cardiovascular path 3 Flashcards
1
Q
The most common congenital heart anomalies are:
- for dog, cat, cattle
A
- Dog: PDA, pulmonic stenosis, subaortic stenosis
- Cat: left AV valvular dysplasia
- Cattle: Ventricular septal defect, aortic transpositions
2
Q
Patent ductus arteriosus (PDA)
- what is it? origin?
- result?
A
- A duct connecting the ascending aorta and pulmonary artery, where they cross just proximal to the aortic arch
- In fetuses, the ductus arteriosus shunts blood from the pulmonary artery to the aorta, so that the blood bypasses the lungs. It usually closes soon after birth, but may remain open (patent) for a week or two in normal foals.
<><><><> - blood is shunted from the aorta (high pressure) to the pulmonary artery (low pressure), resulting in a volume overload on the left atrium and ventricle, with pressure overload on the pulmonary artery
- With time, some cases develop increased resistance to blood flow through the lung— the pulmonary arterioles hypertrophy and won’t let blood through easily
> This leads to pulmonary hypertension.
> Then, blood flow can reverse direction, i.e. from the pulmonary artery into the aorta.
3
Q
Atrial septal defects - significance
A
- usually of little functional importance
- normal within the first week or two of life
4
Q
Ventricular septal defect
- what is it?
- effects?
- progression?
A
- hole in the interventricular septum, usually up near the valves but occasionally down near the apex.
<><><><> - volume overload on the right ventricle, pulmonary circulation, and left atrium and ventricle
> In addition, the right ventricle may have a pressure overload, depending on the size of the ventricular septal defect
<><><><> - Thus, we expect eccentric hypertrophy of the left ventricle, and either eccentric or concentric hypertrophy of the right ventricle
<><><><> - As for PDA, these begin as left-to-right shunts, VSD can rarely progress to right-to- left shunts if there is increased resistance to blood flow through the lung.
5
Q
Subaortic stenosis (SAS)
- who?
- why?
- effects
- significance
- secondary lesions
A
- Newfoundland, boxer, and German shepherd dogs
- developmental abnormality
- clinical signs or death at 6 months or older
<><><><> - white fibrous band thickening the endocardium of the left ventricle, just proximal to the aortic valve > stenosis of outflow > pressure overload > left ventricular concentric hypertrophy
<><><><> - one of the more frequent causes of sudden death in young dogs, and of anesthetic-associated death at the time of spay/ neuter
<><><><> - Turbulent blood flow after the stenosis can cause secondary lesions:
> endocarditis of the aortic valve (turbulence and trauma to the endothelium predisposes to bacterial colonization)
> post-stenotic dilation of the proximal aorta
6
Q
Pulmonic stenosis
- forms
- sequelae
- breeds
A
It can be:
* valvular, in which malformation of the valve causes narrowing of the pulmonic outflow tract, OR
* subvalvular, in which a white fibrous band or a band of muscle located in the ventricle (just proximal to the valve) causes narrowing of the outflow tract
<><><><>
Sequelae:
- right ventricular concentric hypertrophy.
- There may be post-stenotic dilation of the pulmonary artery
<><><><>
- Beagles, bulldogs or Chihuahuas are most frequently affected.
7
Q
hemangiosarcoma in dogs
- typical presentation
- effects
A
- red, white, or mottled masses, usually affecting the right auricle
- In a dog, any red mass on the right atrium or auricle is likely to be hemangio-arcoma
- Rupture causes hemopericardium and cardiac tamponade
- Rupture of lung metastases cause hemothorax.
8
Q
Heart base tumours
- what are they?
- most common?
- effects
A
- neoplasms in the soft tissue dorsal to the heart, in the neighbourhood of the aorta and pulmonary artery
- aortic body tumour is the most common
> The normal aortic body is a mass of neuroendocrine tissue in the wall of the aorta, which regulates blood oxygen levels
> more common in brachycephalics due to chrnoic hypoxemia
> usually benign, but form an expansile mass that may cause heart failure because they obstruct filling of the atria.
9
Q
reaction of vessels to injury
Endothelial cells:
A
- Normally have anticoagulant action through production of prostacyclin, thrombomodulin, plasminogen activator
> inflammation induces procoagulant (thrombus-inducing) activity by endothelial cells - Secrete leukocyte chemoattractants, and express adhesion molecules important for leukocyte migration and platelet function
10
Q
Consequences of endothelial injury
A
- tissue edema > Water leaks out of damaged blood vessels
- thrombus formation > Plasma leaks into the damaged vessel wall where it contacts collagen in the subendothelial basement membrane
> seen histologically as fibrinoid material, sign of vascular damage - hemorrhage > leakage of erythrocytes from damaged vessels > typically petichiae or ecchymoses (as opposed to hematomas)
11
Q
arteritis vs phlebitis
A
inflammation that targets arteries (arteritis) or veins (phlebitis)
12
Q
Some diseases in which vasculitis is an important to the pathogenesis include:
A
- Equine viral arteritis
- Hemophilus somnus encephalitis and myocarditis: vasculitis causes infarcts and inflammation in brain and myocardium
- Erysipelas rhusiopathiae infection in pigs: infarcts + inflammation in skin, kidney
- Feline infectious peritonitis: vascular leakage → protein-rich exudates
- Malignant catarrhal fever
- Heartworm disease
- Strongylus vulgaris larval migration → cranial mesenteric arteritis with thickening and roughening of the intima, thrombosis, embolism→ intestinal ischemia causing colic
- Immune-mediated vasculitis
- Drug reactions
13
Q
Arteriosclerosis
- what is it
- effects and significance
A
- fibrosis (sclerosis, or hardening) of the tunica intima of arteries
- This may cause loss of elasticity, and narrowing of the lumen.
- However, it is often an incidental finding of no consequence
14
Q
Atherosclerosis
- what is it
A
- deposition of lipid in the wall of large arteries
- uncommon in domestic animals
<><><><> - deposition of lipid and lipid-laden macrophages in the arterial wall, which stimulates formation of fibrous tissue, smooth muscle proliferation, and mineralization of vessel walls
- can narrow arterial lumen, cause infarction
- seen occasionally in psittacines
- occasionally seen connected with hypothyroidism in dogs > hypercholesterolemia and altered lipid metabolism
15
Q
Arterial mineralization
- location, lesions
- sequelae
- casues
A
- calcification, typically in aorta
- Grossly, mineralized arteries are hard, brittle, and gritty; or contain gritty plaques. These are prone to rupture, which causes massive blood loss.
<><><><>
Causes: - “Metastatic” mineralization due to hypercalcemia:
> vitamin D toxicity
> iatrogenic (“Downer D”, cows)
> vitamin D-containing rodenticide toxicity in dogs
> toxic plants that contain vitamin D-like substances
> chronic debilitating &/or granulomatous diseases (Johne’s disease, rarely in blastomycosis). - “Dystrophic mineralization” due to vascular damage; eg. damage to the cranial mesenteric artery of horses caused by Strongylus vulgaris larvae.
