Imaging Pearls ❯ Cardiac ❯ Patient Prep: Beta blockers, IV contrast, etc
|
-- OR -- |
|
- “No significant differences were noted in the HR variability or optimal reconstruction phase, despite an increase in HR after the use of nitroglycerin. Nitroglycerin significantly enlarged the coronary artery diameter, and VRs of each coronary segment ranged from 7.54% to 22.26%. As compared with baseline coronary diameter, VRs of minor segments (16.91%) were significantly larger than those of major segments (11.35%), and the magnitude of VR correlated with the baseline coronary diameter. Coronary luminal attenuation significantly increased due to additional administration of contrast material after the use of nitroglycerin (p<0.01), but no significant difference was noted in the image quality after the use of nitroglycerin.”
Coronary vasodilation by the use of sublingual nitroglycerin using 64-slice dual-source coronary computed tomography angiography.
Okada M et al.
J Cardiol. 2014 Jun 30. [Epub ahead of print] - “Nitroglycerin significantly enlarged the coronary artery diameter, and VRs of each coronary segment ranged from 7.54% to 22.26%. As compared with baseline coronary diameter, VRs of minor segments (16.91%) were significantly larger than those of major segments (11.35%), and the magnitude of VR correlated with the baseline coronary diameter. Coronary luminal attenuation significantly increased due to additional administration of contrast material after the use of nitroglycerin (p<0.01), but no significant difference was noted in the image quality after the use of nitroglycerin.”
Coronary vasodilation by the use of sublingual nitroglycerin using 64-slice dual-source coronary computed tomography angiography.
Okada M et al.
J Cardiol. 2014 Jun 30. [Epub ahead of print] - “Sublingual nitroglycerin significantly enlarged the coronary diameters, especially in peripheral small coronary arteries, and increased the evaluable number of coronary segments on coronary CTA.”
Coronary vasodilation by the use of sublingual nitroglycerin using 64-slice dual-source coronary computed tomography angiography.
Okada M et al.
J Cardiol. 2014 Jun 30. [Epub ahead of print]
- Contraindications to the use of β-Blockers
-Asthma or severe COPD
-AV block type II Mobitz or type III
-Severe bradycardia (HR <50 bpm)
-Severe hypotension (systolic blood pressure <100 mm Hg)
-Acute congestive heart failure
-Allergy to β-blocker or its constituents - “ Although some techniques and protocols (eg, dual source CT, multidsegment reconstruction) may not require fixed heart rates for optimal image quality, heart rate reduction allows effective use of prospective triggering, tube current modulation, or single volume data acquisition, which significantly reduces radiation exposure.”
Stable, Efficacy, and Indications of β-Adrenergic Receptor Blockade to Reduce Heart Rate prior to Coronary CT Angiography
Mahabadi AA et al.
Radiology 2010;257;614-623 - “ By virtue of their heart rate-lowering effect, β-blockers result in an improved image quality and diagnostic accuracy of coronary CT angiographic examinations.”
Stable, Efficacy, and Indications of β-Adrenergic Receptor Blockade to Reduce Heart Rate prior to Coronary CT Angiography
Mahabadi AA et al.
Radiology 2010;257;614-623 - “β-Adrenergic receptor blockade is the first-line treatment for reducing heart rate in patients undergoing coronary CT angiography: in the absence of contraindications, short term high dose β-blocker administration is safe and leads to effective heart rate reduction in the majority of patients.”
Stable, Efficacy, and Indications of β-Adrenergic Receptor Blockade to Reduce Heart Rate prior to Coronary CT Angiography
Mahabadi AA et al.
Radiology 2010;257;614-623 - Artifacts in Cardiac CTA
"In MDCT coronary angiography, the use of nitroglycerin has been found to increase proximal coronary artery diameters by 12-21%. However, the added value on diagnostic accuracy is not clear yet.."
Artifacts in ECG-Synchronized MDCT Coronary Angiography
Kroft LJM et al.
AJR 2007; 189:581-591
- "Sublingual nitroglycerin spray significantly dilates the coronary arteries and allows more septal branches to be visualized at coronary CT angiography without diminishing image quality or increasing the number of side effects."
Effects of Sublingual Nirtoglycerin on Coronary Lumen Diameter and Number of Visualized Septal Branches on 64-MDCT Angiography
Decramer I et al.
AJR 2008; 190:219-225
- Nitroglycerin: Potential Side Effects
- Tachycardia
- Flushing
- Headache
- Nitroglycerin: Key Contraindication
- Patients on ED medication like Viagra, Cialis, or Levitra should not be given nitrates. Severe side effects including low blood pressure and death have been reported in patients given nitroglycerin within 24 hours after use of these medications
- "Gd-enhanced contrast medium provides adequate enhancement of coronary vasculature, allowing for diagnostic evaluation of coronary arteries with new CT systems."
Noninvasive Gadolinium-Enhance Three Dimensional Computed Tomography Coronary Angiography
Gul KM et al.
Acad Radiol 2006; 13:840-849.
- Can you do cardiac CTA with Gadolinium rather than iodinated contrast?:
Yes, but read carefully....
"Gd-enhanced contrast medium provides adequate enhancement of coronary vasculature, allowing for diagnostic evaluation of coronary arteries with new CT systems."
Noninvasive Gadolinium-Enhance Three Dimensional Computed Tomography Coronary Angiography Gul KM et al. Acad Radiol 2006; 13:840-849.
- In the article, CT attenuation of vessels was 116HU, (96-125HU) and Gd used was an average of 68 ml (50-80 range)
Noninvasive Gadolinium-Enhance Three Dimensional Computed Tomography Coronary Angiography
Gul KM et al.
Acad Radiol 2006; 13:840-849.
- Contraindications
- 2nd and 3rd degree AV block
- Beta Blockers: Oral Agents
- 50 mg metoprolol
- Range of use is 50-100 mg
- Usually works in 15-30 minutes
- If it is unsuccessful by 60 minutes we bring the patient into the scanner and use IV beta blockers
- Beta Blockers: IV Agents
- Up to 15 mg IV of metoprolol used at 2.5 mg. 2.5 mg, 5 mg and 5 mg over a few minute wait
- Peak effect of metoprolol is seen by 5 minutes
- Some sites use 5 mg doses at 5 minute intervals
- Beta Blockers: Patient Follow Up
- For oral only no monitoring is needed
- For IV a 30 minute observation time is needed
- If heart rate drops too low use atropine up to 0.04 mg/kg or 4 mg for a 100 kg patient
- "Beta blockers can be safely given, orally and intravenously, to most patients to lower the heart rate for cardiac CT. A protocol can be implemented and patients screened for certain contraindications to allow successful administration of these medications by radiologists."
Beta Blockers for Cardiac CT: A Primer for the Radiologist
Pannu HK, Alvarez W, Fishman EK
AJR (in press)
- Beta Blockers: Options
- Acebutolol
- Atenolol
- Betaxolol
- Bisoprolol
- Esmolol
- Metoprolol (Lopressor)
- Metoprolol (Toprol XL)
- Beta Blockers: Contraindications
- Sinus bradycardia ( heart rate <60 bpm or systolic blood pressure under 90 mm Hg)
- Allergy to medication
- Decompensated cardiac failure
- Asthma and using beta agonist agents
- Active bronchospasm
- "Reduction of heart rates with beta-blocker premedication improves the image quality of CT coronary angiography, especially in terms of the visualization of the right coronary artery."
Improvement of Image Quality with Beta-Blocker Premedication on ECG-Gated 16-MDCT Coronary Angiography
Shim SS et al.
AJR 2005; 184:649-654
- When can’t a coronary CTA be done successfully?
- Uncooperative patient
- No IV access or unable to receive IV contrast
- Arrhythmias
- Significant coronary artery calcification
- High heart rate (define high ? >85)
- What is the dose for Nitroglycerin?
- 0.3 mg given sublingually just prior to contrast injection
- Preparing the Patient for a Cardiac CT Exam
- Speak to the patient in advance and reinforce the need for their cooperation to make the study a success
- The key is no surprises!