2/5/2013 1 “Low Risk” Chest Pain Jeffrey Tabas, MD Professor of Emergency Medicine Office of CME UCSF School of Medicine Objectives Improve speed and accuracy in assessing patients with possible ACS! Avoid pitfalls in the use of cardiac markers to exclude AMI Avoid pitfalls in the use of non- invasive testing to exclude Unstable Angina Does this patient have ACS? Does this patient have ACS? Troponin = 35 Objectives Improve speed and accuracy in assessing patients with possible ACS! Avoid pitfalls in the use of cardiac markers to exclude AMI Avoid pitfalls in the use of non- invasive testing to exclude Unstable Angina ACUTE CORONARY SYNDROME The first problem Acute Myocardial Infarction and Unstable Angina are 2 different diseases with 2 different workups! It’s sort of like choledocolithiasis and cholecystitis
Transcript
2/5/2013
1
“Low Risk”Chest Pain
Jeffrey Tabas, MDProfessor of Emergency Medicine
Office of CMEUCSF School of Medicine
Objectives
Improve speed and accuracy in assessing patients with possible ACS!
Avoid pitfalls in the use of cardiac markers to exclude AMI
Avoid pitfalls in the use of non-invasive testing to exclude Unstable Angina
Does this patient have ACS?Does this patient have ACS?
Troponin = 35
Objectives
Improve speed and accuracy in assessing patients with possible ACS!
Avoid pitfalls in the use of cardiac markers to exclude AMI
Avoid pitfalls in the use of non-invasive testing to exclude Unstable Angina
ACUTE CORONARY SYNDROMEThe first problem
Acute Myocardial Infarction and Unstable Angina are 2 different diseases with 2 different workups!
It’s sort of like choledocolithiasis and cholecystitis
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Case 1
54 y.o. M w/ left shoulder ache x 8 hours. Only hx is smoking ¼ ppd
Normal exam except marked Left trapezius muscle spasm
ECG – no ischemia
CXR – Normal
Single 8 hr TnI sent
= 0.09 [0.00 – 0.10 ng/ml]
Case 1
Was AMI appropriately excluded?
1. Yes
2. No
3. Care is never appropriate at a conference lecture
What about Unstable Angina? Other diagnoses?
Case 1
Discharged with Dx of shoulder strain and follow-up by PMDin 1-3 days.
Patient is brought back 12 hours later in cardiac arrest
A lawsuit is brought and settled out of court
Steps in Assessment of ACS
1. Risk Stratify
2. Rule out MI
3. Rule out UA Immediate
Delayed
How do ACS patients present to our EDs?
Gupta, Ann EM 2002 - 720 cases of AMI
CHEST PAIN NO CHEST PAIN(53%) (47%)
Shortness of Breath (17%)
Cardiac arrest (7%)
Dizzy/Weak/Syncope (4%)
Abdominal Pain (2%)
Other (17%)
CHEST PAIN
How do ACS patients present? -Summary
- 50% of patients with ACS present like the text books say
50% of patients with ACS present atypically
Atypical is TYPICAL
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Risk Scores
TIMI Modified TIMI GRACE FRISC HEART
Most derived from pts with definite ACS, not possible ACS (except HEART)
Based on 1st troponin - Aren’t we interested after 2nd?
TIMI Risk Score
TIMI = 0 has sensitivity of 96.6% (91.5-99%)- Hess, AEM, 2010
None of the followingAge 65 or more3 or more CAD risk factorsKnown CAD (stenosis >50%)ASA use in past 7 daysSevere angina (>= 2 episodes w/in 24 hrs)ST changes >= 0.5 mmPositive initial cardiac marker
Simplest Low-risk Score
Risk of events 2% or less Negative initial cardiac marker Near normal ECG
AMI : The Cardiac Markers
In a patient without ischemia on ECG, it’s all about the troponins!
AMI exclusion 6 hours after ONSET is accepted although repeating a level 6 hours after ARRIVAL is common
AMI exclusion 2-3 hours after ARRIVAL is here (but hasn’t reached the guidelines yet)
It’s about the troponins
AMI exclusion is something we can and should do correctly
Excluding AMI
ACEP Clinical PolicyAnnals EM, Sept 2006
AMI: ACEP Policy
A negative cardiac marker at least 8 hours from symptom onset
OR A negative 90 min delta myoglobin + (CKMB or
Troponin)OR A negative 2 hr delta CK-MB + Troponin
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Morrow, Circ, 07
AMI: Lab MedicineA negative cardiac marker at least 6 hours from symptom onset IF Low Risk
A negative cardiac marker at least 12 hours from symptom onset IF Mod-High Risk
No Ischemia on ECG
Initial Cardiac Marker is Negative
What is a Low Risk Patient?
SFGH Protocol for ECG and Troponin Testing
If symptoms are unchanging or resolved
Check at arrival and at 6 hours from ONSET (not 6 hrs after arrival!)
E.g. Onset 2hrs prior to arrival, check on arrival and at 4 hrs
E.g. Onset 6 hrs prior to arrival, check only on arrival
If symptoms are stuttering
Check on arrival, at 3 hrs, and at 6 hours
Case 1
54 y.o. M w/ left shoulder ache x 8 hours.
Nl exam and ECG
Single 8 hr TnI sent
= 0.09 [0.00 – 0.10 ng/ml]
Was AMI appropriately excluded?
Understanding the Lab
Assay limit of detection <0 .01
99th percentile = 0.10
10% coefficient of variance (imprecision) = 0.3
Understanding the Lab
<0.01 = Undetectable
0.01 to 0.1 = Detectable (but within “normal range”)
> 0.1 = Elevated
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Troponin “Leaks”
Aviles and Aviles, EM Clinics, 2005
Tachycardia
CHF
PE
Peri/Myocarditis
Renal Failure
DKA
Sepsis
“Acute Troponin Leaks”
Newby L, JACC 2012
Saunders JT, Circ 2011
Any detectable Troponin level is associated with markedly increased adverse event rate over time
Troponin “Leak” – Pearls
It’s a leak if:
1) They’ve had it in the past (more than once)
2) You repeat and it doesn’t rise
More rapid ED rule outs?
NEJM, Aug 27 2009
Highly sensitive Troponins
More rapid ED rule outs?
1818 patients in Germany, 23% with AMI
Highly Sensitive Trop on arrival: Sens = 100% (for level of detection)
Standard Trop 3 hrs post arrival: Sens = 98.2% (for level of detection)
Keller et al, JAMA, Dec 2011
Current Troponin Assays - Summary
Any detectable level mandates further evaluation- Repeat level and stress testing is safest approach
Although not yet in the guidelines, an undetectable level at 0 and 3 hrs excludes AMI
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Super Sensitive Assays - Summary
Any detectable level mandates further evaluation- Repeat level and stress testing is safest approach
With Highly Senstive Troponins, a 0 and 1 hr level excludes AMI
As sensitivity increases, we will get an increasing number of false positives
Ways to miss AMI w/ a negative 6 hr Trop
UnacceptableMiss the ischemic ECG
Troponin not really negative (i.e detectable)
Not really 6 hours after onset (stuttering)
AcceptableVery tiny percentage of patients still have AMIWe didn’t miss AMI but unstable angina
Unstable Angina: Noninvasive Tests
Understand your non-invasive testing!
Outpatient testing
Sensitivity Specificity # of Patients
Treadmill 68 77 24,074
Nuclear stress 88 77 628
Stress Echo 76 88 1174
Lee NEJM 01
ED Treadmill
Amsterdam, JACC, 2002
1000 ED pts sent for treadmill w/ a single negative troponin
Negative ETT in 64% = 0.2% Event Rate
Positive ETT in 13% = 14% Event Rate
Nondiagnostic in 23% = 3.6% Event Rate
Does Prior Stress Testing Exclude ACS?
“MI evolves most frequently from plaques that are only mildly to moderately obstructive…the risk of plaque disruption depends more on plaque composition and vulnerability (plaque type) than on degree of stenosis (plaque size).”
Falk, et al. Circulation, 1995
Value of prior stress testing?
Nerenberg, AJEM, 07Compared with no prior testing:
A positive prior ETT increases admit rate and rate of adverse events
A negative does NOT change admit rate or rate of adverse events
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Lessons from Treadmill testing
A negative exercise treadmill excludes that the current symptoms are due to ACS
Confirm that test is diagnostic 85% MPHR (> 6 mets, DP > 22.5 K)
Non-diagnostic results need further eval
Previous treadmill helpful only if abnormal
Outpatient Noninvasive Testing in 72 hours?
Anderson, Circ, 11ACC/AHA Recommends noninvasive testing within
72 hours of ED visit
Meyer, Annals EM Showed this was a safe strategy in 1000 low risk
1000 pts w/o CAD, ischemic ECG or initial positive Tn
Randomized to CTCA or usual care
2% AMI, 5% UA
Mean LOS reduced by 7.6 hours (P<0.001)
More D/C’s directly from ED: 47% vs. 12% (P<0.001)
However, even at 1 year, CTCA vs Usual Care resulted in more tests, more radiation (14 mSv vs 5 mSV), and more interventions (32 vs 21)
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CT in ACS- My Take
Excellent Negative Predictive Value
Use only when treadmill unavailable or patient can’t exercise
Probably best for a moderate risk pti.e. > 10% ACS risk
Identifies other diseases! (Causes other diseases?)
How Can We Detect All ACS?
The only way to detect all ACS is to test everyone!
However, we have seen testing lead to wasted time, money, unnecessary complications and further testing due to non-diagnostic or false positive results
DO what you and the patient believe is best
How Can We Detect All ACS?
DOCUMENT their understanding of the risks of the decision, which are always present
How Do We Manage Our Low Risk Chest Pain Patients?
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A Sample Approach - Conservative
TIMI = 1 or moreNegative initial Troponin and ECGCTA or admit to cardiology
TIMI = 0Negative Troponin and ECG at 0 and at least 8 hours after onsetStress test while in ED or as outpatient if unavailable
A Sample Approach - Liberal
Rule Out AMINon-ischemic ECGs and Negative cardiac markers at least 6 hours from symptom onset
Exclude UA (non-invasive testing)In EDIf symptoms intermittent or short duration (and somewhat consistent with anginal pain)
