As we’ve just had Valentine’s Day, we thought we would give you a little introduction to heart disease in dogs and cats, and specifically to the more difficult to diagnose rhythm conditions. These occur when the electrical signals in the heart get confused and can be a result of more common heart conditions, other diseases, or can occur on their own.
Can hearts really skip a beat?
Yes! But it’s pretty rare in dogs and cats – although a lot more common in people. In our canine and feline friends, skipping heart beats usually only happens as a rare complication of other diseases, although some very fit and healthy dogs will skip a beat when they’re breathing. A skipping beat is called an arrhythmia.
The heart contains its own miniature brain called the ‘sinoatrial node’ although you’ve probably heard it called the ‘pacemaker’. This collection of cells regulates the speed at which the heart beats and gives instruction to all of the cells in the heart to ensure they beat at the right time and in the right order. If anything happens to this pacemaker, hearts really can skip a beat. Diseases affecting the heart such as dilated cardiomyopathy or heart failure can cause the pacemaker to stop working correctly, but many diseases affecting the entire body can also cause damage. These include hypothyroidism, urinary obstruction and Addison’s disease. Toxins can also cause problems with heart rate and rhythm, causing a speeding up, slowing down, or missed beats.
There are two main types of arrhythmia that occur; the ‘blocks’ and the ‘pace changes’. Pace changes occur when the pacemaker is running too fast or too slowly, or when the pacemaker is broken altogether, and other cells are taking over and trying to do the same job. A fast or slow heart rate is not always the result of a broken pacemaker, but if your dog’s heart rate refuses to return to a normal rate then it’s certainly possible. ‘Blocks’ occur when the sinoatrial node is working fine, but something is stopping the signal getting to the rest of the heart. This causes true ‘missed beats’.
As arrhythmias often result in a failure of the heart to pump blood correctly, they can cause symptoms of lethargy, difficulty in exercising or breathing, weakness and collapse. Sometimes the collapse appears to be sudden and over quickly, and as such is mistaken for a seizure. As arrhythmias are often a side effect of other diseases in the body, we might find an arrhythmia on a clinical exam or whilst investigating other symptoms.
In order to investigate an arrhythmia, we may take blood tests, do chest x-rays or ultrasound the heart, but an ECG is the most useful test when an arrhythmia is suspected. An ECG is a completely painless procedure that your dog or cat can undergo while conscious. Wires are attached to your pet’s body and the machine started. Over a minute or two, the wires measure the natural electrical pulses moving through the heart. As each pulse of electricity and each beat is recorded separately, we are able to see not only the heart rate, but also the electrical signals that go into making the heart rate, allowing us to identify problems with your dog’s pacemaker or other heart cells. Common findings include the heart beating too fast because the pacemaker has been overrun by another cell, or electrical pulses from the pacemaker that aren’t causing a contraction as they should.
Sometimes the arrhythmia is so infrequent we cannot see it during testing. If we still suspect an arrhythmia, perhaps due to occasional collapse at home, we can do further testing. An ECG monitor vest can monitor your pet continually for 24 or 48 hours, hoping that the arrhythmia will show itself at home. There are also ECG monitors being developed for smartphones, allowing you to monitor an arrhythmia or record an incident when it occurs.
Whatever we find during these investigations, we will keep you up to date with the findings and treatment plans. The prognosis is entirely dependent on the cause of the arrhythmia, but most rhythm disturbances can be medicated for. Treating the underlying cause is of course important, and it is possible that your pet will need lifelong medication.
So, hearts really can skip a beat, and not just on Valentine’s Day. It’s rare, but when it happens it can be quite serious. We recommend bringing your pet in for investigations if you have any suspicion of heart disease. Perhaps you have seen signs, or maybe you know that a close relative of your pet has heart disease. Either way, getting it checked out is definitely sensible, and our vets are on hand to help should you want an appointment.