Practice guidelines in Practice guidelines in MSMS--CT coronarographyCT coronarography

Ladislav Pavic, MD, PhDLadislav Pavic, MD, PhD

Sunce Clinics Zagreb / SarajevoSunce Clinics Zagreb / Sarajevo

Croatia / Bosnia & HerzegovinaCroatia / Bosnia & Herzegovina

Preconditions for adequate imaging work-up

Adequate indication

Adequate imaging technique / procedure

Adequate interpretation & reporting

1. Detection of CAD with prior test results: Evaluation of chest pain syndromeUninterpretable or equivocal stress test result (exercise, perfusion, or stress echo)

2. Detection of CAD: Evaluation of chest pain syndromeIntermediate pre-test probability of CAD, ECG uninterpretable or unable to exercise

3. Detection of CAD: Acute chest painIntermediate pre-test probability of CAD, no ECG changes and serial enzymes negative“Triple rule out” exclude obstructive CAD, aortic dissection, and pulmonary embolism

4. Evaluation of coronary arteries in patients with new onset heart failure to assess etiology

5. Detection of CAD: SymptomaticEvaluation of suspected coronary anomalies

ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology. Hendel RC, et al. J Am Coll Cardiol. 2006;48:1475-1497.

Indications for coronary CTA:

Uncertain indication for coronary CTA:

6. Detection of CAD: Asymptomatic (without chest pain syndrome)High coronary heart disease (CAD) risk (Framingham)

7. Detection of CAD: Post-revascularization (PCI or CABG)Evaluation of bypass graft and coronary anatomyHistory of percutaneous revascularization with stents

8. Risk assessment: General population-asymptomatic (calcium scoring)Moderate CHD risk (Framingham)High CHD risk (Framingham)

ACCF/ACR/SCCT/SCMR/ASNC/NASCI/SCAI/SIR 2006 appropriateness criteria for cardiac computed tomography and cardiac magnetic resonance imaging: a report of the American College of Cardiology Foundation Quality Strategic Directions Committee Appropriateness Criteria Working Group, American College of Radiology, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, American Society of Nuclear Cardiology, North American Society for Cardiac Imaging, Society for Cardiovascular Angiography and Interventions, and Society of Interventional Radiology. Hendel RC, et al. J Am Coll Cardiol. 2006;48:1475-1497.

Ideal:

…to keep patient doses as low as reasonably achievable but consistent with obtaining the desired medical information!

Gerber TC, et al. Ionizing radiation in cardiac imaging: a science advisory from the American Heart Association Committee on Cardiac Imaging of the Council on Clinical Cardiology and Committee on Cardiovascular Imaging and Intervention of the Council on Cardiovascular Radiology and Intervention. Circulation. 2009 Feb 24;119(7):1056-65. Epub 2009 Feb 2.

CCTA imaging technique

CCTA is particularly amenable to radiation dose reduction using hardware and acquisition protocols customized to patients’ characteristics.

Minimal hardware requirement: 64 ≥ slice cardiac CT-scanner

CCTA imaging technique

A radiation consulting team was selected by the Consortium Executive

Committee...

This team created a Best-Practice Model for Scan Acquisition designed to reduce radiation dose.

CCTA imaging techniqueBest-Practice Model for Scan Acquisition

Instructions to the patient and ordering physicians:

At the time of scheduling, the patient should be instructed to avoid solid food or caffeine within 6

hours of the scan, but to take oral fluids liberally to avoid dehydration, and to continue taking

β- blocking drugs; these measures encourage heart rate stability

Medical history: If the patient has taken β-blockers prior to arrival, subsequent doses should be adjusted

Nursing assessment: Vital signs including heart rate, heart rate variability, and blood pressure

are assessed and monitored during the premedication period

CCTA imaging techniqueBest-Practice Model for Scan Acquisition

Administration of β-blockers:

For most current retrospective, gated-acquisition protocols, including dual-source scanners, heart rate control reduces radiation dose by allowing a more narrow acquisition window

For patients with baseline heart rates greater than 65/min, systolic blood pressure greater than 90 mm Hg, and body mass index greater than 18: administer 100 mg of oral metoprolol or comparable dose equivalent 30 minutes to 1 hour prior to the procedure, or comparable intravenous doses with telemetric monitoring

For patients with baseline heart rates greater than 50/min but less than 65/min and blood pressure greater than 90 mm Hg, administer 50 mg of oral metoprolol to block heart rate acceleration during

scan

Nitroglycerin administration: If blood pressure is greater than 90 mm Hg, nitroglycerin generally improves image quality, yielding a lower frequency of repeat scans

CCTA imaging techniqueBest-Practice Model for Scan Acquisition

Protocol parameters:

Because radiation dose is directly proportional to z axis scan length, the field of view should be consistently restricted

from mid-pulmonary artery to the diaphragm;

extended field of view triple rule-out scans should be limited to patients with clinical likelihood of either a pulmonary

embolus or aortic dissection

A simple rule is used to reduce scan voltage from the standard 120 kVp; 100 kVp may be substituted in patients with a body weight of 85 (90) kg or less and a body mass index of less than 30 (32), subject to physician discretion

Tube current modulation by electrocardiographic pulsing should be used in all patients unless atrial fibrillation or frequent premature contractions are present

CCTA imaging techniqueBest-Practice Model for Scan Acquisition

Acquisition window:

For scanners with adjustable acquisition windows during electrocardiographic pulsing, the following adjustments are recommended:

Heart rate lower than 65/min: 65% to 75%

Heart rate of 66/min to 70/min: 60% to 80%

Heart rate greater than 70/min: 35% to 80%

Highly variable heart rates or atrial fibrillation may preclude the use of electrocardiographic dose modulation, but this should be weighed against the patient's age and the suitability of

other diagnostic options

If scanner model allows tube current adjustment, the lowest available tube current outside the acquisition window should be used (eg, 5% of maximal); this is equally applicable in obese patients because the data during systole

will not be used

It was agreed that Ca-scoring should be done only if specifically ordered!

CCTA imaging techniqueAdvanced Cardiovascular Imaging Consortium (ACIC) - Results

CCTA imaging techniqueOur experience

*International PRospective Multicenter Study On RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy IN Daily Practice (PROTECTION I)Hausleiter J, et al. Estimated radiation dose associated with cardiac CT angiography. JAMA. 2009 Feb 4;301(5):500-7.

Characteristics

Sunce, ZagrebSiemens 64Dual-Source

(n = 100)

PROTECTION I* Siemens 64Dual-Source

(n = 100)

Body mass index 31,2 26.3 (24.1-28.7)

Without β-blockers 0 350 (67.2 %)

Heart rate, beats/min 62 (54-65) 64 (56-72)

Tube voltage, kV 100 40 70 (13.4)

≥120 60 451 (86.6)

Scan length, mm 125 (113-142) 133 (121-146)

CTDIvol, mGy 45,9 47.8 (35.8-60.8)

Dose-length product, mGy X cm 721,9 798 (580-1007)

Effective dose estimate, mSv 10 11 (8-14)

CCTA, adequate interpretation & reporting Society of Cardiovascular Computed Tomography (SCCT)Underlying principles of interpreting

Raff GL, et al SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography. J Cardiovasc Comput Tomogr. 2009 Mar-Apr;3(2):122-36. Epub 2009 Jan 29.

CCTA, adequate interpretation & reporting Society of Cardiovascular Computed Tomography (SCCT)Stenosis Grading

Raff GL, et al SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography. J Cardiovasc Comput Tomogr. 2009 Mar-Apr;3(2):122-36. Epub 2009 Jan 29.

CCTA, adequate interpretation & reporting Society of Cardiovascular Computed Tomography (SCCT)Structured reporting

Raff GL, et al SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography. J Cardiovasc Comput Tomogr. 2009 Mar-Apr;3(2):122-36. Epub 2009 Jan 29.

CCTA, adequate interpretation & reporting Society of Cardiovascular Computed Tomography (SCCT)Structured reporting

Raff GL, et al SCCT guidelines for the interpretation and reporting of coronary computed tomographic angiography. J Cardiovasc Comput Tomogr. 2009 Mar-Apr;3(2):122-36. Epub 2009 Jan 29.

CCTA, adequate interpretation & reporting Images, example

Contact: Ladislav.Pavic@sunce.hr