Lab Med Flashcards
(54 cards)
Acute MI
imbalance b/w myocardial O2 supply (ischemia) and demand, resulting in injury to and the eventual death of myocytes
myocardial necrosis is most often associated with what?
- a thrombotic occlusion superimposed on coronary atherosclerosis
- the process of plaque rupture and thrombosis is one of the ways in which coronary atherosclerosis progresses
STEMI
-total occlusion of coronary blood flow = ST elevation
NSTEMI
partial occlusion of coronary blood flow = no ST elevation (could show ischemia as ST depression)
What does the absence of blood flow lead to?
- cardias muscle tissue death
- spilling cardiac biomarkers into the circulatory system
How often is the initial EKG diagnostic for AMI?
-about 30% of patients
When is troponin testing most useful?
when patients are having nondiagnostic EKG tracings
Troponin (cTnI or cTnT)
cardiac regulatory proteins specific to the myocardium that control the Ca++-mediated interaction b/w action and myosin
Troponin is the perferred test for the diagnosis of what?
ACS
troponin establishes the diagnosis of what?
irreversible myocardial necrosis, even when EKG changes are non diagnostic
What is important to know about an elevated troponin?
several distinct pathologies may cause it to be elevated, not all of them involve myocyte necrosis
How is NSTEMI strictly defined in terms of lab values?
-a rise and fall in serum biomarkers (usually troponin) exceeding the 99th percentile of a normal reference population
Time it takes for troponin levels to rise
- 3-6 hrs after onset of ischemic symptoms
- can be delayed from 8-12 hrs
Why is it important to know that troponin levels could be delayed in rising?
need to get serial troponin levels
Why is troponin most useful in NSTEMI
CK-MB and myoglobin are not useful in the diagnosis of ACS w/ mild ischemia w/o necrosis
CK-MB is more relevant to use with what condition?
STEMI
CK-MB levels time to rise
-3-4 hrs after onset of myocardial injury
myoglobin
- early marker for myocardial necrosis
- increases 2 hrs after onset of necrosis
What is the recommendation for when a pt has negative biomarkers w/i 6 hrs of onset of sx?
remeasure 8-12 hrs after onset
What other reasons could CK-MB be elevated?
- MANY (not listing all from lecture)
- necrosis or inflammation of cardiac muscle
- necrosis, inflammation or acute atrophy of striated muscle
- endocrine disorders
- some infections
explain why CK-MB detects muscle problems
-CK (creatine kinase) is an enzyme that controls energy flow within muscle cells
in addition to everything listed that can cause CK-MB to increase, what can cause CK to increase?
she emphasized rhabdomyolysis but there are many more
additional sxs of CHF
- 2-3+ bipedal edema
- b/l diffuse course rales on ausculation
BNP (brain natriuretic peptide)
-a hormone secreted by myocytes in the left ventricle in response to pressure overload/myocyte stretch
