggering: impact of mean heart rate and heart rate variability on image quality.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of mean heart rate (HR) and HR variability on image quality in low-dose computed tomographic coronary angiography (CTCA) using prospective electrocardiographic (ECG) triggering.
  
  
  METHODS
  One hundred thirty-six consecutive patients were scheduled for low-dose CTCA using prospective ECG triggering. The image quality of all coronary segments was rated on a 5-point scale by two independent readers (scores of 1-3 were considered diagnostic, and scores of 4 and 5 were considered nondiagnostic). Intravenous beta blockers were administered targeting HR < 65 beats/min before scanning, but not if HR increased during scanning.
  
  
  RESULTS
  After the exclusion of seven patients because of arrhythmia (n = 4) or mean HRs > 65 beats/min despite using beta blockers (n = 3), 129 patients underwent computed tomographic scanning. The estimated mean effective radiation dose was 2.2 +/- 0.7 mSv (range, 1.1-3.5). The mean HR during scanning was 58.4 +/- 6.6 beats/min (range, 44.2-80.1), with a variability of 1.6 +/- 1.0 beats/min (range, 0.2-5.3). Mean HR (r = 0.49, P < .001) but not mean HR variability (r = 0.14) was related to image quality. Nondiagnostic image quality on CTCA was found in 5% of the coronary segments in 21 of 129 patients. However, on receiver-operating characteristic analysis, a cutoff HR of 62 beats/min was determined, below which nondiagnostic segments were significantly less frequent (2% vs 14%, P < .001).
  
  
  CONCLUSIONS
  Prospective triggering allows low-dose CTCA but requires a low HR. Because a low HR offers a prolonged diastole, widening the optimal phase for scanning, HR variability seems to have a negligible impact on image quality.
authors.affiliation: Cardiovascular Center, University Hospital Zurich, Raemistrasse 100, 8091 Zurich, Switzerland.
authors.forename: Bernhard A
authors.initials: BA
authors.lastname: Herzog
authors.forename: Lars
authors.initials: L
authors.lastname: Husmann
authors.forename: Nina
authors.initials: N
authors.lastname: Burkhard
authors.forename: Ines
authors.initials: I
authors.lastname: Valenta
authors.forename: Oliver
authors.initials: O
authors.lastname: Gaemperli
authors.forename: Fuminari
authors.initials: F
authors.lastname: Tatsugami
authors.forename: Christophe A
authors.initials: CA
authors.lastname: Wyss
authors.forename: Uif
authors.initials: U
authors.lastname: Landmesser
authors.forename: Philipp A
authors.initials: PA
authors.lastname: Kaufmann
mesh_terms: D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*