Cardiology: Valvular Heart Disease Flashcards
What is the most common cardiac disease in the dog?
Myxomatous degeneration of the atrioventricular valves
Usually the mitral valve
What is the mean survival time once a dog develops congestive heart failure?
Less then one year
What is the definition of myxomatous degenerative valvular disease?
Nodular thickening of the cardiac valve leaflets associated with proteoglycan accumulation
- What breeds are affected?
- How are different breeds affected differently?
- Affects small breed dogs in particular- usually middle aged
- Large breeds can be affected and usually progress more rapidly
CKCS have earlier age of onset
What are potential aetiologies of myxomatous degenerative valvular disease
Idiopathic
* Abnormalities in collagen and ECM
* Abnormalities of serotonin signalling
* Mechanical stress
* Genetic basis
Describe the pathology of MDVD?
Macroscopically
* Deformed, thickened leaflets- rolled edges, can prolapse
* Elongation and thickening of chordae tendinae
* Jet lesions/left atrial tears
* LA dilation
* LV dilation
Microscopically- accumlation of glycosaminoglycans
Eccentric hypertrophy- volume overload
Describe the pathophysiology of MDVD
- Prolonged, compensated, preclinical phase- gradual development of left atrial and left ventricular remodelling
- Congestive heart failure develops- severe mitral regurgitation, elevated left atrial pressure and RAAS increases preload
- Pulmonary hypertension occurs to chronially elevated left atrial pressure and can be seen secondary to concurrent respiratory/lung pathology
Describe how mitral regurgitation leads to increased afterload
- Mitral regurgitation causes reduced forward stroke volume
- Increase in volume of blood entering LV in next diastole- volume overload
- This causes drop in blood pressure- activation of RAAS
- Vasoconstriction which increases afterload
- Increased mitral regurgitation
What are the neurohumoral effects of MDVD?
Sympathetic nervous system activation
* Tachycardia
* Positive inotrope
* Vasoconstriction
RAAS
* Retention of Na and fluid
* Increased circulatory volume
* Vasoconstriction
Remodelling
* eccentric myocardial hypertrophy- improved systolic function
What are the sequalae of MDVD neurohumoral effects?
Sympathetic-tachy/vasoconstriction
* toxic for myocytes intracellular Ca overload
* Increased O2 demand
* cell death- decrease in systolic function
RAAS
* Increased volume- congestion- increased hydrostatic pressures
Remodelling- eccentric hypertrophy
* fibrosis (arrhythmias)
* Increased wall stress
* Dilation of the valvular annulus-
What is the ACVIM consensus statement on MDVD staging?
- A- at risk
- B1- murmur no enlargment
- B2- murmur and enlargment
- C1- hospitalised CHF
- C2- CHF at home
- D1- refractors hospitalised
- D2- refractory at home
What are the likely clinical presentations to MDVD?
- Adult dogs
- Small breeds
- Heart murmur- asymptomatic
- Cough
- Breathing changes
- Excercise intolerance
What is marked left atrial enlargment usually associated with?
Severe disease
* Compression of the caudal mainstem bronchi- chronic cough
* Increased filling pressures-backpressure pulmonary oedema
* Forwards/backwards failure leads to reduced capability to excercise
What may the history of MDVD be?
- Abnormal respiration
- Cough
- Excercise intollerance
- Heart murmur
- Collapse, syncope
- family history
- Increased water intake
What should be assessed in a physical examination with suspected MDVD?
- Breathing pattern- before touching patient
- Tacypnoea/dyspnoea
- MMs- often normal
- Ausculatation
Lungs- increased sounds, crackles, tachy/dys (oedema)
Heart
- What different heart diseases hypotension/hypotension suggest?
- How can blood pressure be measured?
- Hypertension- increased mitral regurgitation
Hypotension- CHF - Doppler, oscillometric- forelimb/hindlimb, tail
What are the different cardiac biomarkers used in clinical pathology?
What are they markers of?
NT-proBNP
* marker of heart failure
* released by atrial/ventricular stretch
* Helpful to differentiate resp/cardiac cough
* Severity of disease
* Prognostic
NT-proANP
* released by atrial stretch
* More studies needed
Troponin I
* Myocardial cell damage marker
* Prognostic indicator
* Response to treatment
Pre-renal azotaemia in CHF with reduced cardiac output
What radiographs can be used for diagnosis?
Consider patient stability
DV and right lateral
* Cardiac size- tracheal elevation, bulges, VHS
* Pulmonary vessels
* Lung infiltrate
* Effusions
How is a heart measures using the VHS?
vertebral heart scale
- Draw a line from the base to the apex
- Draw a line at the widest point
- The number of vertabrae transversed from T4 are added together for the VHS
What does this image show?
What is the arrow pointing to?
Cardiomegaly
Arrow = LA
What is the arrow pointing to?
Dilated LA
What does this image show?
Congested pulmonary lobar vessels
What does this image show?
Congested pulmonary lobar vessels
What are common arryhtmias of MDVD?
- Supraventricular premature complexes
- Atrial fibrillation
- Ventricular premature complexes
DOES NOT MEAN CHF
What can echocardiography be used for?
What does it show for MDVD?
Confirm diagnosis, Progression, severity
MDVD
* Enlarged LA>LV
* Significant mitral regurg
* Dilated LV
* Rounded LV
* Hyperdynamic systolic function
* Tricuspid regurg
* Pulmonary hypertension
* LA 1.5x size of aorta
What is the purpose of an ambulatory ECG?
- 24 hr ECG
- Quantification of arrhythmias
- Atrial fibrillation: response to treatment
- VPC- number, complexity
What treatment is indicated at each stage of CHF?
- A- none
- B1- none
- B2- pibobendan
- C- CHF therapy as standard: FPAS
- D- as for C with increasing doses and additional (sequential nephron blockage)
What is the standard CHF therapy?
- Furosemide
- Pimobendane
- ACE inhibitors
- Spironolactone
What drugs can be used for the treatment of the following problems?
1. Arryhtmias
2. Pulmonary hypertension
What neutraceuticals can be given?
- Supraventricular- diltiazem, digoxin
Ventricular- sotalol - Sildenafil, Pimobendan
Neutraceuticals- Omega 3 fish oils, taurine
What are the predictors of prognosis of MDVD?
- LV dimensions
- LA enlargment
- Rupture of major chorda
- NT-proBNP
- What is the definition of endocarditis?
- What are the potential infectious agents?
- Infection of 1 or more endocardial surfaces
- Streptococcus spp, staph, E.coli, Pseudomona, Bartonella
What are the requirements for infective endocarditis?
- Bacteriaemia- infection, IV catheter, surgery (rancid teeth)
- Damaged endothelium- turbulence, high velocities
- Ability to adhere
- Hypercoagulable states
What does infective endocarditis cause in the heart?
- Vegetations on endocardial surface of leaflets- small nodules, polypoid
- Perforated, deformed, calcified
- Microscopic findings- platelets, RBCs, WBCs, bacteria, fibrin, fibrous tissue
How is infective endocarditis diagnosed?
- Haematology
- Biochemistry
- Blood culture- prior to ABs, aseptic technique
- Method- at least 3 puncture sites, 10ml per sample
- Echocadiography
Valvular vegetations
Size- risk embolisation
Regurg- murmur
What are the different features that mean either major criteria or minor criteria for infective endocarditis?
Major
* Positive echo- vegetative, erosive, abscess
* New valvular insufficiency
* Positive blood culture- <2 positive cultures, >3 positive cultures with skin contaminant
Minor
* Fever
* Medium/large breed
* Subaortic stenosis
* Thromboembolic disease
* Immune-mediated disease
* Positive culture not meeting major criteria
* Bartonella serology >1:1024
What therapy can be given for infective endocardititis?
ABs
* Bactericidal
* Combination
* IV initially
* Minimum 6 weeks
Anticoagulation- clopidogrel, asprin
Guarded prognosis
