Cardiac Labs Flashcards
Protein found in cardiac and skeletal muscle that helps with muscle contraction
Released when the muscle cells are damaged
Elevate 2-3 hours after cardiac injury, peak at 12 hours
A troponin must be above the 99thpercentile of the upper reference for the normal range of the assay being used to be considered positive
Level of elevation is dependent on infarct size and can be an indicator of prognosis
Troponin
Troponins I & T are only found in cardiac muscle making them very specific for cardiac injury.
3 types of Troponin – I, T & C
90% sensitive/95% specific for myocardial infarction 8 hours after symptom onset
Remains elevated for 7-10 days post MI
Troponin I
84% sensitive/81% specific for myocardial infarction 8 hours after symptom onset
Remains elevated for 10-14 days post MI
Troponin T
troponins should be measured at presentation and again 3-6 hours later depending on risk
ruling out an infarct
Can be elevated with any type of cardiac injury – not just infarction
Cardiac trauma, CHF, HTN, PE, myocarditis, critical illness (sepsis)
Chronic renal failure – cardiac injury can be determined by looking for a rise and fall in elevation – steady elevation is seen in renal disease
Overall associated with a poorer prognosis no matter the cause
If you are concerned about a re-infarction, troponins are not as helpful due to their persistent elevation post MI however troponin is beneficial in late presentations of M
Troponins
More specific to cardiac muscle but not as specific as troponin
Increases within 3-12 hours of onset of chest pain, peaks within 24 hours and returns to baseline after 48-72 hours.
Can be helpful in detecting re-infarction
Sensitivity and specificity are not as high as troponin – troponin is preferred
CKMB
Found in heart & skeletal muscle and the brain
Elevate with muscle or nerve cell injury
Creatinine Kinase
Secreted from the ventricles of the heart in response to changes in pressure that occur with HF
Increases when HF worsens; Decreases when HF improves
Helps distinguish between lungs and heart for shortness of breath
High creatinine skews it high
Obesity skews it low
B-Type natriuretic peptide (BNP)
BNP levels below 100 pg/mL indicate no heart failure.
BNP levels of 100-300 pg/mL suggest heart failure is present.
BNP levels above 300 pg/mL indicate mild heart failure.
BNP levels above 600 pg/mL indicate moderate heart failure.
BNP levels above 900 pg/mL indicate severe heart failure.
BNP Levels
One of the degredation products released upon clot breakdown
Elevated levels indicate recent or ongoing coagulation and fibrinolysis
Highly sensitive in evaluating for DVT/PE
Poor specificity as elevated levels can be found in many other conditions (pregnancy, renal failure, malignancy, recent trauma, sepsis)
Useful in the evaluation of those with low to moderate clot risk
Positive result indicates need for further evaluation
Those at high risk require imaging
Also think about reliability/accessibility of patient when results are available
D-DIMER
Total cholesterol – HDL + LDL + vLDL (contains triglycerides)
Lipid panel – may have different panel combinations
Total cholesterol
HDL
LDL (calculated)
Triglycerides
VLDL (calculated)
Non fasting: acceptable for baseline screening
Fasting: recommended for high risk, FH, on statin therapy , hypertriglyceridemia
9-12 pre-test
Lipids
low density lipoprotein
major carrier of excess cholesterol to cells
targets: peripheral tissues, excess burrows into arterial walls
LDL vs LDLc
Direct
Indirect – calculated by the Friedewalde equation
Not valid if triglycerides over 400
Tends to underestimate LDL
What treatment guidelines are based on
LDL
high density lipoprotein
binds with excess cholesterol released by cells, brings back to liver to be expelled
“good cholesterol”
HDL
difference between Total cholesterol and HDL
Non HDL Cholesterol
fatty acid chains
transported to tissues for energy
unused calories converted into triglycerides for storage in fat cells
when energy released, transport proteins convert to cholesterol rich particles
-increases LDL, lowers HDL
Most sensitive to fasting
Trigylcerides
very low density lipoprotein
carries mainly triglycerides
difficult to measure, calculated from triglyceride levels
VLDL
0-3: Low risk
4-6: Mod risk
7-10: High risk
Must assess risk for ACS when patient presents with chest pain
Detailed CT images of the coronary arteries
Helps to determine ASCVD risk
Can be useful in determining need for statin, aspirin, etc
Consider in intermediate/borderline risk patients whose decision about statin therapy is uncertain
What does the test entail?
Same amt of radiation as a mammogram
Hooked up to ECG leads
Medication to slow heart rate may be used
Takes 10-15 minutes
No dye is needed, no need to fast
Patients must be able to hold their breath for 10-15 seconds
Agatston score
*0 Agatston units – No identifiable disease
*1 to 99 Agatston units – Mild disease
*100 to 399 Agatston units – Moderate disease
*≥400 Agatston units – Severe disease
Coronary Artery Calcium Scoring (CAC)
Troponin considered positive
must be above the 99th percentile of the upper reference for the normal range of the assay being used to be considered positive
Cardiac Biomarkers
Troponin, Myoglobin, CK
Total Cholesterol
HDL+LDL+VLDL (contains triglycerides)
