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Increased Heart Rate Due to Premature Contractions in Dogs

Ventricular Tachycardia in Dogs

Ventricular tachycardia (VT) is a potentially life-threatening cardiac condition characterized by an abnormal increase in heart rate. This disorder can lead to ventricular fibrillation, where the heart’s lower chambers contract irregularly, potentially resulting in asystole – a sudden cessation of heart electrical activity – and sudden death. VT can arise from underlying heart disease, metabolic issues, or electrolyte imbalances.

The heart comprises four chambers: two atria (upper chambers) and two ventricles (lower chambers). Its electrical conduction system regulates heart rate by generating and transmitting electrical impulses throughout the cardiac muscles, orchestrating their contractions to pump blood throughout the body. Ventricular tachycardia stems from irregular activity within the ventricles.

VT can manifest in structurally normal hearts as hereditary arrhythmias or as a consequence of myocardial abnormalities linked to cardiomyopathy, severe valvular disease, or myocarditis. Currently, there is no known medical intervention to prevent sudden death in dogs suffering from ventricular tachyarrhythmias.

Symptoms and Types

  • Fainting (syncope)
  • Weakness
  • Exercise intolerance
  • Sudden death
  • May manifest without symptoms
  • Elevated heart rate
  • Manifestation of congestive heart failure (CHF)


  • Cardiomyopathy (heart muscle disease)
  • Congenital abnormalities (particularly subaortic stenosis – constriction of the aortic passage)
  • Chronic valve conditions
  • Gastric dilation and volvulus (stomach torsion)
  • Traumatic cardiac inflammation
  • Digitalis toxicity (medication-induced heart issues)
  • Cardiac cancer
  • Myocarditis (heart muscle inflammation)
  • Pancreatitis (pancreatic inflammation)


If your dog’s condition is unstable, immediate treatment will be administered based on observed symptoms, pending further diagnosis of the underlying cause of ventricular tachycardia (VT). For stable cases, your veterinarian will commence with a comprehensive physical examination of your dog. Providing a detailed history of your dog’s health, symptom onset, and any potential triggering events is essential. A thorough blood profile, encompassing a chemical blood panel, complete blood count, urinalysis, and electrolyte analysis, will be conducted. Electrolyte analysis will assess for hypokalemia and hypomagnesemia, while the bloodwork may also indicate signs of pancreatitis and hyperthyroidism.

An electrocardiogram (ECG or EKG) will be performed to assess the heart’s electrical activity and identify any abnormalities in cardiac conduction, crucial for understanding the heart’s contraction mechanism. Additionally, an echocardiogram (ultrasound imaging) will be utilized to examine for structural heart abnormalities. Long-term ambulatory electrocardiograph monitoring, facilitated by a Holter monitor, can be employed to detect transient ventricular arrhythmias in cases of unexplained syncope or weakness. The Holter monitor, worn like a vest, allows your dog to maintain normal mobility, while observations recorded in a diary by the caregiver offer valuable insight into the timing of heartbeat irregularities.


For stable cases, correction of electrolyte imbalances will involve fluid administration. An echocardiogram will be conducted, alongside 24-hour Holter monitoring, to establish a definitive baseline for the quantity and quality of arrhythmias.

In cases where the dog is unstable (manifesting as lethargy, weakness, or frequent fainting), immediate intravenous treatment in a hospital environment with continuous ECG monitoring may be necessary. Once the arrhythmia is managed and blood pressure stabilized, oral medications will be initiated. Medication selection will be tailored to the dog’s overall health, tolerance to VT episodes, and frequency of occurrence. Some medications may aim to suppress future episodes, and activity levels may need to be restricted. Follow-up assessment with a 24-hour Holter monitor will gauge the effectiveness of anti-arrhythmic medication.

Living and Management

Regrettably, sudden death can occur in dogs with ventricular tachycardia. It’s crucial to avoid triggering episodes of ventricular tachycardia by steering clear of stimulating situations that accelerate the heart rate. This caution is particularly pertinent for Boxer breeds. Your veterinarian will arrange follow-up appointments as needed for ongoing monitoring and management of your dog’s condition.

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