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Arrhythmias after Blunt Heart Trauma in Dogs

Traumatic Myocarditis in Dogs

Blunt trauma to the heart can lead to a condition known as traumatic myocarditis, characterized by irregular heartbeats or arrhythmias. However, it’s a misnomer because heart muscle injuries typically involve cell death rather than inflammation as the term “myocarditis” implies. It’s worth noting that direct heart injury may not always be the sole cause of post-traumatic arrhythmias. Non-cardiac factors could be equally or more significant contributors to arrhythmia development.

While serious arrhythmias following blunt trauma are relatively uncommon, some patients do experience clinically significant rhythm disturbances after heart trauma. Therefore, it’s essential to thoroughly assess the heart rhythm of all trauma victims.

Most affected patients tend to develop ventricular tachyarrhythmias, which are abnormal patterns of electrical heart activity originating in the ventricles. These rhythms often manifest relatively slowly and may only be detected during pauses in the normal rhythm. They are best identified as accelerated idioventricular rhythms (AIVRs), characterized by a heart rate exceeding 100 beats per minute (bpm) but generally remaining below 160 bpm. Typically, these rhythms are benign. However, there is a risk of dangerous ventricular tachycardias developing from seemingly harmless AIVRs, posing a sudden death risk to the patient.

Symptoms and Types

  • Suffered trauma 48 hours or less before signs appeared
  • Possible arrhythmias
  • Possible rapid, irregular rhythms
  • Signs of poor blood flow to the body:
    • Weakness
    • Pale gums


The causes of traumatic myocarditis include:

  • Blunt trauma, frequently resulting from road accidents
  • Hypoxemia, characterized by low oxygen levels in the blood
  • Autonomic imbalance, involving the dysregulation of the autonomic nervous system responsible for involuntary actions such as heart rate and digestion
  • Electrolyte imbalances
  • Acid-base disturbances


The veterinarian will conduct a thorough physical examination of your pet, considering the background history of symptoms and any potential incidents that may have contributed to the current condition. A comprehensive blood profile will be performed, encompassing a chemical blood profile, a complete blood count, a urinalysis, and an electrolyte panel. Blood tests will be administered to assess for elevated serum troponin levels, a protein involved in regulating cardiac muscle contractions, indicating myocardial necrosis.

Arterial blood gas analysis and pulse oximetry will be utilized to assess whether the patient is experiencing hypoxemia, or low blood oxygen levels. Additional diagnostic procedures will involve X-ray imaging to identify the nature of traumatic injuries, and an electrocardiogram (ECG) to evaluate ventricular arrhythmias.


Your dog will receive fluid therapy with electrolytes as necessary and be prescribed painkillers. Oxygen therapy will be administered if your dog is experiencing hypoxemia. Treatment will be provided if pneumothorax (air in the chest cavity outside the lungs) is detected. Antiarrhythmic therapy will only be administered if your dog exhibits AIVRs and shows clinical signs of arrhythmia.

Living and Management

Management of arrhythmias resulting from blunt trauma typically entails spontaneous resolution within 2-3 days post-initiation of treatment. Anti-arrhythmic therapy may be ceased after 2-5 days. While perilous arrhythmias can infrequently accompany blunt trauma, the outlook for complete recovery generally hinges on the extent of extracardiac injury.

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