Description

Heart murmurs are abnormal sounds heard when the heart is listened to, usually with a stethoscope. They are caused by turbulent blood flow and they may or may not be associated with heart disease. In other words abnormal heart sounds, or murmurs, are sometimes not associated with primary heart disease. Examples of other causes includeanaemia, hyperthyroidism and fever.

Further diagnostic tests (eg echocardiography) are needed to determine the precise cause of a murmur , although the position and characteristics of the murmur can give a very good indication of the likely cause eg a leaking heart valve.

Inherited defects (eg "hole in the heart" and other abnormalities) are usually detected early in life during routine screening before vaccination.

Common murmurs in dogs

 

Cause	Location (loudest sound)	Usual Characteristics
Innocent murmurs - no cardiac disease present	Left hemithorax usually	Soft, early systolic, radiate poorly, vary with heart rate of the puppy. Disappear by 9 months age.
Aortic valve stenosis	Left or Right Heartbase or subaortic; over the 3rd-4th intercostal space	Crescendo or Crescendo-decrescendo during systolic ejection. High pitched and radiates widely and cranially towards the thoracic inlet.
Atrial septal defect	Left heartbase	May be no murmur present if small defect. Otherwise may be  Crescendo-decrescendo murmur during systolic ejection. Also get abnormal pulmonary sounds due to pulmonary congestion.
Heartworm disease		Decrescendo during diastole
Mitral valve regurgitation	Left apex	Plateau - Regurgitant noise during systole
Mitral valve stenosis		Decrescendo during diastole
Patent ductus arteriosus	Left heartbase. May get a mitral regurgitation murmur at the left apex as well, and a prominent left apical heart beat.	Continuous "machinery" . During systole the murmur radiates, during diastole it is more localised. May get abnormal lung sounds as well due congestion or oedema.
Pulmonic insufficiency		Decrescendo during diastole
Pulmonic stenosis	Left heartbase. Lower 2nd or 3rd intercostal space.  Prominent right ventricular apex beat.	Harsh crescendo or crescendo-decrescendo during systolic ejection. Second heart sound may be split.
Tetralogy of Fallot	Left heartbase pulmonic stenosis murmur, and sometimes a holosystolic right sternal border murmur	Crescendo-decrescendo during systolic ejection. The murmur is loud, but becomes softer as the pulmonic stenosis increases.
Tricuspid valve regurgitation	Right apex	Plateau - Regurgitant noise during systole
Tricuspid valve stenosis		Decrescendo during diastole
Ventricular septal defect	Right cranial sternal border. Occasionally a left heartbase murmur due to pulmonic stenosis is present as well.	Usually a fixed plateau murmur, but may crescendo or crescendo-decrescendo - Regurgitant noise during systole. Usually harsh. Second heart sound may be split.

Last updated : October 2013