Enzymes and cardiac markers

Question 1

Creatine kinase: types (2)

• physiological causes of rasied CK (1)
• Pathological causes of raised CK (3)

Answer 1

Marker for muscle damage

1. CK MM - skeletal muscle
2. CK MB - cardiac muscles

Physiological - Afro-carribean (<5 times ULN - upper limit of normal)

Pathological

1. Duschenne MD (> 10 times ULN)
2. MI > 10 times ULN
3. rhabdomyolysis
4. statin related myopathy

Question 2

Raised ALP

• physiological causes (3)
• Pathological causes (4)

Answer 2

Physiologica

• pregnancy (due to PTHrp from placenta)
• Breast feeding - require Ca for milk prod
• childhood - growth

Path

• Bone > 5 times ULN
  
  • Paget’s
  • Osteomalacia
• Liver > 5 times ULN
  
  • Cholestasis & cirrhosis
• Bone < 5 times ULN
  
  • Tumour, fracture, osteomyeltis
• Liver < 5 times ULN
  
  • hepatitis

Question 3

Troponin I/T

• marker of what?
• when are they measured?
• how long do they take to return to normal levels post MI?

Answer 3

Marker of myocardial injury

• measure at 6 hours & 12 hours post onset of chest pain (100% sensitivity & 98% specificity at 12-24hrs)
• Levels gradually return to normal over 10 days
  
  • ​this makes it a bad marker for reinfarction
  • in this case CKMB is measured as it peaks 24hrs post MI but returns to baseline within 48-72hrs
• ​And Trop I is a better marker than trop T