Cardiac Enzymes Flashcards
Cardiac Enzymes
(List 3, 1 c 2 categories)
- Creatine Kinase (CK)
- Total
- CK-MB
- Troponin T
- Troponin I
MI Enzymatic Changes by Day
Creatine Kinase Indications
(2)
- Support MI dx
- Indicate neurologic or skeletal muscle disease
CK Locations
(3)
- Cardiac muscle
- Skeletal muscle
- Brain
CK Response to Cellular Injury
- Rise: within 6 hrs of cell injury
- Peak: 18 hrs
- Return to baseline: 2-3 days
CK Interpretation
Testing total CK will not reveal which structure is injured (heart, brain, skeletal musc). In the presence of elevated total CK, isoenzyme electrophoresis helps stratify the actual injury.
CK Isoenzymes:
- CKBB (CK1)
- CKMB (CK2) - cardiac
- CKMM (CK3)
CKBB
(Location, 4 Differentials)
Location:
- Brain
- Lung
Differentials:
- CNS disease
- Stroke
- Brain injury
- Cancer
- SAH
- Seizure
- Shock
- Pulmonary infarction
- Adenocarcinoma of lung
- Electroconvulsive therapy (ECT)
CKMB
(Location, 6 Differentials)
Location:
- Myocardial cells
- Skeletal muscles (in small amounts)
Differentials:
- MI
- Ventricular arrhytmia
- Cardiac ischemia
- Myocarditis
- Cardiac surgery
- Cardiac defibrillation
Note: Since it is present in skeletal muscle too it cannot be used alone to dx MI
CKMB Elevation Trend
Rise: 3-5 hours post MI start
Peak: 12-24 hours post MI start
Baseline: 12-48 hours after MI start
*Note: this spike is fairly congruous c troponin but will decline much more rapidly *
CKMB MI Clinical Priorities
(2)
Quantify the following:
- Degree of MI
- Time of MI onset
MI Cardiac Enzyme Procedure
- Order EKG, CKMB, Troponin
- If normal or nonspecific…place pt in observation area for a period of time (6-8hrs) if the pt is stable
- Repeat EKG, CKMB, Troponin
- If normal or nonspecific again, repeat rest period
- Repeat EKG, CKMB, Troponin
- If normal again, send the pt for further workup (usually as out pt but c cardiology consult). Workup usually starts c a stress test
CK MM
(Location, 3 Characteristics, 10 Differentials)
Location: Skeletal muscle
Characteristics:
- Varies according to muscle mass
- Makes up majority of total CK
- Always elevates c CKMB
Differentials:
- Myopathies
- Vigorous exercise
- Multiple intramuscular injections
- Electroconvulsive therapy
- Cardioversion
- Recent surgery
- Crush injuries
- Muscular dystrophy
- Heavy exercise
- Frequenty iron supplimentations (ex - MS)
Troponin
(list 2 types)
- Cardiac troponin T
- Cardiac Troponin I
Troponin Indications
(2)
- Specific indicator for cardiac muscle injury (R/I or R/O MI) for pts presenting c chest pain
- Predict clinical outcome of MI pt due to the intensity of elevation
Troponin Test Explaination
(2 points)
- Endogenous troponin: proteins in skeletal and cardiac muscle that regulate calcium-dependent interaction of myosin c actin for muscle contraction
- Cardiac troponins separate from muscle troponin by two methods:
- Monoclonal antibodies
- Enzyme-linked immunosorbant assay (ELISA)
Specificity, Troponins
(3 points)
- Cardiac troponins will always be normal in noncardiac disease
- Cardiac troponins will become elevated sooner and remain elevated longer than CKMB
- Cardiac troponins are more sensitive to cardiac muscle injury than CKMB
Know these
Troponin Elevation Trend
Rise: early as 3 hours after myocardial injury
Peak: ~ 24 hours after injury
Normal:
- Troponin I, 7-10 days
- Troponin T, 10-14 days
Limitation, Troponin
Due to longer period of troponin elevation, they are not useful in dx recurrent MI as the value may be elevated from first cardiac event. That said, if you are monitoring a pt and see a decrease trend followed by an increase trend you may have be able to use this tool.
Differentials, Troponin
(
- Stable vs noncardiac CP (c EKG and CKMB)
- Estimate MI size
- Elevated troponin @ 4 weeks post MI are inversely proportional to left ventricular ejection fraction
- Poor prognosis
- Unstable angina
- Detect reperfusion asst c coronary recanalization
- ”Washout” - second peak of cardiac troponin indicates that blood reperfused area and is washing the walls where troponin was stuck due to lack of bloodflow Estimate MI size
- Detect peri-operative MI
- Good in heart surgery to differentiate injury of thoracic muscles and cardiac muscles (CKMB cannot do this)
False Elevations, Troponin
(1)
Dialysis pt (which is tricky, because he/she likely has a heart condition if on dialysis)
