title: Failed heart rate control with oral metoprolol prior to coronary CT angiography: effect of additional intravenous metoprolol on heart rate, image quality and radiation dose.
abstract: The purpose of this study was to evaluate the effect of intravenous (i.v.) metoprolol after a suboptimal heart rate (HR) response to oral metoprolol (75-150 mg) on HR control, image quality (IQ) and radiation dose during coronary CTA using 320-MDCT. Fifty-three consecutive patients who failed to achieve a target HR of < 60 bpm after an oral dose of metoprolol and required supplementary i.v. metoprolol (5-20 mg) prior to coronary CTA were evaluated. Patients with HR < 60 bpm during image acquisition were defined as responders (R) and those with HR ≥ 60 bpm as non-responders (NR). Two observers assessed IQ using a 3-point scale (1-2, diagnostic and 3, non-diagnostic). Effective dose (ED) was estimated using dose-length product and a 0.014 mSV/mGy.cm conversion factor. Baseline characteristics and HR on arrival were similar in the two groups. 58% of patients didn't achieve the target HR after receiving i.v. metoprolol (NR). R had a significantly higher HR reduction after oral (mean HR 63.9 ± 4.5 bpm vs. 69.6 ± 5.6 bpm) (p < 0.005) and i.v. (mean HR 55.4 ± 3.9 bpm vs. 67.4 ± 5.3 bpm) (p < 0.005) doses of metoprolol. Studies from NR showed a significantly higher ED in comparison to R (8.0 ± 2.9 vs. 6.1 ± 2.2 mSv) (p = 0.016) and a significantly higher proportion of non-diagnostic coronary segments (9.2 vs. 2.5%) (p < 0.001). 58% of patients who do not achieve a HR of <60 bpm prior to coronary CTA with oral fail to respond to additional i.v. metoprolol and have studies with higher radiation dose and worse image quality.
authors.affiliation: Cardiothoracic Division, Department of Medical Imaging, Toronto General Hospital, University Health Network, Toronto, ON, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Jiménez-Juan
authors.forename: Elsie T
authors.initials: ET
authors.lastname: Nguyen
authors.forename: Bernd J
authors.initials: BJ
authors.lastname: Wintersperger
authors.forename: Hadas
authors.initials: H
authors.lastname: Moshonov
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Crean
authors.forename: Djeven P
authors.initials: DP
authors.lastname: Deva
authors.forename: Narinder S
authors.initials: NS
authors.lastname: Paul
authors.forename: Felipe S
authors.initials: FS
authors.lastname: Torres
mesh_terms: D000284:Administration, Oral; D058671:Adrenergic beta-1 Receptor Antagonists / Q000008:administration & dosage*; D000328:Adult; D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage*; D016009:Chi-Square Distribution; D017023:Coronary Angiography / Q000379:methods*; D003331:Coronary Vessels / Q000000981:diagnostic imaging*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008790:Metoprolol / Q000008:administration & dosage*; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D011237:Predictive Value of Tests; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies
chemical_list: D058671:Adrenergic beta-1 Receptor Antagonists; D000889:Anti-Arrhythmia Agents; D008790:Metoprolol