Supraventricular & Ventricular Tachycardia
September 30, 2016Supraventricular Tachycardia (SVT)
Supraventricular Tachycardia (SVT) is a type of arrhythmia where the heart beats (much) faster than normal. In this type of arrhythmia the heartbeat originates from close to the normal location but it is not controlled by normal feedback loops in the body. SVT may be due to structural cardiac disease such as dilated cardiomyopathy or chronic valvular disease but can also be a primary finding.
Clinical Signs
Supraventricular Tachycardia can cause weakness and lethargy. If the SVT is severe enough and is untreated, it can cause the heart muscle to weaken and dilate. If this happens, difficulty breathing and fluid accumulation can result.
Diagnosis
Supraventricular Tachycardia can only be definitively diagnosed by an electrocardiogram (ECG).
Treatment
Treatment consists of giving a pet medications to slow down the speed of the arrhythmia as it passes through the rest of the heart. Medications sometimes need to be adjusted until a regimen that keeps the heart rate under control is found. The target heart rate is generally between 100-140 beats per minute. In human medicine, SVT is often treated with radioablation techniques where the arrhythmia is permanently stopped by ablating the bit of tissue that is causing the arrhythmia. This can be done “remotely” with catheters inserted into veins or arteries in the patients limbs.
Prognosis
If the arrhythmia is controllable, the patient can often live a relatively normal life span. However, prognosis always depends on the underlying disease process.
Ventricular Tachycardia (VT)
Ventricular Tachycardia is an arrhythmia that is caused by abnormal electrical impulses that are generated somewhere within the ventricles of the heart. These rapid, repetitive extrasystoles or contractions can be intermittent or continuous in nature, and may be caused by cardiac disease, abnormal serum levels of calcium or potassium, as well as splenic or gastrointestinal diseases.
Clinical Signs
Ventricular Tachycardia can be life-threatening, and while some dogs be asymptomatic, this arrhythmia can lead to hypotension, destruction of cardiac muscle tissue, collapse, and even sudden death.
Diagnosis
Ventricular Tachycardia can be diagnosed by an electrocardiogram (ECG).
Treatment
Treatment of this arrhythmia should be initiated if the pet’s heart rate is greater than 200 beats/minute, and the arrhythmia has been diagnosed by an electrocardiograph. Treatment is also necessary if the pet is showing any clinical signs, such as weakness, syncope (collapse), seizures, or shock. Anti-arrhythmic drugs such as lidocaine, procainamide, and sotalol may need to be used initially to convert the arrhythmia in an acute episode, and may need to be continued indefinitely. If the arrhythmia is well controlled, treatment may be slowly decreased after a period of 2 to 3 weeks.