Imaging of the cardiovascular system Flashcards
Indications for CV imaging
Cough
Dyspnoeas: tachypnoea, orthopnoea
Exercise intolerance
Murmurs heard on examination
Pre-treatment checks (doxorubicin, pre-anaesthesia is disease suspected)
Imaging techniques for CV system
Thoracic radiography
Echocardiography
Angiography
Scintigraphy
Computed tomography
Pneumopericardiography (rarely used)
Which radiographic projections are best for imagng the heart?
The dorsoventral and right lateral projections are best because the heart lies in a more consistent position.
Contrast techniques for imaging CV system
Angiocardiography
Pneumopericardiography (following drainage of a pericardial effusion (rarely used)
What can thoracic radiographs provide information about (CV)?
Heart size
Cardiac chamber enlargement
Pulmonary vasculature changes
Lung patterns associated with cardiac disease
Great vessels
Normal heart size in dogs
Varies greatly between different breeds of dog
deep-chested breeds the heart is tall, narrow and upright whereas in barrel-chested breeds it is globular
Lateral
- width 2.5 - 3.5 times intercostal space
- height two-thirds height of thoracic cavity
- short axis + long axis = 9.7 ± 0.5 thoracic vertebral body lengths in most breeds
Dorsoventral
- width two-thirds of width of thoracic cavity
Normal heart size in cats
Lateral - short axis dimension is 2 intercostal spaces
○ vertebral scale system (VHS) 7.5 ± 0.3 vertebral body lengths
○ height two-thirds height of thoracic cavity
Dorsoventral - width two-thirds width of thoracic cavity
Normal variations of heart size on radiograph
Due to technique
○ Cardiac cycle
○ Respiratory cycle
Breed related in dogs
○ Globoid in retrievers
○ Elongated in … ?
Cats: older cats can have a ‘redundant aorta’
○ 30-40% of cats
Position of individual heart chambers on lateral radiograph
cranial and caudal cardiac waists
right chambers cranial
left chambers caudal
12-2 o’clock: left atrium
2-5 o’clock: left ventricle
5-9 o’clock: MPA and right auricular appendage
10-11 o’clock: aortic arch
Position of individual heart chambers on DV radiograph
11 to 1 o’clock - the aortic arch
1 to 2 o’clock- the pulmonary artery
2 to 3 o’clock - the left auricular appendage
2 to 5 o’clock - the left ventricle
5 to 9 o’clock - the right ventricle
9 to 11 o’clock - the right atrium
Pulmonary vasculature on radiography
arteries and veins should be of similar size and run on either side of the bronchi
arteries are dorsal and the veins ventral in the lateral view
diameter of the cranial lobe vessels should be smaller than the proximal third of the 4th rib
CdVC on radiographs
0.75 ± 0.13 vertebral lengths.
CdVC: aorta < 1.5
Cranial mediastinum on radiograph
In dogs, normally no wider than 1-1.5 times the width of vertebral column, except in brachycephalic breeds where it is often larger. In cats, it is normally no wider than the vertebral column.
Concentric hypertrophy
Increased systolic pressure (pressure overload)
Ventricular wall becomes thicker
Chamber size remains the same
Eccentric hypertrophy
Increased diastolic pressure and volume (volume overload)
Dilatation
Lumen size increases
Ventricular size initially the same, then thins
Eccentric is more easily seen radiographically
Left sided cardiomegaly on lateral radiograph
Taller heart resulting in tracheal and bronchial elevation
Splitting of the mainstem bronchi - left dorsal to right
Caudal border straighter and more upright
Left atrium bulges caudiodorsally
Loss of caudal cardiac waist and elevation of the caudal vena cava
Left-sided cardiomegaly in DV radiograph
Increased width of the cardiac silhouette
Rounding of left ventricular border
Heart apex may be displaced to the right
Enlarged left auricular appendage 2 to 3 o’clock
Dilated LA superimposed on cardiac silhouette
Left atrial enlargement on radiograph
Straightening caudo-dorsal cardiac waist
Dorsal deviation of the mainstem bronchi on DV
Elevation of the left caudal mainstem bronchus (separation of the two mainstem bronchi on lateral)
Increased height of the heart
Enlargement of the pulmonary veins
Left ventricle enlargement on radiograph
Hypertrophy = can be radiographically normal
Dilation:
○ Tracheal elevation (entire trachea)
○ Loss of normal dipping of the carina
○ Straight caudal border of the heart
○ In DV view: increased length of the cardiac silhouette, can see rounding of the apex
Secondary features of left sided cardiomegaly on radiographs
Engorgement and tortuosity of pulmonary veins compared to the arteries
Patchy increase in lung density particularly in perihilar region
Right-sided cardiomegaly on lateral radiograph
Heart is enlarged craniocaudally
Rounding of the cranial border
Increased sternal contact
Loss of cranial cardiac waist
Elevation of cranial lobe bronchi and vessels
Elevation of trachea just cranial to carina