Lecture 13 9/17/24 Flashcards
How does pressure differ between systemic and pulmonary circulation?
-systemic circulation is a high resistance/high pressure system
-pulmonary circulation is a low resistance/low pressure system
Why are pulmonary artery pressures lower than systemic arterial pressures in a healthy animal?
because pulmonary vascular resistance is much lower than systemic VR
What is pulmonary hypertension?
abnormal increase in pulmonary vascular pressure
What do echo findings of high pulmonary artery pressure and low left atrial pressure suggest?
pulmonary hypertension is pre-capillary and the result of high pulmonary vascular resistance
What do echo findings of high pulmonary artery pressure and high left atrial pressure suggest?
pulmonary hypertension is post-capillary and the result of left atrial hypertension
What are the potential causes of pulmonary hypertension?
-increased pulmonary blood flow
-increased pulmonary vascular resistance
-increased pulmonary venous pressure
What are the potential causes of increased PVR?
-vasoconstriction
-vascular remodeling
What is the most likely cause of increased pulmonary venous pressure?
left heart disease
What are the classification groups for pulmonary hypertension?
-group 1/pulmonary arterial hypertension
-group 2/left heart disease
-group 3/hypoxia
-group 4/thrombotic
-group 5/parasitic
-group 6/multifactorial or unclear mechanisms
What is the most important group 1 PH disease?
idiopathic pulmonary arterial hypertension
What is the most important group 2 PH disease?
canine mitral valve disease
What are the characteristics of hypoxic vasoconstriction?
-constriction of pulmonary arterioles
-raises pulmonary artery pressure in the setting of lung disease
What is the clinical presentation seen in PH patients?
non-specific signs/history that is difficult to distinguish from signs of primary resp. tract disease and left-sided CHF
What are the potential physical findings in a PH patient?
-tachycardia
-tachypnea
-pulmonary crackles
-systolic murmur best heard on right side; tricuspid valve regurg.
-abnormal jugular vein pulsations
How is PH diagnosed?
using a probability-based diagnostic approach in which velocity is considered in the context of presence/absence of RA/RV enlargement and clinical signs
What are the important syndromes that can cause PH?
-idiopathic
-associated with MVD
-resulting from heartworm disease
What are the characteristics of idiopathic pulmonary arterial hypertension?
-often in older, small-breed dogs
-brachycephalic dogs at increased risk
-clinical signs include cough, tachypnea/resp. distress, and syncope
What causes idiopathic PAH signs?
idiopathic vasoconstriction/vascular remodeling that leads to an increase in PVR
What are the echo findings associated with idiopathic PAH?
small LA and small LV
What are the radiography findings associated with idiopathic PAH?
-potential cardiomegaly
-LAE is absent
Why is diuretic therapy potentially harmful in idiopathic PAH patients?
patients have small left hearts and reduced cardiac output; diuretic therapy would further reduce CO
What signs indicate idiopathic PAH when echo is unavailable?
-absence of LAE
-lack of response/worsening on diuretic therapy
-right apical murmur
How is PAH treated?
orally active vasodilators such as sildenafil/tadalafil
What are the characteristics of sildenafil/tadalafil?
-inhibitors of phosphodiesterase-type 5
-selective vasodilators of the pulmonary arteries
-make it easier for blood to move through lungs; harmful in left-sided cardiac disease patients due to increased LA pressure and pulmonary edema
