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Small Animal Medicine II > Pulmonary Hypertension & Heartworm Disease > Flashcards

Pulmonary Hypertension & Heartworm Disease Flashcards

1
Q

What are 3 characteristics of normal pulmonary vasculature? What does pulmonary arterial pressure equate to?

A
  1. low pressure
  2. low resistance
  3. high capacitance

PAP = RV CO x pulmonary vasular resistance x pulmonary venous pressure

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2
Q

What is normal mean pulmonary artery pressure? What is considered hypertension?

A

14 mmHg

  • pulmonary arterial systolic pressure > 30 mmHg
  • pulmonary arterial diastolic pressure = >19 mmHg
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3
Q

What 3 things lead to pulmonary hypertension?

A
  1. increased pulmonary blood flow - L to R shunt
  2. increased pulmonary vascular resistance - endothelial dysfunction, vascular remodeling, inflammation, increased blood viscosity, stiffness, lung parenchymal destruction
  3. increased pulmonary venous pressure - left heart disease, compression of pulmonary veins
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4
Q

What are the 5 classifications of pulmonary hypertension?

A
  1. pulmonary arteriolar vascular disease - heartworm, systemic-to-pulmonary shunts (ASD, PDA, VSD), necrotizing vasculitis/arteritis
  2. left heart disease (pulmonary venous hypertension) - most common cause in dogs, mitral valve disease, myocardial disease
  3. pulmonary disease/hypoxemia - COPD, high-altitude disease, interstitial pulmonary fibrosis (WHWT), neoplasia
  4. thrombotic/embolic disease - corticosteroids, DIC, endocarditis, Cushings, IMHA, indwelling catheters, neoplasia, pancreatitis, PLN/PLE, sepsis, surgery, trauma, HWD
  5. compressive mass lesions - neoplasia, granuloma
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5
Q

What classic history is associated with pulmonary hypertension? What are some other signs?

A

some exciting event causes fainting/syncope (running to the door when the bell rings) - can’t keep up with CO and RV is thick, CO/SV decreases, lack of oxygen to the brain

  • exercise intolerance
  • chronic cough
  • dyspnea
  • chronic lung disease - crackles, wheezes, harsh lung sounds, increased RR and effort, murmur
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6
Q

How is echocardiography used to diagnose pulmonary hypertension? What 4 signs are seen?

A

estimates pulmonary artery noninvasively (TR > 2.7 m/s, PI > 2 m/s)

  1. RVH due to increased pressure in lungs making it work harder
  2. RA enlargement
  3. septal flattening
  4. poor RV function
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7
Q

What signs of pulmonary hypertension are seen on radiographs?

A

NONSPECIFIC, but helpful

  • enlarged right heart
  • pulmonary artery dilation
  • pulmonary disease evident
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8
Q

What biomarker is used to diagnose pulmonary hypertension?

A

NT-proBNP - rules in or out cardiac disease, but there is often also lung disease associated

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9
Q

What 2 medications are used to treat pulmonary hypertension?

A
  1. PDE5 inhibitors (Sildenafil, Tadalifil) - vasodilation due to increased pulmonary vascular cGMP
  2. vasodilator - Pimobendan
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10
Q

How does heartworm disease affect the heart/lungs? What signs are seen? What 3 things is severity associated with?

A

migration of adults cause damage to pulmonary artiers

cough, exercise intolerance —> total number of heartworms, duration of infection, host and parasite interactions

(disrupt blood flow, sudden death due to caval syndrome)

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11
Q

What 5 complications are associated with heartworm disease?

A
  1. right sided CHF
  2. cor pulmonale
  3. PTE
  4. chronic inflammatory disease
  5. glomerulonephritis (immune complex deposition)
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12
Q

What is the reproductive cycle of heartworms like? How long does this take?

A
  • mosquito bites infected dog with microfilaria
  • microfilaria develop into L1-L3 in the mosquito
  • mosquito bites another dog and injects L3
  • L3 grows into L4 in SQ, fat, and skeletal muscle
  • L4 grows and migrates through the body to reach the pulmonary arteries (some may reach RV)
  • L5 grow in lung vasculature
  • become adults at 6 months and are capable of sexual reproduction to produce microfilaria

7-9 months
(signs can start as early as 2-3 months when they molt to L5, but cannot be detected yet)

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13
Q

How do heartworm cause clinical signs?

A

more associated with damage to vasculature from severe chronic inflammation due to toxic substances, immune responses, or physical trauma, rather than the presence of the worms

  • vessel thickening, inflammation, hypertension, fibrosis
  • arterial obstruction and vasoconstriction by live/dead worms, thromboemboli, and debris
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14
Q

What exacerbates HWD? What does the pulmonary hypertension ultimately result in?

A

exercise and other states of increased CO = escaped inflammatory mediators into lung parenchyma

eccentric hypertrophy, remodeling, tricuspid insufficiency

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15
Q

What 3 other organs can be affected by HWD?

A
  1. kidneys - immune complex formation = glomerulonephritis
  2. vena cava - adult heartworms migrate in a retrograde manner and cause caval syndrome
  3. aberrant migration to all organs (brain, eyes, spinal cord)
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16
Q

What coinfection is associated with HWD?

A

Wolbachia pipientis - endosymbiont bacterial harbored within D. immitis needed to molt to L5, also contributes to inflammation

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17
Q

How do most dogs present with HWD? What other signs are seen?

A

asymptomatic

  • weight loss
  • exercise intolerance
  • lethargy, poor condition
  • cough, dyspnea
  • syncope
  • ascites
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18
Q

Classes of HWD:

A
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19
Q

What diagnostic is most commonly used for HWD? What 3 limitations does it have?

A

ELISA for adult female antigen (ideally with microfilaria test)

  1. misses first 5-8 months of infection time
  2. misses male-only infections
  3. misses low female worm burden infections
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20
Q

How long can antigen tests for HWD be positive after adulticidal therapy?

A

> 8 months —> wait 8-12 months to retest

  • treatment with Ivermectin, Milbemycin oxime, Moxidectin, or Selamectin to clear microfilaria within 6-8 months
  • MUST test before preventatives are given
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21
Q

What are 2 additional tests that can be performed when an antigen test comes back negative in cases highly suspicious of HWD? What limitation do they both have?

A
  1. blood smear - buffy coat
  2. Knott test

number of microfilaria is not associated with number of adult HWs, so these tests cannot be used to assess severity

22
Q

What are 4 causes of a negative ELISA in positive cases of HWD?

A
  1. single sex infection
  2. drugs that kill microfilaria over long periods of time can kill adults (low antigen numbers)
  3. low worm burdens
  4. antigen blocking from Ag-Ab complex formation
23
Q

What are 3 causes of negative microfilaria in positive cases of HWD?

A
  1. single sec infection
  2. immune-mediated destruction of microfilaria
  3. preventatives that kill microfilaria (Ag+, MF-)
24
Q

What can cause both a negative ELISA and a negative microfilaria when HWD is present?

A

prepatent infection before worms are mature

25
Q

Why are confirmatory tests performed before starting preventatives or treating HWD?

A
  1. drugs used in HWD treatment can have severe negative side effects and shouldn’t be used unless adult heartworms are present (no options for cats, treat symptoms)
  2. fully document prevention failure - many companies will cover treatment if dog was on preventatives
26
Q

When can dogs start to be screened for HWD?

A

7 months —> antigen test + microfilaria test

27
Q

Does a negative antigen test confirm a dog is free from HW infection?

A

not necessarily - no antigen was detected in the particular testing method

28
Q

What additional test will most labs perform on blood samples with negative antigen presence if history is indicative of HWD?

A

heat treatment —> releases blocked antigens

  • DON’T do this for screening!
29
Q

How are the 2 views used forr assessing degree of HWD on radiographs?

A
  1. DV - easier to seel caudal lobar pulmonary vessels when larger than the diameter of the 9th rib
  2. LATERAL - easier to see cranial pulmonary artery, usually no larger that is accompanying vein or proximal 1/3 of fourth rib
30
Q

What are some common signs of HWD on thoracic radiographs?

A
  • RV enlargement
  • prominent MPA
  • increased size and density of pulmonary artery
  • pulmonary artery tortuosity and pruning
  • signs of CHF
31
Q

What are 3 signs of HWD on echocardiography? What can be assessed in this diagnostic modality?

A
  1. enlarged and thickened right heart
  2. enlarged pulmonary artery
  3. worms seen in PA +/- RV

pulmonary hypertension

32
Q

What are the 3 most consistent findings on clinical pathology in cases of HWD? What may also be seen?

A
  1. eosinophilia
  2. basophilia
  3. proteinuria (glomerulonephritis!)

low grade non-regenerative anemia, neutrophilia

33
Q

How is HWD prevented? At what time interval?

A
  • Ivermectin (careful in collies)
  • Selamectin
  • Moxidectin
  • Milbemycin

monthly - beyond this interval, efficacy against L4 and beyond declines and is unpredictable since juvenile worms are less susceptible

34
Q

Why must medical therapy of adults be done carefully? What is used?

A

there will always be thromboemboli when killing worms —> restrict exercise and spilt dose to allow less worms to die at once, which causes less thrombotic storms

Melarsomine (Immiticide)

35
Q

What new treatment is available as a medical therapy against adult heartworms?

A

“Moxi-Doxy”- preferred over other non-arsenic protocols

  • covers Wolbachia!
36
Q

HWD diagnosis:

A
37
Q

Are macrocytic lactones recommended as HW adulticides?

A

no - slow kill is not better!

  • worms dying slower allows them to cause more injury
  • lung damage happens early!
38
Q

What is the most common cause of severe thromboembolic complications in cases of HWD?

A

failure to restrict exercise

39
Q

What clinical sign can happen before ability to detect HWD?

A

eosinophilic pneumonitis

40
Q

When is surgery the best option for treating HWD?

A

caval syndrome —> removal with flexible alligator forceps

  • follow up with medication (Melarsomine, preventatives)
41
Q

What is caval syndrome? What 5 things can this lead to?

A

worms back up into the RA and vena cava from the RV and obstruct blood flow through the tricuspid valve (HEAVY infection) —> poor prognosis, fatal in 2 days w/o sx

  1. IMHA (RBC fragility)
  2. liver dysfunction
  3. DIC
  4. hemoglobinuria
  5. microfiloaremia
42
Q

What is prognosis like in dogs with HWD? What helps resolving proteinuria? Lung lesions?

A

VERY GOOD with therapy

split doses

doxycycline therapy and monthly ivermectin one month prior to administration of melarsomine

43
Q

How does clinical manifestation of HWD compare in cats? Why is treatment different?

A
  • much more severe with lower burdens (can be only 1-4 worms!)
  • typically have very reactive airways

death of immature adults can create pulmonary and vasculature lesions

44
Q

How does the lifecycle of HW compare in cats?

A
  • patency can occur 7-8 months post-infection
  • longer in cats (not DH)
45
Q

How do most cats present with HWD?

A
  • heartworm-associated respiratory disease (HARD) - immature larvae cause coughing and vomiting
  • mostly chronic signs: anorexia, lethargy, exercise intolerance, right heart failure, dyspnea

symptoms are treated, not disease

46
Q

What are 2 options for testing for HWD in cats? How is this different compared to dogs?

A
  1. antigen - adult females in the heart (no current reliable test since single worm infection is common)
  2. antibody - circulating larvae that can cause HARD, not guaranteed they will reach adulthood

microfilaria rarely make it to adult stages and the cat is commonly able to kill them

47
Q

What is seen on radiographs and ultrasounds in cases of feline HWD?

A

RADIOGRAPHS - enlarged right caudal lobar arteries, non-specific bronchointerstitial patterns

U/S - adult worms in pulmonary artery

48
Q

What does a positive antibody and antigen test indicate in cats with suspected HWD?

A

ANTIBODY = exposure to HW larvae, which increases the possibility that there is an underlying infection

ANTIGEN = confirms infection and indicates that there are females present (none available)

(MOST CATS HAVE NO MICROFILARIA - not tested for)

49
Q

Is adulticidal treatment recommended in cats with HWD? What is preferred?

A

no - high inherent risk, lack of clear benefit, short life expectancy of HWs in cats

  • preventative and short-term corticosteroids therapy (Prednisolone) to manage respiratory signs
  • if signs recur, alternate-day steroid therapy at the lowest dose possible
50
Q

What treatment is recommended for embolic emergencies in feline HWD?

A
  • oxygen
  • corticosteroids (Dexamethasone, Prednisolone)
  • bronchodilators (Aminophylline, Theophylline)
51
Q

What is prognosis of feline HWD like?

A
  • 40-75% asymptomatic
  • 80% self-cure

lung disease > heart disease

Small Animal Medicine II (57 decks)

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