Diastolic Dysfunction (Pulmonary hypertension) Flashcards
What is pulmonary hypertension?
- Increased pressure in the lungs
Which values are considered pulmonary hypertension
- > 30 mmHg systolic
- > 10 mmHg diastolic
- Pulmonary artery
What affects afterload with pulmonary hypertension?
- Pulmonary venous/left atrial pressure
- Increase in these pressures would increase afterload, decreasing stroke volume and cardiac output
What affects preload with pulmonary hypertension?
- Systemic or pulmonary venous return
- If increased, will increase preload, increase stroke volume, and increase cardiac output?
What can increase pulmonary venous return?
- Any left heart disease that results in increased left atrial size will increase left atrial pressure
- Any pulmonary venous obstruction
- Loss of pulmonary vessels
- Increased right-sided cardiac output (anemia, fever, exercise; large left to right shunts)
- A mass can cause pulmonary venous obstruction too (enlarged hilar lymph nodes too)
What is most common cause of increased pulmonary venous return?
- Any left sided heart disease
What contributes to pulmonary blood pressure?
- Cardiac output X Pulmonary vascular resistance
- SEE TABLE AND THINK ABOUT THIS
What large L–> R shunts can increase pulmonary venous return (AKA increased volume within the lungs)?
- Patent ductus arteriosus (PDA)
- Ventricular septal defect (VSD)
- Atrial septal defect
Exercise induced pulmonary hypertension
- Pushing blood through the lung
What can cause a loss of pulmonary vessels
- Pulmonary thromboembolism
Again, what three things contribute to Virchow’s triad?
- Endothelial injury
- Blood stasis
- Hypercoagulability
What can lead to endothelial injury leading to pulmonary hypertension?
- Heartworm disease***
- Vasculitis
What can lead to hypercoagulability leading to pulmonary hypertension?
- Hyperadrenocorticism
- Protein-losing nephropathy
- Inflammatory disease (e.g. IMHA)
What parts of Virchow’s triad can neoplasia impact?
- Any of them
What can lead to loss of pulmonary vessels
- Pulmonary thromboembolism (anything impacting Virchow’s triad)
- Pulmonary vasoconstriction (hypoxemia)
Impact of hypoxemia on pulmonary vessels?
- NORMALLY leads to vasodilation systemically
- In your lungs, it’s opposite
- They constrict as you don’t want to perfuse an area that’s not ventilated
Causes of hypoxemia
Primary lung disease vs high altitude
Primary lung disease that can lead to hypoxemia
- Chronic obstructive pulmonary disease (COPD or chronic bronchitis)
- Pulmonary fibrosis (West Highland White Terriers)
- Collapsing trachea (COMMON)
Diagnosis pf pulmonary hypertension
- cardiac catheterization
- Echocardiogram
What is the gold standard diagnosis for pulmonary hypertension?
- Cardiac catheterization
- Measures direct pressures in the PA, pulmonary capillaries, and pulmonary veins
Echocardiogram for diagnosis of pulmonary hypertension
- Indirect measurement of pulmonary pressures
- Only definitive if tricuspid or pulmonic regurgitation is present
- Use modified Bernoulli equation to estimate pressures
- Can look for secondary signs like concentric hypertrophy too
Treatment for pulmonary hypertension
- TREAT THE UNDERLYING DISEASE
- Viagra or sildenafil
Sildenafil MOA
- Phosphodiesterase type V inhibitor (specific for the lung)
- Specifically vasodilates the pulmonary vasculature
Prognosis for pulmonary hypertension
- Depends on underlying disease
- Usually guarded
- Most common are left heart disease, which are not curable
- Also have respiratory signs, which are not curable
Who gets Dirofilaria immitis?
- Canines (the favorite)
- Felines (not as often)
Heartworm incidence
- Spreading
- Definitely increasing
What is required for L1 to go to l3?
- 64° for 30 days
- If it dips below 64° average, doesn’t seem to support mosquito survival
Heartworm life cycle
- just know it
What stage of worm does mosquito inject into bite wound?
- L3
- Infective 3rd stage larva
How long does it take to go from L3 to L4?
- 1-2 weeks in the body
How long to become an adult heartworm from L4?
- 2-3 months
- Tunnels to blood vessels and molts to L5
How long to for patency after becoming an adult?
- 3-4 months
How long for patency to occur post-infection?
- 6-7 months
Wolbachia
- Rickettsial intracellular, gram neg bacteria
Wolbachia relationship to D. immitis
- Symbiotic
- Assists with D. immitis development
- Increases D. immitis fecundity
What stages are impacted if you kill Wolbachia?
- Fewer L3 becomes L4, and fewer of those become teenagers
- Wolbachia help with development of life stages and facilitate more L1 larvae
Diagnosis of heartworm
- Heartworm testing
- Antigen testing
- ANtibody testing
- Microfilaria
How long after you wait before you can test for heartworm?
- 6 months post-exposure
What are you testing with antigen testing?
- Female reproductive tract
- Infection
What does positive antigen test mean/
- Have to have an infection
What does antibody test positive means?
- Exposure
What are you looking for with Knotts test?
- Microfilaria
Positive predictive value and heartworm disease
- Depends on prevalence of the disease
- If you are here in Pullman, positive predictive is heartworm test is a lot lower
- Increased likelihood of false positive
- Don’t test random animals for heartworm
- In Mississippi, your negative predictive value will be lower
What are the stages of heartworm disease?
- Asymptomatic
- Respiratory signs
- Cor Pulmonale
- Right sided CHF
- Caval syndrome
Respiratory signs of heartworm disease
- Cough/tachypnea with exercise
Cor pulmonale
- Pulmonary vascular disease –> pulmonary hypertension
What side heart failure happens with heartworm disease?
- Pulmonary hypertension
Caval syndrome
- Hepatic congestion, intravascular hemolysis with hemoglobinuria
- If pulmonary arterioles are full, they will go to the heart
- If it’s even worse, they go the caudal and cranial vena cava syndrome
- These dogs are usually laterally recumbent and dying
Comorbidities of heartworm disease
- Antibody-antigen complex formation –> glomerular deposition –> proteinuria
- Thrombocytopenia
- Anemia
Concurrent diagnostics for heartworm disease
- CBC
- Chemistry
- Urinalysis
- Chest rads
- Echocardiogram
Why do a CBC for heartworm disease?
- Evaluate for anemia and thrombocytopenia
- May see eosinophilia
Why do a chemistry for heartworm disease?
- Renal values
Why do a urinalysis for heartworm disease?
- Proteinuria
- If you have protein, do a urine protein to creatinine ratio
Why do chest rads for heartworm disease?
- Pulmonary parenchymal and vascular changes
Why do echocardiogram for heartworm disease?
- Evaluate pulmonary hypertension
What does melarsomine kill?
- Adults
Preventative
Kills L1, L3, and L4
Slow kill method of heartworm disease
- 2+ years
- Monthly preventative dose of macrocyclic lactones
- Doxycycline PO BID for 1 month every 3 months
Fast kill method
- Adulticide therapy with melarsomine
- 2 dose: 1st dose and 2nd 24 hours later
- 3 dose: 1st dose, 2nd dose 1 month later, 3rd dose 24 hours after 2nd dose
- Exercise restriction the whole time
Which is better: slow or fast kill?
- Fast kill method
- Especially treat ASAP if pulmonary hypertension or other co-morbidities are present
What is treatment of choice for caval syndrome?
- Surgical removal or worms
Why do surgical removal of worms?
- Reduce worm burden to minimize effects of adulticide
Treatment for heartworm
- SEE THE CHART IN THE NOTES
Feline heartworm disease characteristics
- Infection 5-20% of K9 prevalence
- Frequently amicrofilaremic
- Small worm burdens
- Clinical signs are very similar to feline asthma
Diagnosis of heartworm disease in cats
- Antigen: Female reproductive tract
- Antibody
- Microfilaria
- Chest rads
- Echocardiograph
- Probably will have other testing first
Treatment of feline heartworm disease
- Adulticide therapy not recommended
- Treat like an asthmatic cat (steroids and wait for the worms to die)
- Worm extraction?
- Doxycycline
What should be in place throughout all of the heartworm treatment?
- Exercise restriction!!!!
