Arrhythmias after Blunt Heart Trauma in Cats

Traumatic Myocarditis in Cats

The prevalence of serious arrhythmias after blunt trauma is relatively low but some patients develop clinically important rhythm disturbances following  trauma to the heart. Therefore, the heart rhythm of all victims of trauma should be carefully assessed.

Traumatic myocarditis is the term applied to the syndrome of arrhythmias – irregular heartbeats – that sometimes complicates a blunt trauma injury to the heart.  It is a misnomer, because heart muscle injuries are more likely to take the form of cell death than inflammation (as the term myocarditis suggests). Direct heart injury may not be necessary for development of post traumatic arrhythmia. Non-heart related conditions are likely to have equal or greater importance in causing arrhythmias.

Ventricular tachyarrhythmias (abnormal patterns of electrical heart beat activity starting in the ventricles) occur in most affected patients. Ventricular rhythms that complicate blunt trauma are often relatively slow and are detected only during pauses in the normal rhythm. They are most appropriately referred to as accelerated idioventricular rhythms (AIVRs), which is recognized by a heart rate that is greater than 100 beats per minute (bpm) but generally less than 160 bpm. Usually, these rhythms are harmless. However, dangerous ventricular tachycardias can also complicate a blunt trauma and can also evolve from seemingly benign AIVRs, placing the patient at risk for sudden death.

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

Causes

• Blunt trauma, most often road accidents
• Low oxygen in the blood
• Autonomic (the part of the nervous system that regulates involuntary action, like digestion, heart beat, etc.) imbalance
• Electrolyte imbalances
• Acid-base disturbances

Diagnosis

Your veterinarian will perform a thorough physical exam on your cat, taking into account the background history of symptoms and possible incidents that might have led to this condition. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, a urinalysis and an electrolyte panel.  Blood tests can be done to check for high serum troponin concentrations, a protein that is involved in the regulation of cardiac muscle contractions, which would suggest myocardial necrosis.

Arterial blood gas analysis and pulse oximetry should be used to determine if the patient is lacking in blood oxygen (hypoxemic).

Further diagnostic testing will include X-ray imaging to determine the type of traumatic injuries that are present, and electrocardiogram (ECG) to analyze the ventricular arrhythmias.

Treatment

Your cat will be given fluid therapy with electrolytes (if needed) and  prescribed painkillers. Oxygen therapy should be given if your cat is hypoxemic. If pneumothorax (air free in the chest cavity - outside the lungs) is present, it will be treated.  Antiarrhythmic therapy will only be given if your cat has AIVRs and clinical signs of arrhythmia. 

Living and Management

Arrhythmias due to blunt trauma tend to resolve spontaneously within 2-3 days of the beginning of treatment. Anti-arrhythmic therapy can be discontinued after 2-5 days.  Although dangerous arrhythmias occasionally complicate blunt trauma, the prognosis for a full recovery usually depends on the severity of extracardiac (outside the heart) injury.