Murmurs
are abnormal heart sounds longer in duration than normal heart
sounds. They generally
arise from turbulent blood flow (vibrations). The
turbulence can be due to changes in blood viscosity (anemia),
abnormal flow patterns
through
cardiac chambers, or narrowed (stenotic) or floppy (insufficient)
heart
valves.
Murmurs are
graded based on loudness, to aid in communication between
different
examiners
and as a
means for future comparisons.
Grade I
softest audible murmur, heard only with special effort
Grade II
faint murmur clearly heard after a few seconds auscultation
Grade III easily
heard murmur of moderate intensity.
Grade IV loud
murmur which does not produce a palpable thrill
(Thrill
= vibration of chest wall).
Grade
V very
loud murmur which produces a palpable thrill but not heard
when
stethoscope is removed from the chest wall.
Grade
VI very loud
murmur producing a thrill and heard
when
stethoscope is removed from chest.
Types of
murmurs:
Non-Pathologic vs Pathologic
Some soft
murmurs are non-pathological with no evidence of
structural heart
disease. These are most
commonly detected in young animals less than
6 months
of age due to anemia
(decreased number of red blood cells).
Pathologic
murmurs may be classified
as:
Organic
- caused by disease of the heart valves, or chamber wall, etc.
or
Relative -
secondary
to enlargement of the heart or blood vessels.
Causes of
organic heart murmurs include:
Aortic
stenosis, pulmonic stenosis, atrial septal defect, ventricular
septal defect,
patent ductus
arteriosus, AV (Mitral or Tricuspid) valve insufficiency,
Semilunar
(Aortic or Pulmonic) valve insufficiency, or AV valve
stenosis.
As you can see
from the long list of heart diseases, a murmur can be caused
by many
things. Therefore, a cardiac work-up is
recommended to
best determine
the underlying cause and possible
therapy.
A
cardiac work-up may include:
Blood tests to
rule out thyroid disease, kidney or liver disease, and
electrolyte
abnormalities.
Blood Pressure
Measurement
Electrocardiogram
(ECG)
Chest Xray
(radiograph), or
Ultrasound
(echocardiogram).
Following a
cardiac work-up, medications may be prescribed to slow the
progression
of heart
disease, while other pets may just be monitored at
annual exam
visits.
Heart
disease may affect the right, left or both sides of the heart.
Left-sided heart failure clinical
signs include:
Difficulty breathing
Coughing
Decreased stamina.
Right-sided heart failure signs include:
Decreased appetite
Weight
loss
Gradual
abdominal enlargement from fluid build-up,
Occasional vomiting and diarrhea,
and
swollen limbs.
In many
cases, signs of both right and left heart failure are present.
HYPERTROPHIC CARDIOMYOPATHY (HCM)
is
a common cause of heart murmurs in cats and can only be
definitively
diagnosed with an ultrasound of the heart.
Click on
the blue hyperlinks below to learn more about this disease.
http://www.newmanveterinary.com/felhcm.html
http://www.winnfelinehealth.org/Pages/HCM_for_Breeders_rev_2006.pdf
Dr.
Williams' cat Pistol was diagnosed with HCM when he was 3 years old
in 1993
following an echocardiogram at the University of Illinois
College
of Veterinary Medicine by cardiologist Dr. David Sisson.
Pistol is currently taking once daily heart medicine
and
has been
living a long and happy life (knocking loudly on
wood ;-).
