Acute chest pain

Key Differential Diagnosis – Cognitive Reasoning in Chest Pain

• Life Threatening Causes of Chest Pain
  • Aortic Dissection
    • Midline/substernal tenderness
    • Radiation to back
    • Ripping/tearing nature 
    • Associated symptoms (chest pain + 1)
      • Neurology
      • Abdo pain
      • Headache
  • Pneumothorax
    • One side of chest
    • Sudden onset, pleuritic pain
    • Radiates to shoulder and back
    • Associated dyspnoea 
  • Oesophageal Rupture (Boerhaave Syndrome)
    • Substernal pain
    • Sudden onset, sharp pain
    • After vomiting
    • Radiates to back
    • Dyspnoea, diaphoresis is common
    • Signs of sepsis if presents late 
  • Pulmonary Embolus (massive)
    • Sudden onset of whole chest pain
    • Pleuritic
    • Nil radiation
    • Syncope can occur
    • Dyspnoea, unstable vital signs and feeling of impending doom
  • Pulmonary Embolus (subsegmental) 
    • Focal, sudden onset, pleuritic pain
    • Nil radiation
    • Associated with dyspnoea, tachycardia 
  • Pericarditis
    • Substernal pain, gradual onset
    • Sharp pain, constant, can be pleuritic
    • Radiates to back, neck or shoulder
    • Worse when lying flat
    • Hx of recent infection, uraemia, SLE etc 
  • Pneumonia
    • Focal chest pain, usually pleuritic 
    • Sharp pain, gradual onset
    • No radiation 
    • Associated with fever, cough, tachypnoea and signs of sepsis 
  • Perforated Peptic Ulcer 
    • Epigastric pain
    • Severe, sharp
    • Radiates into back and up into chest
    • Associated with acute distress, diaphoresis and varying degrees of instability in vital signs 
• Other Causes of Chest Pain
  • GORD
  • Biliary Colic 
  • Pancreatitis
  • Shingles 
  • Anxiety/Panic Attack
• Causes of Chest Wall Pain
  • Muscle strain
  • Costochondritis (Tietze’s syndrome)

What do we need to do?

• Identify STEMI
• Identify NSTEMI
• Rule out NSTEMI
• Decide who can be sent home without further objective testing
• Decide who needs objective testing as an inpatient or an outpatient

Risk stratification of possible ACS (NHF)

• High risk (25% risk of MI)
  • Persistent or dynamic ST/T wave changes
    • ST depression >0.5mm
    • New TWI >2.0mm in 2 or more contiguous leads
    • Transient ST elevation > 0.5mm in 2 or more contiguous leads
    • ECG changes consistent with Wellen’s/LMCA/DeWinter’s
  • Haemodynamic compromise
  • Ongoing or recurrent pain
  • Sustained VT
  • Syncope
  • Elevated troponin
  • LVEF <40%
  • Previous PCI/CABG/MI in last 6 months
• Intermediate risk
  • No high or low risk factors
  • Transient ECG changes that do not meet above criteria
• Low risk
  • AGE <40
  • Atypical symptoms
  • Remain symptom free
  • Absence of known CAD
  • Normal troponin levels
  • Normal ECG (including no transient changes)

Clinical Risk Scores and Decision Rules

Commentary on scores and
ADP (accelerated diagnostic pathways)

• There is no clear best ADP for acute chest pain presentations
• Greenslade et al. 2017 compared 0/2 hsTn pathways:
  • Vancouver Chest Pain Rule and NOTR rule ruled out 30-day ACS in 15-30% of presentations with >99% sensitiity
    • Well suited to systems aiming to minimise referrals for further objective testing
  • EDACS/HEART/Modified ADAPT classified 50-60% of patients as low-risk but sensitivity was <99% for 30-day ACS
    • Well suited to systems with ongoing referral of patients for further objective testing
• Current AHA guidelines define low-risk patients as those with <1% MACE risk at 30 days:
  • hsTn < level of detection if pain started >3 hours before test
  • Dual hsTn <99th centile
  • Use of validated clinical decision rule with MACE <1% at 30 days
  • Does NOT recommend any one specific clinical decision rule but NOTR and 2020 ESC pathways are the only two with MACE <1% at 30 days as per the AHA guideline
• Specifically states use of dual hsTn alone or single hsTn < LoD (at least 3 hours from onset of pain) (without clinical decision rule) has been validated across 15 studies and >9000 patients to provide a NPV of 99.8% for death or MI at 30 days
• Specifically states there is NO benefit to these patients undergoing stress testing or anatomical testing within 30 days of ED discharge. It emphasises the underlying cardiovascular risk factors are what actually need managing
• Recommends low-risk patients being discharged without further objective testing
  • State that outpatient Coronary Calcium Score can provide further useful information to provide longer term risk stratification
• The most commonly utilised are:
  • HEART pathway
  • EDACS
  • Modified ADAPT
  • 2020 European Society of Cardiology

TIMI score for possible NSTEMI

• Age >= 65
• >= 3 CAD risk factors (FHx of premature CVD, HTN, Dyslipidaemia/low HDL <40mg/dL/, DM or current smoker)
  • Premature CVD = male first-degree relative under 55yo or female first-degree relative under 65
• Known CAD (>= 50% stenosis)
• Aspirin use in last 7 days
• 2 or more episodes of angina in last 24 hours
• Elevated troponin
• ST deviation >= 0.5mm in contiguous leads

TIMI score interpretation

• % risk at 14 days of: All-cause mortality, new or recurrent MI or severe recurrent ischaemia requiring urgent revascularisation
  • 0-1= 4.7% risk
  • 2 = 8.3% risk
  • 3 = 13.2% risk
  • 4 = 19.9% risk
  • 5 = 26.2% risk
  • 6-7 = >40.9% risk

GRACE score

• Age
• HR
• Systolic BP
• Creatinine
• Cardiac arrest at admission
• ST segment deviation
• Elevated troponin
• Killip class

GRACE score interpretation

• % risk at 6 months for all-cause mortality
  • 60-100 – 3% risk
  • 100-140 = 8% risk
  • 140-180 = 20% risk
  • >180 = >40% risk

HEART score

• History
  • Slightly suspicious – 0
  • Moderately suspicious +1
  • Highly suspicious +2
• ECK
  • Normal 0
  • Non-specific repolarisation abnormality +1
  • Significant ST elevation (if >1mm do not use score)/depression not due to LVH/LBBB/digoxin +2
• Age
  • <45 – 0
  • 45-64 + 1
  • >=65 +2
• Risk factors
  • NO known risk factors – 0
  • 1-2 risk factors +1
  • >=3 risk factors or history of atherosclerotic disease +2
  • HTN, dyslipidaemia, DM, obesity, smoking (current or within 3mo), FHx (first-degree before age 65), atherosclerotic disease (prior MI;PCI;CABG;CVA;TIA;PAD)
• Initial troponin 
  • Normal 0
  • 1-3x ULN +1
  • >3x ULN +2

HEART score interpretation

• Score 0-3 = 0.9-1.7% risk of adverse cardiac event (all-cause mortality, MI, intervention)
• Score 4-6 = 12-16.6% risk
• Score 7 or more = 50-65% risk

HEART Pathway

Modified HEART score (Troponin removed)

• History
  • Slightly suspicious 0
  • Moderately suspicious 1
  • Highly suspicious 2
• ECG
  • Normal 0
  • Non-specific repolarisation disturbance 1
  • Significant ST deviation 2
• Age
  • <45yo = 0
  • 45-64 = 1
  • >65 = 1
• Risk factors
  • No known risk factors 0
  • 1-2 risk factors 1
  • 3 or more risk factors 2
• HEART score <4 = low risk
  • Serial Tn (sensitive or hsTn) testing at 3 hours
  • Negative – Early discharge (0.4% 30 day MACE risk)
  • Positive – Cardiology Consult and admission
• HEART score >=4 = High risk
  • Serial Tn (sensitive or hsTn) testing at 3 hours
  • Negative – Admission to Observation Unit/Inpatient for stress testing or imaging
  • Positive – Cardiology Consult and admission for stress testing or imaging

HEART Pathway

• Mahler et al. 2015 introduced concept of Heart Pathway with 0 and 3 hour conventional Tn assays
• Mahler et al. in 2017 compared conventional sensitive Tn assay to hsTn assay at 0 and 3 hours and confirmed equally sensitive and specific
• Further studies have validated a 0/2hr hsTn strategy
• Low risk with dual negative Tn discharged with referral to GP for ongoing clinical assessment and consideration of provocative/stress testing
• Single-centre secondary analysis of a previous prospective observational data set showed utilisation of the HEART pathway with 0/1hr European Society Cardiology Guidelines 2020 with hsTnT measurements had sensitivity >99% and NPV >99.5% for 30-day MACE and AMI
  • Probably warrants prospective implementation study in routine care for validation
• While NPV is very high (given low-risk population), actual sensitivity for 30-day MACE may be as low as 95%
• Approximately 40% discharge from ED rate

EDACS

Variables include age, sex, risk factors, historical features and 0/2hr troponins

EDACS score <16 with negative 0/2hr hsTn with no ischaemic changes on ECG allows for ED discharge in 49% of presentations

Has 30-day MACE sensitivity of 92%

Designed for low-risk group to undergo early outpatient or inpatient objective testing

Original ADAPT

• If high or very high-risk possible ACS
  • Refer for admission and 6 hour troponin
• If no high risk features
  • TIMI score = 0
    • Repeat troponin and ECG testing at 2 hours from symptom onset (I use 6 hours from symptom onset for all generally as troponin should be elevated by 4-6 hours, peaks at 10-24 hours and declines over 10 days)
  • TIMI > 0
    • Repeat troponin and ECG testing at 6 hours from symptom onset
• If any further symptoms, dynamic ECG changes or elevated troponin treat as high risk
• If troponin and ECG both remain normal = Low risk for AMI
  • Consider need for objective testing

• TIMI, ECG and 0- and 2-hour sensitive Tn
• Brisbane and Christchurch
• Low risk = TIMI 0, normal ECG and both Tn below cut-off
• 1975 patients
• 15% primary outcome events (MI mostly)
• 20% of patients identified as low risk
• 1 patient in low risk group had MACE
• If TIMI 0 or 1 utilized as low-risk, resulted in 38.4% of patients designated low risk but reduced sensitivity to 97% and NPV to 98.8%
• 316 of 392 patients in low-risk group had stress testing within 30 days, 88% of which were done in index admission
• Therapeutic and procedural interventions were then performed in 2% of ADP negative patients
• Did not include atypical presentations and predominantly Caucasian group

ASPECT

• 2 hour point-of-care conventional Tn with ECG and TIMI
• ADP identified 9.8% of patients as low risk and suitable for discharge with early follow-up
• Sensitivity of 99.3% for 30 day MACE

Modified ADAPT

• Cullen et al. 2013
• If any high risk features – refer for admission and repeat troponin and ECG at 3 hours
• If no high risk features
  • TIMI 0 or 1 – Repeat troponin and ECG at 2 hours
  • TIMI 2 or more – Repeat troponin and ECG at 3 hours
  • TIMI <= 1 + hsTn allowed ~40% of patients to be classified as low-risk with <1% risk of MACE at 30 days
• 77% rate of further testing for ADAPT cohort + ~25% rate of further testing in APACE cohort
  • Not clear why such different proportions and no detail on whether this testing altered management in any way (majority stress ECG)
• 2 patients in ADAPT cohort and 1 patient in APACE cohort had a 30-day MACE (all NSTEMI)
• 30-day MACE sensitivity of 93%

NOTR

Incoroporates age, risk factors, preious AMI or CAD and 0/2hr hsTn testing

Low-risk

• Age <50
• <3 risk factors
• No prior CAD/AMI
• hsTn and 0 and 2 hours <99th centile

Allows for 28% of patients to be discharged from ED with 30-day MACE <1%.

European Society of Cardiology 2020 NSTEMI Guideline

• Recommend 0/1hr hsTn algorithm
  • Prospectively validated (Twerenbold et al. 2018)
  • 3500 patients in hsTnI cohort and 4368 in hsTnT cohort
  • 44% triaged to rule-out; 33% to observe and 23% rule-in using hsTnI
  • Rule-out group
    • 0 hr TnI undetectable in 10% fo patients
    • Overall NPV 99.7% (5 NSTEMI missed out of 1533 patients)
    • Equal safety in those who presented <3 hours vs. >3 hours from pain onset
  • Rule-in group
    • PPV 62.3%
• Repeat hsTn sampling is mandatory in case of ongoing or recurrent chest pain
• 3 main caveats to using a rapid diagnostic strategy
  • Use in conjunction with clinical information and ECG
  • An additional 3 hour measurement is probably the safest option if presenting within 1 hour of pain onset
  • If clinical suspicion remains high or pain is recurrent, serial troponin testing is the safest pathway
• Does the rule-out group need further testing?
  • The HEART Pathway 0/1hr validation study above shows those with HEART <4 could be discharged without further investigation to their GP for risk factor optimisation
  • Those with HEART >4 warrant discussion with Cardiology for consideration of optimal further risk stratification in the local clinical context
• What happens to the Observe group?
  • 3hr Troponin and Cardiology consultation for consideration of echo and further testing

Beckman cut-offs for 0/1hr TnI

• Very low <4
• Low <5
• No 1h delta <4
• High >50
• 1h delta >15

RACING-MI

Danish study in single centre validating a 0/30 minute rapid rule out algorithm using Siemens ADVIA Centaur hsTn

500 patients in derivation cohort and with 1003 patients included in overall analysis

Myocardial infarction was diagnosed in 8.8% of patients overall.

Overall found it possible to rule out and potentially discharge 50% of patients after 30 minutes, whereas 41% needed further diagnostic workup (Observational Zone).

Rule-in ability of the algorithm was similar to previously published 0/1hr algorithms (PPV 70-84%).

CSANZ COVID Chest Pain Pathway

Specifically written for a COVID pandemic situation to minimise admissions safely

Very low troponin has NPV 99.5% for acute MI in index admission and MACE at 30 days

Low risk: Very low troponin -> Accelerated discharge with action plan for recurrent symptoms and GP follow-up

• No ischaemic changes on ECG
• First hsTn below cut-off (2ng/L for Beckmann)
• Symptom onset >=2 hours before troponin test
• 18 years or over

Low risk: Clinical -> Re-test at 2 hours and if normal Tn and ECG with resolved symptoms -> Discharge as above

• Age <40
• Age <18 for Indigenous Australians
• ECG – No ischaemic changes
• hsTn <99th centile
• Not diabetic
• eGFR >60

Intermediate risk -> Discharge and consider clinic/telehealth follow-up

• Not meeting above criteria

High-risk features -> Admit

• Ischaemic ECG changes
• Tn >99th centile
• LVEF <40%
• New MR
• Haemodynamic compromise
• Syncope
• AMI, PCI or CABG in last 6 months

What to tell patients who are discharged home?

• To seek medical attention should symptoms recur
• Reiterate that coronary artery disease has NOT been excluded
• 30 day risk of MACE is <0.5%

Patients who have undergone previous risk stratification investigations

• The reality is, a completely clean CTCA or invasive angiogram is very reassuring while the presence of any coronary artery disease (irrespective of percent stenosis) suggests a risk of plaque rupture at any stage as we know smaller plaques may be more vulnerable to rupture anyway
• Crucial to still rule out MI through serial hsTn testing but if MI is ruled out, this means plaque is unlikely to have ruptured and the benefit of any further testing is much less
• Dunn
  • Generally no provocative testing required for:
    • Negative stress ECG test in last 6 months
    • Negative stress cardiac MRI, CTCA, stress echo or MPS in last 12 months
    • No significant coronary stenosis >50% in last 5 years
    • CABG >6 weeks and <3 years ago (<5 years in UpToDate)
    • Stenting >4 weeks and <2 years previously who are compliant with antiplatelets
      • <1% rate of in-stent stenosis within 1 year of uncomplicated insertion
• Tintinalli
  • Truly negative angiogram report confers very low risk of AMI for 2 years
  • Prior negative stress test of any sort provides very little reassurance that a current chest pain event is benign
    • Patients with recent negative evaluation for ACS including objective testing (mostly stress ECG testing) have 6 month incidence of AMI as high as 14%
• UpToDate
  • Negative angiogram or CTCA strongly negatively predictive (up to 10 years in some series)
  • Negative stress test not useful to rule out ACS if active chest pain in ED
• AHA Chest Pain Guideline
  • Warranty period of previous testing stated as:
    • Normal angiogram or negative CTCA with NO stenosis or plaque = 2 years
    • Adequately performed stress test = 1 year

NICE guideline

• Divides patients into acute chest pain and stable chest pain
  • Acute chest pain is assessed for AMI + alternative Dx
  • If no diagnosis of MI can be made then consideration is given to whether pain is stable angina or not
• Most people diagnosed with non-anginal chest pain need no further diagnostic testing
  • If have risk factors for cardiovascular disease – refer to primary carer for risk factor modification
  • However, atypical presentations are common and have worse outcomes (UpToDate, Dunn)
• If stable typical or atypical angina suspected:
  • CTCA is first-line
  • Non-invasive functional testing is then indicated if non-diagnostic (stress echo, MPS, MR NOT exercise ECG)
  • Invasive angiography is third-line if non-invasive testing is non-diagnostic 

• Positive CTCA =
  • >70% stenosis (or >50% in LMCA)
  • If 50-70% stenosed, consider if anaemic, proximal, long lesion, LVH as may still be symptomatic

• Three features = Typical
• 2/3 features = Atypical
• 0/3 or 1/3 features = Non-anginal chest pain  NICE advice to exclude diagnosis of stable angina in this group and consider alternative diagnoses + no provocative testing
• Features
  • Constricting discomfort in front of chest, or neck/shoulders/jaw/arms
  • Precipitated by physical exertion
  • Relieved by rest or GTN within about 5 minutes (although NICE guide says NOT to use response to GTN in diagnostic consideration)

Stress testing

• Normal serial ECGs and troponins reduce likelihood of AMI but do not exclude unstable angina or coronary disease, both of which carry risk of future adverse cardiac events
• Non-invasive objective testing is recommended for intermediate-risk patient with normal serial Tn and ECG testing and who remain symptom free
• Australian National Heart Foundcation
  • Patients in whom no further testing is required are those defined as low risk by a validated assessment pathway
    • Age <40
    • Atypical symptoms
    • No known CAD
    • Normal Tn and ECG
    • Symptom free
• AHA
  • Low-risk patients do not need further objective testing (see above)
  • Outpatient coronary calcium scoring can be utilised to provide longer term risk stratification

Timing of testing (NHF)

• High-risk: During index admission
• Intermediate-risk: Early inpatient or outpatient within 7 (or up to 14) days
  • Investigate prior to discharge if high risk of FTA (higher risk of MACE)
• Low risk: Either none or within 30 days if warranted i.e. typical crescendo angina or >40yo

Functional vs. Anatomical

• Based on:
  • Patient criteria (ECG interpretable, ability to exercise)
  • Diagnostic accuracy
  • Local expertise/availability
  • Risks and costs
• ECG exercise testing
  • Utility in prognostication is well understood, cheap, timely
  • Prior to Tn testing had NPV of 97-99% for AMI or death
• Some benefit to stress echo or CTCA but incremental benefit over ECG stress testing is unknown and of limited accessibility

• Options
  • Exercise stress testing in most if ambulatory
  • Chemical stress testing if non-ambulatory
  • Myocardial perfusion scanning
  • Stress echocardiography
  • CTCA
  • Cardiac MRI
  • Angiogram

• Can perform EST if physically able and none of:
  • LBBB
  • LVH
  • Pre-excitation
  • >=1mm ST deviation at rest
  • ECG changes of digoxin
  • Ventricular paced rhythm
• If imaging required:
  • CTCA if no iodine allergy, sinus rhythm and GFR >45
  • Otherwise MPS

EST Contraindications

• Left main stenosis
• Hypotension <=90
• HTN >=170/110
• Ongoing ACS symptoms
• MI within 2 days
• PCI within 2 weeks
• CABG within 6 weeks
• Tachyarrhythmia
• 2^nd degree or higher AV block
• Decompensated CCF
• Active endocarditis
• Acute pericarditis/myocarditis
• Suspected/confirmed PE
• Moderate/severe stenotic valvular disease
• K <=3

MPS Contraindications

• Beta-blocker (cease >24 hours prior)
• Unstable angina
  Ventricular arrhythmias
• Recent MI
• Haemodynamically LV obstruction
• Known or suspected aortic disease

Which stress testing is warranted?

• Exercise stress test
  • In very low pre-test probability, get lots of false positives and in very high pre-test probability get lots of false-negatives
    • Therefore recommended for low to moderate risk patients but NOT very low risk or high risk patients
  • Requires adequate workload ambulation
  • Hyperventilation and tachycardia can reduce quality
  • Lower diagnostic accuracy in women
  • Positive = >=1mm ST horizontal or downsloping elevation or depression for at least 60-80ms
  • Unable to interpret if LBBB, paced ventricular rhythm, pre-excitation syndrome or >1mm ST depression (e.g. LVH or digitalis effect)
  • Sensitivity 68% and specificity 70-77% (worst of all with significant risk of false negative)
  • Duke score – Low risk <1% per year cardiovascular mortality
  • High risk >5% per year cardiovascular mortality

• Stress echo
  • Sensitivity 80-85%; Specificity 84-86%
  • False negatives in single vessel/circumflex territory ischaemia
  • Requires exercise or dobutamine
  • No radiation exposure or environmental impact
  • Exercise or chemical stress testing performed
  • May see transient focal wall motion abnormality with stress suggesting inducible ischaemia
  • Contrast (bubble) scanning improves contrast of endocardial border
  • 0.4-0.9% per year cardiovascular event risk (like asymptomatic population) if normal study
  • NPV 98.4% for MI and cardiac death at 33 months
  • Limited use in obesity and those with prior MI as scarred tissue has resting focal wall motion abnormality making interpretation difficult
  • Operator-dependent
  • Cannot distinguish between acute MI and ischaemia, cannot reliably detect subendocardial ischaemia and can be falsely positive in conduction disturbances, volume overload, heart surgery or trauma
  • Must be timely with symptoms or stress as wall motion abnormalities can resolve within minutes of an ischaemic episode
  • A normal resting echo in ED does not exclude ACS but makes it less likely

• Myocardial perfusion scanning
  • Sensitivity 85-90%; Specificity 80-90%
  • Radiation exposure
  • Risk of false positives due to very high sensitivity
  • Images captured at rest and with stress (either exercise or chemical)
  • Can identify reversible inducible ischaemia
  • In low risk group, has NPV approaching 100% for myocardial infarction and cardiac death at 36 months
  • Normal scan = 0.7% per year CV all-cause mortality/MI/cardiac death (approaching asymptomatic population)
  • Limitations: Radiation (>angiography) and availability of nuclear tracers and experienced staff
  • 201 Thallium
    • Ischaemic cells lack take-up of thallium (K analogue) = cold spots
    • Irreversible cold spots = infarct
    • Higher radiation dose than sestamibi
    • With exercise or dipyramidole single injection, scan 15min later then again 2-4 hours later
  • Tc 99 sestamibi
    • First injection at rest, imaging performed 30-60 min later, second injection later that day (2-3x higher with stress) and repeat imaging 60-90 min later
    • Acute scans (with chest pain) are highly sensitive for significant IHD
• CTCA
  • Less clinically useful in high risk patients as often need to go onto traditional angiography anyway
  • Very high negative predictive value in low-intermediate risk patients
  • Radiation exposure significant (although much improved since prospective gated scanning), approximately the same as traditional angiography and less then myocardial perfusion scanning
  • Functional effect of stenosis remains unknown
  • No data to suggest this is useful for asymptomatic patients

• Electron beam CT
  • New technology with lower radiation than helical CT
  • Provides coronary calcium score
  • Probably most useful in patients <60yo who present with ischaemic sounding chest pain and normal ECG/biomarkers
  • 80-90% sensitive and 40-50% specific

• Cardiac MRI
  • No radiation or iodinated contrast
  • Provides information on RV, LV function (volume, EF, wall motion abnormalities), myocardial oedema to suggest acute injury, perfusion at rest and with stress and detects infarction size and transmurality with delayed enhancement imaging
    • No other technology can perform all of this in one study
  • Real value is in diagnosing true ACS, as manifest by changes in function, perfusion, delayed enhancement and myocardial oedema
  • May also be able to diagnose unstable angina from myocardial infarction
  • Limitations include patient contraindications (i.e. metallic implants), claustrophobia, availability of MRI and skilled reporting, inability to visualise entire coronary tree (unlike CTCA or angiography) and may be undesirable to have patients in scanner with ongoing chest pain

UpToDate Stress Testing

• Exercise stress ECG is first line if can exercise and interpret ECG
• Insufficient evidence to recommend imaging for all patients
• Sensitivity of pharmacological stress ECG alone is not sufficient – need imaging as well

2021 AHA Guideline

Troponin

• Normal level = <99th percentile
• Elevated by 4-6 hours from symptom onset; declines over 10 days
• Peaks at 16-24 hours
• Accelerated protocols have been validated for hsTn only at 2 hours for low risk patients
• Normal protocol is 6 hr troponin in Metro South

99^th centile and Delta

• Beckman Coulter Access hsTni
  • Females = 11.6ng/L
  • Males = 19.8ng/L

Delta

• >=3ng/nL 
  • Baseline to 1-3 hours: Sens 76%, Spec 95%
  • Baseline to 3-6 hours: Sens 87%, Spec 92%
• >=5ng/L
  • Baseline to 1-3 hours: Sens 71%, Spec 97%
  • Baseline to 3-6 hours: Sens 78%, Spec 95%
• Need to ascertain suitable cutoff for specific ED
• Increase the absolute delta = more specific, less sensitive

Delta troponin

• Absolute changes in hsTn have better diagnostic accuracy than relative changes
• If high clinical suspicion of ACS
  • Tn value below or close to 99^th centile, changes of >2-3 SD should prompt additional testing as unlikely to reflect physiological variability

Single troponin

• AHF guideline
  • Symptom-free for 12 hours prior to assessment
  • Present >3 hours after symptom onset with value less than the limit of detection using hsTn assay
• ESC Guideline
  • If initial troponin performed >3 hours from symptom onset and <4ng/L could enter rule out group

What about no troponin testing at all?

• O’rielly et al. 2021
  • External validation through secondary analysis of a prospective cohort study in Canada
  • Showed a HEAR score (HEART without troponin) <=1 enabled 24.6% of patients without a history of CAD and 17% of all-comers to be classified as very-low risk and potentially not undergo Tn testing at all
  • Showed sensitivity of 98.4% (CI 91.6-99.9%) in the cohort without history of CAD and sensitivity of 99.2% (CI 95.6-99.9%) in all-comers with NPV of >99% in both
  • Conclusion is that further study needs to be undertaken to confirm safety of this pathway

Post-CABG Chest Pain

Differential

• Musculoskeletal pain from sternotomy (most common)
• Acute graft stenosis or occlusion
• Pericarditis
• PE
• Sternal wound infection
• Non-union

Saphenous vein graft 10-20% failure at 1 year; 50% at 10 years

Internal mammary artery grafts 90-95% patent @ 10-15 years

Last Updated on January 6, 2022 by Andrew Crofton