Arrhythmias After Blunt Heart Trauma in Dogs

Just like humans, the heart and heart rhythm are the most important part of your dog’s health system and keeps everything flowing through the vital organs such as the lungs, liver, kidneys, and brain. When that rhythm is out of tune, the rest of the body is out of tune as well and will suffer because of it. With traumatic myocarditis, your dog’s heart rate is out of sync (either beating too fast or too slow) and will cause symptoms such as fainting, collapse, and even death. If your dog has suffered a blunt force trauma to the chest from being hit by a vehicle, falling from a great height, or another type of accident, you should be aware that an arrhythmia could happen within the next several days even if your dog has no symptoms right away.

Arrhythmia after blunt heart trauma (traumatic myocarditis) is a dysfunction in the heart rate caused by the heart being damaged from a hard impact against the chest wall. The dog’s heart rate can be either too slow or too fast, but this has to be verified by an electrocardiograph (ECG or EKG). The arrhythmia is caused by an irregularity of electrical impulses in the heart. This is common in dogs who are hit by motor vehicles or in a fall from a high place, but is not noticed until about 12 to 72 hours after the trauma has occurred. An arrhythmia is an irregular heart rate or rhythm that can cause collapse or be fatal if it goes untreated.

Your dog can have a traumatic accident and seem fine for several days until sudden symptoms of heart arrhythmia are noticed. Symptoms of traumatic myocarditis are:

• Fast heartbeat
• Slow heartbeat
• Heart murmur
• Irregular breathing
• Rapid breathing
• Coughing
• Fainting
• Weakness
• Vomiting
• Loss of appetite
• Weight loss

 Types

• Isolated premature ventricular contractions (PVCs) are premature heartbeats that happen from blunt trauma to the chest; PVC consists of a normal beat, extra beat, a pause, and then a stronger beat
• Accelerated idioventricular rhythm (AIVR) is a heart rate between 40 to 120 beats a minute
• Ventricular tachycardia (VT) is a very fast heart rate of more than 100 beats per minute

Any form of strong force to the chest can cause this condition, with the most common causes listed here.

• Hit by motor vehicle
• Attacked by another animal
• Animal abuse (i.e. kicked, hit)
• Falling from a high elevation

The first thing your dog’s veterinarian will do is a thorough physical examination including heart rate, body temperature, and blood pressure. The veterinarian will need to know your dog’s complete medical history as well as the symptoms and when they started. If your dog has had any dietary changes recently your veterinarian will need to know about these. Some tests will need to be done to determine the cause of the arrhythmia and if there is any other injuries. These tests are:

• Digital radiographs (x-rays) of the chest
• Echocardiography
• Blood chemistry panel
• Complete blood count (CBC)
• Electrocardiograph (ECG or EKG)
• Ultrasound
• CT scan
• MRI

These tests may have to be repeated after 72 hours if they do not show any significant myocarditis signs. Your veterinarian may also send you to see a veterinary cardiologist for further examination and testing. They may want to have your dog wear a halter monitor for 24 hours to get a constant ECG while at home. The cardiologist may also want to perform a thoracentesis or pericardiocentesis to check for fluid in the chest cavity.

The treatment given to your dog depends on the extent of the heart damage, type of arrhythmia, and if there are any other injuries that need to be treated. Your veterinarian and cardiologist will have to decide whether it is a fast or slow arrhythmia before they can treat it. In many cases, dogs with traumatic myocarditis do not need any treatment except for a little rest and to be retested once or twice to be sure the heart rate is back to normal. The veterinarian may want to admit your dog to the hospital for observation to be sure the arrhythmia does not return.

Medication

To treat the arrhythmia that is too fast, the veterinarian will want to admit your dog to the hospital to administer lidocaine or some other antiarrhythmic medicine. Once your dog’s heart rate is stable, the veterinarian will start lowering the dosage. If the arrhythmia does not return once your dog is weaned from the medication for a few hours, you will probably be able to go home.

Pacemaker

For a heart rate that is too slow, your dog will probably need to be admitted for surgery to implant a pacemaker. The pacemaker is necessary to keep your dog’s heart beating fast enough to keep the blood flowing as it should. The surgery is common and has very few risks. Without the surgery, your dog may not survive the next time your dog’s heart rate drops too low.

If your dog’s heart rate can be returned to normal with medication, the veterinarian will send you home with instructions on what symptoms to watch for that will let you know if the arrhythmia has returned. If a pacemaker is implanted in your dog, cage rest may be used for the first few days until the incisions heal. Be sure to follow up with your veterinarian if there are any problems and continue to bring your dog to the veterinarian regularly.