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.

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 1S^t 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.