Thoracic imaging 2 Flashcards
The cardiac silhouette is the summation of?
Heart, pericardial contents and pericardium
Cardiac failure must be differentiated from?
Cardiac disease
Compare cardiac disease and failure
- A cardiac disease or murmur can be present for years without failure
- Failure is when disease gets so severe that heart function is compromised and can no longer compensate
Does cardiomegaly occur in cardiac failure or disease?
• Cardiac disease can be present without cardiomegaly: moderate change in shape and/or size must be present to be detectable
But.. most dogs with cardiac failure have some degree of cardiomegaly
Describe forwards HF
= output of the heart (pulmonary artery and aorta)
- Reduced CO
- Difficult to identify on radiographic studies
Describe right sided backwards failure
Pressure in the vena cava increases (congestion) causing fluid to leak into body cavities (predominantly the abdomen)
- Hepatic congestion
- Ascites
- Pleural effusion
Describe left sided backwards failure
Pulmonary venous congestion due to a build up of pressure or fluid which leads to leaking of fluid causing pulmonary oedema
Which factors can affect the cardiac silhouette on a radiograph
- Recumbency: right vs left
- Breed variation
How is the vertebral heart score calculated?
- Compare size of heart (sum of lung and short axis) to vertebral length (T4)
- Often considerable variation between breeds
How might left sided heart disease appear on a radiograph?
- Tracheal elevation (to parallel to spine) and straightening of the caudal cardiac border due to left ventricular enlargement
- Left atrial enlargement or “tenting”
- May see bronchial compression caudal to carina
- Divergence of caudal mainstem bronchi to more than 60-90 degrees
How might right sided heart disease appear on a radiograph?
- Increase in cardiac width and rounding of right side
- Increased R:L ratio
- Increased sternal contact: be aware that some breeds have this as a normal finding
- “Reverse D” shape on DV view as right side rounds out
Describe the normal appearance of cranial and caudal lobar vessels on a dog/cat radiograph
- Cranial lobar vessels: usually not significantly wider than the proximal third of the fourth rib
- Caudal lobar vessels: usually not significantly wider than the ninth rib where they cross
Describe cardiogenic (heart origin) pulmonary oedema
- Interstitial (early/mild) or alveolar (late/severe) perihilar/caudodorsal predisposition
- Left sided cardiomegaly often apparent
- May be pulmonary vascular enlargement
- Left sided heart failure
Describe mitral valve disease
- Tends to be smaller breed dogs
- Typical pattern of progressive left atrial enlargement
- Ultimately pulmonary oedema (when in failure)
Describe the radiographic features of dilated cardiomyopathy
- Often significant cardiomegaly if clinical (may be less obvious if deep chested)
- Significant left atrial +/- right sided enlargement
Describe the different feline cardiomyopathies?
- Hypertrophic (HCM) (the most common)
- Dilated (DCM)
- Restrictive (RCM)
- Unclassified (UCM)
- Chamber enlargement less specific in cats
- May see more generalised cardiomegaly
Describe pericardial effusion and its radiographic appearance
- Fluid within pericardial space (idiopathic/secondary to masses)
- Round and sometimes well-defined cardiac silhouette (especially on DV)
- Generally no-specific chamber enlargement evident
- Subtle evidence of cause may be apparent (heart based-mass)
Describe pulmonic stenosis and its radiographic appearance
- Stenosis of pulmonary outflow tract (valve or another level)
- Can see post-stenotic bulge of the main pulmonary artery
- Beware as may see similar in normal dogs
- Sometimes small pulmonary vessels (only in very severe cases)
- Consequent right-sided enlargement due to pressure overload
Describe a patent ductus arteriosus and its radiographic appearance
- Failure of foetal ductus arteriosus to occlude at birth
- Most common congenital cardiovascular abnormality in dogs
- Increased pulmonary flow, left sided enlargement and aortic enlargement
Describe a persistent right aortic arch and its radiographic appearance
- Most common vascular ring anomaly in dogs
- Left displacement of trachea and deviation to left consistent sign
- May see ventral tracheal deviation and focal megaoesophagus