Topic: Imaging in medical problems
Question: Enumerate the imaging modalities used in the diagnosis of cardiac diseases. List their specific indications in diagnosing cardiac illnesses.
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The major imaging modalities used for the diagnosis of cardiac diseases are:
1. Echocardiography: According to American Society of Echocardiography, echocardiography is recommended as the first-line test for initial cardiac evaluation. It uses ultrasound waves to create images of the heart structures and blood flow.
It can detect:
– Left ventricular hypertrophy or wall motion abnormalities indicating cardiomyopathy.
– Valvular heart diseases like mitral regurgitation/stenosis or aortic stenosis based on parameters such as vena contracta width, pressure half-time .
– Pericardial effusion/constrictive pericarditis using images such as swinging heart sign.
– Congenital heart diseases such as atrial septal defect measuring shunt size.
– Diastolic dysfunction evaluating mitral inflow and tissue Doppler velocities.
– Systolic dysfunction measuring ejection fraction by Simpson’s biplane method.
Stress echocardiography is used to detect coronary artery disease based on wall motion abnormalities.
2. Cardiac Catheterization: According to American College of Cardiology/American Heart Association guidelines, coronary angiography using right heart catheterization is indicated in patients with angina and intermediate pretest probability of coronary artery disease. It is an invasive procedure used to diagnose and treat cardiac diseases.
It can detect: – Coronary artery stenosis/occlusions measuring fractional flow reserve.
– Left ventricular end-diastolic pressure and assess diastolic dysfunction.
– Valvular stenosis severity measuring pressure gradients across valves.
– Intracardiac shunts measuring oxygen saturations/pulmonary to systemic blood flow ratio. Left ventriculography can detect wall motion abnormalities and systolic dysfunction.
3. Coronary Computed Tomography Angiography (CCTA): According to Society of Cardiovascular Computed Tomography guidelines, CCTA is appropriate for evaluation of coronary artery disease in symptomatic patients with low to intermediate probability of obstructive coronary artery disease. It uses computed tomography scan to detect coronary artery disease.
It can identify: – Coronary artery stenosis greater than or equal to 50% based on luminal narrowing.
– Plaque volume/composition as calcified, non-calcified or mixed.
– Anomalous coronary origins and courses.
Radiation exposure and requirement of heart rate control are limitations.
4. Cardiac Magnetic Resonance Imaging (CMR): The European Society of Cardiology recommends CMR for diagnosis of heart muscle diseases, pre-procedural planning and guidance of arrhythmia ablation.
Cardiac MRI uses magnetic resonance imaging to assess:
– Left ventricular mass, volumes and ejection fraction without ionizing radiation or contrast.
– Myocardial tissue characterization detecting edema, fat, iron overload and fibrosis.
– Coronary arteries for anomalies, fistulas using magnetic resonance angiography.
– Pericardial thickening, cysts or masses indicating constrictive pericarditis or tumors. – Congenital heart defects like tetralogy of Fallot, septal defects, etc.
High cost, limited availability and contraindications like metallic implants are limitations.
In conclusion, echocardiography, cardiac catheterization, CCTA and CMR are the main cardiac imaging modalities used for the diagnosis of various heart diseases based on their ability to evaluate heart structures, functions and blood flow in a comprehensive manner. They provide valuable diagnostic information using non-invasive and minimally invasive techniques with their own advantages and limitations.
