Equine Cardiac examination Refresher and Murmurs Flashcards
How does cardiac disease most commonly present in horses?
- Incidental e.g. pre-purchase exam
- History of poor performance
- Systemically ill horse
- Horse presented with evidence of heart failure (rare)
What are the aims of investigation when investigating cardiac disease in horses?
Need to establish significance of any findings:
- Cardiac murmurs/dysrhythmias are COMMON
- Significance for performance?
- Collapse?
- Progression?
- Interpret in context of use/intended use of horse
Describe how to auscultate a horses heart
- Quiet environment
- Take time
- Let horse settle
- Get into the rhythm
Listening on the RHS:
- Pull leg forward
- Stick stethoscope bell right under triceps just dorsal to point of elbow
The apex beat in horses correlates to which valve?
Mitral
Name the valve that lies between the right atrium and ventricles
Tricuspid valve
Name the valve that lies between the left atrium and ventricles
Mitral
Systole = ?
Diastole = ?
Systole = contraction
Diastole = relaxation
Describe the S1 and S2 heart sounds
Ventricles contract:
- S1 : Shutting of AV valves (Mitral/tricuspid)
- “ LUB “
Ventricles relax
- S2 : Shutting of Semilunar valves (Aortic/Pulmonic)
- “ DUP “
Describe the other heart sounds heard in a horse
S4: atrial contraction
- “ B “ Very common
- Just before S1
S3: end of rapid ventricular filling
- “ D “ Less common
- Just after S2
How does mitral valve regurgitation affect the heart sounds in horses?
Causes a loud S3 due to lots of blood going back into the atrium, it is now full of blood, when the ventricle relaxes lots of blood rushes in, causing a loud sound
Describe which heart sounds are loudest in the basal and apical areas of the heart
Basal - S1 quieter, S2 louder
Apical - S1 louder, S2 quieter
Describe the lengths of systole and diastole in the normal heart - normal HR
Systole is much shorter than diastole
Describe the lengths of systole and diastole in the normal heart - high HR
Duration of systole = Duration of diastole
What is a murmur?
Turbulence of blood flow
Reynolds number influences?
Turbulence
Describe the sound made by normal laminar flow of blood
None - silent
Which factors influence turbulence of blood?
Stenosis of a vessel
Valve regurgitation
Increased blood flow
List the 6 methods of describing murmurs
- Grade
- Timing
- Point of maximal intensity
- Radiation
- Shape of murmur
- Quality of the murmur
Describe the 6 grades of heart murmurs
1 = barely audible
2 = definite murmur quieter than S1 and S2
3 = obvious murmur as loud as S1 and S2
4 = very loud murmur, louder than S1 and S2
5 = very loud and has a palpable thrill
6 = audible with stethoscope just off chest wall
Describe how the timing of murmurs can be used to describe them
Systolic / diastolic / continuous
- Early
- Mid
- Late
- ‘Pan’
- ‘Holo’
Describe the meaning of the term ‘pan’ used to describe the timing of murmurs
Fills up the whole of systole and you can’t hear the heart sounds at either end
Describe the meaning of the term ‘holo’ used to describe the timing of murmurs
Fills up the whole of systole but can hear the heart sounds at either end
How can the shape of the murmur be used to describe it?
‘Plateau’
Crescendo
Decrescendo
Crescendo/decrescendo
Name the 2 categories of murmurs
- Physiological/functional
- Pathological
Physiological/functional murmurs are associated with..?
Normal blood flow through heart
Physiological/functional murmurs are associated with..?
Normal blood flow through heart
Pathological murmurs are associated with..?
Underlying cardiac disease
Name the two main types of pysiological/functional murmurs
Flow murmur
Filling murmur
Describe the features of flow murmurs
- Early-mid systole
- Up to 60% normal horses; L>R
- Localised over heart base (aorta)
- May change intensity with HR/exercise
- Always finish before S2
- Crescendo-decrescendo
Describe the features of filling murmurs
- Early diastole, L or R
- Fit, young animals
- Squeak / whoop/ click
- Short duration between S2 & S3
- Localised over heart base or apex
- May change intensity with HR
- Associated with turbulence of blood as it flows into the ventricles in early diastole, but before the walls stop
How common is primary valvular stenosis in horses?
Rare
Describe the murmur caused by Mitral/Tricuspid (AV Valve) regurgitation
- Holo/pansystolic
- Plateau or crescendo
- PMI heart apex
- May radiate dorsal and cranial
At what grades of mitral valve regurgitation is it advised to monitor that horse and what grades require further investigation?
Grade 1-2: Monitor
Grade 3-6: Advise further investigation
At what grades of tricuspid valve regurgitation is it advised to monitor that horse and what grades require further investigation?
Grade 1-3: monitor
Grade 4-6: advise further investigation
Describe the pathological murmur caused by a ventricular septal defect
Loudest on right (occ. left)
Loud – thrill
Radiate cranial/ventral
Pansystolic
Normally young horses
Describe the pathological murmur caused by aortic insufficiency
Common older horses
Descrescendo, buzzing / cooing
Holodiastolic
PMI left heart base
May radiate ventrally
Which murmur of horses is referred to as the ‘teenage murmur’?
Aortic regurgitation
Name the pathological continuous ‘machinery’ Murmur of horses
Patent Ductus Arteriosus
When is a PDA murmur normal?
In neonates up to 5do
Describe the murmur caused by a patent ductus arteriosus
PMI left heart base, also loud right heart base
Waxes and wanes in intensity during cardiac cycle
Name 2 physiological murmurs of horses
Aortic flow murmurs
Ventricular filling murmurs
Name 4 pathological murmurs of horses
Mitral/tricuspid valve regurgitation
Aortic regurgitation
Ventricular septal defect
(Patent Ductus arteriosus)
Name two left and two right systolic murmurs
Left
- Mitral valve regurgitation
- Aortic flow murmur
Right
- Tricuspid regurgitation
- Ventricular septal defect
Name two left diastolic murmurs
- Aortic valve regurgitation
- Ventricular filling defect
