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Approach to ACS

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					 Approach to ACS
    Low Risk Chest Pain

        What is it?

What should we do about it?
       Low Risk Chest Pain

• The MYTHS that govern our daily lives:

  – Myth # 1- Cardiologists are interested in
                    chest pain
  – Myth # 2- The research question and the
    clinical question coincide
  – Myth # 3 -Everyone is interested in the
            evidence
     Low Risk Chest Pain
Pause for equal opportunity cynicism:

More MYTHS
    - Pulmonologists are interested in
 asthma
    - Urologists are interested in
 urolithiasis
    - Surgeons are interested in
 abdominal             pain
      Low Risk Chest Pain
• The REALITY that governs our daily lives
    • Everyone is happier when the diagnosis is made
      in the ED/you are all alone here

    • Evidence ranks low on the reasons for physician
      behavior

    • The research question rarely coincides with the
      EM clinical question

    • To paraphrase that well respected sage, William
      Jefferson Clinton, “It is about the disposition,
      stupid”
 Low Risk Chest Pain/Very Low

• Under 40 yrs of age
  – No cardiac history
  – No risk factors (see workshop on this)
  – Normal ECG
     • Risk of ACS and/or adverse cardiac events= 1%
     • All of the above + one neg marker= 0.14%



     Marsan RJ Evaluation of a Clinical Decision Rule-Acad EM 2005
            Low Risk Chest Pain
                   What is it?
                  NOT HIGH RISK
                   (not an ACS)
       How should we manage it?
         What is our goal here?*

* See WJC above
    Low Risk Chest Pain



     What is low?
What exactly is the risk /
   risk for what?
     Risk to whom?
       Low Risk Chest Pain
What is low?
  • What is a tolerable error rate?
         •10%
         •5%
         •1%
         •0%
  ―Disappointment is related to expectation‖
        Low Risk Chest Pain
           What is low? (con’t)
• Risk for what?
  •Death
  •MI
  •Cath
  •Revascularization
  •Angina
   Low Risk Chest Pain

      What is low? (cont’d)
– Risk for what---and in what time
  period?
   • 7 Days
   • 14 Days
   • 30 Days
   • 90 Days
       Low Risk Chest Pain

      What is low? (cont’d)

•The Sensitivity/ Specificity Dilemma


• The Safety/ Efficiency Dilemma
            Low Risk Chest Pain

Risk to whom?
• Patient
• Emergency physician (career risk)




How to eliminate career risk?
 • Standardize with evidence
           Low Risk Chest Pain


• What exactly is the risk?
  – In multiple studies in multiple
    settings and multiple countries about
    5% of patients seen with chest pain
    and sent home have an MI and 1%
    die----but remember the moving
    target
  – 2% in most recent good US study
    (Pope)
    Low Risk Chest Pain/def

• Normal tropinin (x2)
• Normal or unchanged ECG
• No hemodynamic derangements or
  arrhyythmias


        • What should we do?
Low Risk CP/What to do?
   “The sobering bottom line is that
two decades of research have taught
us that without compelling evidence
 for a non cardiac cause, there is no
  absolutely fail-safe way to exclude
 myocardial ischemia or infarction at
      the time of a patient’s initial
             presentation.”
    Goldman, Ann Intern Med Dec 2003
     Low Risk CP/What to do?
• ―Although the cardiac troponins are useful
  for both diagnosis aad risk stratification of
  patients with chest pain and AMI, cardiac
  marker testing in the ED will not identify
  most ED patients who subsequently develop
  adverse events‖
        – Hollander, J- Text Book of Emergency Cardiovascular Care
Current Risk Stratification: CP and ACS

  • Limited diagnostic value of ECG, early
  biomarkers, and risk stratification tools
  • Most patients admitted for CP turn out to
  not have ACS
  •1-5% missed ACS cause 20% of ED
  malpractice cost:
  •Physician judgment:“Non Cardiac”-8%error
  Testing for Ischemia/When?
• There is a developing standard that the
  test should be done before the patient
  leaves the hospital.

• Why?
Testing for Ischemia/The dilemmas

  • The Sensitivity/Specificity Dilemma

  • The Diagnosis/Prognosis Dilemma

  • The Plaque/Obstruction Dilemma
Testing for Ischemia/The Tests
• Provocative tests
  – Exercise +EKG (ETT)
  – Exercise Tests + Imaging
     • Nuclear
     • ECHO
  – Chemical provocation (pt at rest) +imaging
     • Chemical stimulation-dobutamine
     • Chemical differential flow
     • Adenosine or Dypyridimole/Persantine
   Testing for Ischemia/prov.

Able to Exercise?

• Exercise Tolerance Test
• Exercise Tolerance Tests + imaging
  – ETT MIBI, ETT Echo
Provocative Testing: The tests

Can’t Exercise?
 Imaging with chemical provocation
 • Chemical stimulation (exercise equivalent)
   – Dobutamine Echo and Dobutamine
     MIBI
 • Chemical differential flow
   – Persantine/Dipyridamole or Adenosine
        Provocative ttesting: ETT
 • Purpose: Increase oxygen demand
 • Method: standardized (Bruce)
      protocol (“millions served”)

                      Bruce Treadmill
Stage          1          2          3           4           5     6     7

Speed (mph)   1.7        2.5        3.4        4.2           5.0   5.5   6

Grade (%)     10         12          14         16           18    20    22



              http://www.exrx.net/Testing/CardioTests.html
Provocative Testing/The Tests

• ETT
  – What is measured
    • Heart rate
         – adequate test=80%MPHR   Double Product
    •   Blood Pressure
    •   Duration of Exercise*
    •   ST segment change*         * DUKE SCORE
                                      *Duke Score
    •   Anginal pain*
ETT: The Duke Score
     Provocative Testing/ETT
                  ETT----The Virtues
• Inexpensive
• Readily available; no radiation
• Moderate sensitivity and specificity
      – Accurate test in 85% of those tested
• EXCELLENT prognostic value
      – Duke Treadmill Score
• negative predictive value (99.2%)
• Answers the question: Can I send this patient
  home?
Prognostic Value of the Duke Treadmill Score for Emergency Department Patients with Chest Pain
Manini, A et al Journal of EM Aug 2010
  Provocative Testing/ETT

• Drawbacks
  – Not useful if EKG not interpretable
    • LBBB; paced; pre-existing 1mm ST
  – Not as sensitive as nuclear and echo
  – Not as specific as nuclear and echo
    • therefore better at prognosis than diagnosis
  – Demographic shift means less ability to
    exercise
  Provocative Testing/echo

• Exercise Echo
  – Method: image after exercise
      (DOBUTAMINE if not able to exercise)
  – Measures:
    • wall motion
    • ejection fraction
    • doppler flow
Provocative Testing/The Tests
• ECHO
  – Virtues
    •   Good sensitivity and specificity
    •   More environmentally/equipment friendly
    •   More cardiology friendly
    •   Quicker than nuclear
  – Drawbacks
    • Cost; inter/intra observer variable
Provocative Testing/The Tests

• Nuclear
  – Principle is “differential flow” of nuclear
    tracer (sestaMIBI) between ischemic and
    non ischemic tissue
  – Measures: perfusion pre and post
Provocative Testing/The Tests




• Nuclear
Provocative Testing/Nuclear

• Differential flow is induced by
  – Increasing heart rate
     • Exercise
     • Dobutamine
  – Vasodilation--obstruction doesn’t dilate
     • Adenosine
     • Dypyridimole/Persantine
Provocative Testing/Nuclear

• Virtues:
  – Excellent diagnostic and prognostic test
    performance (Sens/Spec/ PV=97%)
  – Dynamic (vs CATH)
• Drawbacks:
  – Expensive; cumbersome; half day test
  – Less available; environmental concerns
Provocative Testing/best test?

• Which is best test----for ED?
• Can the patient exercise? Y/N
• Is ECG interpretable?       Y/N
  – Yes---ETT
     • Why
        –   Simple
        –   Quick
        –   Reliable
        –   Cheap
        –   Excellent prognostic test
        –   ACC recommended
Provocative Testing/best test?
• No---patient cannot exercise
  – Echo or Nuclear
    • They have near equivalent
      performance
    • Nuclear gives flow information
    • Echo gives anatomical information
    • Echo is slightly cheaper
    • Echo is environmentally friendly and
      cardiologist friendly
                    Approach
Needs provocative
       test


       Yes



      ECG                                      Exercise +
                    No    Can exercise   Yes
 Interpretable                                 imaging



             Yes
       Yes                     No


  Can exercise       No

                            Chemical
                            + imaging
         Yes
       Yes

     ETT
Provocative Testing/summary

• Standardize your practice
  – ECG unchanged
  – Enzymes normal x 2
• Not “very low risk” by Hollander criteria
  – Then provocative test
     • ETT for those who can exercise.
     • Imaging test with chemical provocation for
       those who cannot.
   What About Cardiac CT?
               Rationale
• In 80-95% of patients with ACS,
  significant CAD is the underlying cause
  (FRISC, Tactics II)

• 10-15% have nonsignificant CAD -
  good prognosis, limited treatment
  options (PURSUIT - Roe, Circ 2000)
                             CT for CAD

• Two types of cardiac CT
    – 1) Screening/Not angiography
         • Measures calcium, not obstruction
         • Predictive---more calcium, more events
               – Normal = <100, Severe= 800
               – No data on comparison of predictive power with
                 common risk factors or other diagnostic tests e.g.
                 exercise testing; OK to home
•   Nabi N Coronary Artery Calcium Scoring in the ED Annals of EM Sept 2010
     Testing for Ischemia/CT
            CT Angiography in ED

• Long time in coming because coronary
  arteries are not easy to image
  – They are small
  – They move with each beat and each breath
  – Need contrast
       Testing for Ischemia/CT
 Multi-Center Trials: CORE-64, Accuracy
• CORE-64 reported at AHA 2007 (Toshiba)
   –   291 patients at 9 institutions (BIDMC)
   –   Sensitivity 85%
   –   Specificity 90%
   –   Excluded patients with calcium score >600


• ACCURACY reported at RSNA 2007 (GE)
   – 229 patients at 16 institutions
   – Sensitivity 93%
   – Specificity 82%
Testing for Ischemia/CT




    Hoffmann et al, Circulation. 2006;114:2251-2260.
               Testing for Ischemia/CT
    • Hollander looked at CT angiograms for
      low risk chest pain in the ED
    • 54 patients
    • 85 % discharged with negative CT
    • 8 patients admitted, 6 with coronary
      stenosis
    • 30 day follow up, no patient had
      coronary events

Hollander et al, Acad Emerg Med. 2007;114:112-116.
           Use of
        Coronary CT
         in the ED
    Length of Stay: 3.4 vs. 15.0 hours
         Cost: $1,586 vs. $1872




Goldstein et al, J Am Coll Cardiol 2007;49:863–71
           Testing for Ischemia/CT/cost


            • CT in ED                         •   $2684



                                               •   $3461
            CDU + stress

            • CDU + stress echo                •   $3265




Khare et al Acad Emerg Med. 2008;15:623-632.
                Testing for Ischemia/CT


   4 arms
   • Immediate Coronary
      CT in ED                                 •   $1240
   • CDU + CT                                  •   $2318
   • CDU + stress                              •   $4024
   • Usual Care
                                               •   $2913




Chang et al Acad Emerg Med. 2008;15:649-655.
Testing for Ischemia/Holy Grail
One variant of the legend of the HOLY
GRAIL tells that on finding it there was a
note inside that read:

     “Illic est haud liberum prandium”
    Testing for Ischemia/CT/Rads

     CT Radiation Dosing
10 mSv =1 rem
• Normal background radiation is
  about 1 mSv
• A healthcare worker is allowed 50
  mSv/year
• Chest CTA for PE: 4-5mSv
• Abdomen CT: 10-15mSv depending
  on the exact protocol (number of
            CTA&Radiation
          (JAMA July 2007)
• Estimates of Cancer Risk
  – Women most vulnerable
  – Breast to age 40; lung after 40
• ―…alternative diagnostic modalities that do
  not involve ionizing radiation should be
  considered‖
 Advanced Generation MDCT


• Faster image acquisition

• Higher image resolution

• 3-D reconstruction
                        Culprit Lesion




non-calcified plaque is always present and absence of
calcified plaque is frequent in culprit lesions

   Hoffmann JACC 2006
 Performance Estimates: CT


• Detecting Stenosis (>50%)
  –Sensitivity 96%, Specificity 87%

• Detecting Plaque
  – Sensitivity = 85%, Specificity = 75%
Real world: safety, efficacy, cost-
         effectiveness?
        (Goldstein JACC 2007)

• Definitive diagnosis in 75% of patients -
  >90% CAD excluded

• Reduced time and costs

• Fewer repeat evaluations for CP
 Low Risk Chest Pain/CT angio

• Things to think about (bad)
  – Exclusion criteria
  – Radiation
  – Dye load (what happens if sig.CAD=Cath)
• Things to think about (good)
  – Quick
  – Cheap—compared to CDU+stress
  – 100%NPV
  Chang A Comparison of Four Strategies….Academic EM 2008
Dr. Slovis/ Five Rules to Prevent a
              Mistake
                         Rule #5
 Do an Objective Test:

 – Have a Chest Pain protocol in place that allows
 for an evidenced based approach for each step
 of the evaluation.
 Have a protocol based on risk, ECG,
 age and ability to run.
 Do an ETT,
 a Nuclear
 Study,
 an Echo or
 CT Scan.

 If everyone got an objective test, our miss rates
 would go from 1-2% (or higher) to 1/1000 or even
 less
The End

				
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posted:11/22/2011
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