Small animal valvular heart dx

What is the most common cardiac disease?

Myxomatous degenerative valve disease (MDVD)

List some of the reasons that you can have a valvular leak in the mitral valve?

• MDVD

  • acquired in older animals

  • small breeds

• Mitral dysplasia (congenital young dogs; large breeds)

• Mitral regurg in DCM

• Endocarditis

Explain what is happening during MVDV

• Nodular thickening of valve leaflets

  • glycosaminoglycan + proteoglycan accum

• Chordae lengthen or rupture

What is the aetiology of MVDV? What breed is predisposed

Largely idiopathic but genetic basis

• Abnormalities in collagen & extracellular matrix formation

• Abnormalities of serotonin signalling

• Mechanical stress

• Cavalier King Charles Spaniel

What are the pathological consequences of MVDV?

• LA dilatation

• LV dilatation

• Elongation chordae tendinae

• Thickened leaflets

• Jet lesions —> regurg back up into atrium → damages L atrial wall

Describe the histopathology of MDVD

Accum of GAGs & arteriosclerosis in myocardium

Explain the pathophysiology of MDVD?

• Leakage back into atria

  • L = mitral

  • R = tricuspid

• Reduction in forward SV and inc in volume entering LV in next diastole due to the leakage from prev cycle

  • less blood leaving heart = RAAS = retains vol

  • vol overload

Preload vs afterload

Preload = volume of blood stretching the heart ventricles before they contract

Afterload = pressure / resistance heart must overcome to pump that blood out

Describe hyperdynamic systolic function?

More blood in ventricle @ start

Less blood in ventricle at end

Makes look like contracts well

What are the haemodynamic effects of MDVD?

• Reduced afterload (route into LA, easier than into aorta)

• Increased preload (due to inc vol in the LV)

• SV leaving LV, reduces CO, activating RAAS

• Volume overload of LV = eccentric hypertrophy

What components of the neurohumoral system activate in response to MDVD?

Vasocon = incr. afterload = harder for heart to push against -> more O2 + more ATP needed

Explain the sequelae of MDVD?

Explain the ACVIM staging system for MDVD?

• A = e.g. CKCS or any small breed

• B1 = heart not remodelled

• B2 = heart remodelled —> U/S + BNP bloods (measure of wall stretch)

  • murmur usually G3 or above

• C1 = heart failure —> clinical signs e.g. fluid in lungs = incr. RR, unable to exercise, struggle to breathe

• C2 = heart failure but manageable @ home longterm

At what MDVD stage do you introduce medication?

B2

Pimobendan

How would you recognise MDVD in a consult?

• More typical in small breeds

• Loud harsh heart murmur over LEFT APEX (systolic)

  • LEFT APICAL SYSTOLIC CONDITION!!!

• Adult dog otherwise congenital

  • incr. likelihood as dog gets older

  • puppies are NOT degen dx

• Resp signs if CHF

  • dyspnoea, tachpnoea, crackles

• Hx —> RR + effort, exercise intol, cough

• No clinical signs poss in early stages

How do you diagnose MDVD?

• Auscultation

• BP (Often normal)

  • but hypertension incr. afterload → worsens MDVD

  • but hypotension if forward (systolic) failure —> more likely in DCM

• NTProBNP (biomarker in blood)

• Rads —> R lateral & DV

• ECG / ambulatory ECG if arrhythmia

• Echo / TFAST

What blood tests and biomarkers should you do for a MDVD case?

• Pre renal azotamia, electrolytes esp if going on diuretics

• Biomarker —> NT proBNP

• Troponin I —> used less commonly in MMVD

How do you take thoracic rads?

• Sedation

• DV + right lateral

• Look for cardiac size —> tracheal elevation, cd. vena cava direction, bulges?

• Pulmonary veins —> enlarged

• Lung infiltrate —> interstitial / alveolar

• Veins ventral & central

What changes might you see on rads for MVDV?

• Cardiomegaly

• Auricle bulges

• Congested pulmonary veins (veins are ventral and central)

  

What are the most common arrythmias with MDVD?

• Supraventricular premature complexes

• Atrial fibrillation (L atrium gets large enough)

• Ventricular premature complexes

Which arrythmia indicates that a dog is not in heart failure?

Sinus arrhythmia

What is this showing?

Supraventricular premature complexes

What is this showing?

Atrial fibrillation

Tall and narrow, chaotic, no p wave

What is this ecg showing?

Ventricular tachycardia

What is this ecg showing?

Ventricular premature complexes

Why is echocardiography / TFAST useful in diagnosis of valvular heart dx?

• Confirm diagnosis

• Exclude other conditions

• No sedation needed

• Does not tell you about pulmonary oedema accurately

• B lines

• Progression

• Severity

What would you see on echo of MDVD?

• Enlarged left atrium LA>LV

• Significant mitral regurgitation

• Dilated left ventricle

• Rounded left ventricle

• Hyperdynamic systolic function (walls coming together)

May also see:

• Tricuspid regurgitation

• Pulmonary hypertension

What colour is mitral regurg on doppler?

Green

(BART = blue away, red towards)

What does MDVD look like on M mode?***

Space can be seen on systole (contraction)

What changes can be seen on this normal vs MDVD echo?

***

La enlargement

La:Ao (<1.5x)

List the treatments of MDVD based on stage

• A —> none, monitor @ routine appts

• B1 —> none indicated, murmur present

• B2 —> PIMOBENDAN, monitor breathing rates at home

  • repeat imaging & biomarkers ~6months

• C —> Standard CHF therapy (can’t exercise & can’t breathe) ; (1) furosemide (2) pimobendan, (3) ACE inhib, (4) spironolactone (FPAS) + Ongoing home monitoring.

• D —> as for C w/ incr. doses & additional therapies e.g. sequential nephron blockade, switch of diuretic to torasemide

Recall CHF therapy (stage C and D MDVD) in order of importance

1. Diuretic —> Furosemide, torasemide

2. Pimobendan

3. ACE inhib

4. Spirinolactone

FPAS

What additional therapies (other than PFAS) can be added to CHF treatment?

• Arrythmias present

  • Supraventricular

    • Diltiazem

    • Digoxin

  • Ventricular

    • Sotalol

• Pulmonary hypertension

  • Sildenafil

• Nutraceuticals —> omega 3 fish oil, taurine (DCM)?

• Cough suppressants (figure out why coughing first)

What is the prognosis of MDVD?

• Variable —> some asymptomatic never develop CHF

  • CKCS better prog if earlier onset

• Once in failure = worse

List some of the -ve predictors of outcome of MDVD

• Left ventricular dimensions (echo, chest x-ray)

• Left atrial enlargement

• Rupture of major chorda

• NT-proBNP

What is endocarditis?

• Bacterial infection (usually 1 or more endocardial surfaces i.e. valves)

• Usually affecting left heart (in smallies, right in farm)

  • mitral > aortic (smallies)

  • tricuspid > pulmonic (farm)

What are some infectious agents that cause endocarditis?

• Streptococcus spp

• Staphylococcus spp

• E. Coli

• Pseudomonas

• Bartonellaspp

What are the 'requirements' for endocarditis?

• Bacteriaemia (infection, IV catheter, surgery)

• Damaged endothelium (turbulence, high velocities)

• Ability to adhere to endothelial surface

• Hypercoagulable states

What is being shown here?

• Vegetations endocardial surface of leaflets due to endocarditis

  • Small nodules

  • polypoid

• Perforated, deformed, calcified

What are the microscopic findings of endocarditis?

• Platelets, RBC, WBC, bacteria, fibrin

• Fibrous tissue, calcification

• Bacteria within vegetation

How is endocarditis diagnosed?

• Haem, biochem

• Troponin 1

• Blood culture (often -ve)

• Echo —> valvular vegetations, size, regurg, systolic dysfunction

What does troponin measure in cf to BNP?

Troponin —> damage of myocytes

BNP —> myocardial stretch

Major and minor criteria of endocarditis

How is endocarditis treated?

• IV bacteriocidal AB broad therapy

• Long term oral when discharged

• +/- Anticoagulant (clopidogrel, aspirin)

• +/- CHF tx

Guarded prognosis & recurrence + complications poss, long term valvular damage