MCQs on Cardiac Profile Test / Cardiac Markers

Which cardiac biomarker is the gold standard for diagnosing acute myocardial infarction?
• A) Myoglobin
• B) Troponin I
• C) CK-MB
• D) AST
Answer: B) Troponin I
Explanation: Cardiac troponins (I and T) are the most sensitive and specific biomarkers for myocardial injury. Troponin I rises within 3–6 hours of infarction, peaks at 14–20 hours, and remains elevated for 7–10 days. They are preferred over CK-MB due to higher specificity for cardiac tissue.

Which biomarker rises earliest after myocardial infarction?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin is a low-molecular-weight protein released rapidly from damaged cardiac and skeletal muscle. It rises within 1–3 hours post-infarction, peaks at 6–7 hours, and returns to baseline within 24 hours. However, it is less specific than troponins or CK-MB for cardiac injury.

Which cardiac enzyme is most useful for detecting reinfarction?
• A) CK-MB
• B) Troponin I
• C) AST
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB rises and returns to baseline relatively quickly (48–72 hours), making it useful for detecting reinfarction after an initial myocardial infarction. Troponins remain elevated for several days, so they are less practical for identifying a second acute event within a short interval.

Which isoenzyme is primarily measured in CK-MB tests?
• A) MM
• B) MB
• C) BB
• D) CC
Answer: B) MB
Explanation: CK has three isoenzymes: CK-MM (skeletal muscle), CK-MB (cardiac muscle), and CK-BB (brain). CK-MB is cardiac-specific and its measurement is crucial for diagnosing myocardial infarction. MM is mainly skeletal, and BB is found in the brain and smooth muscle.

Which test is useful for assessing cardiac injury in the first 2–3 hours of chest pain?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin rises very quickly after myocardial injury, often within 1–3 hours, making it a useful early marker. However, due to its lack of cardiac specificity, it is often used in combination with troponins for accurate diagnosis.

Which cardiac marker remains elevated the longest after myocardial infarction?
• A) CK-MB
• B) Troponin I
• C) AST
• D) Myoglobin
Answer: B) Troponin I
Explanation: Troponin I remains elevated for 7–10 days post-myocardial infarction, allowing late diagnosis of cardiac injury. CK-MB normalizes within 48–72 hours, and myoglobin returns to baseline in 24 hours, limiting their utility for late detection.

Which cardiac enzyme shows a "double peak" pattern in myocardial infarction?
• A) AST
• B) LDH
• C) CK-MB
• D) ALT
Answer: B) LDH
Explanation: LDH, particularly LDH1 isoenzyme, shows a double-peak phenomenon after myocardial infarction. LDH1 is elevated in the first peak, declines, and may show a secondary peak due to continued cardiac injury. CK-MB peaks only once.

Which biomarker is most sensitive for early myocardial injury detection?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) AST
Answer: C) Myoglobin
Explanation: Myoglobin is the most sensitive early marker for myocardial injury due to its rapid release from damaged cardiac tissue. Despite high sensitivity, its specificity is low because skeletal muscle injury can also elevate levels.

Which combination of markers improves diagnostic accuracy for acute myocardial infarction?
• A) CK-MB + AST
• B) Troponin + Myoglobin
• C) LDH + ALT
• D) Myoglobin + LDH
Answer: B) Troponin + Myoglobin
Explanation: Combining troponin (high specificity) and myoglobin (early rise) allows both early detection and confirmation of myocardial injury, improving diagnostic accuracy, especially within the first 6 hours of chest pain.

Which isoenzyme of LDH is most indicative of myocardial infarction?
• A) LDH1
• B) LDH2
• C) LDH3
• D) LDH4
Answer: A) LDH1
Explanation: LDH1 is predominantly present in cardiac muscle and red blood cells. Elevation of LDH1 above LDH2 (flipped pattern) is indicative of myocardial infarction. Other LDH isoenzymes are less specific and may rise in liver or kidney damage.

Which biomarker is preferred in patients with renal failure?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: Troponin T can be elevated in chronic renal failure without acute myocardial injury. CK-MB is less affected by renal dysfunction, making it more reliable for detecting myocardial infarction in such patients.

Which biomarker correlates with infarct size and prognosis?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I levels correlate directly with myocardial necrosis extent. Higher concentrations indicate larger infarcts and worse prognosis, guiding clinical decisions regarding intensive management and risk stratification.

Which marker is least specific for cardiac tissue?
• A) CK-MB
• B) Troponin T
• C) AST
• D) Troponin I
Answer: C) AST
Explanation: AST is present in multiple tissues, including liver, skeletal muscle, and heart. Elevation is not specific to cardiac injury, whereas CK-MB and troponins are predominantly cardiac-specific.

Which marker is useful for detecting myocardial injury in skeletal muscle damage?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: A) Troponin I
Explanation: Troponin I is highly specific for cardiac muscle and is not influenced by skeletal muscle injury, unlike CK-MB and myoglobin, which can rise in skeletal muscle damage, potentially causing false positives.

Which enzyme is measured using the immunoinhibition method for cardiac testing?
• A) CK-MB
• B) CK-MM
• C) LDH
• D) AST
Answer: A) CK-MB
Explanation: The immunoinhibition method selectively measures CK-MB by inhibiting CK-MM activity. This increases specificity for cardiac injury detection and reduces interference from skeletal muscle CK-MM isoenzyme.

Which troponin is not influenced by skeletal muscle injury?
• A) Troponin C
• B) Troponin I
• C) Troponin T
• D) CK-MB
Answer: B) Troponin I
Explanation: Cardiac-specific Troponin I is not expressed in skeletal muscle, ensuring high specificity for myocardial injury. Troponin T is expressed at low levels in diseased skeletal muscle, potentially affecting specificity.

Which cardiac biomarker is most useful in reinfarction after 48 hours?
• A) CK-MB
• B) Troponin I
• C) LDH
• D) Myoglobin
Answer: A) CK-MB
Explanation: CK-MB rises and falls rapidly (returns to baseline in 48–72 hours), allowing detection of reinfarction after an initial myocardial infarction. Troponins remain elevated for 7–10 days, masking new injury.

Which cardiac enzyme is part of the standard cardiac panel along with troponin?
• A) CK-MB
• B) AST
• C) ALT
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB is included in standard cardiac panels due to its rapid rise and cardiac specificity. Together with troponins, it helps in early detection, reinfarction diagnosis, and prognosis of acute coronary events.

Which cardiac marker is elevated in unstable angina?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: A) Troponin I
Explanation: Troponin I may be mildly elevated in unstable angina due to minor myocardial necrosis, whereas CK-MB often remains normal. Its high sensitivity allows early diagnosis and risk stratification in acute coronary syndromes without ST-elevation.

Which biomarker helps in assessing myocardial injury after cardiac surgery?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I is highly specific for cardiac muscle and remains elevated for several days, making it useful to assess myocardial injury post-cardiac surgery. CK-MB may also rise but is less reliable due to perioperative skeletal muscle release.

Which marker is a heme protein released from damaged muscle?
• A) Troponin I
• B) Myoglobin
• C) CK-MB
• D) LDH
Answer: B) Myoglobin
Explanation: Myoglobin is a small heme protein released from both cardiac and skeletal muscle upon injury. It rises within 1–3 hours, peaks at 6–7 hours, and returns to baseline in 24 hours. Its lack of cardiac specificity limits its use as a sole diagnostic marker.

Which cardiac biomarker is recommended for risk stratification in NSTEMI?
• A) CK-MB
• B) Troponin I
• C) LDH
• D) AST
Answer: B) Troponin I
Explanation: Troponin I elevation in NSTEMI reflects myocardial necrosis and correlates with prognosis. Higher troponin levels indicate greater risk of complications, guiding aggressive management strategies and early intervention.

Which biomarker can indicate myocardial injury in chronic renal failure?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) LDH
Answer: B) Troponin T
Explanation: Troponin T can be chronically elevated in patients with renal failure without acute myocardial injury. CK-MB is less influenced by renal dysfunction. Clinical correlation is required to interpret troponin T accurately in these patients.

Which enzyme is elevated in pericarditis along with myocardial injury?
• A) CK-MB
• B) AST
• C) Troponin I
• D) Myoglobin
Answer: C) Troponin I
Explanation: Troponin I may be mildly elevated in pericarditis due to minor myocardial involvement. CK-MB and myoglobin elevations are usually minimal. Troponins help differentiate pericarditis with myocardial injury from myocardial infarction.

Which LDH isoenzyme is predominantly found in the heart?
• A) LDH1
• B) LDH2
• C) LDH3
• D) LDH4
Answer: A) LDH1
Explanation: LDH1 is present mainly in cardiac muscle and red blood cells. An LDH1/LDH2 “flip” indicates myocardial infarction. Other isoenzymes (LDH2–LDH5) are more abundant in liver, kidney, and skeletal muscle, reducing cardiac specificity.

Which test is useful for detecting reinfarction within 48 hours?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB returns to baseline within 48–72 hours, allowing detection of reinfarction shortly after an initial event. Troponin levels remain elevated for several days, limiting their use for detecting early reinfarction.

Which biomarker is affected by skeletal muscle injury, causing false positives?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin is released from both skeletal and cardiac muscle. Skeletal muscle injury can elevate levels, causing false-positive results. Troponins remain specific to cardiac tissue, and CK-MB can also be influenced to a lesser extent.

Which cardiac biomarker correlates with infarct size and prognosis?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I levels are directly proportional to myocardial necrosis extent. Higher levels indicate larger infarcts, worse prognosis, and increased risk of complications. This helps clinicians plan intensive management strategies.

Which test differentiates cardiac vs. skeletal muscle injury?
• A) CK-MB
• B) Myoglobin
• C) AST
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB is predominantly cardiac-specific. CK-MM predominates in skeletal muscle. Measuring CK-MB, especially by immunoinhibition methods, helps distinguish myocardial injury from skeletal muscle damage.

Which biomarker is released in both myocardial infarction and skeletal muscle injury?
• A) Troponin I
• B) Myoglobin
• C) CK-MB
• D) Troponin T
Answer: B) Myoglobin
Explanation: Myoglobin is released from both skeletal and cardiac muscle upon injury, making it sensitive but non-specific for myocardial infarction. It is useful for early detection but requires confirmation with troponins for cardiac specificity.

Which troponin is used as the primary biomarker in acute coronary syndrome?
• A) Troponin C
• B) Troponin I
• C) Troponin T
• D) CK-MB
Answer: B) Troponin I
Explanation: Troponin I is highly specific for cardiac injury and is the preferred biomarker in diagnosing acute coronary syndromes, including NSTEMI and STEMI. It remains elevated for 7–10 days, allowing both early and late detection.

Which cardiac marker is measured using immunoassay techniques?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I is measured by immunoassay due to its high specificity and sensitivity. These assays allow early detection of myocardial injury, quantify infarct size, and guide clinical management in acute coronary syndromes.

Which marker peaks earliest after myocardial infarction?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin rises within 1–3 hours after myocardial injury, peaking at 6–7 hours. CK-MB and troponins rise later. Despite early rise, myoglobin lacks specificity and is best used with troponin for accurate diagnosis.

Which enzyme returns to normal within 2–3 days post-infarction?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB peaks 18–24 hours after myocardial infarction and returns to baseline in 48–72 hours. This property is useful in detecting reinfarction and monitoring post-infarction recovery.

Which biomarker is preferred for detecting minor myocardial injury?
• A) CK-MB
• B) Troponin I
• C) LDH
• D) AST
Answer: B) Troponin I
Explanation: Troponin I is highly sensitive and specific for even minor myocardial injury. Small elevations can indicate microinfarctions or ongoing ischemia, providing important diagnostic and prognostic information in acute coronary syndromes.

Which marker is useful for early diagnosis of acute myocardial infarction in the emergency setting?
• A) Myoglobin
• B) CK-MB
• C) Troponin I
• D) LDH
Answer: A) Myoglobin
Explanation: Myoglobin rises quickly after myocardial injury, making it valuable in emergency settings for early diagnosis. Due to low specificity, positive results should be confirmed with troponins for cardiac-specific diagnosis.

Which enzyme is measured in the immunoinhibition assay for cardiac specificity?
• A) CK-MB
• B) CK-MM
• C) LDH
• D) AST
Answer: A) CK-MB
Explanation: Immunoinhibition assays inhibit CK-MM activity, allowing selective measurement of CK-MB. This enhances specificity for detecting myocardial injury and reduces interference from skeletal muscle CK isoenzymes.

Which biomarker is recommended for late diagnosis (after 5 days) of myocardial infarction?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I remains elevated for 7–10 days post-infarction, making it ideal for late diagnosis. CK-MB and myoglobin normalize earlier, limiting their usefulness in delayed presentations.

Which biomarker shows the LDH “flip” pattern in myocardial infarction?
• A) LDH1 and LDH2
• B) CK-MB and CK-MM
• C) Troponin I and T
• D) AST and ALT
Answer: A) LDH1 and LDH2
Explanation: In myocardial infarction, LDH1 becomes higher than LDH2, creating an LDH “flip,” which is diagnostic. This pattern occurs due to selective release of LDH1 from cardiac tissue, while other isoenzymes remain normal or less elevated.

Which biomarker is elevated in both acute myocardial infarction and skeletal muscle trauma?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin is released from both cardiac and skeletal muscle. It rises quickly within 1–3 hours, peaks at 6–7 hours, and returns to baseline in 24 hours. Due to low specificity, results must be confirmed with troponins for accurate cardiac diagnosis.

Which biomarker is most useful for diagnosing reinfarction after initial MI?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: B) CK-MB
Explanation: CK-MB returns to baseline within 48–72 hours, allowing detection of reinfarction shortly after an initial myocardial infarction. Troponins remain elevated for 7–10 days, making them less reliable for identifying new injury within this time frame.

Which marker is most specific for cardiac muscle injury?
• A) AST
• B) CK-MB
• C) Troponin I
• D) Myoglobin
Answer: C) Troponin I
Explanation: Troponin I is highly specific to cardiac muscle and is not expressed in skeletal muscle, unlike CK-MB or myoglobin. It is the gold standard for diagnosing myocardial infarction and assessing myocardial injury severity.

Which biomarker is recommended for early diagnosis in emergency chest pain?
• A) CK-MB
• B) Myoglobin
• C) Troponin I
• D) LDH
Answer: B) Myoglobin
Explanation: Myoglobin rises rapidly after myocardial injury (1–3 hours) and peaks at 6–7 hours, making it useful for early diagnosis. Due to low specificity, it should be confirmed with troponins.

Which LDH isoenzyme shows a “flip” pattern in myocardial infarction?
• A) LDH1 and LDH2
• B) LDH2 and LDH3
• C) LDH3 and LDH4
• D) LDH4 and LDH5
Answer: A) LDH1 and LDH2
Explanation: In myocardial infarction, LDH1 becomes higher than LDH2, creating a characteristic “flip” pattern. This is due to selective release of LDH1 from damaged cardiac tissue, providing a diagnostic clue for myocardial injury.

Which cardiac marker is least influenced by renal failure?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB is less affected by renal dysfunction, making it reliable for detecting myocardial infarction in patients with chronic kidney disease. Troponin T may be chronically elevated in renal failure, leading to potential false positives.

Which biomarker is used to assess myocardial injury after percutaneous coronary intervention (PCI)?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I is sensitive to minor myocardial injury, making it ideal for detecting cardiac damage following PCI. CK-MB may also rise but is less sensitive in detecting subtle myocardial injury.

Which marker remains elevated for up to 10 days after MI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I rises within 3–6 hours, peaks at 14–20 hours, and remains elevated for 7–10 days. This prolonged elevation allows detection of myocardial infarction even if presentation is delayed.

Which biomarker is elevated in unstable angina?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: A) Troponin I
Explanation: Troponin I may be mildly elevated in unstable angina due to minor myocardial necrosis. CK-MB and myoglobin are often normal. Troponin I helps in risk stratification and early intervention in acute coronary syndromes.

Which enzyme is measured using immunoinhibition to enhance cardiac specificity?
• A) CK-MB
• B) CK-MM
• C) LDH
• D) AST
Answer: A) CK-MB
Explanation: Immunoinhibition assays inhibit CK-MM activity, allowing selective measurement of CK-MB. This improves specificity for myocardial injury and reduces interference from skeletal muscle CK isoenzymes.

Which cardiac marker helps in prognosis and risk stratification?
• A) Myoglobin
• B) CK-MB
• C) Troponin I
• D) LDH
Answer: C) Troponin I
Explanation: Troponin I correlates with infarct size and severity, aiding prognosis and risk stratification in acute coronary syndromes. Higher levels indicate more extensive myocardial injury and worse clinical outcomes.

Which marker is useful for detecting reinfarction after 48 hours?
• A) CK-MB
• B) Troponin I
• C) LDH
• D) AST
Answer: A) CK-MB
Explanation: CK-MB returns to baseline in 48–72 hours, making it useful for detecting reinfarction shortly after an initial myocardial infarction. Troponin remains elevated for several days, limiting its utility for early reinfarction detection.

Which biomarker rises within 1–3 hours after MI onset?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin is released rapidly from damaged cardiac and skeletal muscle. Its early rise allows prompt detection of myocardial injury, but confirmation with cardiac-specific markers like troponin is necessary due to low specificity.

Which marker is highly specific for myocardial necrosis and not influenced by skeletal muscle injury?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I is expressed only in cardiac muscle, providing high specificity for myocardial injury. Skeletal muscle injury does not affect its levels, unlike CK-MB or myoglobin.

Which LDH isoenzyme is most indicative of cardiac damage?
• A) LDH1
• B) LDH2
• C) LDH3
• D) LDH5
Answer: A) LDH1
Explanation: LDH1 predominates in cardiac muscle. Elevation above LDH2 (flip pattern) indicates myocardial infarction. Other isoenzymes are less cardiac-specific, often elevated in liver, kidney, or skeletal muscle injury.

Which biomarker is preferred in early detection of reinfarction?
• A) CK-MB
• B) Troponin I
• C) LDH
• D) AST
Answer: A) CK-MB
Explanation: Due to its rapid rise and return to baseline within 48–72 hours, CK-MB is ideal for early detection of reinfarction, whereas troponins remain elevated for several days.

Which biomarker is useful for early chest pain evaluation in ER?
• A) Myoglobin
• B) CK-MB
• C) Troponin I
• D) LDH
Answer: A) Myoglobin
Explanation: Myoglobin rises within 1–3 hours of myocardial injury, allowing rapid assessment in emergency settings. Confirmation with troponins is needed due to low specificity.

Which marker peaks around 18–24 hours after MI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB peaks 18–24 hours after myocardial infarction, returning to baseline in 48–72 hours. This timeline aids diagnosis and reinfarction detection.

Which biomarker remains elevated longest after myocardial infarction?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I remains elevated 7–10 days post-MI, allowing late diagnosis. CK-MB and myoglobin normalize sooner, limiting their utility in delayed presentations.

Which cardiac marker is most reliable for minor myocardial injury detection?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I is highly sensitive for minor myocardial injury, enabling detection of microinfarctions or ongoing ischemia, assisting early intervention and prognosis assessment.

Which biomarker is preferred for detecting myocardial injury in renal failure?
• A) CK-MB
• B) Troponin T
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB is less affected by renal dysfunction, making it reliable for myocardial injury detection in chronic kidney disease. Troponin T may be elevated without acute myocardial damage, potentially leading to false positives.

Which biomarker is most useful for detecting reinfarction after initial MI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: A) CK-MB
Explanation: CK-MB returns to baseline within 48–72 hours, allowing reinfarction detection. Troponin I remains elevated for 7–10 days, making it less useful for identifying new infarction shortly after the first.

Which cardiac marker rises within 3–6 hours and peaks at 14–20 hours post-MI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I rises 3–6 hours post-infarction, peaks at 14–20 hours, and stays elevated 7–10 days. This timeline makes it ideal for both early and late detection of myocardial injury.

Which biomarker is highly specific for cardiac muscle and unaffected by skeletal muscle injury?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I is only expressed in cardiac tissue, unaffected by skeletal muscle injury. It is the gold standard for diagnosing myocardial infarction and assessing even minor myocardial necrosis.

Which biomarker is released earliest after myocardial infarction?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin rises within 1–3 hours, peaks at 6–7 hours, and returns to baseline within 24 hours. Its early appearance makes it useful for prompt detection, though low specificity necessitates confirmation with troponins.

Which LDH isoenzyme predominates in cardiac muscle?
• A) LDH1
• B) LDH2
• C) LDH3
• D) LDH5
Answer: A) LDH1
Explanation: LDH1 is concentrated in cardiac muscle and red blood cells. In myocardial infarction, LDH1 exceeds LDH2, creating a characteristic “flip” pattern indicative of cardiac injury.

Which marker is used to assess myocardial injury after cardiac surgery?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I detects minor myocardial injury after cardiac surgery due to its high sensitivity and specificity, whereas CK-MB can be elevated by skeletal muscle trauma.

Which marker is useful for early emergency diagnosis of MI within the first 2–3 hours?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin rises rapidly, within 1–3 hours, making it useful for early diagnosis. Due to low specificity, confirmation with troponin is necessary to ensure cardiac origin.

Which marker is most specific for detecting myocardial necrosis?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I is cardiac-specific and unaffected by skeletal muscle injury. It is highly sensitive and specific, allowing detection of even minor myocardial necrosis and guiding prognosis.

Which biomarker returns to normal within 24 hours post-MI?
• A) CK-MB
• B) Myoglobin
• C) Troponin I
• D) LDH
Answer: B) Myoglobin
Explanation: Myoglobin peaks quickly and returns to baseline within 24 hours. Its early rise is useful for prompt detection, but low specificity necessitates confirmatory tests such as troponin I.

Which marker helps in risk stratification in acute coronary syndrome?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I levels correlate with infarct size and clinical severity, assisting in risk stratification and guiding therapeutic decisions in acute coronary syndromes.

Which cardiac marker is elevated in unstable angina?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: A) Troponin I
Explanation: Mild elevation of troponin I can occur in unstable angina due to minor myocardial injury. CK-MB often remains normal, making troponin a more sensitive marker in these cases.

Which assay method is used for selective CK-MB measurement?
• A) Immunoinhibition
• B) Enzyme colorimetric
• C) ELISA
• D) Spectrophotometry
Answer: A) Immunoinhibition
Explanation: Immunoinhibition selectively inhibits CK-MM activity, allowing accurate measurement of CK-MB and improving specificity for cardiac muscle injury.

Which biomarker is ideal for late diagnosis of MI after 5 days?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I remains elevated for 7–10 days post-MI, enabling detection of myocardial infarction in patients presenting late. CK-MB and myoglobin normalize sooner, limiting their utility.

Which marker is released from both cardiac and skeletal muscle?
• A) Troponin I
• B) CK-MB
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin is released from cardiac and skeletal muscle. Its rapid rise aids early detection, but low specificity necessitates confirmation with cardiac-specific markers.

Which marker is least affected by skeletal muscle injury?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I is highly specific to cardiac tissue and is unaffected by skeletal muscle damage, providing reliable detection of myocardial injury.

Which biomarker is elevated earliest after myocardial infarction?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: C) Myoglobin
Explanation: Myoglobin rises within 1–3 hours post-infarction, allowing early detection. Its specificity is low, so confirmation with troponins is essential.

Which LDH isoenzyme predominates in cardiac tissue?
• A) LDH1
• B) LDH2
• C) LDH3
• D) LDH5
Answer: A) LDH1
Explanation: LDH1 is abundant in cardiac muscle. Elevation of LDH1 above LDH2 indicates myocardial infarction, known as the LDH “flip,” a classical diagnostic marker.

Which marker is used to assess myocardial injury post-PCI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) AST
Answer: B) Troponin I
Explanation: Troponin I detects minor myocardial injury after percutaneous coronary intervention, providing sensitive and specific evaluation for procedure-related cardiac damage.

Which marker remains elevated for up to 10 days post-MI?
• A) CK-MB
• B) Troponin I
• C) Myoglobin
• D) LDH
Answer: B) Troponin I
Explanation: Troponin I remains elevated 7–10 days, allowing diagnosis in late-presenting patients. CK-MB and myoglobin normalize earlier, making them less useful in delayed cases.