MultiSlice CT for Coronary Calcium Scoring and Coronary Angiography

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Multi-Slice CT for Coronary Calcium Scoring and
Coronary Angiography

• John D. Symanski, M.D., F.A.C.C
• The Sanger Clinic, PA and Carolinas Medical Center

No Disclosures
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Objectives

• Show lots of pretty pictures
• Overview fundamental principles of MSCT
  technology
• Review strengths and limitations of MSCT
• Raise awareness of current indications and
  clinical scenarios for which to consider CT
  angiography

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Case Presentation

• 64-year-old female with stage 1 CLL
• Dyslipidemia (untreated) No HTN, diabetes, or
  tobacco use
• Negative stress echo previously
• Atypical chest pain
• Stress echo septal hypokinesis at rest, LVEF
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• Referred for calcium scoring and CTA

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CT Angiogram Interpretation

• Calcium Volume Score ZERO
• CT angiography
• Left Main, Circumflex, and Right coronary
  arteries normal
• LAD eccentric, soft plaque adjacent to origin of
  first diagonal (60 stenosis)
• Correlation recommended

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SummaryCardiovascular Imaging - State of the Art

• Multi-slice CT (MSCT) not likely to replace
  conventional angiography
• Post-processing of images for MSCT angiography
  time labor intensive
• Major strength of CTA is its high negative
  predictive value
• CMR to become the preferred cardiac imaging
  modality in the future

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Which Test for Which Patient?

• All modalities are improving
• No single modality fits all applications and all
  patients
• Choice of initial test depends on the specific
  clinical question in individual patient

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Cardiac Magnetic Resonance
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Viability AssessmentCMR Delayed Hyper-Enhancement
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Hazards of MRIMagnet-Seeking Projectiles
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First whole-body CT cross-section through a human
thorax, generated by Ledley et al in 1974
(Science 1974186207)
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The Examination
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Current Generation Scanners

• Spatial resolution 0.4 mm - conventional coronary
  angiography 0.15-0.25 mm
• Temporal resolution (shutter speed) improved to
  166 msec with faster gantry rotation (330 msec)
  conventional angiography 6 msec
• Up to 64 slices in one rotation

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4 to 64 Slice ScansFive Heart Beats
10 mm detector Pitch 0.25 3 cm in 5 sec
20 mm detector Pitch 0.25 6.2 cm in 5 sec
40 mm detector Pitch 0.25 12.5 cm in 5 sec
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64-Slice CT Scanner

• More coverage (volume) with each heart beat
• Entire heart imaged in 5-15 seconds
• Less contrast required
• No increase in rotation speed, but with
  overlapping slices, can use segments from
  different heart beats to improve temporal
  resolution

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3-D Volume Rendered Image
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Maximum Intensity ProjectionSoft Plaque in
Proximal LAD
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Curved Planar Image
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Quantification of Obstructive and Nonobstructive
Coronary Lesions by 64-Slice Computed Tomography

• 59 patients with stable angina subjected to CTA
  before catheter-based angio
• Diagnostic image quality in 55 of 59
• Sensitivity for detection of stenosis lt50, gt50,
  and gt75 (79, 73, and 80, respectively)
• Excellent accuracy with proximal lesions

Leber AW et al. J Am Coll Cardiol. July 5,
200546147-54
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Diagnostic Accuracy of Noninvasive Coronary
Angiography Using 64-Slice Spiral Computed
Tomography

• 70 patients undergoing invasive cath
• Of 1,065 segments, 935 evaluated (88)
• Quantitative assessment in 773 of 935 segments by
  MSCT and QCA
• Sensitivity, specificity, () PV, (-) PV
• By segment- (86, 95, 66, and 98)
• By artery- (91, 92, 80, and 97)
• By patient- (95, 90, 93, and 93)

Raff GL et al. J Am Coll Cardiol. Aug 2,
200546552-7.
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Coronary Calcium Scoring

• Initial ACC/AHA guidelines may be useful in
  selected patients
• Added prognostic power to conventional risk
  stratification tools (Framingham)
• Revised guidelines (and reimbursement for
  service) likely forthcoming

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Calcium Volume Scoring
Area 8 mm2 Peak CT 290 Score 8 x 2 16
Area 15 mm2 Peak CT 450 Score 15 x 4 60
Total Score S
Hn x-factor (Agatston Scoring)
130-199 1 200-299 2 300-399
3 gt400 4
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The Calcium Scale

• The calcium scale is a linear scale with 4
  calcium score categories
• 0 none
• 199 mild
• 100400 moderate
• gt400 severe
• Calcium score correlates directly with risk of
  events and likelihood of obstructive CAD

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Ethnic Differences in Coronary CalcificationThe
Multi-Ethnic Study of Atherosclerosis (MESA)
6814 men and women aged 45-84 years
Bild DE et al. Circulation. 20051111313-1320.
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Five-Year Mortality Rates in Framingham Risk
Subsets by Coronary Calcium Score

plt0.001


Shaw et al. Radiology 2003 228826-833
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Progression of Coronary Artery Calcium and Risk
of First MI495 Asymptomatic Patients Started on
Statin Therapy

• MI in 41 pts during 3.2 0.7 years
• LDL levels similar in MI and non-MI pts
• Relative risk of MI in presence of CAC
  progression was 17.2-fold higher (Plt0.0001)

Raggi P et al. Arterioscler Thromb Vasc Biol.
2004241272-77.
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Coronary Disease Progression
Calcified Plaque Detected by CT
gt60 stenosis () stress/imaging
? Role for CTA
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Soft Plaque Visualization
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CTA Limitations

• Rapid (gt80 bpm) and irregular HR
• High calcium scores (gt800-1000)
• Stents
• Contrast requirements (Cr gt 2.0 mg/dl)
• Small vessels (lt1.5 mm) and collaterals
• Obese and uncooperative patients
• RADIATION EXPOSURE

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Effective Dose of Selected Radiologic Examinations

• PA/Lateral CXR 0.04-0.06 mSv
• Head CT 1-2 mSv
• Chest CT 5-7 mSv
• Abd/Pelvis CT 8-11 mSv
• Diagnostic Cor Angiogram 3-5 mSv
• MSCT angiography 9.3-11.3 mSv

Average annual background radiation in U.S 3.6
mSv
Morin et al. Circulation 2003107917-22.
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Radiation Risks

• Exact quantification of harmful effects of
  radiation difficult to ascertain
• For a child under age 15, the risk of cancer
  death from a single CT scan is approximately 1 in
  500
• For a 45 year old adult, the risk of death from
  cancer from a single CT exam is about 1 in 1,250

Brenner et al. Radiology, 231(2)440-445.
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Clinical Indications for MSCT

• Calcium Scoring (CS) - risk stratification in the
  intermediate risk patient
• Non-invasive coronary angiography (CTA) in the
  symptomatic low-risk patient or asymptomatic
  intermediate-risk patient
• A negative test (normal CTA) has a 98 chance
  of revealing normal coronary arteries on invasive
  angiography

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Test Selection According to Pretest Probability
of CAD
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Association for the Eradication of Heart Attacks
(AEHA.org)
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When to Consider MSCT

• Equivocal stress test or persistent symptoms
  despite negative stress test
• Prior to non-coronary cardiac surgery (valve or
  congenital repair)
• Patients with difficult access or on therapeutic
  warfarin
• Suspected coronary anomalies

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CFX
LAD
RCA
Lt Main
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When to Consider MSCT(continued)

• Idiopathic dilated cardiomyopathy
• Cardiac transplant evaluation
• Patients to undergo electrophysiologic
  intervention (AF ablation, BiV pacing)
• Selected patients pre- and post-bypass surgery
  (aortic pathology, graft patency)

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Mikaelian BJ et al. Circulation. 2005112e35-e36.
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Pulmonary Vein Stenosis
Vasamreddy et al. Heart Rhythm (2004) 1, 78-81.
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Aortic Coarctation Visualized by 16-Row Detector
MSCT
Fröhlich, G et al. Circulation. 2005112e81.
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Pericardial CalcificationMulti-Slice CT Scanning
Superior to MRI
Hoffmann et al. Circulation 108 (7) 48e Figure
IG1
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Future Indications
Nikolaou et al. Cardiology Clinics.
21(2003)639-655.
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The Great Promise of MSCTThe Triple Rule-Out
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Appropriateness Criteria

• an appropriate imaging study is one in which the
  expected incremental information together with
  clinical judgment exceed the expected negative
  consequences by a sufficiently wide margin that
  the procedure is generally considered acceptable
  care and a reasonable approach for the
  indication.

include risks of the procedure and the
downstream impact of poor test performance such
as delay in diagnosis (false -) or
inappropriate diagnosis (false )