Troponins: a selective review

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Troponins a selective review

• July 4th, 2002
• ECG/Lab rounds
• Rob Hall PGY3

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What is Troponin?

• Regulatory protein (NOT enzyme) found on
  contractile apparatus of striated muscle
• Initiates sliding of thin and thick filaments
• Troponin C, T, I
• Cardiac and skeletal muscle forms are genetically
  different ----gt assays use an antibody specific
  for cardiac form

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CONTEXT

• 45yo male intermittent chest pain
• Troponin lt 0.03 at..
• 2hr
• 4hr
• 6hr
• 10hr
• When is maximal sensitivity reached?

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EBELL June 2000

• Systematic review of Troponins and MI
• Prospective studies
• Physician determining dx of AMI blinded
• AMI defined as per WHO criteria
• History ECG CKMB
• Sensitivity reported from onset of pain (not
  presentation)

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EBELL 2000
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EBELL 2000

• Problems
• Were the exact same assays used?
• ? Methodology of combining data from several
  studies?

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TROPONIN T AND SENSITIVITY

• Troponin should NOT determine disposition
• Sensitivity will depend on cutoffs for normal
• General Numbers to remember
• 6 -----------------gt 60 sensitive
• 8 -----------------gt 80 sensitive
• 10 -----------------gt 90 sensitive

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TROPONIN AND SPECIFICITY

• Why does troponin sensitivity max out at 90
• Gold Standard definition of AMI is based on Hx
  ECG CKMB
• What does the patient with ve troponin and -ve
  CKMB represent?

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Troponin ve and CKMB -ve

• Troponin is released from reversible ischemia of
  myocardial cells
• UNSTABLE ANGINA

• Troponin is released from microinfarction
  (irreversible)
• MYOCARDIAL INFARCTION

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Troponin ve and CKMB -ve

• Unstable angina vs small MI?
• WHO CARES -------------gt Troponin ve and CKMB
  -ve do WORSE and thus should be treated
  aggressively

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Troponin ve and CKMB -ve

• Hamm NEJM 1997
• Anhman NEJM 1996
• FRISC (Eur Heart Journal 1997)
• FRISC (NEJM 2000)
• Anhman NEJM 2000
• INCREASED RATES OF CV EVENTS AND MORTALITY AT 30
  DAYS

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Doesnt really sound like ACS but Troponin ve...

• Myocarditis
• Pericarditis
• Severe CHF
• Hypertensive crisis
• Trauma
• Post arrythmias
• Post CV surgery
• Post angioplasty

• Post cardioversion
• Post CPR
• Infiltrative cardiomyopathy
• Cardiotoxic drugs (chemotherapy)
• RENAL FAILURE
• PULMONARY EMBOLISM

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TROPONINS AND RENAL FAILURE

• Dialysis patient with CP and troponin 0.3
• Troponins are elevated in dialysis patients
• Debate in the literature whether the troponin
  level is predictive of poor outcome
• Frankel 1995
• 70 of CRF patients on dialysis will have
  troponin level gt 0.1

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TROPONINS AND RENAL FAILURE

• Why are troponin levels elevated?
• Decreased clearance
• Chronic ongoing ischemia/microinfarction
• Uremic pericarditis
• Re-expression of cTnT in muscles due to myopathy
• UNKNOWN

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CHRONIC RENAL FAILURE butNOT ON DIALYSIS

• Chest pain Troponin 0.15
• Scr 150
• Scr 250
• Frankel 1995
• Elevated troponins in 3/10 patients with Scr gt
  300 and no evidence of MI
• Small, no long term follow up
• ESSENTIALLY UNKNOWN

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CASE

• 75yo male, dementia
• Chest pain ? Pressure ? Sharp ? Pleuritic
• Known CAD
• PE RF immobilization in nursing home
• Exam not helpful (Sat 90 RA)
• ECG sinus tach CXR clear
• Troponin 0.2

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TROPONIN and PULMONARY EMBOLISM

• Giannitsis, Circulation 2000
• 56 Consecutive patients with PE
• PE dx by angio, high probability V/Q, TEE
• Troponin gt 0.1 in 32 of patients with massive
  (hypotensive) or moderate-severe presentations
  (RV dysfunction on TEE)
• No troponin elevation in small PE

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TROPONIN and PULMONARY EMBOLISM

• Elevated Troponin in Submassive PE Douketis,
  Arch Int Med Jan 2002
• Prospective, N24
• PE dx by angio, high prob V/Q, or non-diagnostic
  V/Q DVT on ultrasound
• Excluded
• BP lt 90, cardiogenic shock, ventilated patients,
  documented CAD, CHF, CM, Scr gt 150

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TROPONIN andPULMONARY EMBOLISM

• Elevated Troponin in Submassive PE Douketis,
  Arch Int Med Jan 2002
• 20 had elevated troponins gt 0.4
• Small study BUT
• DONT FORGET ABOUT PE IN CHEST PAIN AND VE
  TROPONIN

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TAKE HOME POINTS

• Sensitivity not great until 8 - 10 hrs
• Troponin ve, CKMB -ve predicts poor outcomes
• There are many causes of a false ve troponin
• Renal Failure dialysis (? Non-dialysis pts)
• Pulmonary Embolism big and small