cardiac lab eval Flashcards
1
Q
What are the cardiac biomarkers?
A
- troponin (main one)
- CK-MB
- myoglobin
2
Q
Lab tests for CV risk assessment?
A
- hs-CRP
- homocystine
3
Q
When do you use BNP?
A
- in HF management
4
Q
When are cardiac biomarkers used?
A
- in dx and risk stratification of pts with cardiac sxs
- not necessary for dx of pts who present with ischemic chest pain and EKGs with ST elevation
- follow the trend to peak
- useful to assess myocardial injury
- proteins that leak from myocardium secondary to ischemia
- differences b/t various biomarkers: time from ischemic injury to elevation of the lab values, and variable degrees of specificity for myocardial injury
5
Q
What is troponin a high specific marker for?
A
- cardiac muscle cell death
- it is a protein that is integral to muscle contraction
- found in skeletal and cardiac muscle
- Troponin I and T are isolated proteins specific for cardiac muscle
- released into systemic circulation when there is myocyte necrosis that leads to cell membrane disruption
6
Q
Troponin can ID pts at increased risk for what?
A
- adverse cardiac events
- several trials have demonstrated direct correlation b/t level of troponin in regards to mortality rate and adverse cardiac event rate in ACS
- higher the troponin the worse the outcome - large MI will have very high elevation of troponin -
7
Q
Different troponins?
A
- check either I or T (depends on facility)
- mult different assays so reference ranges may vary
- POC troponin used in the ER for rapid dx may be useful
8
Q
When do troponin levels rise and when do they peak?
A
- rises within 2-3 hours after cardiac insult and may stay elevated for 10 days to 2 weeks after event
- peak at 12-16 hrs
- wash out after thrombolytics will cause sig rise in troponins (won’t be true elevated marker)
9
Q
Troponin and CK-MB levels with and without reperfusion?
A
- with reperfusion - very elevated over 100, peaks and falls off quickly
- without: up to 75, not as high as with reperfusion but peaks longer
- CK-MB: with reperfusion preaks quickly, higher than with no reperfusion
- CK-MB: with reperfusion peaks longer, not as elevated
10
Q
What cardiac causes other than ACS will result in elevated plasma cardiac troponin?
A
- cardiac contusion
- cardiac surgery
- cardioversion
- endomyocardial biopsy
- CHF
- aortic dissection
- post PCI
- rhabdomyolysis
- myocarditis
- aortic valve disease
- hypertrophic cardiomyopathy
- tachyarrhythmia
- bradyarrhythmia, heart block
- apical ballooing syndrome
- pericarditis
- endocarditis
11
Q
What are noncardiac causes of elevated plasma troponin?
A
- PE
- severe pulm HTN
- renal failure
- stroke
- subarachnoid hemorrhage
- infilt disease: ex - amyloidosis
- cardiotoxic drugs
- sepsis
- critical illness
- extensive burns
- extreme exertion
12
Q
How is troponin used to dx MI?
A
- measure at presentation to ED
- repeat in 3-6 hrs post sx onset, may take up to 6 hrs post sxs/MI for lab test to rise
- highly sensitive assays have high negative predictive value for NSTEMI in setting of CP 2 hrs post onset of sxs (if neg after 2 hours, most likely they don’t have MI)
- may repeat beyond 6 hrs if:
initial troponin normal, EKG changes present, pt has many high risk features
(if pt has renal failure - troponin will stay stable, won’t increase like it would in an MI)
13
Q
What biomarker should you use for dx MI?
A
- troponin
- other cardiac biomarkers are not as sensitive or specific
14
Q
What is creatine kinase?
A
- enzyme found in muscle cells
- elevations suggest muscle damage and can be indicative of injury, rhabdomyolysis, MI, myositis, and myocarditis
- elevated in 1% of pts on statins
- may increase in hypothyroidism: when T3 is low, CK becomes elevated
15
Q
What are the 3 isoenzymes of creatine kinase?
A
- CK-MM: skeletal muscle and heart: elev in muscle damage to heart or skeletal muscle, crush injury, seizures
- CK-MB: heart - elevated in MI, inflammation of heart muscle, RV and LV strain
- CK-BB: elevated in brain injury, meningitis, severe shock, stroke, hypothermia, restricted blood flow to bowel
