Radiology: The Heart and Great Vessels: Imaging for Second Year Medical Students
Terms
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- CXR
- acronym for
- four fluid compartments that are readily assessed on the CXR
- 1. Central vascular volume (the fluid in the great veins and right heart). // 2. Pulmonary vascular volume (the fluid in the pulmonary arteries and veins). // 3. Pulmonary interstitial volume. This is the fluid compartment surrounding the pulmonary vessels and bronchi in the skeleton of the lung // 4. Systemic interstitial volume. This is the fluid in the systemic interstitial space
- Method for assessing Central vascular volume
- This is best estimated by comparing size of the vascular pedicle (superior vena cava (SVC) and aorta) on sequential studies. (A 0.5 cm change is about a 1 L change in the central vascular volume)
- Method for assessing pulmonary vascular volume
- This is assessed by evaluating the width and peripheral extent of the pulmonary arteries and veins.
- Method for assessing changes in pulmonary interstitial volume
- Increased fluid in this space shows such signs as vascular and bronchial blurring (cuffing) as well as septal lines
- Method for assessing systemic interstitial volume
- can be assessed by comparing chest wall width on successive studies
- Mitral stenosis (MS) in plain film
- Enlarged left atrium, Pulmonary venous hypertension, Signs of interstitial edema, Enlarged pulmonary arteries (secondary to the pulmonary venous hypertension), Normal left ventricular size. [Calcification of the mitral valve is rarely seen on plain chest films., Mitral stenosis and insufficiency (regurgitation) often occur together, so the dominant physiology must be correctly diagnosed]
- Manifestations of enlarged left atrium in CXR
- Enlarged left atrial appendage (LAA); Double density of the enlarged LA on the frontal view; Posterior protrusion of the LA on the lateral view
- Manifestations of pulmonary venous hypertension in plain film
- Cephalization of flow (increase in the diameter of the upper lobe vessels relative to the lower lobe vessels measured at an approximately equal distance from the hilum on an erect film)
- Signs of interstitial edema on plain film
- (vascular blurring, bronchial cuffing, septal lines and pleural fluid)
- dilative cardiomyopathy (due to a mechanical dilatation and resultant insufficiency of the mitral apparatus) signs on plain film
- Enlarged left atrium, Pulmonary venous hypertension, Signs of interstitial edema, Enlarged pulmonary arteries (secondary to the pulmonary venous hypertension), enlarged left ventricle
- main etiologies of aortic stenosis
- Congenital bicuspid aortic valve ((Visible calcification begins about age 30), Rheumatic valvular disease(Visible calcification begins about age 30, 7 yrs after stenosis begins), Degenerative stenosis over age 65
- imaging of Aortic stenosis, modalities and manifestations
-
1 heart is usually normal in size,
2. Echocardiography, MRI, and CT scanning all will show the calcified valve and post-stenotic dilatation,
2 Echo and MRI can show the stenotic jet as well. - Aortic Insufficiency imaging, modalities and manifestations
-
1 dilation of left ventricle,
2 LV enlargement (frontal and lateral projections),
3 enlargement of aortic root,
4 echo and MRI show the LVE, aortic dilatation, as well as the regurgitant jet - Cardiomyopathy (or myocardiopathy) fundamental types
- Dilative(90% ischemia, alcohol, infection, etc), hypertrophic (familian or pressure overload), Restrictive (ventricle cannot dilate normally in diastole due to muscular thickening)
- Cardiomyopathy imaging
-
1) evidence of pulmonary venous hypertension
2) enlarged cardiac shadow
3) relatively normal vascular pedicle is suspicious for dilative myocardiopathy.
4) Cross-sectional imaging (CT, Echo, or MRI all will show the thickened cardiac muscle
5) dynamic modalities (Echo and MRI) will show the depressed myocardial contraction. - Coronary Artery Disease imaging modalities
-
1 NM perfusion imaging with thallium-201 or technetium-99m-sestamibi (mibi scan),
2 Multi-planar sectional imaging reconstruction techniques with single photon emission computed tomography (SPECT),
3 Coronary angiography, Echocardiography - NM perfusion imaging with thallium-201 or technetium-99m-sestamibi (mibi scan)
- is widely used for evaluating coronary artery insufficiency. These exams are commonly performed as rest-stress studies, which allow evaluation for areas of reversible coronary ischemia.
- Multi-planar sectional imaging reconstruction techniques with single photon emission computed tomography (SPECT) in coronary artery disease injury
- display the heart in multiple sections, allowing more accurate localization and diagnosis of ischemic areas
- Coronary angiography
- is a more invasive procedure that requires placement of a catheter, usually via the common femoral artery, directly into the coronary arteries. Injection of contrast and rapid filming of the flow (cine cardiography) gives very high resolution images of the coronary arteries (Figures 14a,b). Dilatation or stenting of lesions may be undertaken at this point in the cath lab, or the patient may require surgical grafting.
- Echocardiography for coronary artery disease
- may be used to evaluate cardiac wall motion for areas of dysfunction or aneurysm from ischemia. Doppler techniques allow detection and quantification of cardiac output, valvular function, and pulmonary artery pressure
- imaging modalities for congestive heart failure
- The PA and Lateral CXR as well as even the supine portable CXR
- Diagnostic imaging signs of hydrostatic pulmonary edema
-
1 An enlarged cardiac silhouette (the maximum transverse cardiac diameter is normally <= half the chest diameter, measured from the inner margin of the rib cage at its widest point above the diaphragm on the erect frontal view) //
2 Increased vascular pedicle width (normally 4-6 cm in the erect PA film) //
3 Venous cephalization on the erect film //
4 Signs of interstitial pulmonary edema: Vascular blurring centrally in the lung, Bronchial cuffing, Septal (Kerley) lines //
5 Pleural fluid //
6 Alveolar flooding in severe cases - The role of the CXR in pulmonary embolism
- The role of this modality in pulmonary embolism is basically confined to:1.Evaluating for other processes (pneumonia, pneumothorax, rib fractures, etc.) that may be accounting for the patient’s symptoms // 2. Correlation with NM ventilation perfusion scanning (V/Q) scanning.
- Perfusion scanning (the Q in V/Q)
- involves injection of on the order of 500K technetium-99m (Tc-99m) labeled macroaggregated albumin (MAA) particles into a peripheral vein and imaging the lungs to detect the perfusion pattern. Because many things (emphysema, pneumonia, etc.) can alter the perfusion pattern, another isotope (either xenon-133 gas or Tc labeled DTPA) is inhaled by the patient to provide a map of the lung ventilation. Comparison of the two studies can reveal areas that are not perfused but ventilated and therefore suspicious for embolism
- the gold standard for the diagnosis of pulmonary embolism
- Pulmonary angiography, an invasive procedure that involves placing a catheter (from an arm, neck or leg vein) into the pulmonary artery or one of its branches and directly injecting contrast
- CT imaging for pulmonary embolism
- contrast injection and very rapid scanning with multi-slice scanners. The embolus appears as a filling defect in the pulmonary arteries. CT has the advantages of speed, availability, and the ability to diagnose other conditions which may be causing the patient’s symptoms, as well as to image the venous system for abdominal, pelvic or leg clots). However, CT may have difficulty with smaller, non-segmental vessels, and its accuracy has not yet been rigorously established
- imaging of Aortic Aneurysm
-
1 The CXR may demonstrate enlargement of the aortic arch (normally <= 4cm measured from the trachea to the outer wall). Multi-planar imaging techniques are commonly used to diagnose and follow aneurysms: //
2. Echo, including trans-esophageal (TEE) technique //
3. CT //
4. MRI //
5 Angiography can also directly demonstrate the aneurysm, but may underestimate the size because thrombus can fill in part of the aneurysm. - imaging diagnosis of dissection of the aorta
-
1) CXR is not very sensitive in the diagnosis of dissection of the aorta, may show medial displacement of the intimal calcification.
2) TEE, CT, MRI and angiography are the usual imaging techniques used. These studies are primarily searching for the intimal flap that is displaced away from the rest of the aortic wall as blood dissects along the wall of the aorta - aortic laceration imaging
- CXR is not at all specific for the diagnosis of aortic laceration, it has been my experience that it is exceedingly rare for the study to be normal in the face of a laceration. Widening of the aortic arch, pleural fluid (blood), rib fractures, displacement of the nasogastric tube or trachea away from the arch may all be seen. While it is true that the diagnosis may be established by TEE or MRI, CT has become the workhorse of diagnosis. With contrast injection and rapid scan techniques, especially with the multi-slice scanners we are now using, the arch is routinely and very rapidly well-visualized, with the added bonus of excellent visualization of the remainder of the chest for associated pathology