Marker

What It Is

Tissue Source

Reason for Increase

Time to Increase

Time Back to Normal

When/How Used

CK

Enzyme - three different isoenzymes exist

Heart, brain, and skeletal muscle

Injury to muscle and/or heart cells

4 to 6 hours after injury, peaks in 18 to 24 hours

48 to 72 hours, unless due to continuing injury

Ordered in combination with CK-MB

CK-MB

Heart-related isoenzyme of CK

Heart primarily, but also in skeletal muscle

Injury to heart and/or muscle cells

4 to 6 hours after heart attack, peaks in 12 to 20 hours

24 to 48 hours, unless new or continuing damage

Less specific than troponin, may be ordered when troponin is not available 

Myoglobin

Oxygen-storing protein

Heart and other muscle cells

Injury to  muscle and/or heart cells

2 to 3 hours after injury, peaks in 8 to 12 hours

Within one day after injury 

Sometimes ordered with troponin to provide early diagnosis

Cardiac Troponin

Regulatory protein complex.

Two cardiac-specific isoforms: T and I

Heart 

Injury to heart

4 to 8 hours

Remains elevated for 7 to 14 days

Diagnose heart attack, assess degree of damage