1. The Role of Cardiac CT in CHD Risk Assessment
CRT Washington, DC
Wm. Guy Weigold, MD, FACC
Director, Cardiac CT
Washington Hospital Center
Washington, DC

2. Guy Weigold, MD DISCLOSURES Grants/Contracted Research
Philips Healthcare

3. Cardiac CT: Coronary CT Angiography

4. Cardiac CT: Coronary Calcium Scan
1990
Calcium scoring method
Agatston, Janowitz, Hildner, Zusmer, Viamonte, Detrano
Agatston AS et al. JACC 1990; 15:827-32

5. The Problem
Coronary Heart Disease remains a leading cause of death and disability
> 45% of MI’s are fatal
> ½ million deaths per year (US)
> 4 million deaths (all CVD) per yr (Europe)
25% of deaths from CHD occur before hospitalization
At least 25% of SCD and non-fatal MI occur without prior symptoms
Heart and Stroke Statistical Update.
European Guidelines on CVD Prevention. EHJ 2007 (28)
Myerburg RJ, Kessler KM, Castellanos A. Ann Int Med. 1993;119:

6. The Detection Gap

7. The Detection Gap ATP III: 36 million in US require Rx for LDL
10-15 million in US on lipid-lowering Rx
Est. prevalence of HTN: 50 million in US
Guidelines est. one-third HTN undetected
Est. 650,000 primary SCD and MI per year
High risk individuals: 2% risk per year
32 million at high risk

8. 34th Bethesda Conference (Oct. 2002)
“A major problem of detection, treatment, and prevention of CHD exists in the large population who have no symptoms of heart disease yet are at increased risk to develop CHD.”
“A detection gap in CHD prognosis exists. The precise size of this gap is unknown, but is likely substantial.”

9. Current Approach to Cardiac Risk Stratification
Greenland P, Smith JS Jr, Grundy. Circulation 2001; 104:1863-7

10. Is There a Role for Non-Invasive Testing in Risk Stratification?
Most clinical risk predictors are only moderately accurate and may underestimate or misclassify patients
Wilson PW, D'Agostino RB, Levy D, et al. Circulation 1998; 97:
Multivariate risk prediction based on Framingham data
AUC = 0.7
Similar / referencing articles???

11. Broad Intermediate Risk Group
NHANES
Men and Women
Referencing articles???
Ford et al, JACC 2004;43:1791 11

12. Rationale for an imaging approach
Pathologic substrate is required for event
Quantification of disease burden
Disease burden should correlate with events
Calcium!
Where did this come from? Point?

13. Arterial Calcification is an Integral Part of Arterial Wall Plaque
Calcification colocalizes with macrophages and SMC.
Good correlation with overall plaque burden
Poor correlation with stenosis

14. The “Calcium score” Originally developed with EBCT- subsequent MDCT
CAC score = Area x weighting factor
Originally developed with EBCT- subsequent MDCT
Good reproducibility, low radiation exposure
Alternative scoring systems improve reproducibility
Volume scoring
Mass scoring
The calcium score is derived from regions of interest drawn around foci of calcium, measured according to their area and density. The sum of the area and density product terms for all the CT scan slices gives us the calcium score. 14 14

15. Comparable CACS by EBCT and MDCT
AJR 2004; 183: 15 15

16. Four prospective studies of CACS
South Bay Heart Watch: Middle aged, higher risk
PACC Project: Aged 40-50, low risk
Taylor et al, JACC 2005;46:
Greenland. JAMA 2004;291:
Rotterdam: Elderly
St. Francis: Middle aged
2-10X  risk
Guerci et al. JACC 2005;46:158
Vliegenthart. Circulation 2005;112:572

17. Incremental predictive value of CACS
Arch Intern Med. 2004;164(12): 17

18. From JACC 2007 consensus: CHD death or MI
Higher CAC scores associated with higher event (CHD death or MI) rates and higher RR ratios
High risk rate: 4.6%
Very high risk rate: 7.1%
(rates at 3-5 years)
Summary RR ratios reveal that higher CAC scores are associated with higher event rates and higher RR ratios.
An average CAC risk score (CACS 1-112) associated with summary RR ratio of 1.9 compared to CACS=0.
At higher risk scores, RR increases in an incremental fashion, to as high as 10.8 when CACS > 1000.
Pools CHD death or MI rates at the “high risk” and “very high risk” categories were 4.6% and 7.1% at 3 to 5 yr.
Greenland P, Bonow RO, Brundage BH, et al. JACC 2007;49:

19. Pooled data from 4 studies: Intermediate Framingham risk patients only (10-20% 10-yr risk)
All patients initially classified as intermediate risk (10-20% 10-yr risk) based on Framingham
Analysis of pooled data from 4 studies looking only at individuals at intermediate risk by Framingham risk score demonstrates that while indeed the average risk was in the 10-20% 10-yr risk range, those in the highest tertile of CACS (400 or greater) actually had an event rate that meets the definition of HIGH 10-yr risk (>20% 10-yr risk). This suggesting that especially within this INTERMEDIATE risk group, there is heterogeneity, and that CACS can be used to identify individuals who, despite being at INTERMEDIATE Framingham risk, will actually face a HIGH-risk event rate. These patients would then be treated more aggressively, essentially with secondary prevention measures: lifestyle modification with weight loss, diet, and exercise; smoking cessation; a BP goal of 115/70; an LDL goal of 70; an HDL goal of ???; an A1c goal of ???; a ??? goal of ???.

20. Prognosis is excellent in setting of zero or very low CAC scores
…but not 0 when CACS=0
Number of vessels involved is important
Even with CAC < 100
Check journals: JACC, JACC imaging, Circ, Circ imaging, NEJM, JAMA, AJC, Arch IM, Annals IM for calcium
J Am Coll Cardiol 2007;49:1860–70 20 20

21. The mortality rate associated with a CACS=0 is 0
The mortality rate associated with a CACS=0 is 0.87/1000 person-yr 44,052 asympto adults referred by risk ff; screening EBCT
Men
Women
Blaha M, Budoff MJ, Shaw LJ, et al. JACC Img 2009;2:

22. Meta-analysis of 71,595 asymptomatic adults Mean f/u 4 yr
29,312 (41%) had CACS=0  0.47% had event
42,283 had CAC  4.14% had event
Summary RR ratio 0.15 [ , p<0.001]
Sarwar A, Shaw LJ, Shapiro MD, et al. JACC Img. 2009;2:675-88

23. ACCF/AHA 2007 Expert Consensus on Coronary Calcium Scoring
Asymptomatic individuals with intermediate CHD risk (10-20% 10-yr risk)
Reasonable to use CAC measurement
Potentially reclassify to high risk
Asymptomatic, low risk (<10% 10-yr risk)
CAC measurement not recommended
Asymptomatic, high risk (>20% 10-yr risk)
Asymptomatic, intermediate risk, CACS=0
Insufficient evidence to recommend reducing treatment intensity: continue to treat as intermediate risk
CACS>400: further testing (stress, angio)?
No evidence to support
Check latest guidelines: ACC, AHA, SCCT
Greenland P, Bonow RO, Brundage BH, et al. JACC 2007;49:

24. Recap There is a significant CHD risk detection gap
Clinical risk stratification tools alone may underestimate and misclassify risk
Coronary calcium scanning predicts CHD events, independent of and in addition to clinical risk stratification
Best suited for intermediate risk popl’n
Absence of coronary calcium confers excellent prognosis

25. But…
…what about non-calcified plaque?

26. 34 yr old man
30 min chest pain at rest
Initial ECG normal
Recurred with ECG changes
CK 800, TnT 1.85 ug/L

27. Cardiac CT in ACS
Non-obstructive, non-calcified plaque in mid LAD

28. Cardiac CT in ACS
IVUS confirms CAD and demonstrates plaque fissure and thrombus.
“After considerable deliberation”: DES

29. Acute MI and Near-Normal Coronaries
Caussin et al Am J Cardiol 2003;92:849-52
% diam sten QCA 17-34%
Stephan’s paper about findings by CTA of acute coronary syndromes 29

30. Noncalcified plaque: uncommon when CAC = 0 in lower risk patients
zero or low (<50) CAC scores
Prevalence
6.5% in patients with 0 CAC
65.2% in those with low CAC
AJC 2007;99:1183–1186 30 30

31. 1138 CorCTA pts categorized by Angiographic CAD Index (Mark, 1994) vs matched MPS cohort
Follow-ups?
Shaw LJ, Berman DS, Min JK, Polk DM, Callister TQ AHA 2006

32. Outcomes of Cor CTA 1,127 pts w/chest discomfort Mean f/u 15 mo.
Follow-ups?
Min JK, Shaw LJ, Devereux RB, et al. JACC 2007;50:

33. Outcomes of Cor CTA 1,127 pts w/chest discomfort Mean f/u 15 mo.
1127 pt (symptomatic) (70% intermediate or high pretest likelihood of signif. CAD)
Endpoint: death
Min JK, Shaw LJ, Devereux RB, et al. JACC 2007;50:

34. Events following CTA 1,256 pts 64-slice CT Mean f/u 18 mo. (96%)
Death, MI, Unstable angina (hosp)
Death, MI, UA, Revasc

35. Events following CTA 1,256 pts 64-slice CT Mean f/u 18 mo. (96%)
Low event rates when no obstructive CAD

36. Pooled data: 6,603 pts
Shaw LJ, Narula J. JACC Img. 2009;2:524-26

37. Recap Outcome data for coronary CTA are accumulating
Normal study, or mild/non-obstructive disease confers very good prognosis (akin to CACS=0)
Obstructive disease, its extent and distribution, correlate with increasing risk
In some studies, events driven by revascularization, but in others CTA is a predictor of total mortality
It remains to be seen whether cor CTA adds incremental value above & beyond CACS
Radiation & contrast: down to 3-5 mSv and 50 mL is now routine… < 1 mSv is currently under study

38. Thank you