Cardiac Markers and Enzymes — MCQs
Post-myocardial infarction on the 10th day, which of the following enzyme levels is raised?
Which condition is indicated by 'Q waves' and 'ST elevation' in leads II, III, and aVF?
Which biomarker is typically elevated in the plasma of patients with chronic heart disease?
Which of the following is not a diagnostic criterion for SIRS?
A patient presents 12 hours following a myocardial infarction. Which of the following enzymes will be elevated at this period?
Which of the following statements about C-reactive protein (CRP) is true?
Which of the following is the best inotrope agent for use in right heart failure secondary to pulmonary hypertension?
Patient shows ST depression, troponin rise 6h post-surgery. Next best step is:
What is the most sensitive biochemical marker for a 7-day old myocardial infarction?
Which of the following conditions masks low serum haptoglobin in hemolysis?
Cardiac Markers and Enzymes Indian Medical PG Practice Questions and MCQs
Question 1: Post-myocardial infarction on the 10th day, which of the following enzyme levels is raised?
- A. LDH
- B. CPK
- C. Troponin (Correct Answer)
- D. Myoglobin
Explanation: ***Troponin*** - **Cardiac troponins (cTnI and cTnT)** are highly sensitive and specific biomarkers for myocardial injury. - They typically remain elevated for **10-14 days** after an acute myocardial infarction, making them detectable on day 10 [2], [3]. *LDH* - **Lactate dehydrogenase (LDH)** is a non-specific enzyme and its levels begin to rise later than troponin, peaking around 3-4 days. - While elevated in MI, it usually returns to normal within **7-14 days**, making its elevation less reliable or prominent on day 10 compared to troponin [1]. *CPK* - **Creatine phosphokinase (CPK)**, particularly the MB isoenzyme (CK-MB), rises within 3-12 hours after MI [2]. - However, CK-MB levels typically return to normal within **2-3 days**, making it unlikely to be significantly elevated on day 10. *Myoglobin* - **Myoglobin** is one of the earliest markers to rise, appearing within 1-4 hours after MI. - Due to its rapid clearance, myoglobin levels also normalize quickly, usually within **24 hours**, and would not be elevated on day 10.
Question 2: Which condition is indicated by 'Q waves' and 'ST elevation' in leads II, III, and aVF?
- A. Lateral myocardial infarction
- B. Pericarditis
- C. Inferior myocardial infarction (Correct Answer)
- D. Anterior myocardial infarction
Explanation: Current ECG leads II, III, and aVF reflect the electrical activity of the inferior wall of the left ventricle [2]. Inferior myocardial infarction is typically indicated by ST elevation and subsequent Q wave formation in these leads [2], [3]. Q waves indicate necrosis (infarction), and ST elevation signifies acute ischemia in the myocardial territory often supplied by the right coronary artery (RCA) [3]. Lateral myocardial infarction typically manifests with changes in leads I, aVL, V5, and V6, which correspond to the lateral ventricular wall [2]. In contrast, an anterior myocardial infarction is characterized by changes, including Q waves and ST elevation, in leads V1, V2, V3, and V4 [1]. Pericarditis typically presents with diffuse ST elevation across multiple leads and does not typically involve the formation of pathological Q waves.
Question 3: Which biomarker is typically elevated in the plasma of patients with chronic heart disease?
- A. Endothelin-1
- B. Troponin T
- C. B-type natriuretic peptide (BNP) (Correct Answer)
- D. Cortisol
Explanation: ***B-type natriuretic peptide (BNP)*** - **BNP** is a hormone secreted by **ventricular cardiomyocytes** in response to increased wall stretch and pressure overload, making it a strong indicator of **myocardial stress** and **chronic heart failure** [1]. - Elevated levels correlate with the **severity of heart failure**, aiding in diagnosis and prognosis [1]. *Endothelin-1* - **Endothelin-1** is a potent **vasoconstrictor** involved in vascular tone regulation and endothelial dysfunction. - While it can be elevated in conditions like **pulmonary hypertension** and **atherosclerosis**, it is not a primary diagnostic biomarker for chronic heart disease in general. *Troponin T* - **Troponin T** is a cardiac-specific protein that is released into the bloodstream following **myocardial injury or necrosis**. - While it is a crucial biomarker for **acute coronary syndromes** (e.g., heart attack), persistently elevated levels are not typical for stable chronic heart disease unless there is ongoing subclinical myocardial damage. *Cortisol* - **Cortisol** is a **stress hormone** produced by the adrenal glands, involved in metabolism, immune response, and blood pressure regulation. - While chronic stress can impact cardiovascular health, cortisol itself is not a specific diagnostic biomarker for chronic heart disease.
Question 4: Which of the following is not a diagnostic criterion for SIRS?
- A. Hypotension (Correct Answer)
- B. Tachypnoea
- C. Leucocytosis
- D. Tachycardia
Explanation: ### Hypotension - **Hypotension** is a criterion for **sepsis** and **septic shock**, but not for **SIRS** itself. - **SIRS** criteria are based on inflammatory responses, while hypotension indicates a more severe systemic compromise. *Tachycardia* - **Tachycardia**, defined as a **heart rate >90 beats per minute**, is a diagnostic criterion for **SIRS** [1]. - It reflects the body's physiological stress response to a systemic inflammatory state [1]. *Tachypnoea* - **Tachypnoea**, indicated by a **respiratory rate >20 breaths per minute** or a **PaCO2 <32 mmHg**, is a diagnostic criterion for **SIRS** [1]. - This symptom shows the body's effort to compensate for metabolic acidosis or increased oxygen demand. *Leucocytosis* - **Leucocytosis**, defined as a **white blood cell count >12,000/mm³** or **<4,000/mm³**, or the presence of **>10% immature neutrophils (bands)**, is a diagnostic criterion for **SIRS** [1]. - This indicates a significant systemic inflammatory response in the blood [1].
Question 5: A patient presents 12 hours following a myocardial infarction. Which of the following enzymes will be elevated at this period?
- A. Lactate dehydrogenase
- B. Creatine phosphokinase (Correct Answer)
- C. Myoglobin
- D. Serum glutamate oxaloacetate transferase (SGOT)
Explanation: ***Creatine phosphokinase*** - **Creatine phosphokinase (CK-MB)** levels begin to rise within **3-6 hours** after an MI, peak at **12-24 hours**, and return to baseline within **48-72 hours**. - At 12 hours post-MI, CK-MB would be significantly elevated and near its peak, making it the most reliable marker for diagnosis at this timepoint. *Lactate dehydrogenase* - **Lactate dehydrogenase (LDH)** levels rise much later, typically around **24-48 hours** after an MI, and peak at **3-6 days**. - At 12 hours post-MI, LDH elevation would be minimal or non-existent. *Myoglobin* - **Myoglobin** is one of the earliest markers to rise, appearing within **1-4 hours** post-MI and peaking around **6-7 hours**. - While elevated at 12 hours, it may already be declining, and it **lacks cardiac specificity** (also released from skeletal muscle injury), making it less reliable than CK-MB for MI diagnosis. *Serum glutamate oxaloacetate transferase (SGOT)* - **SGOT (AST)** levels start to rise around **6-12 hours** post-MI, peak at **18-36 hours**, and return to normal within **3-7 days**. - While it would be beginning to rise at 12 hours, **CK-MB** is more elevated and more specific for cardiac injury at this timepoint.
Question 6: Which of the following statements about C-reactive protein (CRP) is true?
- A. It is detected by agglutination test.
- B. It is raised in acute pneumococcal infection. (Correct Answer)
- C. It is an antibody.
- D. It is detected by precipitation with carbohydrate.
Explanation: ***It is raised in acute pneumococcal infection.*** - **C-reactive protein (CRP)** is an **acute-phase reactant** whose levels rise rapidly and significantly in response to inflammation and infection [1]. - **Pneumococcal infection** (e.g., pneumonia) is an acute bacterial infection that triggers a strong inflammatory response, leading to increased CRP synthesis by the liver [1]. *It is detected by agglutination test.* - While some tests for CRP can involve **agglutination assays**, this statement describes a method of detection rather than a fundamental property or primary clinical utility of CRP itself. - CRP is more commonly quantified via methods like **nephelometry** or **turbidimetry** in modern laboratories due to their higher sensitivity. *It is an antibody.* - **CRP** is a **pentameric protein** produced by the liver, belonging to the **pentraxin family** of proteins. - It functions as a non-specific innate immune molecule, primarily involved in binding to damaged cells and pathogens to facilitate their clearance, but it does **not possess antigen-specific binding** characteristic of antibodies. *It is detected by precipitation with carbohydrate.* - **CRP** was originally named for its ability to precipitate the **C-polysaccharide** of *Streptococcus pneumoniae*. - However, this historical observation describes a specific interaction rather than the general method by which CRP is clinically detected or its primary biological function. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 109-111.
Question 7: Which of the following is the best inotrope agent for use in right heart failure secondary to pulmonary hypertension?
- A. Milrinone (Correct Answer)
- B. Dobutamine
- C. Digoxin
- D. Dopamine
Explanation: ***Milrinone*** - Milrinone is a **phosphodiesterase-3 inhibitor** that increases myocardial contractility and causes **pulmonary and systemic vasodilation**. - Its vasodilatory effect is particularly beneficial in **pulmonary hypertension** as it can help reduce **pulmonary vascular resistance (PVR)**, a critical factor in right heart failure. - The combination of **positive inotropy** and **selective pulmonary vasodilation** makes it the optimal choice for right ventricular failure secondary to pulmonary hypertension. *Dobutamine* - Dobutamine is a **beta-1 agonist** that primarily increases myocardial contractility with some beta-2 mediated vasodilation. - While it improves cardiac output, its lesser effect on **pulmonary vascular resistance** compared to milrinone makes it less ideal for right heart failure specifically complicated by pulmonary hypertension. *Digoxin* - Digoxin is a **cardiac glycoside** that increases contractility but has a slow onset of action and a narrow therapeutic window, making it less suitable for acute management. - It does not significantly reduce **pulmonary vascular resistance** and is primarily used for chronic heart failure or rate control in atrial fibrillation. *Dopamine* - Dopamine is a **catecholamine** with dose-dependent effects: at moderate doses (5-10 mcg/kg/min), it acts as a **beta-1 agonist** providing inotropic support. - However, at higher doses it causes **alpha-adrenergic vasoconstriction** which can **increase pulmonary vascular resistance**, potentially worsening right heart failure in pulmonary hypertension. - Unlike milrinone, it lacks specific pulmonary vasodilatory properties beneficial for reducing RV afterload.
Question 8: Patient shows ST depression, troponin rise 6h post-surgery. Next best step is:
- A. 12-lead ECG
- B. Echocardiogram
- C. Cardiology consult (Correct Answer)
- D. Start heparin
Explanation: ***Cardiology consult*** - A cardiology consult is the most appropriate next step given the presence of **ST depression** and a **troponin rise** post-surgery, indicating a likely myocardial infarction (MI). - This allows for prompt comprehensive evaluation, risk stratification, and initiation of specialized cardiac management by an expert. *12-lead ECG* - While a 12-lead ECG is an important diagnostic tool, the patient's existing **ST depression** suggests it has already been performed or noted. - A repeat ECG might be useful for tracking changes, but it doesn't replace the need for expert cardiac evaluation and management. *Echocardiogram* - An echocardiogram can assess **cardiac function**, wall motion abnormalities, and valvular issues, which are relevant in MI. - However, it's a diagnostic test that should be ordered and interpreted in the context of a broader cardiac workup, which a cardiologist can best coordinate. *Start heparin* - **Heparin** is an anticoagulant that may be part of the management for an MI, especially in certain types or for prevention of clot extension. - However, initiating anticoagulation should be done after a thorough assessment of the patient's cardiac status, bleeding risk post-surgery, and in consultation with cardiology, rather than as the immediate next best step.
Question 9: What is the most sensitive biochemical marker for a 7-day old myocardial infarction?
- A. CPK MB
- B. LDH
- C. Myoglobin
- D. Troponin I/T (Correct Answer)
Explanation: ***Troponin I/T*** - **Cardiac troponins (I and T)** are highly sensitive and specific biomarkers for **myocardial injury**. - While they rise quickly after an MI, they also remain elevated for an extended period, typically **7 to 10-14 days**, making them ideal for detecting a 7-day-old event. *CPK MB* - **Creatine phosphokinase MB (CPK-MB)** is a well-known cardiac marker, but its elevation is more transient, usually returning to normal within **2-3 days** post-MI. - Therefore, it would likely be undetectable or near baseline 7 days after the event, making it insensitive for this duration. *LDH* - **Lactate dehydrogenase (LDH)** used to be used as a cardiac marker, but it is **non-specific** and found in various tissues. - While it can remain elevated for an extended period after an MI (up to 10-14 days), its lack of specificity makes other markers, particularly troponins, much more reliable for confirming myocardial damage. *Myoglobin* - **Myoglobin** is one of the earliest markers to rise after myocardial injury, but it is also **rapidly cleared** from the bloodstream, usually within 24 hours. - Due to its short half-life, myoglobin would not be elevated 7 days after an MI, making it unsuitable for detecting such a remote event.
Question 10: Which of the following conditions masks low serum haptoglobin in hemolysis?
- A. Bile duct obstruction (Correct Answer)
- B. Liver disease
- C. Malnutrition
- D. Pregnancy
Explanation: **Explanation:** The primary clinical utility of **Haptoglobin** is as a marker for **intravascular hemolysis**. Haptoglobin is an acute-phase reactant synthesized by the liver that binds free hemoglobin. During hemolysis, haptoglobin levels drop significantly as it is cleared by the reticuloendothelial system. **Why Bile Duct Obstruction is correct:** Haptoglobin is a **positive acute-phase reactant**. In conditions like **bile duct obstruction (obstructive jaundice)**, inflammation or biliary stasis triggers an increase in the hepatic synthesis of haptoglobin. This elevation can artificially "mask" or normalize the low levels typically seen in hemolysis, leading to a false-negative result for hemolytic anemia. **Analysis of Incorrect Options:** * **Liver Disease:** Since haptoglobin is synthesized in the liver, severe liver disease (e.g., cirrhosis) leads to **decreased** production. This would mimic or exacerbate low levels rather than masking them. * **Malnutrition:** Protein-energy malnutrition leads to a generalized decrease in plasma protein synthesis, including haptoglobin, resulting in **low** levels. * **Pregnancy:** Pregnancy is associated with a physiological decrease in haptoglobin levels (estrogen effect), which would not mask a hemolytic state. **NEET-PG High-Yield Pearls:** * **Gold Standard for Hemolysis:** A **decreased** serum haptoglobin level is one of the most sensitive markers for confirming hemolysis. * **Acute Phase Reactants:** Remember that haptoglobin levels rise in infection, trauma, and malignancy, which can confound the diagnosis of co-existing hemolysis. * **Neonate Fact:** Haptoglobin levels are naturally very low or absent in newborns (physiologic ahaptoglobinemia) and reach adult levels by 6 months of age.
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