Which form of metoprolol (beta blocker), succinate or tartrate, is more commonly used at a dose of 50mg in a Coronary Computed Tomography Angiography (CCTA)?

Metoprolol Tartrate is the Preferred Agent for CCTA Heart Rate Control

For Coronary Computed Tomography Angiography (CCTA), metoprolol tartrate 50mg is more commonly used than metoprolol succinate for heart rate control. 1

Rationale for Metoprolol Tartrate in CCTA

Pharmacokinetic Considerations

• Metoprolol tartrate has a more immediate onset of action compared to the extended-release succinate formulation, making it ideal for the acute heart rate control needed during CCTA procedures
• The immediate-release properties of tartrate allow for rapid titration to achieve the target heart rate of ≤60 beats per minute required for optimal CCTA image quality

Protocol-Based Evidence

• Coronary CTA requires low heart rates (ideally ≤60 beats per minute) to avoid motion artifacts and improve image quality 1
• The 2008 AHA scientific statement on noninvasive coronary artery imaging specifically mentions that β-receptor blocking agents are administered 60-90 minutes before the scan orally, or intravenously immediately before the scan 1
• This timing aligns with the pharmacokinetic profile of metoprolol tartrate rather than the extended-release succinate formulation

Dosing Considerations for CCTA

Typical Administration Protocol

• Metoprolol tartrate 50mg oral dose is typically administered 60-90 minutes before the scan
• If needed, additional intravenous doses may be given immediately before scanning for patients whose heart rate remains elevated
• The goal is to achieve a heart rate of ≤60 beats per minute to minimize coronary motion artifacts

Comparison of Formulations

• While metoprolol succinate 50mg once daily is used for chronic conditions like hypertension, heart failure, and atrial fibrillation 1, it is not the preferred agent for the acute heart rate control needed during CCTA
• Metoprolol tartrate 25-100mg can be administered intravenously as a 2.5-5.0mg bolus over 2 minutes (up to 3 doses) for rapid heart rate control 1

Clinical Context

Image Quality Considerations

• Lower heart rates significantly improve CCTA image quality by:
  • Prolonging the cardiac rest period when coronary artery velocity is low
  • Reducing motion artifacts that can obscure coronary anatomy
  • Allowing for better assessment of calcified segments and in-stent stenoses

Scanner Technology Considerations

• For scanners with temporal resolution of 250ms, a heart rate of 60 beats per minute is needed to minimize motion artifacts
• For scanners with temporal resolution of at least 167ms, heart rates up to 75 beats per minute may be acceptable
• For dual-source CT scanners, acceptable image quality can be obtained at up to 90 beats per minute 1

Common Pitfalls and Caveats

• Avoid using metoprolol in patients with:

  • Severe bradycardia
  • High-degree heart block
  • Cardiogenic shock
  • Decompensated heart failure
  • Severe COPD or asthma with bronchospasm

• Remember that nitroglycerin is often administered sublingually immediately before CCTA to achieve coronary vasodilation, which has been shown to improve image quality 1

• While metoprolol succinate and tartrate are equivalent in total daily dose (metoprolol tartrate 100mg twice daily equals metoprolol succinate 200mg once daily) 2, the immediate-release properties of tartrate make it more suitable for the acute heart rate control needed during CCTA procedures

In summary, metoprolol tartrate 50mg is the preferred beta-blocker formulation for CCTA due to its immediate-release properties that allow for rapid heart rate control to optimize image quality.