Lecture 8: CDV 3 Flashcards
You are performing a necropsy on a horse that died acutely of heart failure. You note large areas of pallor and mottling in the ventricular myocardium. Which toxin is most likely responsible for this? And how would the horse have gained access?
An ionophore such as monensin should be high in your differential list. Ionophores are extremely toxic to horses, even at low doses. Horses typically gain access through access to ruminant feed (grain bin or feeding trough raids), through horse feed accidentally mixed with ruminant feed, or through horse feed contaminated with ionophores in a mill producing poultry, cattle, and horse feeds.
You are performing a necropsy on a dog and notice roughened, firm, gritty plaques on the ventricular and atrial endocardium and along the tunica intima of great vessels. What are some of your potential diagnoses?
This is endocardial mineralization. In dogs the potential diagnoses include: (1) excess vitamin D from rodenticide toxicity; (2) metastatic calcification caused by hypercalcemia of malignancy.
Which types or breeds of dog are predisposed to myxomatous valvular degeneration (endocardiosis)?
Small and medium breeds, especially cavalier King Charles spaniels
Canine myxomatous valvular degeneration (endocardiosis) could be expected to have associated atrial dilation. True or false? Please explain / justify your answer.
True. Affected valves are incompetent (leaky), resulting in a jet of blood passing backwards from the ventricle into the atrium with each heart beat. This causes eccentric dilation of the atrium through volume overload.
Canine myxomatous valvular degeneration (endocardiosis) could be expected to have associated ventricular jet lesions. True or false? Please explain / justify your answer.
False. Affected valves are incompetent (leaky), resulting in a jet of blood passing backwards from the ventricle into the atrium with each heart beat. This causes turbulence of blood within the ATRIUM (not ventricle) and trauma to the ATRIAL endocardium. Chronically this results in endocardial proliferation and fibrosis, manifesting as streaks, wrinkles and roughening or “jet lesions.” These are found in the atrium, not the ventricle.
Which domestic animal species is most predisposed to development of myxomatous valvular degeneration (endocardiosis)?
Dogs
Deficiency of which substance is the most common cause of nutritional myocardial necrosis in calves and lambs? And what is the lay term for this disease?
Vitamin E or selenium. “White muscle disease.”
What gross cardiac lesion may be produced by all three of the following conditions: (1) septicemias, especially those with endotoxins; (2) electrocution and anoxia; (3) agonal change at death?
Endocardial and epicardial hemorrhage. Remember that the endocardial and epicardial hemorrhage caused as an agonal change at death is a non-significant lesion, which should be ignored.
Explain the difference between endocardiosis and endocarditis.
Endocardiosis is caused by degeneration of collagen in atrioventricular valves. In endocardiosis: the cusps of the atrioventricular valves are shortened, nodular, and SMOOTH.
Endocarditis is caused by bacterial colonization of valve cusps, predisposed to by bacteremias and turbulent blood flow. In endocarditis affected valve cusps have large, friable, grey-yellow masses or “vegetations” that, chronically, may become wart-like. Their ROUGH surfaces are distinct from the smooth surfaces of valves with endocardiosis.
Explain the pathogenesis whereby a subcutaneous abscess in a cow may lead to severe heart disease.
Abscess -> invasion into tissues -> bacteria released to circulation -> bacteremia -> formation of bacterial vegetations on heart valves or (less commonly) showering of myocardium via coronary arteries -> heart disease
What are three reasons why cardiac endocardial and epicardial hemorrhage could be present at necropsy?
(1) Septicemias, especially those with endotoxins; this is a true lesion; (2) Electrocution or anoxia; this is a true lesion; (3) Agonal change at death; this is a non-significant lesion, which should be ignored
Dilated cardiomyopathy is the most common cause of congestive heart failure in dogs. True or false?
False. Myxomatous valvular degeneration (endocardiosis) is the most common cause of congestive heart failure in dogs.
Explain the key gross difference between the cause of valvular endocardiosis versus the cause of valvular endocarditis.
Endocardiosis is caused by degeneration of collagen in atrioventricular valves.
Endocarditis is caused by bacterial colonization of valve cusps, predisposed to by bacteremias and turbulent blood flow.
What are three possible broad causes of endocardial mineralization?
(1) Excess vitamin D intake: calcinogenic plants in grazing animals or rodenticide toxicity in dogs; (2) Granulomatous disease: Johne’s disease in ruminants; (3) Hypercalcemia of malignancy (i.e., metastatic calcification)
What is another name for an aortic body tumor?
A chemodectoma. The aortic body is one of several small clusters of peripheral chemoreceptors, baroreceptors, and supporting cells located along the aortic arch.
Canine myxomatous valvular degeneration (endocardiosis) leads to which type of cardiac hypertrophy: concentric or eccentric? And why?
Eccentric hypertrophy. This type of hypertrophy results from VOLUME overload, as is seen when valves are incompetent and allow blood to move backwards as well as forwards.
Myxomatous valvular degeneration (endocardiosis) is the most common cause of congestive heart failure in cattle. True or false?
False. Myxomatous valvular degeneration (endocardiosis) is the most common cause of congestive heart failure in DOGS.
What s the term for a MALIGNANT tumor arising from the cells of the myocardium?
Cardiac rhabdomyosarcoma (Note that the term rhabdomyosarcoma means a malignant tumor of ANY striated muscle. It is not particular to the heart, and could also apply to any skeletal muscle in the body. Hence the “cardiac” part of cardiac rhabdomyosarcoma.)
Which heart valves (atrioventricular, pulmonic, or aortic) are most commonly affected by myxomatous valvular degeneration (endocardiosis)?
Atrioventricular valves. Left AV (mitral) valve [66% of cases] > Right AV (tricuspid) valve [33% of case]»_space;> Aortic or pulmonic valves [rare]
In which domestic animal species is heart failure caused by ruptured chordae tendineae most common?
Horses
Describe the characteristic gross appearance of cardiac lesions caused by Clostridium chauvoei in cattle.
Severe necrohemorrhagic myocarditis, possibly with areas of crepitus caused by gas bubble formation.
What is a chemodectoma?
A neoplasm of the aortic body. The aortic body is one of several small clusters of peripheral chemoreceptors, baroreceptors, and supporting cells located along the aortic arch.
Myxomatous valvular degeneration (endocardiosis) is the most common cause of congestive heart failure in dogs. True or false?
True. Small and medium breeds, especially cavalier King Charles spaniels, are predisposed.
What s the term for a BENIGN tumor arising from the cells of the myocardium?
Cardiac rhabdomyoma (Note that the term rhabdomyoma means a benign tumor of ANY striated muscle. It is not particular to the heart, and could also apply to any skeletal muscle in the body. Hence the “cardiac” part of cardiac rhabdomyoma.)
You are performing a necropsy on a dog and notice roughened, firm, fibrous “streaks” on the left atrial endocardium. What is the most likely diagnosis for this and what is the pathogenesis?
These are “jet lesions”, where an incompetent (leaking) left AV valve has resulted in a jet of blood passing backwards from the left ventricle into the left atrium with each heart beat. This causes turbulence of blood within the left atrium and trauma to the endocardium. Chronically this results in endocardial proliferation and fibrosis, manifesting as streaks, wrinkles and roughening.
You are performing a necropsy on a dog and notice roughened, firm, fibrous “streaks” on the right atrial endocardium. What is the most likely diagnosis for this and what is the pathogenesis?
These are “jet lesions”, where an incompetent (leaking) right AV valve has resulted in a jet of blood passing backwards from the right ventricle into the right atrium with each heart beat. This causes turbulence of blood within the right atrium and trauma to the endocardium. Chronically this results in endocardial proliferation and fibrosis, manifesting as streaks, wrinkles and roughening.
