For most scanners, a low heart rate (HR) is required for optimal image quality with cardiac computed tomography (CCT). Intravenous (IV) metoprolol is commonly given prior to scanning to achieve HR <60 beats per minute (bpm). Local and published protocols often call for small doses to be given incrementally, which can be time-consuming. The ability to predict the minimum dose likely to be required in a given patient would speed up the process and potentially create additional scanner time.Methods
Patients undergoing CCT at a tertiary centre Jul 16-Aug 17, with baseline HR 60 bpm requiring IV metoprolol, were retrospectively identified from the Radiology database. Patients with a contraindication to beta-blockade or an indication for CCT other than coronary disease were excluded. HR at baseline and at the time of scanning were recorded, together with the total dose of IV metoprolol administered.Results
Of 234 patients identified, 109 (47%) achieved HR <60 with IV metoprolol. Patients who achieved target HR had lower baseline HR. They received a lower radiation exposure due to tight prospective gating and a lower tube voltage (Table 1). Table 2 shows the doses of metoprolol administered, stratified by baseline HR. There were no cases of symptomatic bradycardia/hypotension in the study population.Conclusions
Patients with baseline HR 80 could reasonably be given 10–15 mg of metoprolol IV stat, with additional doses as required. Patients with baseline HR 100 could be given 20 mg.