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Feline Cardiomyopathies

by Andrea Jensen
Spring 2007


Introduction

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Feline heart disease can take on many forms, and can be congenital or acquired.  The complex anatomy of the heart requires all components to be functioning in perfect balance for long term health.  Increases as well as decreases in the efficiency of blood flow through the four chambers of the heart, to and from the lungs, and out to the body can become progressive and lead to heart failure by a variety of pathways and compensatory feedback mechanisms.  Any abnormalities upon auscultation such as heart murmurs, arrhythmias, gallop rhythms, tachycardia, or bradycardia should be carefully evaluated even in a patient that is otherwise asymptomatic regardless of age.  Cats are notorious for hiding clinical signs until the condition advances to a dangerous level, and the most common cardiac diseases in cats are best managed early.

Heart disease may result from disruptions in function of any of the valves of the heart, function of the papillary muscles or cords that attach to the valves, the size or tone of the major vessels flowing into or out of the heart, the size of the chambers, or the thickness of the chamber walls.  In the geriatric feline, the most common cause of heart disease is myocardial, or related to heart muscle.  The chamber walls are composed of cardiac muscle tissue, and are susceptible to excess or insufficient development from multiple causes.  This discussion will focus primarily on cardiomyopathies commonly seen in the geriatric feline.

First, a brief summary of the flow of blood through the heart may be useful.  After circulating through the body and delivering oxygen to tissues, blood returns to the heart via the vena cava.  It empties into the right atrium, passes through the right atrioventricular valve (tricuspid valve) into the right ventricle, then passes through the pulmonary valve into the pulmonary artery where it is carried to the lungs to become oxygenated.  Fresh, oxygenated blood returns to the heart via the pulmonary vein and empties into the left atrium.  From the left atrium, it passes through the left atrioventricular valve (mitral valve) into the left ventricle, which pumps fresh blood through the aortic valve and into the aorta.  The aorta is the primary artery which leads oxygenated blood away from the heart to feed the body.

Cardiomyopathies

Discussion

Each of the cardiomyopathies described have two things in common.

They are difficult to recognize early without a full evaluation, and they each have the potential to rapidly progress to full congestive heart failure.  When discovered early, they may be managed and kept under control, and sometimes cured depending on the etiology of onset.  As damage progresses, prognosis also progresses from good to guarded or grave.  In late stage cardiomyopathy, there are drug therapies to manage symptoms and temporarily alleviate discomfort, which are a topic for a later discussion, but there is usually no cure for advanced congestive heart failure.  Early detection is the key to recovering from cardiomyopathy of any kind.


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