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cardiac murmurs and abnormal sounds, Innocent and physiological murmurs:…

- - - - normally over 5th or 6rh intercostal spaces at the level of the costochondral junction on the left, one or two intercostal spaces further cranially on right
    - - events at start of ventricular systole
        
        left (mitral) and right (tricuspid) AV valves close and the ventricles start to contract
        
        the AV valves, chordae and papillary muscles come into a state of tension and generate vibrations (S1)
- - - - e.g. hypothyroidism, DCM
- - - - early diastole
      - ventricular filling causes vibrations
      - CHF of any cause
      - AV valve or aortic regurgitation
      - high output states e.g. severe anaemia, hyperthyroidism
      - varies with intensity during respiratory cycle and accentuated by exercise
    - - just before S1
      - arises from the inflow of blood into the ventricles by atrial contraction and transient exposure of AV valves
      - like s3 esp. audible when ventricular compliance is reduced e.g. hypertrophic cardiomyopathy
    - - note: sometimes heard in normal cats after sedation
- - - - asynchronous activation of the ventricles
- - - - leads to turbulence, vortices and micro bubble formation
    - - changes in blood viscosity
      - increased velocity of blood flow
      - changes in the shape of the chamber or vessel within which the blood is flowing
        
        passage of blood from a narrow region into a much larger one
  - - - e.g. due to congenital AV valve dysplasia
      - e.g. due to acquired endocardiosis, endocarditis, or chordal rupture
      - e.g. secondary to valve annulus due to another cause e.g. cardiomyopathy
    - - VSD, PDA
    - - congenital or pulmonary or (sub) aortic stenosis, aortic valve endocarditis
    - - 'relative stenosis'
      - left to right shunting through an atrial septal defect leads to abnormal flow through the right AV valve and pulmonary outflow tract
  - - - e.g. anaemia
        
        if Hb levels falls bellow approx. 6g/dl
      - hypoproteinaemia
      - fever
      - hyperthyroidism
      - stress
      - following sedation
  - - - innocent puppy/kitten murmurs are thought to be caused by an increased stroke vol relative to aortic size
    - - no structural defects or other abnormalities can be detected