In supraventricular tachycardia (SVT), the heart beats too fast, so it can’t fill completely with blood. It usually beats 150–250 beats per minute (bpm), instead of the normal 60–100 bpm. The abnormal rhythm (arrhythmia) starts in the top heart chambers (atria). SVT includes arrhythmias from chronic atrial fibrillation (AFIB) to paroxysmal sinus tachycardia. AFIB is the most common type of SVT. Others are known as atrioventricular (AV) nodal reentry tachycardia (AVNRT) and atrioventricular reciprocating tachycardia (AVRT), including Wolff-Parkinson-White syndrome. SVT starts and ends suddenly and often occurs in people without heart disease.
Both men and women can have SVT, but it appears to be most common in women. It’s the most common arrhythmia in children.
Normally, the electrical signal that starts in the heart’s sinoatrial (SA) node starts the contraction of the atria. Then, ventricles contract. SVT occurs when an extra electrical pathway triggers fast heartbeats. Causes include medicines (such as digoxin, theophylline) and lung conditions (such as chronic obstructive pulmonary disease, pneumonia). Alcohol, caffeine, illicit drugs, and smoking increase the risk of SVT. One type of SVT known as Wolff-Parkinson-White (WPW) syndrome may be inherited.
The most common symptom is palpitation (feeling a racing or pounding heart). Others include dizziness, shortness of breath, fainting, chest pain, tiredness, sweating, and nausea. Symptoms may start and stop suddenly and last for a few minutes to hours.
The health care provider uses a physical examination, medical history, electrocardiography (ECG), laboratory tests, and chest X-ray for the initial diagnosis. The health care provider may order a Holter monitor, a portable 24-hour ECG, to determine how often SVT occurs during a 24-hour period. The health care provider may also want an electrophysiology study (EPS). In this test, flexible wires are put into a vein and threaded into the heart. Electrodes at the wire tips get information about the electrical activity of the heart.
People without symptoms may not need treatment. For symptoms, treatment includes vagal maneuvers, such as the Valsalva maneuver or coughing, and splashing ice water on the face. Drugs include adenosine and verapamil. Electrical cardioversion may be used for emergency treatment or if other treatments don’t work. In electrical cardioversion, a brief electric shock is given to reset the heart’s rhythm. For recurring SVT, drugs (such as beta-blockers), pacemakers, catheter ablation, and surgery may be used.
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Copyright © 2016 by Saunders, an imprint of Elsevier, Inc.
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