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DOM Morning Report: Coronary CT Angiography CCTA

Objectives. To understand the radiation doseTo understand the meaning of a positive testTo know the applications considered appropriate by the AHA and the ACC. Disadvantages of Angiography. Complications0.2-0.3% incidence of major eventsDeathMyocardial infarctionStroke1-2% incidence of mi

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DOM Morning Report: Coronary CT Angiography CCTA

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    1. DOM Morning Report: Coronary CT Angiography (CCTA) Week of April 13, 2009

    2. Objectives To understand the radiation dose To understand the meaning of a positive test To know the applications considered appropriate by the AHA and the ACC

    3. Disadvantages of Angiography Complications 0.2-0.3% incidence of major events Death Myocardial infarction Stroke 1-2% incidence of minor events Modest amount of discomfort

    4. Disadvantages of Angiography Expensive Costly equipment Time and skill of highly trained personnel Information pertains only to lumen

    5. Background Noninvasive imaging Rationale for development Improving safety Improving cost Difficult Small caliber Tortuous course Almost constant motion Modalities must possess high resolution

    6. Background Clinical use Widely available Increasingly popular Screening asymptomatic pts inappropriate Aggressive marketing Direct to consumers Often available without referral

    7. Multidetector Technology Has supplanted electron-beam CT 16 to 256 rows of detectors High radiation dose necessary Continuous irradiation for 8-20 seconds Overlapping slices Specific requirements for x-ray tubes Current Voltage

    8. Radiation Dose Effective dose for scanning protocols 13 milliSieverts (mSv) with a 16 slice scanner Up to 21mSv in modulated 64 slice scanners ~ 3-4mSv per year from background radiation 0.05mSv for a chest x-ray ~ 2-6mSv for a diagnostic angiogram Inappropriate in population at very low risk

    9. Patient-related Factors Heart rate > 60-70 beats/min Irregular rhythm Inability hold breath for = 15-20 seconds Reconstruction artifacts Calcification Stents Small vessel caliber Risk for adverse effects of IV contrast

    10. Appropriateness Detection of symptomatic CAD Intermediate pre-test probability CP syndrome Un-interpretable EKG OR unable to exercise Intermediate pre-test probability acute CP No EKG changes AND serial enzymes negative Evaluation of suspected coronary anomalies Un-interpretable or equivocal stress test

    11. Symptomatic Disease Studies Single center Experienced observers Small numbers of patients High prevalence of disease Active chest pain Referred for cardiac catheterization

    12. Symptomatic Disease Stenosis Degree determined by visual estimate > 50% considered “significant” Single center Sensitivity = 98% Specificity = 88% Multicenter Sensitivity = 85-99% Specificity = 64-90%

    13. Symptomatic Disease Predictive value Positive 91-93% Patient-based evaluations Left main coronary artery Coronary bypass grafts 69-84% for other coronary arteries Negative Generally high Interest in use for “ruling out”

    14. Symptomatic Disease Native vessel stenosis caveats Detection of in-stent re-stenosis challenging High pretest probability Clinical benefit unlikely Intervention likely necessary Bypass graft assessment difficult

    15. Coronary Artery Anomalies Accurate assessment Benefit compared with angiography Detection Characterization Congenital Origin Course Acquired

    16. Other Uses Left bundle branch block Pre-op risk stratification Dilated cardiomyopathy Cardiac allograft vasculopathy Plaque imaging Coronary venography Pulmonary vein imaging Coronary artery stents

    17. Limitations Purely diagnostic Lower spatial resolution than angiography Associated risks Nitroglycerin ß-blockers Potential for patient self-referral Requires IV injection of iodinated contrast Radiation exposure

    18. Guidelines “Reasonable” Symptomatic patients Intermediate risk Equivocal stress tests Limit radiation exposure Patients with very low likelihood Patients with high likelihood Calcification reduces usefulness Evaluation of coronary anomalies

    19. Questions Remain What is the next step following a “positive” test? Do the location and degree of stenosis impact decision making? Do the patient’s comorbidities matter?

    20. Objectives Revisited Radiation dose 5x > cath, 300x > CXR Inappropraite for low risk patients Positive test Subjective > 50% stenosis

    21. Objectives Revisited Appropriate applications Detection of symptomatic CAD Intermediate risk chest pain Anomalous anatomy Equivocal stress test

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