Cardiac imaging modalities

Cardiac imaging modalities

Cardiac imaging modalities

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Echocardiography - Heart's Ultrasound Selfie

  • Non-invasive ultrasound to visualize heart structure, function, and hemodynamics. Two primary modes:
    • Transthoracic (TTE): Standard, non-invasive view through the chest wall. Quick, safe, and widely available.
    • Transesophageal (TEE): Invasive probe in the esophagus. Provides clearer images, especially of posterior structures (e.g., left atrium, mitral valve, aorta). Used for endocarditis, aortic dissection, and guiding procedures.
  • Key Assessments:
    • Structure: Chamber size, wall thickness, valvular morphology, pericardial effusion.
    • Function: Ejection Fraction (EF), wall motion abnormalities (ischemia), diastolic function.
    • Doppler: Measures blood flow velocity and direction to assess valvular stenosis/regurgitation and shunts.
  • Stress Echocardiography: TTE at rest and after exercise/dobutamine to detect inducible ischemia.

⭐ TEE is superior to TTE for detecting small valvular vegetations (<5 mm) in suspected infective endocarditis.

TEE probe placement and resulting echocardiogram

Cardiac CT & MRI - Slicing the Ticker

  • Cardiac CT (CCT): Best for coronary anatomy & calcification.
      • Coronary Artery Calcium (CAC) Score: Risk-stratifies asymptomatic patients. A score >100 indicates moderate plaque burden.
      • Coronary CT Angiography (CCTA): High negative predictive value to rule out CAD in low-intermediate risk patients. Involves radiation & iodinated contrast.
  • Cardiac MRI (CMR): Gold standard for function, mass, and tissue characterization. No radiation.
      • Assesses viability (scar), inflammation, and infiltrative disease.
      • Key for differentiating ischemic vs. non-ischemic cardiomyopathies.

Cardiac Imaging Modalities: Anatomy and Perfusion

⭐ Late Gadolinium Enhancement (LGE) on CMR is the gold standard for assessing myocardial viability. The pattern of enhancement (e.g., subendocardial) helps determine ischemic etiology.

Nuclear Cardiology - Glowing Hearts Club

  • Principle: Uses radiotracers (e.g., Thallium-201, Technetium-99m sestamibi) to assess myocardial perfusion and viability, primarily via SPECT or PET scans.
  • Stress Methods:
    • Exercise: Treadmill (preferred).
    • Pharmacologic: Vasodilators (adenosine, regadenoson) or inotropes (dobutamine).
  • Key Findings:
    • Reversible Defect: Ischemia (impaired perfusion on stress, normal at rest).
    • Fixed Defect: Infarction (impaired perfusion on both stress and rest).

Non-invasive Cardiac Imaging Modalities Overview

⭐ PET is the gold standard for assessing myocardial viability, distinguishing stunned or hibernating myocardium (viable) from scar tissue. Hibernating tissue shows a perfusion-metabolism mismatch.

Coronary Angiography - Dyeing to See Arteries

  • Gold standard for diagnosing Coronary Artery Disease (CAD).
  • Procedure: Involves percutaneous femoral or radial artery access. A catheter is guided to the coronary ostia, followed by injection of iodinated contrast.
  • Visualization: Provides real-time X-ray imaging (fluoroscopy) of coronary arteries, revealing:
    • Stenosis (% narrowing)
    • Thrombosis (clots)
    • Anomalous origins
  • Risks: Bleeding/hematoma at access site, vessel dissection, arrhythmias, stroke, and contrast-induced nephropathy (CIN).

Clinical Significance: A stenosis of >70% is generally considered hemodynamically significant and often warrants intervention (e.g., stenting). For the left main coronary artery, >50% stenosis is critical.

High‑Yield Points - ⚡ Biggest Takeaways

  • Echocardiography (TTE) is the initial test for most cardiac pathology, assessing valvular function and ejection fraction.
  • Transesophageal Echo (TEE) provides superior views of posterior structures (e.g., left atrial appendage, mitral valve), crucial for endocarditis and thrombus.
  • Stress testing with imaging (Echo or Nuclear) is key to diagnosing myocardial ischemia in stable coronary artery disease.
  • Cardiac MRI (CMR) is the gold standard for assessing myocardial viability, infiltrative cardiomyopathies, and right ventricular analysis.
  • Cardiac CT Angiography (CCTA) excels at ruling out CAD in low-to-intermediate risk patients.

Practice Questions: Cardiac imaging modalities

Test your understanding with these related questions

A 57-year-old man presents to his family physician for a routine exam. He feels well and reports no new complaints since his visit last year. Last year, he had a colonoscopy which showed no polyps, a low dose chest computerized tomography (CT) scan that showed no masses, and routine labs which showed a fasting glucose of 93 mg/dL. He is relatively sedentary and has a body mass index (BMI) of 24 kg/m^2. He has a history of using methamphetamines, alcohol (4-5 drinks per day since age 30), and tobacco (1 pack per day since age 18), but he joined Alcoholics Anonymous and has been in recovery, not using any of these for the past 7 years. Which of the following is indicated at this time?

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Flashcards: Cardiac imaging modalities

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_____ is the progressive onset of heart failure over many years due to chronic ischemic myocardial damage

TAP TO REVEAL ANSWER

_____ is the progressive onset of heart failure over many years due to chronic ischemic myocardial damage

Chronic ischemic heart disease

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