Arrhythmias

Posted on June 12, 2015

An arrhythmia is an electrical disturbance in the heart from cardiac or non-cardiac causes.  The disturbances can cause excessively slow or fast heart rates.

Examples causing a slow heart rate are as follows.

1.       Atrioventricular block  (AV block)

2.       Sick sinus syndrome

These examples ultimately require the use of a pacemaker.

Examples causing a fast heart rate are as follows.

1.        Atrial fibrillation (AF or A-fib)

2.       Supraventricular tachycardia (SVT)

3.       Ventricular tachycardias (VT, V-tach)

Arrhythmias can cause a dog or cat serious blood flow and blood pressure issues.  When arrhythmias cause syncope or exacerbation of heart failure, medications called antiarrhythmics can be warranted.  A dog or cat’s normal reaction to heart failure is sinus tachycardias, a fast heart rate.  Medicine will slow the heart rate and allow for the heart chambers to better fill and function.

A veterinarian will assess the heart to determine the cause.  Here’s a list of some possible tests.

1.       X-rays (radiographs)

2.       Blood tests,

3.       Electrocardiography (EKG)

4.       Holter monitoring (24 hour EKG)

5.       Blood Tests

6.       Event monitoring echocardiography (ultrasound of the heart)

Drugs a veterinarian prescribes depend on the type of arrhythmias.  All antiarrhythmics medications require monitoring by a veterinarian.

1.       Sodium-channel blockers- Commonly used to treat ventricular tachycardia to create electrical excitement in diseased cells of the lower portion of the heart.

2.       Beta-blockers- Used to treat congestive heart failure by helping to slow scarring and lower the heart rate.  Beta-blockers cause the heart to contract using less energy.  It is prescribed for animals with atrial fibrillation and supraventricular tachyarrhythmias.  Side effects such as low blood pressure, collapse or worsening of congestive heart failure needs monitoring.

3.       Potassium-channel blockers- Act to reduce initiation of arrhythmias.  Used to treat ventricular tachycardias and animals with fainting and Sotalol, a drug for rhythm disturbances.

4.       Calcium-channel blockers- Used for supraventricular tachycardias including atrial fibrillation. Some selectively act on smooth muscle in the peripheral arteries. Calcium-channel blockers are also used to treat high blood pressure.  May be used in conjunction with other drugs.