Cardiac + PAH Flashcards
How does sildenafil work?
Phosphodiasterase V inhibitor
decrease the break-down of cyclic GMP which ultimately decrease intracellular calcium concentration causing vasodilation.
what are the classes and etiology of PAH
Class I - Pulmonary arterial hypertension
Mechanism: increased pulmonary vascular resistance
Etiology:
- Congenital vascular resistance
- Heartworm disease
- Congenital left-right shunt
Class II - Pulmonary Hypertension with left-sided heart disease
Mechanism: elevated left atrial pressure causes an increase in pulmonary venous pressure
Most common cause of pulmonary hypertension ~ 50% of cases
Etiology: if caught early changes could potentially become reversible
- Myxomatous mitral valve disease
- Congenital valvular disease
- Left ventricle systolic or diastolic dysfunction
- Inflow obstruction (e.g., if blood cannot enter the left atrium)
Class III - Pulmonary hypertension associated with chronic lung disease and hypoxemia
Mechanism: pulmonary lung disease causes fibrosis and scarring which increase vascular resistance
2nd most common cause of pulmonary hypertension ~ 24% of cases
Etiology:
- Interstitial lung disease
- Sleep apnea
- Long term exposure to high altitude
Class IV - Chronic pulmonary hypertension caused by thrombotic or embolic disease
Mechanism: There is a thrombus in the pulmonary vasculature causing increased resistance to blood flow
Etiology:
- Pulmonary thromboembolism
- Non-thrombotic pulmonary embolism
- Neoplasia
Class V; Pulmonary Hypertension secondary to parasitic disease
Mehanism: lungworm and heartworm will cause lesions which are a mix of class II and Class IV
Etiology:
- Heartworm disease
- Lungworm disease
Class V- miscelaneous
Mechanism: compression of the pulmonary vasculature
Etiology: mass, granuloma, etc…
