Cardiac Labs Flashcards
Infarction
- The cardiac tissue lacking oxygen long enough until the tissue actually dies
- IRREVERSIBLE
Ischemia
- Cardiac tissue temporarily lacking oxygen that can be restored without damage to heart
- REVERSIBLE
Stable vs unstable angina
Main difference
- Stable: CP relieved at rest; only exertion
- Unstable: CP not relieved at rest; during exertion and rest
When you order an ECG for someone w/ACS and see No ST elevation and you order cardiac enzymes what does it indicate when…
Enzymes DECREASED =
Enzymes INCREASED =
- DECREASED = Unstable angina
- INCREASED = NSTEMI
What is troponin?
When is it released?
- Protein found in cardiac and skeletal MM that helps w/MM contraction
- Released when mm cells are damaged
When is Troponin positive?
Troponin must be above 99th percentile of upper reference to be considered POSITIVE
When is troponin ELEVATED post cardiac injury? Timing
- ELEVATES 2-3 hrs after any type of cardiac injury (acute MI), peaks at 12hrs
- Measure AGAIN 3-6HRS later
What does the level of infarct size indicate?
Indicator of prognosis; higher the elevation = poorer prognosis
Which conditions elevate troponin?
- Cardiac trauma, CHF, HTN, PE, myocarditis, critical illness (spesis)
- Chronic renal failure - can determine by looking at steady rise and fall in elevation
Three types of Troponin
Troponin I, T, C
Which troponin enzyme(s) is/are ONLY found in CARDIAC MM?
I & T
Troponin T
How long does it stay elevated?
- Remains elevated for 10-14d post MI
- Less sensitive and specific than Troponin I
Troponin I
How long does it stay elevated?
- Remains elevated for 7-10d post MI
- More sensitive and specific for MI 8hrs after symptom onset
HEART Score ranges
Low risk
Mod risk
High Risk
What composes of the HEART score?
0-3: Low risk
4-6: Mod risk
7-10: High risk
History, EKG, Age, Risk factors, Troponin
What is the troponin level after re-infarction compared to initial infarction? When is it best to measure?
Troponin level not as helpful in persistent elevation post-MI (not same response); Troponin level beneficial in LATE presentation of MI
CK-MB
Found in? Elevated in?
Found in heart and skeletal MM and brain
Elevated w/MM or nerve cell injury
CK-MB
Timing of increase w/CP
Compared to troponin
Increased w/in 3-12hrs of onset of CP, peaks w/in 24hrs and returns to baseline after 48-72 hrs
- Good for detecting in re-infarction
TROPONIN PREFERRED OVER CK-MB
Cardiac Biomarker Timing GRAPH
STEMI
What? Where do you send a pt w/this?
ST elevation in EKG
Send them immediately to Cath lab
Cardiac Catheterization
If you visualize coronary artery blockage…
- Measures pressure in heart chambers, blood flow to coronary arteries, and valve dysfunction
- PCI = percutaneous coronary intervention
- Coronary angioplasty with/without stenting
- ONLY IF there’s an occluded artery
Lipid labs (list)
Lipid panel (list)
- Total cholesterol: HDL + LDL + vLDL (w/TGs)
- Lipid panel
- Total cholesterol
- HDL,
- LDL (calculated)
- TGs
- vLDL (calculated)
- Total cholesterol - HDL = non-HDL cholesterol
How are TGs affected by non-fasting?
Are the other Lipid labs affected by non-fasting?
Falsely elevated if NON-FASTING
NOPE
Non-fasting lipid labs vs. Fasting labs indications
- Non-fasting
- Acceptable for baseline screening
- Fasting
- Recommended for high risk, FH, statin therapy (maintenance), hyperTG
- 9-12h pre-test - overnight fast
HDL
- High density lipoprotein
- Binds w/excess cholesterol released by cells, brings them back to liver to be expelled
- “GOOD CHOLESTEROL” - helps get rid of bad cholesterol
LDL
- Low density lipoprotein
- Major carrier of excess cholesterol by cells
- Targets: peripheral tissues, excess burrows into arterial walls
- “BAD CHOLESTEROL”
LDL vs. LDLc
How is it calculated? When is it not valid?
- Direct (LDLc)
- Indirect (LDL)
- Calculated by Friedewalde equation
- Not valid if TGs > 400
- Tends to underestimate LDL
- What treatment guidelines are based on
- Calculated by Friedewalde equation
VLDL
- Very low density lipoprotein
- Carries mainly TGs
- Difficult to measure, calculated from TG levels
Triglycerides (TGs)
- Fatty acid chains
- Transported to tissues for energy
- Unused calories converted into TGs for storage in fat cells
- When energy released, transport proteins → cholesterol rich particles
- ⇡LDL ⇣HDL
- MOST SENSITIVE TO FASTING
Lipid screening in children/Adolescents
Risk is low in age group d/t age
BNP
Secreted from? When is it elevated? When is it decreased?
- B-Type natriuretic peptide
- Secreted from ventricles of heart in response to changes in pressure that occur with HF
- Elevated
- HF worsens
- High Cr skews it high
- Decreased
- HF improves
- Obesity skews it low
What does BNP help distinguish?
Distinguishes between lungs and heart for SOB
BNP algorithm for HF
NP = BNP
D-dimer
What is the lab? Indications for elevated levels?
- One of degradation products released upon clot breakdown
- Useful in evaluation of those with low to moderate risk
- ELEVATED levels → recent/ongoing coagulation + fibrinolysis (fibrin breakdown needed for clotting cascade)
D-dimer specificity and sensitivity level
- HIGHLY sensitive
- POOR specificity - elevated levels can be found in different conditions
- Pregnancy, renal failure malignancy, recent trauma, sepsis
Calculating risk for DVT
Calculating risk for PE
