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

“Cat” scan

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

Functional testing: the consequences of stenosis

Early detection of atherosclerotic plaque with coronary CT

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

1963: the Bruce protocol

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

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?)

5 year risk

Coronary artery calcium score (CACS)

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

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

Interpreting CACS

CACS vs traditional risk (EHJ 2013)

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

Interpreting CACS “The power of zero”: patients aged >40 with CACS 0 have an excellent prognosis (event rate 0.1-0.2%/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

CACS and age

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

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

Using CACS to guide aspirin therapy?

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

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!