Ventricular Tachycardia in Cats
Ventricular tachycardia (VT) is a potentially life-threatening disease of the heart that causes arrhythmia, an abnormally fast heartbeat. This may be due to an underlying heart disease, a metabolic disease, or an electrolyte imbalance. Ventricular tachycardia can degenerate into ventricular fibrillation, a condition in which the ventricles (the bottom two heart chambers) become disorganized, contracting chaotically. This state can result in asystole – a sudden lack of electrical activity in the heart – and sudden death.
Ventricular tachycardia may occur in structurally normal hearts, as hereditary arrhythmias, or may be a consequence of myocardial abnormalities associated with cardiomyopathy (heart muscle disease), significant valvular disease, or myocarditis (heart muscle inflammation). To date, there is no medical therapy available that is known to prevent sudden death in cats afflicted with ventricular tachycardia arrhythmias.
Symptoms and Types
- Fainting (syncope)
- Exercise intolerance
- Sudden death
- May be without symptoms
- Increased heart rate
- Signs of congestive heart failure (CHF)
- Cardiomyopathy (left ventricle heart disease)
- Congenital defects (especially subaortic stenosis – narrowing of the aortic passage)
- Chronic valve disease
- Digitalis toxicity (heart medication)
- Hyperthyroidism - overactive thyroid gland
- Cancer of the heart
- Myocarditis - inflammation of the heart muscle
- Pancreatitis - inflammation of the pancreas
If your cat is unstable, your doctor will apply treatment based on the symptoms before diagnosing the cause of the ventricular tachycardia. (See the treatment section below.) If your cat is stable, your veterinarian will begin with a complete physical exam of your cat. You will need to give a thorough history of your cat's health, onset 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. The electrolyte panel will show if there is hypokalemia and hypomagnesemia. The bloodwork may show evidence of pancreatitis and hyperthyroidism.
An electrocardiogram (ECG, or EKG) recording can be used to examine the electrical currents in the heart muscles, and may reveal any abnormalities in cardiac electrical conduction (which underlies the heart’s ability to contract/beat), and an echocardiogram (ultrasound imaging for the heart) will be performed to check for structural heart disease. A long-term ambulatory (portable) electrocardiograph recording of the heart's electrical activity, using a Holter monitor, can be used for detecting temporary ventricular arrhythmias in patients with unexplained syncope or weakness. The Holter can be especially useful for animals, since it can be worn as a vest, allowing the animal freedom of normal movement, which, when taken into account with a diary kept (by the pet caretaker) while the monitor is being worn, can give your veterinarian a reference frame for when the heartbeat irregularities are most likely to occur.
If your cat is stable, electrolyte abnormalities will be corrected using fluid administration. Echocardiogram and use a 24-Holter to establish a true baseline of the arrhythmia quantity and quality.
If the cat is unstable (inactive and lying down, weak, or frequent fainting), immediate intravenous treatment in a hospital setting with continuous ECG monitoring may be required. Once the arrhythmia is controlled and your cat's blood pressure has stabilized, oral medication should be started. The medication will be based on your cat's overall health, and how well your cat is able to tolerate the episodes of VT and how frequently they occur. Medications may be given to suppress future episodes. A follow-up 24-hour Holter will be required to test the efficacy of the anti-arrhythmic medication.
Living and Management
Unfortunately, cats with ventricular tachycardia can sometimes die suddenly. Your veterinarian will schedule subsequent follow-up appointments with you for your cat as necessary to try to avoid this possibility.