title: Lowering heart rate with an optimised breathing protocol for prospectively ECG-triggered CT coronary angiography.
abstract: OBJECTIVE
  The aim was to prospectively characterise the effect of the level of breath-hold on heart rate in CT coronary angiography (CTCA) with prospective electrocardiogram (ECG) triggering and its impact on coronary artery attenuation.
  
  
  METHODS
  260 patients (86 women; mean age 59 ± 11 years) underwent 64-slice CTCA using prospective ECG triggering. Prior to CTCA, heart rates were recorded during 15 s of breath-hold at three different levels of inspiration (normal, intermediate and deep). The inspiration level with the lowest heart rate was chosen for actual CTCA scanning. Coronary artery attenuation was measured, and the presence of backflow of contrast material into the inferior vena cava (as an indicator of increased intrathoracic pressure) was recorded.
  
  
  RESULTS
  The mean heart rate at breath-hold was significantly different for the three inspiration levels (normal, 60 ± 8 bpm; intermediate, 59 ± 8 bpm; deep, 57 ± 7 bpm; p<0.001). The maximum heart rate reduction in each patient at breath-hold averaged 5.3 ± 5.1 bpm, and was observed at a normal inspiration depth in 23 (9%) patients, at an intermediate inspiration depth in 102 (39%) patients and at deep inspiration in 135 (52%) patients. Overall, there was no association between the level of breath-hold and coronary vessel attenuation (p-value was not significant). However, the backflow of contrast material into the inferior vena cava (n = 26) was found predominantly at deep inspiration levels (p<0.001), and, when it occurred, it was associated with reduced coronary attenuation compared with patients with no backflow (p<0.05).
  
  
  CONCLUSIONS
  The breath-hold level to best reduce heart rate for CTCA should be individually assessed prior to scanning because a mean heart rate reduction of 5 bpm can be achieved.
authors.affiliation: Department of Radiology, Cardiac Imaging, University Hospital Zurich, Zurich, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Husmann
authors.forename: B A
authors.initials: BA
authors.lastname: Herzog
authors.forename: A P
authors.initials: AP
authors.lastname: Pazhenkottil
authors.forename: R R
authors.initials: RR
authors.lastname: Buechel
authors.forename: R
authors.initials: R
authors.lastname: Nkoulou
authors.forename: J R
authors.initials: JR
authors.lastname: Ghadri
authors.forename: I
authors.initials: I
authors.lastname: Valenta
authors.forename: I A
authors.initials: IA
authors.lastname: Burger
authors.forename: O
authors.initials: O
authors.lastname: Gaemperli
authors.forename: C A
authors.initials: CA
authors.lastname: Wyss
authors.forename: P A
authors.initials: PA
authors.lastname: Kaufmann
mesh_terms: D001822:Body Burden; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods*