Cardiology>>>>>CT, CMR, And Nuclear Imaging
Question 3#

Concerning heart rate in cardiac CT, which of the following statements is false?

a. On-table intravenous metoprolol may be administered
b. 50–100 mg of oral metoprolol 2 hours prior to the study is recommended
c. On-table oral beta-blocker is not useful
d. Heart rate of ≤65 bpm is ideal
e. Non-ionic low-osmolar intravenous contrast has been reported to have an antiarrhythmic effect on administration

Correct Answer is E


A heart rate of ≤65 bpm is ideal for cardiac CT (see Answer 2).Beta-blockers are the main pharmacological agents used for heart rate control in the context of cardiac CT, and metoprolol is commonly used. A well-recognized protocol involves 50–100 mg oral metoprolol 2 hours prior to the scan. If this is insufficient, further metoprolol can be given intravenously on the table immediately prior to the scan, given its short onset and duration of action. Typically, 5 mg IV is given slowly, with pulse and blood pressure monitoring. This can be repeated with careful titration to an optimal heart rate. Oral metoprolol on the table is not useful given its long onset of action. Therefore it is ideal if patients referred for cardiac CT are optimally prepared with cardiology advice. Contrast-induced nephropathy is a major cause of hospital-acquired acute renal failure, and its risk is significantly increased in patients with diabetes mellitus. The standard non-ionic low-osmolar contrast agents used routinely in contrast-enhanced CT are much safer and have fewer side effects than ionic low-osmolar agents. In addition, it has been reported that newer non-ionic iso-osmolar agents have less tachycardic and arrhythmic effects.