Papillary muscles:
Those are the muscles located inside the left and right ventricle, at the
walls and attached to "threads" which are in the other end attached to the
mitral valve. These threads show on the screen as white lines. Papillary
muscles can be enlarged, but they can also be longer than average. This is
easy to confuse with thickening but is entirely different. Some cats can have
split papillary muscles or extra small ones. These anomalies do not seem to
affect the cats at all, contrary to enlarged papillary muscles.
"Another thing are the papillary muscles: If
the papillary muscles are enlarged (and no other anomalies are observed),
they cat will be assessed as equivocal. That is according to Dr Kittleson's
criteria. Some cats just have slightly larger papillary muscles in their
genetic make-up. But it could also be the first signs of HCM; so they are
considered equivocal. We just don't know at that point what it is. If
however a cat has BOTH enlarged papillary muscles and SAM, Dr Kittleson says
HCM positive."
VERY IMPORTANT: Equivocal
means that anomalies have been observed but at the time of the testing, it
is not clear what those anomalies mean or will mean. Not every cat who is
assessed as equivocal, will develop HCM. On the other hand, the possibility
does exist.
Papillary Muscle Measurements in Cats with Normal Echocardiograms and Cats
with Concentric Left Ventricular Hypertrophy
Lindsey M. Diley
Darcy B. Adin, DVM, DACVIM
Department of Small Animal Clinical Sciences, College of
Veterinary Medicine,
University of Florida, Gainesville, FL 32610 USA
Hypertrophic cardiomyopathy (HCM) is a primary myocardial
disease characterized by left ventricular concentric hypertrophy.
Papillary muscle thickness is often noted either concurrently with left
ventricular wall thickness or as the only indication of HCM. Papillary
muscle assessment is subjective. The patient is labeled as normal or
enlarged and accuracy is dependent on the experience of the
echocardiographer. Definitive normal values have been established for left
ventricular wall thicknesses of cats, but cats with normal wall thicknesses
may still have HCM that is manifested as either only papillary muscle
hypertrophy or papillary muscle hypertrophy may be the first
indication of disease.
The objective of this study was to echocardiographically
determine measurements for the left ventricular anterior and posterior
papillary muscles in the right parasternal short axis view for
normal cats and cats with HCM. The study consisted of prospective and
retrospective case reviews of 44 normal cats and 40 cats with HCM. Standard
echocardiographic measurements were recorded for each cat. Three methods of
papillary muscle measurements were taken by one author (LD) in
triplicate from right-sided short axis images at end diastole and averaged
for normal cats and HCM cats. The methods of papillary muscle
measurement evaluated were: 1) area subtraction method; 2) direct area trace
method; 3) diameter method.
This study showed that cats with HCM were older and had
significantly greater septal, left ventricular free wall and left atrial
measurements than normal cats (P < 0.0001). Cats with HCM had significantly
larger papillary muscle measurements as compared to normal cats by
all measurement methods (P < 0.0001). In conclusion, we found that cats with
HCM had larger papillary muscles than those of normal cats
using all three methods of measurements. This study is the first to describe
three novel objective methods for feline papillary muscle assessment
and report ranges for normal and HCM cats. These objective measures of
papillary muscle size will aid in the echocardiographic assessment of
cats being screened for HCM.
Papillary Muscle Articles (humans)
The left ventricular
papillary
muscles
appear to be the last portions of the heart to be perfused by coronary
arterial blood. As a consequence they are sensitive anatomic markers of
myocardial ischemia. Foci of necrosis or fibrosis therefore are commonly seen
in these structures, particularly the posteromedial
papillary
muscle, which has a poorer blood supply than does the anterolateral muscle.
Coronary arterial luminal narrowing is the most common cause of necrosis or
fibrosis of the left ventricular
papillary
muscles.
Other conditions, all associated with inadequate cardiac output, which may
produce these lesions include left ventricular outflow tract obstruction,
especially that resulting from congenitally malformed aortic valves, acute
valvular regurgitation (infective endocarditis), various cardiomyopathies, and
primary endocardial fibroelastosis with or without anomalous origin of one or
both coronary arteries from the pulmonary trunk. Various infiltrative
diseases, including inflammation (Aschoff bodies, sarcoid, abscesses), amyloid,
iron, and neoplasms, also may involve the
papillary
muscles.
Their most common congenital malformation is the parachute or single
papillary
muscle. Fibrosis or necrosis of adjacent left ventricle free wall without
involvement of the papillary
muscles
themselves may simulate clinically "papillary
muscle dysfunction." The anterior
papillary
muscle of the right ventricle is frequently affected by conditions which also
affect the left ventricular
papillary
muscles.
Whether or not necrosis or fibrosis of the right ventricular
papillary
muscle causes tricuspid regurgitation, however, is unknown at present.
Back
to Resource Page
home