Nibbles and Bits - September 2008

We’ve been discussing some geriatric issues in our older pets the past few months. This month we will deal with a set of problems that affect older animals certainly, and our younger patients as well, and that is heart disease.

The most common cause of death in people is heart-related diseases, most commonly myocardial infarction or “heart attack”. It actually means that part of the heart muscle (the myocardium) dies due to lack of blood supply, often from arteriosclerosis. This is not something we see in our pets particularly, but we do see a variety of other heart problems.

Small dogs in particular are prone to MI/TI which stands for mitral insufficiency/tricuspid insufficiency. The mitral and tricuspid are valves in the heart. Valves keep blood going in one direction as the heart beats so it doesn’t backflow the wrong way. In older smaller breeds, these valves can become stiff or thickened as they age and so they no longer close all the way. Blood starts to flow back the way it came into the heart. This overloads the heart and makes it have to work harder for pump more blood. Over time, the heart will enlarge and become less efficient. These dogs will start to cough and have exercise intolerance. The good news is, we can often detect the disease before it becomes severe, which allows us to treat them sooner and help the pet live longer. These dogs will generally have a heart murmur which we can hear during the regular physical exam. At that point, we may want to do X-rays to see the size and shape of the heart and also see if there is evidence of fluid in the lungs. We may also want to perform an echocardiogram- an ultrasound of the heart- to better evaluate the function. Once we know what is going on in the heart, we can choose the best medications to help the heart do its job easier and more efficiently.

Large and giant breed dogs and also cocker spaniels are more prone to Dilated Cardiomyopathy (DCM), which is caused by the heart muscle becoming very thin, so decreasing its ability to pump blood. X-rays and ultrasound are used to diagnose this serious disease. It can be harder to detect early because there is not always a murmur present and also because it can progress very rapidly. These dogs tend to become tired easily, may cough, lose weight and may even have episodes of fainting (called syncope). They can have irregular heart rhythms as well (called arrhythmias). DCM can affect older dogs and younger ones as well.

Cats are not immune to heart disease. Older cats can get Hypertrophic Cardiomyopathy which is a thickening of the heart muscle. It can become so thick that there is not much room inside the heart for blood to flow through. The heart will beat faster and faster as it tries to circulate the blood but this eventually backfires and decreases the bloodflow. Sometimes we hear a murmur and sometimes we hear a “gallop rhythm”- an extra heartbeat sound. Older cats with hyperthyroidism (an over-active thyroid) will get a similar disease, but treating the thyroid problem will usually reverse the heart problem. X-rays help to diagnose heart disease in cats, but often an echocardiogram is also needed since many of the changes occur inside the heart and don’t change the outside shape much.

Having your older pet get a physical exam once to twice a year helps us to find these problems earlier and the sooner they are diagnosed and started on treatment, the longer and better quality of life we can give them.

Next month, we will go more into heart diseases of younger animals.