Accelerated Diagnostic Protocol for Chest Pain Not Useful in a US Population?

16 Apr
April 16, 2015

Accelerated Diagnostic ProtocolThere are approximately 8 to 10 million patients coming to Emergency Departments (EDs) in the United States annually. In the US, we use a very liberal testing strategy in order to avoid acute coronary syndrome (ACS) in patients presenting with chest pain. This results in over 50% of ED patients with acute chest pain receiving serial cardiac biomarkers, stress testing, and cardiac angiography at an estimated cost of $10 to $13 billion annually and yet fewer than 10% of these patients are diagnosed with ACS.

The 2-hour accelerated diagnostic protocol (ADAPT) combines  0 and 2 hour cardiac troponin (cTn), electrocardiograms (ECGs), and an adapted Thrombolysis in Myocardial Infarction (TIMI) score to help identify ED patients safe for early discharge. Previous studies show that this strategy can identify as many as 20% of patients for early discharge with a high sensitivity of 97.9% to 99.7% for major adverse cardiac events (MACE) at 30 days. This ADP has yet to be tested in a US population until now.

What article is being reviewed?

Mahler et al. Performance of the 2-hour Accelerated Diagnostic Protocol Within the American college of Radiology Imaging Network PA 4005 Cohort. Acad Emerg Med. 2015 Apr; 22(4): 452 – 60. (25810343)

Background: The 2-hour accelerated diagnostic protocol (ADAPT) (22578923) was a decision rule designed to identify ED patients with chest pain for early discharge, but the validity of this risk stratification in a US ED population has yet to be studied.

What they did:

  • A secondary data analysis of 1,140 patients enrolled in the American College of Radiology Imaging Network (ACRIN) PA 4005 Cohort
  • Determine the validity of ADAPT in a group of US ED patients with suspected ACS with an initial TIMI 0 – 2 and no evidence of acute ischemia on ECG
  • Early discharge rate and sensitivity for MACE (i.e. cardiac death, myocardial infarction (MI), or coronary revascularization) at 30 days were calculated

Results:

  • MACE occurred in 2.7% of patients in this population
  • ADAPT identified 551 or 48.3% of patients for early discharge
  • 5/551 (0.9%) of patients had MACE at 30 days
    • 0 Deaths
    • 1 Acute MI
    • 5 Requiring revascularization
  • ADAPT was 83.9% sensitive identifying 26/31 patients with MACE
  • 669 patients had CCTA with 331 patients safe for discharge by ADAPT, but 26 had ≥50% coronary stenosis
  • 351 patients had a stress test with 146 patients safe for discharge by ADAPT, but 10 had inducible ischemia

Limitations:

  • This was a very low risk ED patient population (2.7% MACE Rate), was an even lower risk than the patient population in the ADAPT trial (15.3% MACE Rate)
  • This is a secondary analysis of patients from a study that looked to compare CCTA to traditional care, and not the evaluation of clinical decision rules
  • This trial uses a composite endpoint of MACE (i.e. death, acute MI, and coronary catheterization)

Article Conclusion: “In this first North American application of the ADAPT strategy, sensitivity for MACE within 30 days was 83.9%.  One missed adverse event was a MI, with the remainder representing coronary revascularizations.  The effect of missing revascularization events needs further investigation.”

My Thoughts

My Thoughts:

  • This is the first study evaluating the application of accelerated diagnostic protocols (ADPs) in a US population
  • MACE revascularization rates in the original ADAPT study was 8.3% (26/302) vs 96.8% (30/31) in the ACRIN PA trial. There is no evidence that percutaneous coronary intervention is superior to medical management in treatment of patients with stable coronary artery disease (CAD). The COURAGE Trial (17387127) failed to show a difference in risk of MI or death among patients with stable coronary artery disease receiving percutaneous coronary intervention vs medical management
  • Coronary CTA and stress testing identify CAD, but ADAPT was not created to identify CAD, but instead who would have bad outcomes
  • Through an email conversation, one of my friends, Rick Body (Twitter: @richardbody), a clinical researcher in cardiology, also mentioned patients were investigated with relatively poor troponin assay and a troponin cutoff higher than the 99th percentile at one of the study sites (i.e. Alere Cardiac Triage troponin assay was used, which has an issue with imprecision and that site also used a URL of 0.4 mcg/L). That’s probably why the troponin assays by themselves had such low sensitivity at 2-3h (32%!)
  • The use of composite endpoints in a clinical trial can be justified if the individual components of the composite are clinically meaningful and of similar importance to patients.  I am not sure that in this patient population of low risk chest pain patients the endpoint of coronary catheterization is as important as death and acute MI.
  • Our obsession with anatomically defining pathology, and the assumption that early invasive strategies are beneficial in patients with stable CAD, forces us to continue to chase clinically irrelevant endpoints (i.e. cardiac catheterization)

Others Thoughts on Accelerated Diagnostic Protocol:

Post Peer Reviewed By: Anand Swaminathan (Twitter: @EMSwami)

Bibliography

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Salim Rezaie

Emergency Physician at Greater San Antonio Emergency Physicians (GSEP)
Creator & Founder of R.E.B.E.L. EM
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1 reply
  1. J. Scott Wieters says:

    I think the US is ready for a more formal approach to what many are already doing informally. We (knowingly or unknowingly) use the HEART score to risk stratify our patients. TIMI keeps getting applied to the wrong cohort in the ED when it was intended to eval inpatient ACS. Very low risk patients can be evaluated in the ED and have an outpatient followup. I agree with Sal, endpoints of getting a cath aren’t MACE we care about! (STEMI maybe) but just getting a cath isn’t MACE. If we look at true MACE, there was maybe 1 death in 551. There are few pathways that can take a dangerous CC and get to <1% true bad outcomes.

    Reply

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