Should nitro (nitroglycerin) patches be removed before a CT scan?

Nitroglycerin Patches and CT Scans

Nitroglycerin patches do not need to be removed before a CT scan, but their use should be carefully considered based on the specific clinical indication for the CT and the patient's hemodynamic status.

When Nitroglycerin May Be Administered for Cardiac CT

• For coronary CT angiography (CTA), sublingual nitroglycerin is routinely administered immediately before the scan to achieve coronary vasodilation and improve image quality 1
• The use of nitroglycerin has been shown to improve image quality in coronary CTA studies 1
• Nitroglycerin is NOT routinely administered for cardiac CT performed to evaluate endocarditis or device-related infections, as these patients may be hemodynamically unstable and the medication could be hazardous 1

When to Avoid Nitroglycerin During CT

• Beta-blockers and nitroglycerin may be contraindicated in patients with conditions such as aortic stenosis and should be used with caution depending on clinical status and in consultation with the referring cardiologist 1
• In patients undergoing cardiac CT for endocarditis evaluation, nitroglycerin should not be routinely administered and may be hazardous in cases of hemodynamic instability 1
• Nitroglycerin can cause inadvertent systemic hypotension, resulting in reflex tachycardia and worsening myocardial ischemia 1

Safety Considerations for Transdermal Patches

• All transdermal medication patches, including nitroglycerin, should be removed from the chest before defibrillation to prevent arcing and potential small explosions from the aluminum backing 1, 2
• While this is a defibrillation concern rather than a CT concern, patches should not be placed directly over where AED electrode pads would be positioned 1
• The patch itself does not interfere with CT imaging quality or pose radiation safety concerns

Practical Algorithm

For coronary CTA:

• If the patient is wearing a nitroglycerin patch, it can remain in place 1
• Administer sublingual nitroglycerin (0.3-0.4 mg) immediately before scanning for coronary vasodilation 1
• Ensure the patient can tolerate nitroglycerin (no recent phosphodiesterase inhibitor use, adequate blood pressure) 1

For non-coronary cardiac CT (endocarditis, device evaluation):

• Do not routinely administer nitroglycerin 1
• Existing patches may remain unless the patient is hemodynamically unstable 1

For any CT scan:

• Remove patches only if they are positioned where they would interfere with emergency defibrillation access 1, 2
• Document patch location if fentanyl patches are present to avoid placement under warming devices 1