Endocarditis/Myocarditis and Heartworm Flashcards
What is infective endocarditis?
Invasion of valvular endothelium by microorganisms —> proliferative or erosive lesions
T/F: Infective endocarditis is a disease localized only to heart tissue
False
Produces systemic dense affecting multiple organs like the kidney and joints
What valves are most commonly affected in infective endocarditis ?
Mitral and aortic
What are risk factors for infectious endocarditis?
Bacteremia of any cause
Subaortic stenosis
Immunosuppressive/corticosteroid therapy
Periodontal disease/fetal procedure
T/F: DMVD is a risk factor for endocarditis?
False
What syndromes can cause endocarditis?
Immune mediated disease —> Ag-AB formation and deposition
Congestive heart failure —> destruction and necrosis of value resulting in regurgitation
Thromboembolic Disease
What is the signalment of infectous endocarditis?
Middle aged to older
Medium to large breed dogs
What is the most common presenting complaint due to infectious endocarditis?
LAMENESS
Other common signs: lethargy, hyporexia, tachypnea, cough, dyspnea, weakness, fever
T/F: most dogs with infectious endocarditis have a heart murmur
True
Mitral: left apical systolic
Aortic: left basilar diastolic+bounding femoral pulse
*absence of murmur does not rule out IE
T/F: Fever and arrhythmias are common findings in infectious endocarditis?
True
What are common CBC abnormalities seen with IE?
Leukocytosis Neutorphilia Monocytotosi Thrombocytopenia Mild anemia
What are common biochem changes seen with IE?
Hypoalbuminemia Azotemia Elevated liver enzymes Proteinuria Hematuria Pyruria Hemoglobinuria Bacteruria
If IE causes glomerular disease, what protein can be lost (besides albumin) that can lead to one of the primary clinical syndromes?
Antithrombin III —> thromboembolism
Do you do a urine culture in IE patients?
Yes.. can provide an causative organism
How should you collect samples for blood culture of IE?
Prior to antibiotic therapy
3-4blood samples should be collected aspetically from different venous sites —> aerobic and anaerobic cluture
Bartonella : 2ml of EDTA blood frozen
What may you see on an echo of a dog with IE?
Vegetative lesions on the mitral/aortic valves
mitral/aortic regurgitation,
LA/LV dilation
erosive lesions, and abscess
What bacteria are common causes of IE?
Strep intermedius/canis Staph aureus E.coli Pseudomonas Bartonella
What is the therapy for IE?
Long term bactericidal antibiotics
1-2weeks IV is possible followed by 6-8weeks of oral
CHF therapy
What is the prognosis for IE?
Valve damage is often permanent
Aortic IE is usually grave prognosis
Only mitral involvement, better prognosis, may live >1year
Depends on other factors: gram neg infection, refractory CHF, renal failure, thromboembolic , hypoalbuminemia,.. etc
How can you prevent IE?
Peri procedural antibiotics in dogs with congenital heart disease esp subaortic stenosis
Antibiotics in these patients if immmunosuppressed
What is myocarditis?
Myocardial inflammation, in absence of ischemia, resulting in myocyte damage and cardiac dysfunction
What can be predisposing factors to myocarditis?
Respiratory or GI infection Vaccination Surgery Trauma Drug exposure
Clinical signs associated with myocarditis?
Fever Lethargy Hyporexia Respiratory signs (cough, tacypnea, dyspnea) Syncope Muscle pain Diarrhea
What diagnostics can be used to determine myocarditis?
ECG- ventricular premature complexes are common
Thoracic radiographs -unremarkable —> CHF or pulmonary infection
Echo- rules out other disease
Cardiac troponin —> often increased with acute myocarditis
What is the treatment for myocarditis?
Anti-arrhythmic drugs and supportive care
Specific treatment of underlying cause if there is one
What is a common cause of myocarditis in dogs in Texas/other parts of southern US?
Trypanosoma cruzi (Chagas’ disease)
What are the acute and chronic stages of Chagas’ disease?
Acute: lethargy, generalized lymphadenopathy, pallor, hepatospenomegaly, sudden death
Chronic: progressive Rsided dysfunction, often CHF
How do you diagnose Chagas’ disease?
Serology
Traomastigotes on blood smear
What is the lifecycle of Diroflilaria immitus in dogs?
180-210days
Adult in pulmonary aa
—> females release microfilaria into circulation
—> mosquito and develop to L1 larvae
—>develop to L3 over 8-17days
—> L3 transmitted to dog
—> L3 and L4 in tissue for 1-12days
—> L5 migrates into tissue and migrates of vascular system and PA
What are the features of HWD?
Pulmonary artery and pulmonary parenchyma injury
Pulmonary hypertension
Rsided cardiac dysfunction
Glomerulonephritis
Anemia
Thrombocytopenia
Caval syndrome
DIC
What is the primary location of adult heartworms?
Caudal pulmonary artery
What damage do heartworms cause within the pulmonary artery?
Inflammation Endothelial damage Myointimal proliferation Disruption of vascular integrity Fibrosis Pulmonary hypertension
Can cause mechanical obstruction in the aa.
Dead worms induce thrombosis
Structural changes of the lumen and narrowing of the pulmonary arteries has what effect on afterload? And pulmonary vascular resistance?
Increases afterload of the right ventricle
Increased pulmonary vascular resistance
Increased pulmonary arterial pressure has what effects on the heart?
RV hypertrophy
Increases RV and RA pressure
Tricuspid regurgitation
—> increased systemic pressure and R-sided CHF
Because of the increased afterload caused by narrowing and increased resistance of pulmonary arteries, what are consequences of decreased CO?
Decreased pulmonary arterial flow
- > thrombosis
- > hypoxemia
- > decreased preload to LA and LV
What is Wolbachia? How does it interact with Drofliaria immitus?
Intracellular, gram neg bacteria
Symbiotic with Drofliaria
Endotoxins and surface proteins
What is effective at reducing or eliminating Wolbachia?
Doxycycline
Why can a glomerulonephritis result from heartworm infection?
Secondary to antigen-antibody deposition
Results in albuminuria
What is caval syndrome?
Mechanical obstruction of blood flow in the Rside of the heart and vena cava
Only occurs if worm burden is heavy
Can result in hemolytic anemia and cardiogenic shock
What are clinical signs of heartworm ?
Majority are asymptomatic
Exercise intolerance Weight loss Lethargy Cough, tachypnea, dyspnea, hemoptysis Abdominal distention Syncope or collapse Hematuria (hemoglobinuria)
PE findings with heartworm?
Weight loss/poor body condition
Split S2
Murmur due to tricuspid regurgitation (right apical systolic)
Gallop
Abnormal lung sounds
Tachypnea, dyspnea
Right-sided CHF: hepatomegaly, ascites, jugular venous distention/pulsation
What are your next diagnostic steps if your heartworm antigen test is positive?
Heartworm infection is present
-> run a modified Knott or filter test (evaluate for microfilaria)
CBC Biochem and UA Thoracic radiographs Preventative Doxycycline Melarsomine in 2 months
If positive for microfilaria —> pretreat with antihistamine and glucocorticoids
What are CBC abnormalities that can be associated with HWD?
Neutrophilia, eosinophilic, basophilia, anemia, thrombocytopenia
What radiographic signs would be suggestive of pulmonary hypertension?
Pulmonary artery > pulmonary veins
Right sided cardiomegaly —> backwards D shaped
Bulge at 1-2:00 —>MPA
Tortuous pulmonary artery
What is part of the treatment plant to reduce risk of thromboembolism
Exercise restriction
What do you use to reduce/eliminate microfilaria and destroy developing L3/L4?
Macrocyclic lactose
When is macrocyclic lactose treatment started?
The day HW is diagnosed
Or delay a day if microfilaria are detected —> pre treatment with glucocorticoids and antihistamine
What are some of the macrocyclic lactose preventative?
Ivermectin
Selamectin
Moxidectin
Milbemycin oxime
When is milbemycin contradincated?
Potent microfilaria I’ve
Microfilarermic dogs —> cause anaphylactic rxn
What is the adulticide therapy for HW?
Melarsomine dihydrochloride
What are the protocols for adulticide therapies with melarsomine?
Usually delayed for 1-2months to allow immature worms to become adults, and for Wolbachia to be cleared
3 dose (split dose) -> effective at removing adult worms and reduces the risk of PTE
Can macrocyclic lactose be used to treat adult stages of HW?
Yes “slow-kill” method
Not recommended
Takes 2+ years for all adult worms to be killed
What are common drugs used for melarsomine injections?
Opioids, corticosteroid or NSAID
Caution using NSAIDS: corticosteroid therapy is the primary treatment for pulmonary complications of HWD
What is the purpose of corticosteroids in HWI?
Prevent and treat adverse rxn to microfilaricides
Treat pneumonitis, pulmonary granuloma, pulmonary thromboembolism
Analgesia for melarsomine injections
When are melarsomine injections administered?
Day 60
Day 90
Day 91
What are complications of hearworm treatment?
Anaphylaxis -microfilaria -> pretreat with diphenhydramine and glucocorticoids, avoid milbemycin
Eosinophilic penumonitits/granulomatosis -corticosteroids
Pulmonary thrombosis/thromboembolism - corticosteroids
Pulmonary hypertension - sildenafil
CHF- furosemide, sildenafil, and and abdominocentitis
Caval syndrome- emergency surgery to remove worms
What is the prognosis for HW?
Asymptomatic -> good
Mild-moderate disease -> generally good but possible complication (guarded)
What are the differences in dirofilaria immitis life cycle in cats?
Cats are not a preferred target for mosquitos
Have to feed on infected dog first
Unnatural host -> none to few adults
Longer life cycle: 7-8months
Aberrant migration more common
What is heartworm associated respiratory disease (HARD) ?
Inflammatory and proliferative disease of pulmonary arteries, bronchioles, and pulmonary parenchyma in cats WITHOUT mature infections
_____% of cats with immature HW infections develop HARD
50
What contributes to the profound inflammatory rxn to immature (S5) and dead worms in HARD?
Pulmonary intravascular macrophages (PIMs)
Symptoms of HARD are similar to what other feline disease?
Asthma
- coughing, wheezing
- dyspnea
- lethargy
- hyporexia, weight loss
- exercise intolerance
- vomiting
- Rsided CHF
Current antigen tests for heartworm detect what? When can you get false negatives?
Antigens produced in the reproductive tract of adult females
False negs
- > not fully mature worms
- > only males
- > only 1 female
What does the the antibody test for heartworm detect?
Can develop L4 larvae
If Ab test is positive -> need to do Ag test
When can you have false negative Antibody heartworm tests?
Too early in infection to detect (<6-90 days post transmission)
What pattern do you usually see in cats with HARD?
Mostly parenchymal inflammation
Diffuse/ patchy bronchointerstitial pattern
Why is adulticide therapy not recommended in cats?
High risk of morbidity and mortality
What is the treatment for heartworm in cats?
Short term corticosteroids in cats with respiratory signs
Embolic/anaphylactic emergency: o2, corticosteroid, and bronchodilator
Doxycycline and clopidogrel
