Context

• Overtaking functional testing as first-line testing for stable CAD* in some recent guidelines (e.g. NICE 2017), in part due to excellent test characteristics and highest cost efficacy for the correct diagnosis of CAD for all non-invasive methods
• Recent landmark trials (below) show noninferiority of CCTA compared to functional imaging, and suggest decreased MI/coronary death, better yield on coronary angiography, and better preventative therapy initation.
• New evidence is NOT reflected in most up-to-date CCS guidelines (2014).

Pros

• Very sensitive to detect coronary calcifications (associated with atherosclerosis) and can provide noninvasive angiography of the proximal coronary arteries.
  • Therefore, negative CCTA is very favourable for prognosis.
  • Identifies both obstructive and nonobstructive CAD -- better overall prognostic information (Link to PROMISE subgroup analysis showing this)

Cons

• No functional information -- no idea of reversibility of RWMA or exercise capacity, for example.

Method

• Requires rate limitation for clear pictures:
  • Beta-blockers (e.g. metoprolol 50 mg afternoon before, night before, and then 1 hour before). Therefore cannot use with AVB, active reactive airway disease
  • Cannot do with uncontrolled atrial fibrillation/flutter.
• Requires breath-holding for clear pictures (?respiratory status @ baseline)

Key Studies re: CCTA

1. PROMISE (NEJM 2015) evaluated CCTA versus functional testing (exercise ECG, nuclear stress test, or stress echocardiography) in patients suspected to have symptomatic CAD, but no formal diagnosis of such yet. Overall finding was that there was no difference in MACE, but CCTA led to fewer catherizations showing no obstructive CAD (3.4% vs 4.3%). Overall median radiation exposure per patient lower with CCTA, but overall exposure higher. Median 2 yr followup. Link to study
2. SCOT-HEART (NEJM 2018) randomized 4146 patients with stable chest pain to CCTA + standard care, or standard care alone. Overall, CCTA decreased coronary death or nonfatal MI at 5 years (2.3% vs 3.9%), and increased preventative therapies (19.4% vs 14.7%). Increased early coronary angiography. Lower delayed angiography. No significant differences in rates of long-term coronary angiography or coronary revascularization. Median followup 5 years. [Link to study](https://pubmed.ncbi.nlm.nih.gov/30145934/
   1. Likely driven by earlier + targeted revascularization if needed
   2. Not driven by long-term increased revascularization.
   3. Likely also driven by earlier initiation of preventative management (ASA/statin), and higher sensitivity to nonobstructive CAD.
3. Jørgensen et al (JACC 2017) evaluated retrospectively 87,000 stable patients undergoing initial noninvasive cardiac testing with CCTA or functional testing (exercise ECG, nuclear stress test). Overall finding was that CCTA was greater use of statins, aspirin, and invasive procedures, and higher costs than functional testing (within 120 days only). Coronary CTA was associated with a lower risk of MI, but a similar risk of all-cause mortality. Link to study
4. DISCHARGE (NEJM 2022) compared CCTA with invasive angiography for initial diagnostic strategy in patients with stable chest pain with intermediate pretest probability of obstructive CAD who were referred for invasive angiography. This approach had no significant effect on MACE (over 3.5 years) or anginal symptoms, but did show a lower risk of major procedure-related complications and revascularization procedures. Link to study
5. SCOT-HEART 2 (pending) investigates whether CTA or risk scores are superior in guiding the use of preventive therapies in asymptomatic patients