1. CT coronary angiography and coronary calcium scoring
What’s in the box?

2. “Cat” scan

3. What is CT coronary angiography?
Non-invasive coronary angiography using ECG-gated computed tomography with intravenous contrast

12. Functional testing: the consequences of stenosis

14. Early detection of atherosclerotic plaque with coronary CT

16. Limitations of CT coronary angiography
AF or poor HR control
Heavy coronary calcification
Stents (esp <2.5mm)
?Increase invasive angiography rates

17. 1963: the Bruce protocol

18. What are the aims of non-invasive CAD testing
Detection of ischaemia/ obstructive plaque?
Prognostication/ risk stratification?

19. What are the aims of non-invasive CAD testing
Detection of ischaemia/ obstructive plaque? (CTCA more sensitive!)
Prognostication/ risk stratification?
(Assessing for the presence of non-obstructive CAD?)

20. 5 year risk

23. Coronary artery calcium score (CACS)

24. What is CACS? 3-5 second single breathhold non-contrast CT
Algorithm derived from plaque volume and density
<$100 cost
1.5mSv dose (= 4 x mammograms, 1 x CT head, 6 mths background radiation)
Superior to CRP, CIMT, ABI, family history for event prediction
Validated in general population >40 , diabetics, and the elderly

25. Risk stratification
A key step in medical decision making, allowing the tailoring of medical treatment to individual risk
Identification of high risk individuals allows therapy to be concentrated on those most likely to derive a benefit
CACS is one of the most powerful tools available for CAD risk stratification

28. Interpreting CACS

29. CACS vs traditional risk (EHJ 2013)

30. CACS vs traditional risk (EHJ 2013)
6700 individuals
7 yr follow up
RFs: smoking, LDL >3.4, HDL < 1.0, HT, DM
Total end points: MI, revascularisation, angina without revascularisation, cardiac death
‘Hard’ end points: MI, resuscitated cardiac arrest, cardiac death

34. Interpreting CACS
“The power of zero”: patients aged >40 with CACS 0 have an excellent prognosis (event rate %/yr) out to 15 years
CACS>300 has similar event rate to those who have had previous infarction
Use stratification for age to interpret scores 1-300

35. CACS and age

36. Using CACS to guide statin therapy
In a recent US study1, 50% of patients who met ACC/AHA guidelines for statin therapy would have had CACS O, and thus very low risk, and unlikely to benefit
CACS
NNT with statin to prevent one CAD event/ 5 years
549
1-100 94
>100 24
(>400
17)2
1 - Blaha, Budoff et al; Lancet 2011, 2- St Francis Heart Study subanalysis; Circ CV Outcom 2014

37. Using CACS to guide statin therapy
CACS zero
Low risk
Lifestyle advice
CACS 1-300
and
>75th percentile for age
Moderate risk
Low dose statin
CACS >300
High risk
High dose statin

38. Using CACS to guide aspirin therapy?

39. Using CACS to guide treatment
Avoids overtreating those who are actually low risk
Identifies high risk patients without FRS
risk factors (eg: FHx)
Visualising plaque aids compliance

40. Preventative cardiology
We are stuck in the mindset of an era of medicine when we didn’t know what was “in the box”, and used functional testing and risk stratification systems to guess
Cardiac CT lets us peek in the box!