Prince, a ten-year-old terrier, had started to cough. When I examined him with a stethoscope, I heard the classic sign of heart valve disease: a heart murmur.
My dictionary defines the word “murmur” as “ a low, indistinct sound, like that of running water”.  This definition applies accurately to different uses of the word, whether it is a “murmur going around a crowded room” , or a “vet listening to a heart murmur”.

A normal heart has the classical “thump thump” sound that we have all heard before, often as the soundtrack to music or at the movies. More specifically, the noise is usually described as “lub, dup”, since when you say these words, it sounds more like a real heart than “thump thump”. The “lub” and “dup” sounds are caused by the different valves of the heart snapping shut, a bit like tiny doors being slammed inside your chest.

When a dog has a heart murmur, you can hear a low, rustling sound in between the “lub” and the “dup”. If you write down the effect, it is like “lub…shhhhh… dup”, repeated over and over. Heart murmurs are classified according to their volume, from grade one to five, with five being the loudest.

Heart murmurs can be caused by anything that upsets the normal smooth flow of the blood through the heart. The normal blood flow is silent, like a wide, quiet river of water. Heart murmurs are the equivalent of streams, rapids or waterfalls. The noise is produced by the blood flowing turbulently, just as water makes a noise in these situations.

What makes blood flow turbulently? There are many causes, including narrowed valves, irregular contractions of the heart muscle and abnormal structures inside the heart.
The diagnosis for Prince was made via an ultrasound examination which showed a colour, three-dimensional, moving image of his heart. The blood leaking through one of the heart valves showed up in a brighter colour on the screen.

Why does a valve start to leak? For reasons that we do not understand, the structure of some heart valves degenerates prematurely. A normal heart valve fits neatly into place, sealing the entrance to or exit from the heart like a tightly fitting jigsaw piece. A leaky valve is like a jigsaw piece that has been soaked in water overnight. It no longer fits properly, and so blood can escape through the gaps around it.

When a heart valve leaks, the heart is prevented from pumping efficiently, and as a result, fluid accumulates in the lungs. This fluid irritates the airways, causing the cough that was bothering poor Prince.

The only long term cure for a leaky valve is to replace it with a new one. Unfortunately for Prince, the complex surgical techniques involved are not yet available for animals.
Instead, Prince has been treated with a combination of medications designed to make it easier for his heart to cope with the continual workload of pumping the blood around the body.  He started off on one tablet, and his cough resolved completely for a while. After some months, the cough recurred, and a second tablet was added.
Nowadays, Prince is on three tablets, given several times daily. He is in great form, and to an outsider, he looks like a perfectly healthy terrier, exercising normally and enjoying life. His owner knows that he will not live as long as a normal dog, but Prince doesn’t know this, and he is a happy, busy, active terrier. Let’s hope he carries on this way for as long as possible.

Read Pete’s Pets every week in Ireland’s Own