#46 Chest pain, coronary CT angiography, and coronary artery disease

July 3, 2017 | By Matthew Watto, MD

Master the evaluation of acute and chronic chest pain with coronary CT angiography (CCTA). We deconstruct this game changing technology w/experts from the Society for Cardiovascular Computed Tomography (SCCT), Dr. Todd Villines and Dr. Ahmad Slim. We’ve got answers on what to do when a patient with chest pain has a prior CAC score of zero, and/or a CCTA with non-obstructive disease. Plus: how to select, prepare, and counsel patients; how to interpret reports; choosing between myocardial perfusion study and CCTA, and more!

Special thanks to Dr. Emilio Fentanes from SCCT for setting up this interview.

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Case: 45 yo F active duty Colonel with chronic chest pain syndrome despite negative conventional stress test and CAC score of zero.

Clinical Pearls:

1. “Conventional testing” or “functional testing for chest pain includes exercise electrocardiography (EKG), exercise or pharmacologic nuclear stress testing, and stress echocardiography (PROMISE NEJM 2015)
2. Coronary artery calcium (CAC) scoring: Non-contrast CT scanned that assesses overall coronary plaque burden, NOT stenosis. Use in asymptomatic patients to determine strategy for prevention. Radiation dose is 1 mSV or less.
3. Coronary CT angiography (CCTA): Non-invasive CT of the coronary arteries w/IV contrast to assess stenosis and plaque characteristics. Modern scanner w/radiation dose 3 mSV or less (versus 3.6 mSV from solar radiation annually and over 15 mSV w/nuclear stress imaging). Has ability to identify non-obstructive coronary disease missed on conventional stress testing, and nuclear imaging. Evidence suggests CCTA may be able to prevent acute coronary syndrome (SCOT-HEART).
4. Patient counseling: Avoid phosphodiesterase inhibitors (e.g. viagra, levitra, cialis) because nitroglycerin given during scan. Must be fasting for 4 hours. Beta blocker (e.g. metoprolol 50-100 mg) given 1 hour prior to test. Incidental findings e.g. nodules and incidentalomas w/about 7% of scans. Avoid CCTA if acute kidney injury, or CKD 3-4 (Cr and eGFR cut-off is institution dependent). Average radiation dose w/CCTA slightly less than annual solar radiation.
5. Controversy w/CCTA: May lead to more revascularization…BUT less patients sent for left heart cath inappropriately [i.e. have non-obstructive coronary artery disease (CAD)].
6. CCTA for acute chest pain syndrome: Patient in ER with negative troponin (or low level/equivocal troponin) and non-ischemic EKG with low to intermediate risk for acute coronary syndrome (ACS). NOT for high risk presentations with high suspicion for ACS.
7. CCTA for chronic chest pain syndrome: Consider for low to intermediate risk patients with a chest pain syndrome w/o known CAD. Consider CCTA if unreadable EKG, or equivocal results on previous “conventional testing”. Leads to reduction in myocardial infarction (MI) by identification of non-obstructive disease.
8. Clinical scenario: CAC of zero in patient w/acute chest pain syndrome: Controversial area because CAC score of zero means less than 5% risk for obstructive CAD as cause of chest pain. Consider further risk stratification (e.g. CCTA or functional testing) if multiple CV risk factors, or if patient tells a “good” story. Consider performing CCTA on these patients if not previously performed.
9. Clinical scenario: CAC of zero and CCTA w/non-obstructive CAD in patient w/acute chest pain syndrome: For patients w/ “non-obstructive” CAD must consider number of segments involved (e.g. more than 4-5 means higher risk), plaque characteristics, and traditional CV risk factors. Consider a “functional” treadmill test if concerned. If stenosis less than 50%, then risk of ACS is very low. If stenosis 50% or more and “high risk” plaque features, then admit patient rule out ACS and perform functional testing.
10. CAD RADS: Score 0 = warranty 2-5 years; Score 1-2 = non-obstructive disease; Score 3 = moderate 50-69% obstruction; Score 4-5 = 70% or above. Consider left heart catheterization if score 3 or above (see Table 2 in SCCT/ACR/ACC Guideline 2016) .
11. Cardiac risk categories by annual event rate for myocardial infarction (MI) or cardiac death: Low risk = less than 1%. Intermediate risk = 1-3%. High risk = above 3%.
12. Annual event rate for MI or cardiac death w/a negative CCTA is 0.02% versus 0.8% w/exercise stress test versus 0.65% with nuclear exercise stress test versus 1.8% w/chemical stress test.
13. Annual event rate for MI or cardiac death with a positive CCTA is ~3% versus 2% w/exercise stress test.
14. High risk occupations: Risk for sudden cardiac death is 3 fold higher in high risk occupations (e.g. military, police, firefighters, pilots, etc.) after age 45. Reasonable to screen age 45 years and above w/CAC scoring followed by CCTA, or functional testing if CAC score suggests risk for obstructive CAD.
15. Nuclear medicine myocardial perfusion study: Good test if known CAD w/prior stents, or grafts.

Goal: Listeners will appropriately utilize CCTA to evaluate acute and chronic chest pain syndromes.

Learning objectives:

By the end of this podcast listeners will:

1. Define CAC and CCTA
2. Differentiate between CAC and CCTA
3. Counsel patients about CCTA and preparation for testing
4. Correctly identify appropriate patients for CCTA
5. Utilize CCTA to evaluate acute chest pain
6. Utilize CCTA to evaluate chronic chest pain
7. Interpret CCTA reports
8. Choose between CCTA and myocardial perfusion study

Disclosures:

Dr. Slim is Chairman of Advocacy for SCCT. He has no relevant financial disclosures. Dr. Villines is President-Elect of SCCT. He has no relevant financial disclosures.

Time Stamps
00:00 Intro
04:00 Rapid fire questions
08:23 Book recommendations
10:14 Defining terms CCTA vs CAC
12:47 Script for counseling patient about CCTA
14:34 Prep for CCTA
16:40 Why is CCTA controversial?
19:37 Patient selection for CCTA both acute and chronic
25:20 Chronic chest pain and CCTA
27:58 CAC and CCTA in high risk occupations
33:25 Clinical case
36:10 Acute chest pain in patient w/CAC score zero
39:18 Acute chest pain in patient w/CAC score zero and previous CCTA w/non-obstructive CAD
41:22 How to read a CCTA report
45:48 CCTA versus conventional testing and risk MI, death
49:18 Use of CCTA in outpatients
52:16 Plaque characteristics and risk ACS
55:51 CCTA w/non-obstructive disease in patients with acute chest pain
58:14 When is myocardial perfusion scanning better?
61:00 Listener question on small vessel disease
62:09 Take home points
65:00 Curbsiders recap
69:33 Outro

Links from the show:

1. The Prince (book) by Niccolo Machiavelli
2. Team of Teams (book) by Stanley McChrystal
3. TED Talk Stanley McChrystal
4. The Tim Ferriss Show podcast interview w/Stanley McChrystal
5. SCCT Advocacy Website
6. Appropriate Use of Cardiac Imaging in Emergency Department Patients With Chest Pain JACC 2016
7. SCCT Appropriateness criteria for CCTA 2010
8. CAD RAS practice guidelines 2016 SCCT/ACC/ACR
9. Diamond and Forrester score NEJM 1979
10. Job stress and risk sudden cardiac death BMJ 2014
11. Underlying coronary lesion in MI. Often stenosis is under 50% Clin Cardiol 1991
12. Promise trial NEJM 2015
13. CONFIRM Registry JACC 2013
14. SCOT-HEART Lancet 2015
15. MESA Trial for calcium scoring JACC 2009
16. COURAGE Trial NEJM 2007