Cardiac CT Techniques — MCQs
A man presents with chest pain, and his ECG shows ST segment depression in leads V1 to V4. Which of the following medications is contraindicated?
A patient posted for Lap Cholecystectomy had drug eluting stent placed two years back. Patient has no symptoms since then. Which of the following set of investigation should be done in this patient?
Most sensitive method of monitoring cardiovascular ischemia in the perioperative period is -
Which contrast agent is not used for CT scans?
Hot spot in heart is seen in which scan
Which of the following studies has given coronary risk factors?
Which imaging modality delivers the highest dose of radiation?
Tc-labeled RBCs are used for all except:
In aortic dissection, the most accurate investigation is:
Boot shape of heart in TOF is due to:
Cardiac CT Techniques Indian Medical PG Practice Questions and MCQs
Question 1: A man presents with chest pain, and his ECG shows ST segment depression in leads V1 to V4. Which of the following medications is contraindicated?
- A. Morphine
- B. Aspirin
- C. Beta blocker
- D. Thrombolytic (Correct Answer)
Explanation: ***Thrombolytic*** - The ECG findings of **ST segment depression** in leads V1-V4 suggest **ischemia** or possibly a **non-ST elevation myocardial infarction (NSTEMI)** or **posterior MI**, but not an **ST elevation myocardial infarction (STEMI)**. - **Thrombolytics** are contraindicated in NSTEMI and are primarily reserved for STEMI when PCI is not available or delayed, due to the risk of bleeding without significant benefit [1]. *Beta blocker* - **Beta blockers** are often indicated in chest pain suspected to be cardiac in origin to reduce myocardial oxygen demand and improve outcomes, unless contraindicated by **bradycardia**, **hypotension**, or **heart failure** [1]. - They help decrease **heart rate** and **blood pressure**, lessening the workload on the heart [2]. *Morphine* - **Morphine** is used for significant pain relief in acute coronary syndromes, including NSTEMI, as it can reduce pain and anxiety [3]. - It works by reducing **preload** and **afterload** through systemic venodilation, which in turn reduces myocardial oxygen demand [3]. *Aspirin* - **Aspirin** is a cornerstone of therapy for acute coronary syndromes, including NSTEMI, due to its **antiplatelet effects** [4]. - It inhibits **platelet aggregation**, preventing further thrombus formation and reducing the risk of ischemic events [4].
Question 2: A patient posted for Lap Cholecystectomy had drug eluting stent placed two years back. Patient has no symptoms since then. Which of the following set of investigation should be done in this patient?
- A. Coronary angiography, Thallium scan
- B. ECG, CBC, Coronary angiography
- C. ECG, CBC, Stress echocardiography (Correct Answer)
- D. ECG, CBC, Stress echocardiography, coronary angiography
Explanation: **ECG, CBC, Stress echocardiography** - A patient with a **drug-eluting stent (DES)** placed two years prior, who is now asymptomatic, typically requires a **non-invasive cardiac assessment** before surgery. [1] - **Stress echocardiography** is an appropriate investigation to assess for inducible ischemia in an asymptomatic patient with a history of DES, especially when determining readiness for non-cardiac surgery. [1] *Coronary angiography, Thallium scan* - **Coronary angiography** is an invasive procedure and is generally not indicated for asymptomatic patients two years post-DES unless there are new symptoms or high-risk findings on non-invasive tests. [2] - A **Thallium scan** (myocardial perfusion scintigraphy) is a valid stress test, but **stress echocardiography** provides similar information regarding ischemia and ventricular function without radiation exposure. [1] *ECG, CBC, Coronary angiography* - While **ECG** and **CBC** are standard preoperative tests, **coronary angiography** is an invasive procedure and is not the first-line investigation for an asymptomatic patient two years post-DES without other indications. [2] - The patient's asymptomatic status suggests that invasive testing is not immediately warranted for surgical clearance. *ECG, CBC, Stress echocardiography, coronary angiography* - Performing both **stress echocardiography** and **coronary angiography** in an asymptomatic patient two years after DES placement is **redundant** and subjects the patient to an unnecessary invasive procedure. [1], [2] - The results of a non-invasive stress test like stress echocardiography would guide the need for any further invasive intervention.
Question 3: Most sensitive method of monitoring cardiovascular ischemia in the perioperative period is -
- A. NIBP
- B. ECG
- C. Pulse oximeter
- D. TEE (Correct Answer)
Explanation: ***TEE*** - **Transesophageal echocardiography (TEE)** is the most sensitive method for detecting perioperative myocardial ischemia because it can visualize **regional wall motion abnormalities** and changes in **ventricular function** much earlier than ECG. - **Ischemia** directly impairs the contractility of the affected myocardium, leading to subtle changes in wall motion that TEE can identify. *NIBP* - **Non-invasive blood pressure (NIBP)** monitoring can detect **hemodynamic changes** (like hypotension or hypertension) that may precede or accompany ischemia. - However, these changes are **non-specific** and occur relatively late, making NIBP a less sensitive indicator of early ischemia. *ECG* - **Electrocardiography (ECG)** monitors the electrical activity of the heart and can detect **ST-segment changes** indicative of ischemia. - While useful, ECG changes may appear later than wall motion abnormalities, and **silent ischemia** can be missed if the leads are not optimally placed or if the ischemia does not produce significant electrical changes. *Pulse oximeter* - A **pulse oximeter** measures **oxygen saturation** in the peripheral blood. - It is primarily used to assess **respiratory function** and tissue oxygenation, and it does not directly monitor myocardial ischemia or cardiac function.
Question 4: Which contrast agent is not used for CT scans?
- A. CO2 (Correct Answer)
- B. Iodinated high-osmolality contrast media
- C. Barium compounds
- D. Gadolinium-based contrast agents
Explanation: ***CO2*** - **CO2** (carbon dioxide) is **not used as a contrast agent in CT scans**. - CO2 is primarily used in **angiography** (especially for peripheral vessels in patients with iodine allergy or renal insufficiency) where it acts as a negative contrast agent. - In CT, CO2 would appear as air/gas density and create artifacts rather than providing diagnostic enhancement, making it unsuitable for routine CT imaging. *Iodinated high-osmolality contrast media* - These are **iodinated contrast agents** that contain iodine atoms which strongly attenuate X-rays, making them highly effective for **CT imaging**. - High-osmolality contrast media (HOCM) like **diatrizoate** and **iothalamate** were the standard CT contrast agents historically. - They have largely been replaced by **low-osmolality** and **iso-osmolality** agents due to higher incidence of **adverse reactions**, but they are still used for CT scans. *Barium compounds* - **Barium sulfate** suspensions are widely used as **oral or rectal contrast agents** for CT imaging of the gastrointestinal tract. - Barium has high atomic number and effectively attenuates X-rays, making the **GI lumen clearly visible** on CT scans. - Used in **CT enterography**, **CT colonography**, and routine **abdominal/pelvic CT** protocols. *Gadolinium-based contrast agents* - **Gadolinium-based contrast agents (GBCAs)** are primarily designed for **MRI** due to their **paramagnetic properties**. - However, gadolinium DOES attenuate X-rays and can be used **off-label for CT** in patients with **severe iodine allergy** or **contraindications to iodinated contrast**. - While less effective than iodinated agents for CT (requiring higher doses), gadolinium-enhanced CT is a recognized alternative in special clinical circumstances.
Question 5: Hot spot in heart is seen in which scan
- A. Thallium
- B. Gallium
- C. Albumin labelled
- D. Tc pyrophosphate scan (Correct Answer)
Explanation: ***Tc pyrophosphate scan*** - A **technetium-99m pyrophosphate (Tc-PYP) scan** demonstrates a "hot spot" in the heart in cases of **acute myocardial infarction** due to the tracer binding to calcium deposits in necrotic cardiomyocytes. - This hot spot indicates recent myocardial damage and is particularly useful in diagnosing **amyloidosis** (specifically transthyretin cardiac amyloidosis) where the tracer binds to amyloid fibrils. *Thallium* - **Thallium-201** is used in myocardial perfusion imaging to assess areas of reduced blood flow or infarction, creating a "cold spot" (decreased uptake). - It acts as a potassium analog and is taken up by viable myocardial cells, thus areas of ischemia or necrosis appear as defects rather than hot spots. *Gallium* - **Gallium-67** scans are primarily used to detect infection and inflammation, as well as certain tumors. - While it can accumulate in areas of inflammation in the heart (e.g., myocarditis), it does not create a characteristic "hot spot" associated with acute myocardial infarction. *Albumin labelled* - **Technetium-99m labeled albumin** (e.g., Technetium-99m macroaggregated albumin, MAA) is typically used for lung perfusion scans to diagnose pulmonary embolism or for gastrointestinal bleeding studies. - It is not used for direct assessment of myocardial damage or to create a "hot spot" in the heart for ischemic events.
Question 6: Which of the following studies has given coronary risk factors?
- A. Framingham (Correct Answer)
- B. Stanford study
- C. MONICA
- D. North Karelia
Explanation: ***Framingham*** - The **Framingham Heart Study** is a landmark prospective cohort study that has identified many of the well-known **risk factors for cardiovascular disease**, including hypertension, high cholesterol, smoking, and diabetes. - This ongoing study, started in 1948, has been instrumental in shaping our understanding of **coronary artery disease** development and prevention strategies. *North Karelia* - The **North Karelia Project** was a comprehensive community-based prevention program in Finland that successfully reduced cardiovascular disease risk factors. - While influential in demonstrating how to **implement prevention strategies**, it applied already-known risk factors rather than discovering new ones. - The program focused on reducing smoking, cholesterol, and blood pressure in the population. *Stanford study* - While Stanford University has conducted numerous influential medical studies, there isn't a single "Stanford study" primarily recognized for giving us the comprehensive list of coronary risk factors. - Many institutions contribute to medical knowledge, but the **Framingham Heart Study** stands out for this specific contribution. *MONICA* - The **MONICA (Monitoring Trends and Determinants in Cardiovascular Disease)** Project was a multinational WHO project that aimed to monitor cardiovascular disease trends and determinants. - While it provided valuable data on the **epidemiology of cardiovascular disease** and its risk factors, it primarily assessed trends in established risk factors rather than initially identifying them.
Question 7: Which imaging modality delivers the highest dose of radiation?
- A. Cardiac perfusion scan (Correct Answer)
- B. CT scan of the chest
- C. Mammogram
- D. CT scan of the brain
Explanation: ***Cardiac perfusion scan*** - A **cardiac perfusion scan (nuclear cardiology)** involves the administration of a radioactive tracer, and the radiation dose can be significant due to the nature and energy of the isotopes used. - While varying, the effective dose for these scans can range from **10 to 30 mSv**, placing it among some of the highest radiation exposures from medical imaging. *CT scan of the chest* - A **CT scan of the chest** provides a relatively high radiation dose compared to plain X-rays, typically ranging from **5 to 7 mSv**. - This is generally lower than some nuclear medicine studies, particularly complex or prolonged cardiac perfusion scans. *Mammogram* - A **mammogram** involves a relatively low dose of radiation, typically in the range of **0.2 to 0.7 mSv**. - Its objective is to image the breast tissue with minimal exposure, making it one of the lower-dose imaging modalities available. *CT scan of the brain* - A **CT scan of the brain** usually delivers a moderate radiation dose, estimated to be around **1 to 2 mSv**. - This is often less than a chest CT due to the smaller volume and different shielding considerations, and significantly less than a cardiac perfusion scan.
Question 8: Tc-labeled RBCs are used for all except:
- A. Liver adenoma (Correct Answer)
- B. LV function
- C. GI bleeding
- D. Liver hemangioma
Explanation: ***Liver adenoma*** - Tc-labeled RBCs are primarily used to highlight a specific type of tissue or process. **Liver adenomas** do not typically show an affinity for **Tc-labeled RBCs**, as they are benign epithelial tumors with a different vascular composition. - While adenomas can be vascular, they do not inherently contain the **vascular pooling** or blood volume characteristics that would be specifically targeted by **Tc-labeled RBCs** for diagnostic imaging. *LV function* - **Tc-labeled RBCs** (or Tc-99m-pertechnetate) are commonly used in **gated blood pool imaging** (MUGA scan) to assess **left ventricular (LV) function**, including **ejection fraction** and wall motion abnormalities. - This technique directly visualizes the blood pool within the cardiac chambers, making it suitable for assessing functional parameters of the heart. *GI bleeding* - **Tc-labeled RBCs** are a standard imaging agent for detecting and localizing **active gastrointestinal (GI) bleeding**, especially when the bleeding rate is intermittent or slow. - The labeled RBCs extravasate at the site of hemorrhage, creating a 'hot spot' that can be identified over time. *Liver hemangioma* - **Tc-labeled RBCs** are highly effective in diagnosing **liver hemangiomas**, which are benign vascular tumors composed of large, dilated blood vessels. - These lesions show characteristic uptake and retention of **labeled RBCs** due to their slow blood flow and large intravascular space, appearing as early peripheral enhancement with subsequent centripetal filling.
Question 9: In aortic dissection, the most accurate investigation is:
- A. MRI scan
- B. ECG
- C. Aortography
- D. CT scan (Correct Answer)
Explanation: ***CT scan*** - **CT angiography** of the chest is the **gold standard** and most accurate readily available imaging modality for diagnosing acute aortic dissection, with sensitivity and specificity both >95%. - It offers **rapid acquisition** (3-5 minutes), high spatial resolution, and is widely available in emergency settings. - It clearly visualizes the **true and false lumens**, intimal flap, entry/re-entry tears, extent of the dissection (Stanford/DeBakey classification), involvement of branch vessels, and any associated complications like pericardial effusion or mediastinal hematoma. *MRI scan* - **MRI/MRA** offers comparable diagnostic accuracy (sensitivity ~98%, specificity ~95%) without radiation exposure and is excellent for chronic dissections or surveillance. - However, its use in acute settings is limited by **longer acquisition times** (20-30 minutes), limited availability in emergency departments, and contraindications (pacemakers, metallic implants, claustrophobia). - It is **not feasible** in hemodynamically unstable patients requiring rapid diagnosis and intervention. *ECG* - An **ECG** is routinely performed to evaluate chest pain and rule out acute coronary syndrome, but it does **not visualize** the aorta or diagnose dissection. - It may show non-specific ST-T changes or signs of **myocardial ischemia** if coronary ostia are involved in the dissection, but these findings are neither sensitive nor specific for aortic dissection. *Aortography* - **Conventional aortography** (invasive catheter-based angiography) was historically the gold standard but has been **replaced by CT and MRI** as first-line imaging. - It has lower sensitivity (~85-90%) than modern cross-sectional imaging and carries procedural risks including **arterial access complications**, contrast-induced nephropathy, and stroke. - Currently reserved for cases where intervention is planned or when non-invasive imaging is inconclusive.
Question 10: Boot shape of heart in TOF is due to:
- A. Right ventricular hypertrophy (Correct Answer)
- B. Enlargement of the left atrium
- C. Enlargement of the right atrium
- D. Hypertrophy of both ventricles
Explanation: ***Right ventricular hypertrophy*** - The characteristic **boot-shaped heart (coeur en sabot)** seen in Tetralogy of Fallot (TOF) on a chest X-ray is primarily due to **right ventricular hypertrophy** and the small pulmonary artery. - The hypertrophied right ventricle lifts the cardiac apex, while the concavity in the area of the pulmonary artery (due to **pulmonary stenosis**) gives the heart its distinctive shape. *Enlargement of the left atrium* - Left atrial enlargement is not a feature of **Tetralogy of Fallot**; in fact, chronic pulmonary outflow obstruction often leads to a relatively normal or small left atrium. - This condition involves right-sided heart abnormalities, and left atrial enlargement would suggest increased left-sided pressures, which are not typical for TOF. *Enlargement of the right atrium* - While right atrial enlargement can occur in severe cases of TOF due to increased resistance to blood flow, it is **right ventricular hypertrophy** that is the primary determinant of the classic boot-shaped cardiac silhouette. - Right atrial enlargement alone does not create the specific "boot" appearance which is largely due to the ventricular contour. *Hypertrophy of both ventricles* - In Tetralogy of Fallot, the primary ventricular abnormality is **right ventricular hypertrophy**, driven by the need to pump blood through a stenosed pulmonary artery. - The left ventricle typically maintains a normal size and function, as it primarily pumps into the systemic circulation and is not directly affected by the primary defects in the same way as the right ventricle.
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