Radiographic Examination of Cardiovascular System
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This document discusses how to interpret cardiac radiographs in dogs. It provides guidance on when cardiac radiographs should be used and limitations. It describes how the appearance of the heart can vary between breeds and positioning. Signs of enlargement of the left atrium, left ventricle, right atrium, and right ventricle are outlined. Methods for measuring heart size using the vertebral heart score are also explained.
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Radiographic Examination of Cardiovascular System
- 7. Cardiac radiography should be reserve: As a screening tool for assessing marked cardiac abnormalities For evaluation of the pulmonary circulation To assess whether cardiac decompensation has occurred To evaluate response to therapy Radiographs are not very accurate for assessing either cardiovascular function or morphology
- 8. Muscular dogs or those with a barrel-shaped thorax often have a heart that looks large The normal heart in breeds with a laterally compressed but deep thoracic cavity, such as greyhounds and collies, can look abnormally small
- 9. Lateral thoracic radiographs from a normal Normal Labrador retriever Normal pug
- 10. VD thoracic radiographs from a normal borzoi Normal Labrador retriever Normal pug
- 11. Ventrodorsal (VD) Dorsoventral (DV Lateral
- 12. In DV radiographs, the diaphragm is displaced cranially, which will physically push the heart cranially and into the left hemithorax. The magnitude of this displacement is more pronounced in medium and large dogs than in cats or small dogs
- 13. VD (A) and DV (B)thoracic radiographs of a normal dog.
- 14. Alternately, VD views of the heart in large-breed dogs will have significant magnification when compared with DV views of the same heart. It is important to realize that the cardiac silhouette is composed of tissues other than the heart.
- 15. The pericardium will blend with the heart, thereby contributing to the overall size and shape of the cardiac silhouette Obese patients- fat will be visible as a region of decreased opacity immediately adjacent to the heart
- 16. Lateral radiograph of the thorax of a Dobrman pinscher.
- 17. CLOCK FACE Cardiac silhouette can be visualized in terms of a clock face. The origin of bulges on the cardiac silhouette caused by dilation of different parts of the heart or great vessels can be predicted by using this clock analogy
- 18. CLOCK FACE
- 19. How to Calculate the Vertebral Heart Score (VHS) 1. Using a lateral thoracic radiograph, ensure the thoracic vertebrae T4 to T12 are clearly delineated. 2. Using calipers, measure the longest axis of the cardiac silhouette from the carina of the mainstem bronchus to the apex (designated “L”). 3. Transfer this long axis measurement to the vertebrae, starting at the cranial edge of T4, and count the number of vertebrae that fall within the caliper points.
- 20. How to Calculate the Vertebral Heart Score (VHS) 4. Using calipers, measure the short axis at the widest part of the cardiac silhouette, perpendicular to the long axis measurement (designated “S”). 5. Transfer this short axis measurement to the vertebrae, starting at the cranial edge of T4, and count the number of vertebrae that fall within the caliper points. 6. Sum the two measurements. VHS = S + L
- 21. How to Calculate the Vertebral Heart Score (VHS)
- 22. RADIOGRAPHIC SIGNS Radiographic Signs of Specific Cardiac Chamber Enlargement Left Atrium Left Ventricle Right Atrium Right Ventricle Generalized Cardiomegaly
- 23. Most frequently encountered cardiac enlargement Almost always caused by dilation Left atrial dilation is usually a result of mitral valve disease but can occur with left-to-right pulmonary overcirculation causing volume overload of the left atrium
- 24. In the lateral view, dilation of the left atrium causes a change in shape of the dorsocaudal aspect of the cardiac silhouette. Formation of a slight concavity on the caudal margin of the heart
- 25. Lateral radiograph of a dog with a dilated left atrium. The enlarged atrium has created a concave shape change on the caudal margin of the heart (white arrow). This is a very common sign of left atrial dilation.
- 26. Left atrial dilation also causes an increase in height of the caudodorsal heart border and elevation of the tracheal bifurcation. If left atrial dilation is severe, the left principal bronchus may become selectively elevated or even compressed between the left atrium and adjacent tissues dorsally
- 27. Lateral (A),DV (B),radiographs in a dog with marked left atrial dilation. In A,there is elevation of the trachea and compression of the left principal bronchus as it is trapped between the left atrium and tissues dorsal to the heart (black arrow).The left cranial lobe pulmonary vein is also distended (white arrow), consistent with pulmonary venous hypertension. In B, the dilated left atrium appears as a region of increased opacity caudal to the tracheal bifurcation (black arrows)
- 28. Dogs with bronchial compression secondary to left atrial dilation may exhibit a cough A massively dilated left atrium may also lead to a region of increased opacity superimposed over the cardiac silhouette in the VD or DV view that creates the appearance of a double wall
- 29. Lateral (A)and DV (B)radiographs of a dog with extreme dilation of the left atrium.
- 30. Dilation of the left atrial appendage (auricle) occurs less frequently than dilation of the left atrium 2 to 3 o’clock position An extremely enlarged left atrium can also result in lateral displacement of the left auricle, resulting in its visualization without the auricle actually being dilated
- 31. DV radiograph of a dog with pronounced left atrial dilation. The enlarged atrium has caused abaxial displacement of the principal bronchi (black arrows).There is also a bulge on the left aspect of the cardiac silhouette that is consistent with left auricular dilation or lateral displacement of the left auricle by the dilated left atrium (white arrows).
- 32. May enlarge as a result of hypertrophy or dilation Concentric hypertrophy Eccentric hypertrophy
- 33. Lateral view Straightening of the caudal cardiac silhouette Elevation of the trachea and carina DV View Enlarged left ventricle may elongate the cardiac silhouette Cardiac apex may appear rounder and be displaced to the left
- 34. response to chronically increased preload and is often associated with cardiac failure Dilation of the left ventricle may either contribute to an overall appearance of generalized cardiomegaly or result in the elongation of the left ventricle, causing the tracheal elevation
- 35. Radiographic detection of an enlarged right atrium is uncommon. Visualization of isolated right atrial enlargement can be found in dogs with tricuspid dysplasia
- 36. When visible in the lateral view, right atrial enlargement causes a bulge or mass effect in the craniodorsal aspect of the cardiac silhouette. In the VD or DV projection, an increased bulge in the right heart border from the 9 o’clock to 11 o’clock position may be present.
- 37. Left lateral (A)and DV (B)radiographs of a Labrador retriever with tricuspid dysplasia.
- 38. May enlarge as a result of hypertrophy or dilation Common causes of hypertrophy are heartworm infection and pulmonic stenosis
- 39. In VD or DV views, a hypertrophic right ventricle appears more rounded and protrudes farther into the right hemithorax than normal, giving the cardiac silhouette a reversed letter D shape
- 41. Results from combinations of chamber enlargement, or all four chambers Myocardial dysfunction
Editor's Notes
- heart condition: the failure of the heart to maintain adequate circulation because of various stresses upon it because the range of the normal cardiac appearance is very wide in dogs and the appearance of the cardiac silhouette is affected by radiographic positioning. IMPORTANCE: Cost-effective and accessible Extremely informative Establishes a baseline Evaluates severity of disease Monitors disease progression over time and response to therapy Helps evaluate prognosis Rules out other thoracic diseases Adds validity to a client record
- Barrel- cylindrical
- can have a profound effect on the appearance of the cardiac silhouette
- In the DV radiograph, the heart appears wider and is displaced into the left hemithorax. This displacement if often misinterpreted as abnormal.
- Pericardium- any fluid or tissue in the pericardial space, and any tissue or fluid in the mediastinum immediately adjacent to the heart Obese because fat in the mediastinum silhouettes with the heart, increasing the size of the cardiac silhouette.
- There is a fat around the heart in the mediastinum, leading to the cardiac silhoutte being larger than the heart itself. The less opaque fat creates contrast for visualization of the real margin of the heart (black arrows). This dog has left atrial dilation that causes a concavity on the dorso-caudal heart border (white arrow).
- cough, which may lead the clinician to think erroneously that the patient is in heart failure. double wall. This is caused by a summation effect of the enlarged left atrium being projected superimposed on the remainder of the heart
- In A,there is a large mass effect in the dorsocaudal region of the cardiac silhouette and a concave shape change of the caudal cardiac margin (white arrows).When radiographed for the DV view, the enlarged left atrium becomes superimposed on the remainder of the heart, creating a summation shadow that creates a double-wall effect. In B,the black arrows depict the margin of the enlarged left atrium.
- hypertrophy, a likely response to increased afterload such as with aortic stenosis, mainly occurs at the expense of lumen volume and may lead to no or nonspecific radiographic signs. Eccentric hypertrophy is likely a response to increased preload, as in patent ductus arteriosus or mitral insufficiency, and can cause visible left ventricular enlargement.
- Debate has occurred, even among experienced radiologists, about the accuracy with which left ventricular hypertrophy or dilation can be diagnosed from survey radiographs, so it is safest to describe the change as left ventricular enlargement and use echocardiography to differentiate the cause
- As with the left atrium, enlargement of the right atrium is usually caused by dilation.
- A bulge is visible in the region of the right atrium consistent with right atrial enlargement. How far ventral (A)and caudal (B)the enlarged right atrium extends on the cardiac silhouette is often surprising.
- It is important not to confuse this with the normal shape of the heart in VD and DV views, which might also be described as a reversed letter D shape.
- Hypertrophy mainly occurs at the expense of lumen volume and may lead to no or unrecognizable radiographic signs. Radiographs are more sensitive for detection of right ventricular hypertrophy than for left ventricular hypertrophy Because the right ventricle is normally in contact with the sternum, its enlargement, whether from dilation or hypertrophy, often causes an increased sternal contact in the lateral view. ; this may be related to the normally thinner wall of the right ventricle, with hypertrophy then causing more obvious changes in cardiac size and shape.
- Subjectively, the cardiac silhouette appears larger than expected, but specific chamber enlargement may or may not be evident. Myocardial dysfunction is a common cause of generalized cardiomegaly. Generalized cardiomegaly may also be misinterpreted because of underinflation of the lungs, making the thoracic cavity appear smaller than normal. This, in turn, makes the heart appear larger relative to the amount of aerated lung surrounding it.