38 Questions
What is the primary function of cardiac biomarkers?
To detect acute myocardial infarction or minor myocardial injury
What is the main reason for the evolution of criteria for the definition of myocardial infarction?
Improvement in detection technologies, particularly biomarkers
What is the term for diseases that affect the circulatory system?
Cardiovascular disease
What is NOT a type of cardiovascular disease?
High blood sugar
According to the American College of Cardiology and European Society of Cardiology, what is the recommended biomarker for diagnosing acute myocardial infarction?
Troponin
What is the old criteria for diagnosing acute myocardial infarction, according to the World Health Organization (1979)?
Based on 2 out of 3 of WHO criteria, including symptoms of ischemia, ECG changes, and cardiac biomarker concentrations
What is the term for heart and blood vessel diseases?
Cardiovascular disease
What is NOT a type of cardiovascular disease mentioned in the content?
Diabetes
What is the main characteristic of the fourth group of patients who present to the emergency department?
They have clear ECG evidence of AMI
What is the ideal characteristic of a biomarker for detecting AMI?
Rapid release into blood following myocardial injury
What is the main difference between various biomarkers of myocardial injury?
All of the above
What is the function of the troponin complex in muscular contraction?
Regulation of interaction between actin and myosin filaments
Why is troponin C not a suitable cardiac-specific marker?
Its amino acid sequence is identical in skeletal and cardiac muscle
What is unique about troponin T and I?
They have amino acid sequences that differ between adult skeletal and cardiac muscle
What is the significance of the cardiac-specific forms of troponin T and I?
They are immunologically separable
What is a characteristic of an ideal biomarker for detecting AMI?
Blood levels correlate with extent of myocardial injury and prognosis
What is the molecular weight of Troponin T?
37 kDa
What is the nature of the protein of Troponin I?
Catalytic
What is the duration of elevation of Troponin T?
Upto 14 days
What is the likelihood of ischemic complications in patients with unstable angina who have normal CK-MB and increased TnI?
30%
What does an increase in plasma troponin concentration indicate?
Myocardial injury, but not necessarily MI
When does Troponin I appear in the blood after myocardial damage?
Within 3-12 hours
What is the cutoff for acute myocardial infarction on a Beckman Coulter DXi analyzer?
0.5 ng/mL
What is the pattern of release of Troponin I in Myocardial Infarction (MI)?
Biphasic
What does a normal TnI and elevated CK-MB usually indicate?
Skeletal muscle injury
Why is Troponin I beneficial in detecting infarctions in late presenting patients?
It is elevated for a longer time
What is a common non-ischemic cause of elevated plasma TnI concentration?
All of the above
What percentage of patients with unstable angina have elevated Troponin I?
30-40%
Why is Troponin I a better risk indicator in angina than CK-MB?
It is more specific to myocardial damage
What does two normal TnI levels indicate in a patient with unstable angina?
Dischargeable patient
What is a likely diagnosis for a patient with elevated TnI and normal CK-MB?
Unstable angina or late admission after an acute infarction
Based on the case study, has the 66-year-old man suffered a myocardial infarction?
Yes, likely
What does the patient's 2-year history of angina of effort suggest?
A high risk of acute myocardial infarction
Based on the elevated CK and CK-MB levels, what is the most likely diagnosis for the marathon runner?
Muscle damage due to intense physical activity
What is the primary concern for the 52-year-old man with severe chest pain?
Ruling out acute myocardial infarction
What is the significance of the CK-MB percentage in the marathon runner's laboratory results?
It is a specific indicator of cardiac muscle damage
What is the relevance of the patient's attendance at the chest pain clinic to the current diagnosis?
It indicates a history of cardiovascular disease
What is the purpose of requesting specific tests from the biochemistry laboratory for the 52-year-old man?
To rule out acute myocardial infarction
Study Notes
Cardiovascular Disease (CVD)
- CVD includes heart and blood vessel diseases that affect the circulatory system.
- Examples of CVD include:
- Coronary heart disease (heart attack)
- Cerebrovascular disease (stroke)
- High blood pressure
- Congestive heart failure
- Congenital cardiovascular defects
- Peripheral vascular disease
Cardiac Biomarkers
- A cardiac biomarker is a clinical laboratory test used to detect acute myocardial infarction (AMI) or minor myocardial injury.
- Cardiac biomarkers are most useful when patients have nondiagnostic ECG tracings.
Evolving Definitions of Myocardial Infarction (MI)
- The criteria for the definition of MI have evolved over the years, partly due to improvements in detection technologies, including biomarkers.
- The old diagnosis of AMI was based on 2 out of 3 of WHO criteria (1979), including:
- Symptoms of ischemia (prolonged chest pain)
- ECG changes
- Cardiac biomarker concentrations (enzymes)
- The new definition of AMI is based on documenting an increase in cardiac troponin or CK-MB mass in the context of myocardial ischemia.
Ideal Marker to Detect AMI
- An ideal marker should have:
- High concentration in myocardium
- Absence from non-myocardial tissues
- High sensitivity and specificity in circulation
- Rapid release into blood following myocardial injury
- Remain in blood for several days to allow detection
- Blood levels correlate with extent of myocardial injury and prognosis
- Rapid, simple, and automated commercial assays available
Troponins
- Troponins are regulatory proteins in striated muscle responsible for calcium-modulated interaction.
- There are cardiac-specific forms of troponin, including:
- Troponin T (TpnT)
- Troponin I (TpnI)
- Troponins T and I have different characteristics, including:
- Molecular weight (37 kDa vs 22.5 kDa)
- Nature of protein (structural vs catalytic)
- Kinetics of release (biphasic vs single peak)
- Duration of elevation (up to 14 days vs 5-7 days)
Troponin Release Kinetics
- Troponin release is biphasic, with:
- Detectable in blood 3-12 hours after MI
- Peak levels at 12-38 hours
- Remain elevated for 5-10 days
- TnI remains elevated longer than CK-MB due to ongoing release of the myofibril-bound fraction.
Clinical Applications of Troponins
- Elevated TnI is found in 30-40% of patients with unstable angina and is a better risk indicator than CK-MB.
- Serial monitoring of TnI over 8-12 hours is becoming common practice in many well-developed institutions.
- To rule out an acute myocardial infarction, many centers are ordering CK-MB and TnI on admission and again at either 8 or 12 hours.
- An increase in plasma troponin concentration is indicative of myocardial injury, but not synonymous with MI.
Non-Ischemic Causes of Elevated Troponin
- Congestive heart failure
- Hypertension
- Circulatory shock
- Pulmonary embolism
- Covid-19
- Mechanical injury
- Cardiac contusion
- Cardiotrophic viral infections
- Chemotherapy
- Renal failure
- GI bleed
This quiz covers cardiovascular disease, including heart and blood vessel diseases, and biomarkers. Topics include coronary heart disease, cerebrovascular disease, high blood pressure, and more.
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