What is the place of CT coronary angiography in ED chest pain?

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CT coronary angiography is a relatively new modality for identifying coronary artery disease. What is its place in ED chest pain assessment. See the evidence -and the evidence gaps- and judge for yourself where it might fit!

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What is the place of CT coronary angiography in ED chest pain?

  1. 1. Anne-Maree Kelly Director, Joseph Epstein Centre for Emergency Medicine Research@Western Health, Melbourne
  2. 2.  No relationships with cardiac diagnostic or imaging companies  Co-author of National Heart Foundation (Australia) guidelines for the management of ACS (and addenda)  Supervisor of PhDs in CTCA’s role in chest pain  Editorial boards of: ◦ Annals of Emergency Medicine ◦ Emergency Medicine Australasia ◦ Hong Kong Journal of Emergency Medicine
  3. 3.  To explore the role of CTCA in ED chest pain patients, with a focus on those that ‘rule out’ for ACS in ED  To explore the cost-benefit of a CTCA compared to alternatives  To provoke debate about the rational place of CTCA in ED chest pain work-up!
  4. 4. From Schussler JM. Cardiac computed tomography:Emergeing cardiac devices and technology. Asian Hospital and Healthcare Management. http://www.asianhhm.com/diagnostics/cardiac_computed_tomograp hy.htm • Non-invasive • Nice pictures • Can ‘see’ if there are lesions or not
  5. 5. Three major studies have suggested that CTCA for ED chest pain patients: • Reduces ED length of stay • Reduces admissions • That negative scans have good prognostic performance • That CTCA may be more ‘accurate’ in identification of CAD than alternatives ROMICAT II ACRIN-PA CT-STAT
  6. 6. ACRIN-PA ROMICAT II  50% reduction in admissions (23% vs. 50%)  25% reduction in LOS (18 hours vs. 25 hours)  67% reduction in median LOS (9 hours vs. 27 hours)  19% reduction in ED costs Litt HI et al. N Engl J Med 2012; 366:1393-403. Hoffmann U et al. NEJM 2012; 367:299-308
  7. 7. CT-STAT  54% reduction in time to diagnosis (3 hours vs. 6 hours)  38% reduction in costs  No difference in events Goldstein et al. J Am Coll Cardiol 2011;58:1414-22
  8. 8.  In Victoria, estimated 40,000 patients undergo ACS rule out in ED annually  The ‘rule in’ rate for ACS is ~15-20% ◦ Depends how you count  About 32,000 have ACS ruled out and (according to ACS guidelines) need a further assessment strategy to rule out clinically significant CAD Based on Dept Health Victoria data and estimates of chest pain presentations by Goodacre (UK): Goodacre et al. Heart. 2005; 91: 229–230. Victoria, Australia Population 5.6 million
  9. 9.  Highly variable  Options ◦ Exercise test ◦ Nuclear medicine studies ◦ CTCA ◦ GP or cardiologist can decide! ◦ Nothing (active choice)
  10. 10. TIMI score Demographics  0 33%  1 18%  2 18%  3 11%  4 11%  5+ ~9%  Male =60%  Average age=62  Known CAD = 33% Based on data from cohort study @ WH 2009
  11. 11.  Is CTCA sensitive for the detection of CAD?  Is CTCA suitable for the ED chest pain patient cohort?  Does a negative CTCA have good prognostic performance for future ACS events?  Does CTCA improve outcomes for patients?  How does CTCA perform in comparison to alternative investigation strategies?  Which patients should have this test rather than an alternative?
  12. 12.  Depends on whether analysis is at patient level or segment level ◦ Patient level is of prime importance in the ED context  Simple answer is ‘YES’  In a recent systematic review/ meta-analysis, CTCA had 94% (61-99%) sensitivity and 87% (16-100%) specificity for CAD.  Another meta-analysis of 64-slice +, reports sensitivity of 99% (95% CI 97- 99%)  BUT about 9% of tests are non-diagnostic/ inconclusive •Goodacre et al. Health Technol Assess 2013;17:1-188 •Mowatt et al. Technol Assess. 2008; 12:iii-iv, ix-143.
  13. 13.  Remember, the question being asked is “Is there CAD”?  Just over 50% of the patient cohort is suitable for CTCA  About 30-40% of patients already have known CAD ◦ Other investigation pathways are more suitable in most of these  Other ‘contra-indications’: 10-15% ◦ Metformin ◦ Inability to control rate adequately ◦ Renal failure/ impairment ◦ Thyroid disease ◦ Irregular rhythms Hamid S et al. Am J Emerg Med. 2010;28:494-8
  14. 14.  Safety ◦ Short term adverse events related to the scan are very rare ◦ Contrast allergy at expected rate (1/2,500-1/25,000) ◦ Adverse effects due to rate control-usually minor ◦ Radiation risk  Feasibility ◦ Limited by access to scanner and availability of experienced readers ◦ ‘In hours’ only availability does not match ED 24/7 patient flow ◦ ‘Competition’ with other patients needing CT scan
  15. 15.  In meta-analysis:  I death from 1334 patients  No PCI, MI etc  Rate = 0.07% (95% CI 0.01% to 0.4%) Goodacre et al. Health Technol Assess 2013;17:1-188  In cohort study:  No PCI, MI, deaths in 508 patients at median 47 month follow-up  Rate = 0% (95% CI 0% to 0.07%) Simple answer is ‘YES’ Nasis et al. Radiol 2014; April 14
  16. 16.  In meta-analysis:  39 events in 332 cases  12 MI  Two thirds of events were revascularisations  Rate 12% (95% CI 9-16%)  Only one study was blinded to CTCA results: ◦ Showed CTCA result (presence of stenosis) was independently associated with MACE (HR 17) Goodacre et al. Health Technol Assess 2013;17:1-188. S Schlett CA et al. JACC Cardiovasc Imaging. 2011;4: 481–491.
  17. 17.  A growing literature with several points of view  Focus is the sub-population without known CAD ◦ 65-70% of cohort (about 25,000 patients annually in Victoria)  Available data suggests background rate of asymptomatic CAD ~5-8%.
  18. 18.  Cost benefit depends on: ◦ Sensitivity of the tests being compared ◦ Prevalence of clinically relevant CAD, especially in low risk subgroups ◦ Relative costs in the healthcare system in question ◦ Patterns of investigation/ intervention especially for intermediate or indeterminate tests ◦ The risk of adverse events associated with CAD ◦ The time period of follow-up ◦ The community’s willingness to pay (e.g. $ per QALY) ◦ Any negative impact of CT delay for other patients e.g. acute stroke, head injury, etc.
  19. 19.  CTCA asks “Is there plaque”?  I am not sure that is the right question
  20. 20.  What is the risk of MACE in patients without known CAD, with non-diagnostic ECG and normal serial biomarkers in ED? ◦ This prognostic information is still evolving ◦ Complicated (and simplified) by new higher sensitivity biomarkers  At what MACE risk level is ‘routine’ testing indicated?
  21. 21.  What is the risk of MACE in patients without known CAD, with non-diagnostic ECG and normal serial biomarkers in ED?  A. 5%  B. 2%  C. 1%  D. 0.5% Fitzgerald P et al. Acad Emerg Med 2011;18:488–95.
  22. 22. Test Sensitivity NPV (MACE) CTCA 94-99% >99% MPS 87% 97.2% Exercise ECG (EST) 20-30% As low as 86% Conti et al. Nucl Med Commun 2011 32;1223
  23. 23.  Varying study design, populations and outcomes studied  In meta-analysis  Rate of MACE for negative EST 0.7% (95% CI 0.5- 1.2%)  But sensitivity questionable ◦ Some studies around 30% sensitivity for occlusive CAD Goodacre et al. Health Technol Assess 2013;17:1-188. S Schlett CA et al. JACC Cardiovasc Imaging. 2011;4:481–491.
  24. 24.  Not enough data in the specific population of interest to draw conclusions
  25. 25.  Positive predictive value for CAD at segment level is only moderate (78%) ◦ False positives: over-estimation of lesion severity in presence of calcified plaques  Scanning 15,000 patients in Victoria/year will pose access issues for CT scanners!
  26. 26.  An ‘elephant in the room’  Retrospectively gated protocols, risk estimated at: ◦ 0.11 to 0.13% for men ◦ 0.27-0.37% for women  Prospectively gated protocols, risk estimated at: ◦ 0.014-0.017% for men ◦ 0.035-0.06% for women  Risk is inversely related to age  Significant ethnic variation Huang et al. Br J Radiol. 2010;83(986):152-8.
  27. 27. ACRIN-PA  50% reduction in admissions (23% vs. 50%)  25% reduction in LOS (18 hours vs. 25 hours)  No patient with negative CTCA had death, MI within 30 days  Only 2/1357 (0.15%) of patients not diagnosed with MI at index visit had MI within 30 days  Trial conditions re CT availability  TIMI 0-2 ◦ >85% TIMI 0 or 1 Litt HI et al. N Engl J Med 2012; 366:1393-403.
  28. 28. CT-STAT  54% reduction in time to diagnosis (3 hours vs. 6 hours)  38% reduction in costs  Only included ED costs  Trial conditions re CT availability  Highly selected cohort  In CTCA cohort, 6 times greater rate of additional non-invasive tests after ED discharge ◦ Cost ◦ Radiation, etc Goldstein et al. J Am Coll Cardiol 2011;58:1414-22
  29. 29. ROMICAT II  67% reduction in median LOS (9 hours vs. 27 hours)  19% reduction in ED costs  Eventual hospital costs actually 50% higher in CTCA group  Higher rate of additional testing (27% vs.12%)  No difference in events  Trial conditions re CT availability  Selected population ◦ 40-74 ◦ No AF or renal disease or BMI<40Hoffmann U et al. NEJM 2012; 367:299-308
  30. 30.  Data from administrative dataset ◦ Age 66+ ◦ Non-emergent, non-invasive test for ?CAD ◦ No known CAD  Compared CTCA vs. stress myocardial perfusion scan  Results: Outcome CTCA MPS Cardiac catheter 23% 12% PCI 7.8% 3.4% CABG 3.7% 1.3% All cause mortality 180 days 1.05% 1.28% Hospitalization for MI 180 days 0.19% 0.43% Schreibati et al. JAMA 2011; 306:2128-36
  31. 31.  1. That a test to rule out CAD before discharge is needed in ED chest pain patients ◦ This is unproven! ◦ The rationale for any test (compared to no test) is that it improves outcome ◦ Event rates are so low (<1%) in all arms that it is impossible to tell if CTCA provided benefit  2. All lesions found were cause of symptoms ◦ 5% rate of occlusive lesions found in screening of asymptomatic patients With risk of dye, radiation, extra tests etc. harm is likely to seriously compete with any benefit!
  32. 32.  In Australasia: ◦ ~75% of patients are discharged from ED/SSU ◦ Most do not have additional testing before discharge ◦ Median LOS of the order of 6-10 hours, depending on centre and protocol (some much shorter) ◦ LOS likely to reduce as accelerated diagnostic biomarker pathways are implemented
  33. 33.  SCCT/AHA/ACC: ◦ Symptomatic patients without known CAD with ‘intermediate’ pre-test probability ◦ Symptomatic patients without known CAD with ‘low’ pre-test probability who cannot perform a functional test or with equivocal functional test results ◦ Not suitable for high pre-test probability patients due to:  High likelihood of plaques  Limited spatial and temporal resolution  These should have CA or functional test Taylor AJ et al. J Am Coll Cardiol 2010:56:1864-94.
  34. 34.  CTCA is not indicated as a ‘routine’ test in ED patients with chest pain without known CAD and with normal biomarkers and ECG  It may be useful in a subgroup based on risk, but how this risk might be defined in unclear  There is a reasonable case for no further testing in significant proportion of ED chest pain patients who have had ACS ruled out by clinical evaluation, ECG and biomarkers
  35. 35.  Comparison of DM, ‘metabolic syndrome’ and other (MPS study)  Metabolic syndrome defined as at least 3 of: ◦ Fasting glucose >110mg/dl ◦ High BP ◦ Low HDL ◦ High triglicerides ◦ High waist circumference  Rate of MACE at 1 year ◦ DM 30% ◦ Metabolic syndrome 26% ◦ Others 15% Conti et al. Nucl Med Commun 2008; 29:1106-12. Could similar parameters identify a subgroup of patients who might benefit from CTCA?
  36. 36.  CTCA is a test looking for its role in the ED chest pain population  More data regarding patient selection and patient- centred outcomes is needed before its place can be better defined

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