35. Cardiovascular system (+ extra bits) Flashcards
List three reasons why rx not accurate for cardiac evaluation
1) Variations in normal
2) Effect of positioning on appearance
3) Poor correlation between morphological and physiological abnormalities
Which radiographic projections comparatively influence the appearance of the cardiac silhouette most profoundly? How / why?
DV vs VD
DV: Diaphragm billows forward, displacing heart cranially and to the left to a varying degree -> more pronounced in medium / large breeds
VD: Magnification of the heart in LARGE BREEDS due to distance from plate
Describe the vertebral heart scoring system. Why is it used?
- Theoretically allows normlisation for body size
Technique:
- Measure long axis and short axis -> SUM
- Measure from cranial margin of T4
Normal: 8.7-10.7 (Too variable!)
**Up to 1.0 may vary with cardiac / resp cycle**
=> Best used for serial images in same patient
DOES NOT PERFORM BETTER THAN QUALITATIVE
What is the most common chamber dilation in the dog? Why?
LA -> Prevalence of MMVD
Why does LA dilation result from L->R shunting?
Pulmonary overcirculation and VOLUME OVERLOAD
In the DV projection, what structures are identified at the 12-1; 1-2; and 2-3 positions on the clock face? Where is the RA identified?
Why do dogs with LAE cough?
Possibly some inpingment from LA BUT USUALLY DUE TO CHONDROMALACIA
-> NO association between canine CHF and coughing
How can LAE and TB LN+ be distinguished?
BOTH cause divergence of prinipal bronchi
LAE: Ventral to bifurcation
TB LN: Dorsal to bifurcation (typically)
List radiographic features of LAE in the dog
Lateral:
Dorsocaudal bulge
Flattening / concavity of caudal margin
Loss of cardiac waste
DV:
Divergence of principal bronchi
“Double wall” - appearance of enlarged LA superimposed on heart
L Auricular enlargement / displacement
List radiographic features of LAE in the cat
**MAY APPEAR NORMAL**
Lateral:
- Concavity of caudal margin
DV:
- Valentine shape heart -> Due to increased diameter of heart base. DOES NOT REFLECT BIATRIAL DILATION!!!!
List features of LV enlargement (dog and cat same)
Lat:
- Elongation -> Secondary elevation of trachea
=> Narrowing of angle between trachea and thoracic vertebrae
VD/DV:
- Rounding of left heart border
- Blunted apex
Provide examples that cause LV eccentric vs concentric hypertrophy
Eccentric => INC PRELOAD
- PDA
- MVD
Concentric => INC AFTERLOAD
- Ao Stenosis
Cause of isolated RA enlargement?
RARE
Tricuspid dysplasia
Rx features of RAE
Lateral:
- Enlargement at craniodorsal aspect -> NOTE may reflect enlargement of aorta or MPA
DV/VD
- 9-11 o clock bulge
Hypertrophy of which chamber may be identifiable radiographically?
RV -> More so than LV
Possibly due to thinner wall -> more obvious changes
Define the amount of sternal contact described in normal dogs of different breeds
Deep chested (Dobi, wolfhound): 1.5-2 ICS
Average dog: 2.5-3 ICS
Barrel chested (bulldog): 3-3.5 ICS
>3 often described to support RV enlargement
Rx features of RV Enlargement
Lat:
- Increased sternal contact (Approx > 3 ICS)
- Elevation of heart apex from sternum
DV/VD
- Reverse D
What 2 measures are used to determine CaVC enlargement?
- diameter > length of 5th or 6th thoracic vertebral body
- diameter > 1.5x descending Ao
=> NOTE: Variability with cardiac and resp cycle. Should be consistent finding
Rx features of Ao enlargement
Lat:
- Inc. mass at craniodorsal aspect
VD/DV:
- Widening of precardiac mediastinum
- Focal bulge (e.g. Ao stenosis, PDA)
- **BEWARE** older cats with tortuous Ao, may be projected laterally to left, and appear as pulmonary nodule
Causes of RV hypertrophy
INC AFTERLOAD:
- Pulm stenosis
- Pulm hypertension (e.g. heartworm)
Which projection is best used to evaluate the size of the cranial pulmonary arteries and veins?
LEFT LATERAL
=> in right lateral, often superimposed vessels interfere
Which measures are used to evaluate peripheral pulm art and vvs?
- Are they similar in size?
- Relative to thickness of 9th rib
BOX: Enlarged pulm a and v
What is the most common cause of pulm art distension without vein?
Pulmonary hypertension 2ry to HEARTWORM
BOX: Pulm art enlargement ONLY
What is the distribution of pulmonary vascular lesions most commonly seen in heartworm disease? What additional feature was commonly seen in cats with experimental heartworm?
- CAUDAL vessels typically
- R caudal more common than L caudal
=> CAN AFFECT ANY VESSEL / ALL VESSELS
**50% cats had persistent Bronchointerstitial pattern**
Similar to asthma -> consider these cases suspect
What is the most common cause of pulmonary TE?
- HEARTWORM (…according to this book from US..)
What is the reported progression of PTE?
- Heterogeneous pattern, becoming alveolar
- MAY BE NORMAL
- PERIPHERAL!
Typical radiographic features of heartworm?
- MPA / Pulmonary artery enlargement
- Pulmonary vessel tortuousity, “truncation” or “Pruning” (abrupt termination)
- RV enlargement
- Evidence of PTE
- Signs of R heart failure
What is the most common cause of pulm V enlargement only?
- Mitral valve disease
BOX: Enlargement of Pulm V ONLY
BOX: Reduced size of both Pulm art and vv
WHAT WORD SHOULD YOU USE WHEN DESCRIBING SMALL Vs and As?
HYPERLUCENT LUNG
Describe pathophysiology of left heart failure inc. radiographic appearance
- Reduced output -> increased end diastolic pressire in LV
- Flows back into LA and Pulm V (Rx: Pulm v distension)
- Eventually, transudation -> pulm parenchyma (Rx: Patchy unstructured interstitial pattern-> alveolar)
- Oedema: Patchy, FOCAL (43/61 in 1 study), often dorsocaudal, uncommonly perihilar!
- **MAY** cause pulm arterial hypertension -> backing up at capillaries, AND morphological changes to increase resistance to flow
How does mitral valve jet location effect oedema?
Central jet: Symmetrical pulmonary changes
Eccentric: Assymetrical pulmonary changes
Features of R heart failure?
- Pleural effusion +- atelectasis
- Hepatosplenomegaly
- Ascites
What are the 3 most common acquired cardiac lesions in clinical practice?
- MMVD
- Cardiomyopathy
- Heartworm
What poorly understood phenomenon is observed in canine DCM?
- Mixed bronchointerstitial pattern (= atypical / peribronchial oedema)
- > More classically seen with inflammatory disease
List 4 breeds predisposed to DCM
- Doberman
- G Dane
- Cocker
- Boxer
Rx features of DCM
- Normal!
- Generalised cardiomegaly
- LAE
- Pulm V +- A dilation (artery likely due to retenion as a result of decreased renal perfusion, and activation of RAAS)
- R failure
- Mixed bronchointerstitial pattern
Rx features of HCM
- LAtrial enlargement (valentine)
- NORMAL LV as usually concentric change
- Pulm v distension (rarer in cats)
- Pulm oedema
- Pleural effusion
Rx features of pericardial effusion
- Globoid
- Clearly marginated
- May contact walls of thorax if +++
- R heart failure
=> if moderate may go undetected
Rx signs of PDA
- Dilation of proximal descending Ao
- MPA and Pulm a + v enlargement
- LA / auricular enlargement (Three knuckled appearance)
- LV enlargement
Rx features of PS
- Dilation of MPA
- RV enlargement
- Normal / small pulm vessels (reduced CO)
What type of Ao Stenosis is most common?
SUBVALVULAR > valvular
Rx features of Ao stenosis?
- DIlation of Ao arch
- LV enlargement
+- LA enlargement
+- Pulm vessel enlargement (if mitral inufficiency)
MAY BE NORMAL
Rx features VSD
DEPENDS ON VOLUME -> Typically quite dorsal, so empty directly into MPA
- Mild RV Enlargement
+- mild pulm vessel enlargement
Rx features of tricuspid dysplasia
- RA enlargement
+- small pulm vessels if poor CO
Causes of microcardia
- Hypovolaemia
- Dehydration (chronic)
- Metabolic disease -> THINK ADDISONS!
Detail formation of the cardiac atria
Briefly, how does the interventricular septum form
Detail the early embryological structures of the heart
What do the endocardial cushions develop into?
- Left and right AV ostia
Embryology - PDA
Embryology - ASD
Embryology - PS
Embryology - AS
Embryology - AV dysplasias
Embryology - Endocardial cushion defects
Embryology - Conotruncal defects
Embryology - Tetralogy / pentatology
Embryology - NORMAL Aortic arch formation / other arteries
Embryology - MOST COMMON VASCULAR RING
Embryology - aberrant left subclavian
Embryology - DOUBLE AORTIC ARCH
Embryology - AORTIC COARCTATION
Embryology - Cor triatriatum. Which type is more common?
- Dexter more common
Embryology - Name the major embryological components forming the vena cava. Which components fail to regress in persistent left CrVC and in duplication of the caudal VC?
Label the major arteries
Describe species differences in arterial supply to the brain
List the 5 arteries supplying the different portions of the brain. Which vessels feed them?
Briefly, detail the vertebral / paravertebral venous system
