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
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The purpose of this study was to evaluate the effect of intravenous (IV) 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 IV 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 IV 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 IV (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 IV metoprolol and have studies with higher radiation dose and worse image quality.
KeywordsHeart rate Beta-blocker Coronary artery disease Image quality Radiation dose 320 MDCT
Conflict of interest
Narinder S. Paul has received research support from Toshiba Medical Systems.
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