Equine Cardiac Auscultation: When is a Murmur Significant? Flashcards
what are the 3 causes of murmurs
- regurgitation
- increase in velocity of flow
- decrease in blood viscosity
what are the things you need to consider when looking at a murmur (6)
- intensity
- timing
- frequency
- topographic location
- shape
- radiation
what a systolic murmur
begins with or after S1 and ends before/with S2
lusssshhh-dup
what is a diastolic murmur
begins with or after S2 and ends with or just before S1 of next cycle
lub-dup-psssshh
what are the grades of murmurs
grade I: soft, audible after careful auscultation
grade II: faint but clearly audible
grade III: equivalent intensity to S1 and S2
grade IV: increased intensity but no palpable thrill
grade V: palpable thrill
grade VI: audible anywhere on body with detectable thrill
what are the murmur shapes
what are nonpathological murmurs
functional murmurs without organic heart disease
what are systolic functional murmurs
usually < grade III early to mid-systolic
common in young fit/excited horses
common in neonates
accompany colic/colitis/endotoxemia
what are diastolic functional murmurs
low grade presystolic or early diastolic murmur
lub-dub-sh
very short
what are metabolic murmurs
- increased turbulence of bloodflow due to decreased viscosity (anemia, babesia, severe thrombocytopenia)
- altered hemodynamics
- altered peripheral resistance (colic, endotoxemia)
what are systolic pathological murmurs
- tricuspid valve regurgitation
- mitral insufficiency
- ventricular septal defect
- acute onset following rupture of chordae tendinae
what are pathological diastolic murmurs
aortic insufficiency
what are the most common valve regurgitation
- tricuspid
- mitral
- aortic
- pulmonic
where is the point of maximal intensity (PMI) of mitral insufficiency
on the left side
with dorsal radiation
can you still hear S1 and S2 in mitral insufficiency
yes if below grade III
what type of murmur sound is a mitral insufficiency
plateau
what might be audible in mitral insufficiency
buzzing if there is vibration of the valve leaflets caused by rupture of chordae tendineae
what is the significance of mitral insufficiency if it is quite and localized
unlikely to be relevent in near future but may deteriorate over months/years
what is the significance of mitral insufficiency if its > grade 3 or if there is widespread radiation
advise against purchase for athletic use unless echo shows no volume overload
if echo shows no abnormality consider rate of progression and discuss
what is the prognosis of mitral insufficiency if there is exercise intolerance
guarded if there is exercise intolerance or FS % < 30%
what can significant mitral insufficiency lead to
left atrial dilation and pulmonary hypertension
atrial fibrillation may be sequel to atrial enlargement with resulting exercise intolerance
what does M-mode ultrasound of the heart show
- can measure the % fractional shortening
- measure the ventrical internal diameter during diastole and systole
where is the PMI for tricuspid insufficiency
on right side in the tricuspid valve area with dorsocaudal radiation
what type of murmur sound is tricuspid insufficiency
plateua systolic murmur
are S1 and S2 still audible in tricuspid insufficiency
yes
can tricuspid insufficiency affect athletic performance
rarely
but grade 3/6 right-sided systolic murmur in horse with atrial fibrillation –> tricuspid regurgitation and right atrial enlargement could affect performance
what do negative prognostic indicators in tricuspid insufficiency include (3)
- structural valve lesions (endocarditis, rupture chordae tendinaea, flail leaflet)
- clinical signs of CHF
- or severe mitral regurgitation and pulmonary hypertension
when is echocardiorgraphy recommended to investigate a tricuspid insufficiency further
in a horse intended for athletic function with > grade 3/6 right sided systolic murmur
but remember these are common and often not significant
if there is severe tricuspid insufficiency what might be some clinical signs you would see
- positive jugular pulse, venous distension
- ventral edema
- signs of right sided heart failure (tachycardia, ventral edema)
what pathology can severe tricuspid insufficiency lead to
leads to regurgitation of blood into right atrial –> right atrial dilation –> jugular pulsation and peripheral edema
what can tricuspid insufficiency be secondary to
severe tricuspid insufficiency may be secondary to pulmonary hypertension –> mitral valve regurgitation and increased preload waiting to return to left side –> eventually contributes to secondary pulmonary hypertension which can cause tricuspid regurgitation
scrutinize for concurrent left sided disease or pulmonary disease
what type of murmur will a ventricular septal defect produce and where is the PMI
grade 4/6-5/6 band shaped systolic murmur
PMI: right cranioventral thorax
is S1 and S2 audible in a ventral septal defect murmur
no it obliterates S1 and S2
wide radiation and thrill
what type of murmur is similar to ventricular septal defect
similar murmur heard on left base with PMI over pulmonic valve
caused by relative pulmonic stenosis due to L-R shunt
if not audible on left, tricuspid valve regurgitation is more likely
what side of the thorax is a ventricular septal defect heard more loudly
on the right but it is detectable on the left as well
are horses with ventricular septal defect suitable for athletic use
no
when could a horse with ventricular septal defect be suitable for athletic use
if there is restrictive size
normal RV volume
nromal interventricular septum motion dectected on echo
but unlikely to be suitable top performers
when will a horse with ventricular septal defect likely start to decompensate
usually 3-4 years
what is shown here
ventricular septal defect
what are the risk factors for ventricular septal defect
- young animals
- arab foals
- welsh ponies
how is ventricular septal defect diagnosed
echocardiography
shows an LV outflow tract view and lesions beneath aortic valve leaflets
what size of ventricular septal defect can horses live a normal life
if its less than 5mm
what are good prognositc indicators of ventricular septal defect
- small defect (0.5-2.5cm)
- high velocity jet of >4.5 m/s
- no significant increase in LV dimension
- no significant concurrent aortic or mitral regurgitation
what are poor prognostic indicators of ventricular septal defect
- large defect >2.5cm
- low velocity jet (higher volume)
- increase in LA and LV dimension
- significant concurrent aortic or mitral regurgitation
what is tetralogy of fallot
- over-riding right sided aorta
- pulmonic artery stenosis
- ventricular septal defect
- RV hypertrophy
what type of murmur occurs with tetralogy of fallot
left sided systolic murmur > grade 3/6
how is tetralogy of fallot diagnosed
- cyanosis and poor growth
- R-L shunting across VSD because of RV outflow obstruction (stenotic PA)
- left sided systolic murmur > grade 3/6
what type of murmur is aortic insufficiency
grade 2/6-4/6 holodiastolic murmur
where is the PMI of aortic insufficiency
left base over aortic valve radiating to left cardiac apex
what is the signalment of aortic insufficiency
usually in older horses with degenerative changes to the valve
what should you also do when grading an aortic insufficiency murmur
measure the HR
resting HR >40 bpm may be significant
also palpate the pulse pressure –> bounding or weak
why is it important to palpate the pulse pressure in aortic insufficiency
if it’s bounding the murmur is likely significant
but if the horse is decompensating then it may be weak
what can aortic aortic insufficiency lead to
left sided overload can lead to pulmonary hypertension which can cause right sided failure –> exercise intolerance and if horse is decompensating then it will have a rapid heart rate and decrease the oxygen getting to the heart and cause fatal dysrhythmia –> potential for acute collapse
what is more likely to cause right sided failure in horses
left sided overload
what predisposes a horse to atrial fibrillation
atrial enlargement that occurs with significant aortic or mitral insufficiency
what are poor prognosis indicators of aortic insufficiency (6)
- weak or bounding pulse
- LV overload and hyperkenesis
- valve thickening
- enlargement of aortic root
- concurrent ventricular dysrhythmia
- concurrent mitral regurgitation
what does severe aortic regurgitation lead to
left ventricle enlargement
how do you assess the severity of aortic regurgitation
- area of regurgitant jet and velocity
- size of left ventricle
- pulmonary hypertension and PA distention
- exercising ECG for presence of ectopic beats
- any mitral valve regurgitation
- measure size of aortic route
what is the significance of aortic insuficiency
significance in young animals
grades > 2/6 need careful evaluation
rate of progression must be assessed
may be extreme tachycardia and poor ventricular bloodflow at higher levels of exercise
acute cardiac output failure at exercise may lead to acute collapse
where is the PMI of pulmonic insufficiency
rarely able to auscultate
very unlikely to cause cardiac compromise
how is pulmonic insufficiency diagnosed
echocardiography
what is the pathogenesis of bacterial endocarditis
- damage to endothelium/valve substance
- platelet adhesion and fibrin formation
- bacterial colonization
what bacteria can cause bacterial endocarditis
Streptococcus or Actinobacillus
what valves are most commonly affected in bacterial endocarditis
aortic > mitral > tricuspid > pulmonary valve
what are the clinical signs of bacterial endocarditis (7)
- intermittent fever
- murmur
- weight loss
- lethargy
- depression
- secondary septic arthritis
- renal or pulmonary complications
how is bacterial endocarditis diagnosed
- echo
- blood culture when febrile
- inflammatory leukogram and raised acute phase proteins
how is bacterial endocarditis treated
gentamicin (6.6 mg/kg QID) and penicillin G (50,000 IU/kg QID IV) prior to bacterial culture results
what is the prognosis of bacterial endocarditis
guarded
persistant valvular incompetence
what are the causes of pericardial effusion and pericarditis
- septic
- non-septic
- neoplastic
- idiopathic
what might pericardial effusion be a sequel to
pleuropneumonia
EHV-1
or part of generalized congestive heart failure
how does pericardial effusion and pericarditis lead to cardiac insufficiency
- fluid accumulation and thickened/inflammed pericardium
- cardiac tamponade
- decreased diastolic filling
- cardiac insufficiency
what other tests could be used to diagnose murmurs
- blood work
- PaO2
- PaCO2
- pH
what blood work indicators can assist with murmur diagnosis
- chemistries: may reflect hypoperfusion of organs if heart failure (prerenal azotemia, increased liver enzymes, lactic acidosis)
- serum cardiac troponin I may be increased with myocarditis
- white blood cell counts informative if any inflammatory response (left shift neutrophilia)
- increased fibrinogen and in serum A amyloid in endocarditis
