Cardiac Flashcards
What is troponin?
Troponin I and T are components of the contractile apparatus of myocardial cells.
3 isoforms of Troponin I?
Slow twitch skeletal muscle
Fast twitch skeletal muscle
Cardiac
Difference between cardiac troponin and skeletal muscle forms?
31aa post-translational tail on N terminus of the mcule
Natural history of cTnI elevations post-MI
cTnI levels rise within hours, peaking at 12-16 hours and can remain elevated for 4-9 days postMI. Biomarker release is substantially dependent on blood flow resulting in significant variability in the time to peak value (velocity).
Why is serial monitoring of cTnI important?
Other causes of cTnI elevation do not exhibit the typical rise and fall in cTnI that MI does
Non-MI causes of cTnI increase?
Congestive heart failure, acute and chronic trauma, electrical cardioversion, hypertension, hypotension, arrhythmias, pulmonary embolism, severe astham, sepsis, critical illness, myocarditis, stroke, non-cardiac surgery, extreme exercise, drug toxicity, ESKD, rhabdomyolysis with cardiac injury
Preferred biomarkers for diagnosis of myocardial injury and infarction?
cTnI and cTnT
Which is more cardiac specific - cTnT or cTnI and why?
TnI. Injured skeletal muscle expresses proteins detected by cTnT assay.
Definition of myocardial injury? Acute vs chronic?
Blood levels of cTn increased above 99th percentile URL.
Acute injury evidenced by newly detected dynamic rising and/or falling pattern of cTn values above 99th percentile.
Chronic injury in the setting of persistently elevated cTn levels.
Definition of acute myocardial infarction?
Biochemical evidence of myocardial injury (rising/falling cTn with at least 1 value >99th percentile URL) caused by myocardial ischaemia (evidence includes symptoms, ECG changes, imaging evidence of new loss of viable myocardium/new regional wall motion abnormality, identification of coronary thrombus)
Mandatory imprecision for hsTn assays?
CV < or equal to 10% at 99th percentile URL
If cTn is not available, what is the best alternative?
CK-MB measured by mass assay, although this is less sensitie and less specific.
Define an increased CK-MB value
> 99th percentile URL (use sex specific CK-MB values
How are hs-cTn assays differentiated from contemporary or PCO cTn assays?
High-sensitivity cTn assays are ones with which >50% of healthy individuals will have a measurable cTn result above the assay’s LoD.
Post-analytical problems with contemporary cTn assays
Interpretation of results with multiple zeros and decimal points.
