Analysis of heart rate and heart rate variation during cardiac CT examinations.
OBJECTIVE
We sought to examine heart rate and heart rate variability during cardiac computed tomography (CT).


METHODS
Ninety patients (59.0 +/- 13.5 years) underwent coronary CT angiography (CTA), with 52 patients also undergoing coronary artery calcium scanning (CAC). Forty-two patients with heart rate greater than 70 bpm were pretreated with oral beta-blockers (in five patients, use of beta-blocker was not known). Sixty-four patients were given sublingual nitroglycerin. Mean heart rate and percentage of beats outside a +/-5 bpm region about the mean were compared between baseline (free breathing), prescan hyperventilation, and scan acquisition (breath-hold).


RESULTS
Mean scan acquisition time was 13.1 +/- 1.5 seconds for CAC scanning and 14.2 +/- 2.9 seconds for coronary CTA. Mean heart rate during scan acquisition was significantly lower than at baseline (CAC 58.2 +/- 8.5 bpm; CTA 59.2 +/- 8.8 bpm; baseline 62.8 +/- 8.9 bpm; P < .001). The percentage of beats outside a +/-5 bpm about the mean were not different between baseline and CTA scanning (3.5% versus 3.3%, P = .87). The injection of contrast had no significant effect on heart rate (58.2 bpm versus 59.2 bpm, P = .24) or percentage of beats outside a +/-5 bpm about the mean (3.0% versus 3.3%, P = .64). No significant difference was found between gender and age groups (P > .05).


CONCLUSIONS
Breath-holding during cardiac CT scan acquisition significantly lowers the mean heart rate by approximately 4 bpm, but heart rate variability is the same or less compared with normal breathing.
Zhang
Jie
J
Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN 55455, USA.
Fletcher
Joel G
JG
Scott Harmsen
W
W
Araoz
Philip A
PA
Williamson
Eric E
EE
Primak
Andrew N
AN
McCollough
Cynthia H
CH
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017023:Coronary Angiography; D004562:Electrocardiography; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed