CVRS Flashcards
What are the heart sounds indicating
S1 - Closure of AV valves and the beginning and systole
S2 - Closing of SL valves, beginning of diastole
*S3 - end of ventricular filling
*S4 - atrial contraction
* pathogenic if heard in cats and dogs.
However normal to hear s4 and possibly s3 in horses
What is heart failure and what are the different types
Inability to maintain normal cardiac output at normal filling pressure
> Forward failure - Inadequate delivery of blood into arterial vessels
> Congestive/backward failure - Normal output but abnormal pressures
> Forward and Backward failure - Inadequate CO and Abnormal pressure
What can taurine deficiency cause
Dilated cardiomyopathy in cats
Define the terms pump failure, Volume overload and pressure overload
> Pump failure - Failure of systolic function of myocardium results in inadequate stroke volume = decreased CO. (e.g DCM)
> Volume overload - Disease resulting in chamber chronically increasing output resulting overwork and eventually failure. ( e.g valvular insufficiency, chronic anaemia or a shunting disease)
> Pressure overload - Diseases that chronically increase pressure in which ventricle ha to pump blood eventually causing failure of myocardium. (e.g hypertension or pulmonic/aortic stenosis)
What is fractional shortening
Percentage change in LV diameter in diastole in comparison to systole
What are the principles of heart disease treatment
> Diuretics - Furesomide is most commonly used at 2mg/kg. Used when signs of pulmonary oedema. Will cause Hypokalaemia long terms
> Venodilators - Decrease venous pressure causing a decrease in preload. Include glyceryl trinitrate
> Venodilators - Cause a decrease in afterload. include ACE inhibitors such as enalapril. These reduce resistance to outflow (increasing SV) reduce cardiac work ( decreasing the myocardial 02 demand).
> Positive inotropes - Contraindicated in HCM cases but work for any dilated cardiomyopathy. Pimobendan best drug, Increase the Ca+2 ability to bind to troponin. Also thought to inhibit RAAs system.
> Increase diastolic function - Useful in HCM cases. use betablockers like atenolol
What are functional murmurs in horses
These are mumours which are physiological with no attached pathology. Always < grade III
> Usually a high pitch ‘wheap’ heard after S2. Due to aortic flow.
> Can also be seen due to valve regurgitation in training thoroughbreads. PMI at AV’s (apex)
What are the most common causes of heart murmours in horses
> Mitral regurgitation - PMI over L 5th intercostal space. Always systolic. Risk of pulmonary artery rupture = death
> Tricuspid regurgitation - PMI over R intercostal space. Always systolic
> Aortic regurgitation - Often due to endocardiosis in old horses. Usually progressive. Holodiastolic. A bounding arterial pulse seen.
> Patent PDA - young horses 7-10d. Continous washing machine murmour, systole and diastole. grade 3-5. PMI over L base.
- Valve regurg is said to be pathological if associated with poor performance, resting tachycardia, arythmias or any signs of hear failure
What causes septic pericarditis in cattle, what is the clinical signs and how is it diagnosed and prevented
Caused by ingestion of wire/nails, which forces through the wall of the reticulum, punctures into the peritoneal cavity, through diaphragm and into pericardial sac. Causes a fibrous cheesy exudate.
> Early signs - Fever, anorexia and depression
Later signs include right sided heart failure
On exam will have muffled heart sounds, washing machine murmur, tachycardia.
Diagnosis based on ultrasound
What causes pericarditis in pigs and what are the clinical signs
Caused by haemophilus parasuis.
> Clinical signs include fever, depression, effusions in CNS.
What Causes endocarditis
Usually secondary to bacteraemia e.g metritis, mastitis, peritonitis e.t.c.
Clinical signs include
> CHF murmur
> Fever and tachycardia
> Fibrinogen, anaemia and leucocytosis ( increased white blood cells)
Treatment with a broad spec antibiotic
What causes cardiopulmonary disease
Chronic pulmonary disease causes hypoxia in alveoli. results in pulmonary vasoconstriction and hypertension causing right sided heart failure
Whats an aneurysm
Vascular dilation due to weakening of the elastic tissue
Describe thrombophlebitis in horses
Inflammatory process causing blood clot to form in the vein, causing pain, swelling and thickening of the vein.
> Associated with catheters that are left in for 24-48 hours.
> increased risk if in hypercoaguable state.
Treatment involves removing catheter, broad spec antibiotics, ant inflam and anticoagulants
Describe features of Degenerative mitral valve disease and the stages
Distortion in the leaflets causing insufficiency. Increase in ventricular SV causing dilation of the ventricle and increasing leakage into the atrium causing atrial dilation Typically effecting small breeds.
Classification:
> B1 - Leak in the heart but no enlargement
> B2 - Leak and enlargement of heart but no clinical signs
> C - clinical signs associated with pathology
> A - Refractory signs of heart failure
Diagnosis - Left systolic murmur with varying grades, exercise intolerance, dysponea or signs of RCHF.
> On radiograph can see pulmonary venous congestion and pulmonary oedema.
Describe features of bacterial endocarditis in dogs
Infection of endocardium, typically valvular. Clinical signs: > Pyrexia > Lameness > Sepsis > Changing murmur Blood culture and echo needed Treatment involves antibiotics.
Describe Dilated cardiomyopathy
Due to systolic failure of the myocardium, causing excessive dilation of the ventricle due to increased end diastolic pressures.
Clinical signs:
> Forwards failure - Intermittent collapse, weakness, sudden death
> Backward failure - cough, exercise intolerance, dyspnoea and ascites.
> Systolic murmur
What are the diagnostic techniques used for arrythmias in horses
> Clinical pathology - Haematology/biochem, acid and base, selenium (white muscle disease) and gluthanione peroxidase, viral serology and blood bacterial culture, creatine kinase (heart parameter)
> Echocardiography - used to rule out valvular disease and congenital heart disease.
> ECG - Size and shape of the heart not reflected accurately on ECG because the purkinje fibres run along endocardium and into epicardium meaning theres less cell to cell propagation unlike in carnivores where purkinje fibres run along endocardium only. ( positive electrode on left apex and negative on left base)
* ambulatory ecg left on for 24 hours
.
What are specific equine arrythmias
> First degree av block - Delayed conduction through AV node (physiological)
> Second degree AV block (physiological) - Intermittent block of conduction through AV node ( due to high vagal tone = increased refractory)
> Third degree AV block - always pathological. Complete block of conduction through AV node
> Atrial fibrilation - Easily confused with secondary AV block. Initiated by:
- Large atrial mass with normal or horse regurgitation
- Slow SA node route = increased vagal tone
- variable refractory period - due to myocardial disease or increased refractory period.
Lots of refractory myocardium, must travel through non refractory muscle.
Only effects animal at excercise because only 15% of ventricular filling is due to active phase. no 4th heart sound
What is the treatment for atrial fibrilation in horses
If its a incidental finding no treatment
If in a competitive horse given quinidine
If in heart failure, furosemide, ACE I and digoxin
> Quinidine - Prolongs effective refractory period, class 1a antiarrythic, slows fast Na channels. But causes vagolytic effects (ventricular tachycardia), hypertension, GI ulcers. Therefore >Treated with digoxin prior, control vagolytic effects. stomach tube every 2 hours for 6 doses or until signs of toxicity ( tavchycardia, colic/diarrhoea or QRS widespread by 25%)
What is the treatment of choice for horses with ventricular arrythmias
Procainamide
Describe the result of HCM
Lv doesnt relax and becomes stiff causing diastolic dysfunction. Also no extra blood vessels for the extra muscle causing ischaemia and scar tissue formation.
> Results in pulmonary oedema, intra cardiac thrombus due to stasis in the LA, thrombus lodges in bifurication of aorta, causing ischaemic damage to nerves in the hindlegs causing saddle thrombus = euthanasia.
What is SAM
Systolic anterior motion of the mitral leaflet. At systole, anterior leaflet of mitral valve moves towards ventricular septum causing narrowing o the outflow tract and allows regurgitation into left atrium. LV must work harder to push blood out of outflow tract possibly causing ischaemia
What is clopidogrel
ADP inhibitor. Used for animals with a large left atrium, reducing the risk of thromboembolism.
