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Pulmonary pressure and resistance are about _________ of systemic pressure and resistance.
1/5 - 1/6
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___________ may cause pulmonary arterial vasoconstriction.
Alveolar hypoxia
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Describe the effects of exercise on pulmonary circulation. (3)
increased flow--> vasodilation, recruitment of additional vessels to decrease resistance (zone 1 to zone 3)
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Why don't we get pulmonary edema every time we exercise due to increase flow?
flow reserve capacity of pulmonary vasculature beds to so high- 400-600% with vasodilation
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__________ reduction of vascular cross-sectional area must occur in order for significant pulmonary hypertension to occur because of the ____________ of the pulmonary circulation.
>60%; high flow reserve capacity
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What is Poiseulle's Law?
- concept to explain relationship b/w pressure, flow, and vascular resistance
- R= Δp/Q= (8 x length x viscosity) ÷ (pi x radius4)
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What can increase the pulmonary vascular resistance? (3)
increasing blood viscosity, decreased radius of vessel, increased flow
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In what vessel is pressure built in the development of PHT?
small muscular arteries and arterioles [NOT in the large pulmonary arteries]
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What are the characteristics of a vascular response pattern? (9)
- reactive vasoconstriction, intimal proliferation, fibrosis, medial hypertrophy, arteritis and fibrinoid necrosis, plexiform lesions
- [auxiliary lesions] exudative inflammation, thrombosis, plaque formation in elastic arteries
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What is a pathognomonic finding in PHT?
plexiform lesions: injured arterial branches develop into aneurysm-like dilatations--> proliferation of endothelial cells with capillary-like channels (looks like a glomerulus)
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What is a normal systolic PA pressure in a dog at rest?
15-25 mmHg
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PHT is characterized by...
increased pulmonary vascular resistance and remodeling of small pulmonary arteries--> RV hypertrophy and right heart failure
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Loss of __(2)__ is a hallmark of PHT.
endothelial NO and prostaglandin driven cGMP/cAMP signaling
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What the the hemodynamic definition of PHT (ie. the systolic PAP at which we call it PHT)?
PAP > 30mmHg
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What are the 3 classifications of PHT in animals?
arteriolar (pre-capillary), venous (post-capillary, passive), mixed
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What is the Wood Classification of PHT?
- 1. Flow- related: hyperkinetic
- 2. Resisitve: reactive (vasoconstrictive) or obstructive/obliterative
- 3. Congestive: passive
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Balance b/w ___________ and ____________ determines the PA pressure.
volume (flow); resistance (vessel tone)
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What is Cor pulmonale?
RV hypertrophy and dilatation due to PH with the primary lesion located within the pulmonary parenchyma or pulmonary vascular bed
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What is a classic example of cor pulmonale?
heartworm disease
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What are precapillary causes of secondary PHT? (3 primary problems and 7 specific diseases)
- increased flow due to cardiac shunts
- increased arteriolar resistance due to PTE, HWD, lung fibrosis, polycythemia
- decreased oxygen delivery due to brisket disease, anesthesia
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What are capillary causes of secondary PHT? (2)
loss of lung tissue, pneumonia
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What are post-capillary causes of secondary PHT? (1)
impedance of pulmonary venous draining- left heart disease
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What is brisket disease?
R-CHF due to PH secondary to chronic hypoxia at high altitude
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What are the signs (2) and treatment (2) of brisket disease?
- Signs: R-CHF (distended jugular vein, SQ edema, resp abnormalities), death
- Txt: move cattle to lower altitude, diuretics
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Idiopathic pulmonary fibrosis most often occurs in ____________; it is... (2)
West Highland White Terriers; idiopathic interstitial dz or end-stage of chronic bronchial dz
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What are the 3 distinct histopathologic patterns of idiopathic interstitial pulmonary fibrosis?
- severe thickening of interstitium, fibrosis, destruction
- Type II pneumocyte hyperplasia
- mild inflammation
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What are the clinical signs of interstitial pulmonary fibrosis?
diffuse respiratory crackles*** (hallmark), progressive chronic respiratory dz, exercise intolerance, shortness of breath, cyanosis, weakness
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What are the clinical signs of PHT? (10)
tachypnea, cough, weakness, syncope, cyanosis, exercise intolerance, accentuated S2, jugular distention, ascites, edema
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What is the most important mechanism inducing syncope in dogs with PHT?
abnormal cardiac reflexes- neurocardiogenic syncope
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What are some radiographic signs consistent with PHT? (6)
[non-specific] pleural effusion, right-sided cardiac enlargement, large torturous PAs, infiltrates, wide caudal vena cava, hepatomegaly
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What is the clinical gold standard for diagnosis of PHT?
echocardiography
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What are the 2-D and M-mode findings associated with PHT? (5)
right heart enlargement and concentric hypertrophy, flattening of the IVS, dilatation of the main pulmonary artery and branches, RV systolic dysfunction, LV underfilling and pseudohypertrophy
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What does flattening of the IVS on echo suggest PHT?
the IVS usually bulges into the RV b/c pressure is higher in the LV; flattening means the RV is under higher pressure than normal
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What are the Doppler findings associated with PHT?
abnormal PA flow signal, increased tricuspid regurgitation (indicated increased systolic PAP), increased PI (indicated increased diastolic PAP)
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What equation is used to predict systolic PAP?
- sPAP (mmHg) = 4 x TRpeak2 (m/s) + RAP (mmHg)
- Modified Bernoulli Equation
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What are the principals of managing cor pulmonale? (4)
- Correct underlying cause
- Decrease pulmonary vascular resistance- vasodilators
- Increase RV CO- Pimobendan
- Reduced volume overload- low salt diet, +/- diuretics (avoid if you can)
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What drugs are used to decrease pulmonary vascular resistance? (3)
Sildenafil, nitrates, L-arginine (metabolized to NO)
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