27 - Ischemic Heart Disease and Lab Diagnosis Flashcards
Why are cardiac enzymes relevant to diagnosing ischemic heart disease?
Serum biomarkers will be present when you draw blood from patients with myocardial injury
What does it mean when cardiac enzymes (serum biomarkers) are present?
It reflects myocardial necrosis or cell death
Describe why cardiac enzymes would be found in the serum during ischemia/infarction
- Ischemia and infarction lead to an imbalance between supply and demand of oxygen
- Cardiac injury is due to the disruption of myocyte membrane and intra-cellular constituents are lost into the extracellular space and blood
What two enzymes are serum biomarkers of ischemia/infarction?
- Troponin
- Creatinine kinase
Which one is ONLY found in cardiac muscle cells?
Troponin
Why are troponin levels so clinically relevant?
It is the most SENSITIVE and SPECIFIC indication of cardiac injury
Why are CKMB levels somewhat helpful, but not as important as troponin levels?
- There is a higher percentage of creatinine kinase MB in the heart compared to skeletal muscle, but it still exists in skeletal muscle
- If you have a patient in a car accident with skeletal muscle injury, they will also have elevated CKMB levels
How soon after an MI will troponin levels begin to rise?
2-3 hours
Elevated levels persist for 10-14 days
How soon after an MI will CKMB levels begin to rise?
4-6 hours after MI, but it will not be elevated in all patients until 12 hours
Levels return to base line 36-48 hours post-MI
What is CKMB most helpful in diagnosing now?
RE-infarction because the levels will go down after 36-48 hours, so if you suspect a re-infarction four days later, you will be able to tell based on whether or not CKMB levels are elevated
Why would you not want to send a patient with a suspected MI home right away, even if their troponin levels are not elevated?
Troponin levels may not rise for up to 6 hours after the onset of symptoms, the measurement should be repeated if the initial troponins are negative at 6 hours
What is the most important anti-ischemic therapy for an NSTEMI?
Beta blockers (IV or oral)
NSTEMI = non-ST elevation myocardial infarction
Need to treat with medication because you can’t use cath or thrombolytics
What effect do beta blockers have on patients who have suffered an MI?
- Decrease myocardial oxygen demand
- Lower HR and BP
- Decrease dysrhythmias
- Useful in hyperdynamic state
Overall, these will IMPROVE outcomes!!!
When would beta blockers be contraindicated?
- Hypotensive patients
- Bradycardic patients
- Patients in decompensated LV failure
What are thrombolytics?
A class of drugs which will break down clots in an attempt to reperfuse the tissue affected by an MI
