Norwegian Forest Cat HCM DNA Research Project


Papillary Muscle Articles & Links

useful data compiled from various sources as noted below

submitted by Colleen McGrady/Finnishline, NY

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.

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