CT ScannerIt is well known that taking a good history and physical, getting a non-ischemic EKG, and serial cardiac biomarkers, results in a risk of death/AMI of <5% in 30 days. Patients, in whom you still suspect have CAD, should undergo provocative testing within the next 72 hours based on the AHA/ACC guidelines. Their guidelines deem provocative testing as including:

  • Exercise treadmill stress test,
  • Myocardial perfusion scan,
  • Stress echocardiography, and/or
  • Coronary CT angiography (CCTA).

Myocardial perfusion scans and stress echos have a sensitivity of 85–90% and specificity of 75–80%. In contrast, CCTA’s have been shown to have a sensitivity of 93-97% and specificity of 80-90%.

 Recently two landmark trials were published in NEJM discussing the use of CCTA in the emergency department.

ACRIN-PA Trial1

What they did: 
  • Non-inferiority study
  • 5 Pennsylvania EDs
  • 1,370 patients, Age > 30 years
  • Inclusion criteria: TIMI score of 0–2, EKG without ischemic changes, and negative first set of Cardiac Biomarkers
  • Randomized 2 patients to CCTA arm (908 patients) for every 1 patient to Standard Stress arm (462 patients)

Primary Outcome:

  • MI or Death from CAD at 30 days

Secondary Outcomes:

  • Rate of discharge from ED
  • Length of stay (LOS) in ED
  • Rate of detection of CAD
  • Resource utilization

What they found:

  • 640/908 pts (70.5%) who underwent CCTA had coronary stenosis of <50% and none had MI or death due to CAD at 30 days
  • Discharge from ED 49.6% with CCTA vs 22.7% with standard stress arm
  • ED LOS 18 hr in CCTA arm vs 24.8 hr in standard stress arm

Conclusion: CCTA allows early discharge of low to intermediate risk patients presenting to the ED with possible ACS.

ROMICAT II Trial2

What they did:
  • Randomized controlled trial
  • 9 EDs in the US
  • 1,000 patients with acute chest pain with ages 40–74 years
  • CCTA (501 patients) versus Standard Evaluation (499 patients)

Primary Outcome:

  • Hospital length of stay

Secondary Outcomes:

  • Cardiovascular events at 28 days
  • Rate of discharge from ED
  • Time to diagnosis
  • Cost
  • Utilization of resources

What they found:

  • Hospital LOS decreased by 7.6 hr in CCTA group
  • Rate of discharge from ED 47% in CCTA arm vs 12% in Standard Evaluation Arm
  • No difference in cardiovascular events at 28 days
  • Cost was similar between two groups $4,289 CCTA vs $4,060 in Standard arm

Conclusion: CCTA decreases length of stay without an increase in rate of cardiovascular events.

Discussion Points

  • CCTA with 0 lesions is NEGATIVE: These patients can certainly be discharged home with primary care follow up with a nearly 100% NPV for ACS/AMI.
  • CCTA with <50% lesion is NOT NEGATIVE: This patient has CAD. It may not be clinically significant, but we can see plaques. 2/3 of AMIs occur from plaques that have <50% stenosis. Certainly we can start risk factor modification with beta blockers, ASA, and statins, but there are no studies looking at how this group of patients will do long term.
  • CCTAs are anatomic studies and not functional studies. Identified lesions will lead to more diagnostic tests, which is one of the big arguments against CCTA. CCTA identifies CAD more often than standard stress modalities, which leads to more heart catheterizations and PCIs.
  • As the number of CT slice increases, radiation dose decreases:
  1. A 64 slice CT = 10 – 15 mSv of radiation
  2. A 128 slice CT = 5 – 10 mSv of radiation
  3. A 256 slice CT = 1 – 5 mSv of radiation
  4. In contrast, a single-view CXR = 0.02 mSV of radiation
  • There is currently an ongoing National Heart, Lung, and Blood Institute-funded trial called the PROMISE (Prospective Multi-center Imaging Study for Evaluation of Chest Pain) Study with 10,000 patients. Patients with symptoms suggestive of CAD will be randomized to a CCTA vs usual care with a functional test.  What’s interesting about this study is it is being performed in the offices of primary care physicians and cardiologists rather than EDs. The study authors hypothesize that medically optimizing patients identified, as having non-obstructive CAD will yield improved long-term outcomes.

Final Thoughts

It is well known that in low risk patients, doing a good H&P, having a negative EKG (no ischemic changes), and negative serial cardiac biomarkers gives us about 99% NPV & 99% sensitivity for ACS/AMI. This is even without additional testing, such as CCTAs.

So are CCTAs worth the cost and potential harms in this low-risk group to add another 1% to the 99% NPV and 99% sensitivity rates? In my opinion, that answer is NO.

Additional Reading
  1. Jancin B. Comparing Technologies for Imaging Chest Pain in the ED.  ACEP News 2013 Mar; 32(3): 1-11.
  2. Goldstein JA. A Randomized Controlled Trial of Multi-Slice Coronary Computed Tomography for Evaluation of Acute Chest Pain. JACC 2007;49: 863–71. PMID: 17320744
  3. Goldstein JA. The CT-STAT (Coronary Computed Tomographic Angiography for Systematic Triage of Acute Chest Pain Patients to Treatment) Trial. JACC 2011 Sept; 58: 1414–22. PMID: 21939822
  4. Hulten E. Outcomes After Coronary Computed Tomography Angiography in the Emergency Department: A Systematic Review and Meta-Analysis of Randomized, Controlled Trials. JACC 2013 Feb; 61: 880–92. PMID: 23395069

1.
Litt H, Gatsonis C, Snyder B, et al. CT angiography for safe discharge of patients with possible acute coronary syndromes. N Engl J Med. 2012;366(15):1393-1403. [PubMed]
2.
Hoffmann U, Truong Q, Schoenfeld D, et al. Coronary CT angiography versus standard evaluation in acute chest pain. N Engl J Med. 2012;367(4):299-308. [PubMed]
Salim Rezaie, MD

Salim Rezaie, MD

ALiEM Associate Editor Clinical Assistant Professor of EM and IM University of Texas Health Science Center at San Antonio Founder, Editor, Author of R.E.B.E.L. EM and REBEL Reviews
Salim Rezaie, MD

@srrezaie

EM/IM Doc; Founder of REBEL EM & REBEL Cast; Doing my Part to Cut Down on KT Time; Viva #FOAMed #FOAMcc (Tweets are opinion only)