From the Guidelines
Beta blockers are ordered for CT angiography to slow the heart rate, typically to below 60 beats per minute, as this has been shown to decrease motion artifacts and improve image quality on coronary CTA scans 1. To achieve this, medications such as metoprolol (5-15 mg IV) or oral beta blockers (such as metoprolol 50-100 mg) can be administered 1-2 hours before the scan. The primary goal of using beta blockers in this context is to prolong the rest period during the cardiac cycle, allowing for better visualization of coronary arteries. Some key points to consider when using beta blockers for CT angiography include:
- The desired heart rate is 60 beats per minute or less for scanners with a temporal resolution of 250 ms 1
- For scanners with a temporal resolution of at least 167 ms, a heart rate of 75 beats per minute may result in acceptable image quality 1
- Dual-source CT scanners may not require pharmacological heart-rate control, as acceptable image quality has been obtained at up to 90 beats per minute 1 Contraindications for beta blockers, such as severe asthma, high-degree heart block, decompensated heart failure, or hypotension, should be carefully considered before administration. In cases where beta blockers are contraindicated, alternative rate-control agents like non-dihydropyridine calcium channel blockers (such as diltiazem) may be considered, although these are generally less effective for this purpose.
From the Research
Importance of Beta Blockers in CT Angioplasty
- Beta blockers are used to control the heart rate prior to coronary computed tomography (CT) angiography, as a low and regular heart rate is necessary for optimal visualization of the coronary arteries on CT 2, 3.
- The administration of beta blockers can be done orally or intravenously, and a protocol can be implemented to screen patients for contraindications and allow successful administration of these medications by radiologists 3.
Efficacy of Beta Blockers in Achieving Target Heart Rate
- Studies have shown that beta blockers can effectively reduce the heart rate and achieve the target heart rate of ≤60bpm, with a significant reduction in motion artifacts and improvement in image quality 2, 4, 5, 6.
- However, the efficacy of beta blockers in achieving the target heart rate can be limited, and improvements in CT scanner temporal resolution are mandatory to achieve consistently high image quality independent of heart rate and beta blocker administration 4.
Contraindications and Alternative Approaches
- Contraindications to beta blockade are present in a substantial proportion of patients, resulting in suboptimal heart rate control and image quality, indicating the need for alternative approaches for heart rate reduction 5.
- Alternative approaches, such as the use of other medications or adjustments to the CT scanner protocol, may be necessary to achieve optimal image quality in patients with contraindications to beta blockade 5.
Administration of Beta Blockers
- Beta blockers can be administered orally or intravenously, with oral administration being a safe and effective option for most patients 2, 6.
- The timing and dosage of beta blocker administration can vary, with some studies suggesting that bedtime administration of a long-acting beta blocker the night before coronary CT angiography can be an effective option to achieve the target heart rate at the time of examination 2.