CARDIAC MARKERS IN MI, AMI and Myocardial Injury

CARDIAC MARKERS IN MI

  • Serum proteins released in blood from necrotic heart muscles after AMI are called serum markers .

 

Creatinine phosphokinase (CK)

  • Rises in 4 – 8 hours.
  • Returns to normal in 48 – 72 hours.

 

CK increased in :

  • IM injections
  • Stroke
  • Surgery
  • Trauma
  • Skeletal muscle diseases
  • Electrical cardioversion
  • Hypothyroidism
  • Convulsions, Prolonged immobilization.

Acute Myocardial Infarction 1

Serum Markers of Myocardial Injury

 

MB Isoenzyme of CK :

  • Increased in Myocardial diseases
  • Electrical cardioversion
  • Cardiac surgery.

Some Properties of Serum Markers of Myocardial Injury

  • Marker Time to Appear ,Time to Peak and Time Return to Normal
  • Myoglobin 0.5-2h Marker Time to Appear 5-12h  Time to Peak 18-30h  Return to Normal
  • CPK-Isoforms 1-4h Marker Time to Appear 4-8h  Time to Peak 12-24h  Return to Normal
  • CPK-MB 3-8h   Marker Time to Appear 9-30h  Time to Peak 2-3d  Return to Normal
  • CPK-Total 3-8h   Marker Time to Appear 10-36h  Time to Peak 3-4d  Return to Normal
  • Cardiac Troponins 3-6h  Marker Time to Appear 10-24h  Time to Peak 5-15d  Return to Normal
  • LDH 8-18  Marker Time to Appear 2-3d   Time to Peak 6-10d  Return to Normal

 

Ratio of CKMB :

  • CK > 2.5 su _g~sts MI (but not diag­nostic).
  • Requires series of measurements obtained over 1St 24 hrs.
  • Skeletal muscle CKMB pattern a Pla­teau.
  • Myocardial form CKMB is CKMB2.
  • KMB2 : CKMB1 ratio of > 1. 5 (diagnostic for AMI 4-6 Iirs after coronary occlusion.

 

Cardiac Troponins

  • C TnT and C TnI.
  • Cardiac specific troponin T and I are biochemical markers of choice.
  • TnI – remains elevated upto 10 days.
  • C TnT may be elevated for 10 – 14 days.
  • Early recanalization of coronary occlusion by mechani­cal means or drugs results in early peaking and higher peaks.
  • In microinfarctions CKMB normal but cTnT or I elevated.

 

Myoglobin

  • Rises few hours after AMI and comes to normal within 24 hours.
  • Elevation of LDH and isoenzymes is upto 48 hrs Not used now.
  • CKMB may be useful only for repeat episodes in 2 ~eeks otherwise-only cTnI and / or cTnT may be do~e.
  • Ideally serum cardiac markers should be measured at time of admission, 6-9 hrs after admission and 12­24 hrs after admission.

 

Non specific lab tests

  • Leucocytosis
  • Increased ESR.