EMS Treatments for SVT

SVT, or Supraventricular Tachycardia, is a fast, abnormal heart rhythm. All heart rhythms have a site within the heart that initiates and paces the rhythm. In the normal heart, pacing is the job of the Sino Atrial (SA) node, but in diseased or injured hearts, the pacing function might arise almost anywhere within the heart. The word tachycardia simply means “rapid heart rate,” so supraventricular tachycardia translates as “rapid heart rate from above the ventricles.”

Initial Assessment & Treatment

• For emergency medical services (EMS), determining the patient’s complaint and relative stability are critical, as these factors will direct treatment. Although identification of SVT is dependent on an electrocardiogram (ECG), it is possible, and occasionally imperative, to begin treatment for SVT before the rhythm has been identified. Any patient who presents with some combination of chest pain, difficulty breathing, rapid respiratory rate, pallor/cyanosis, sweating, altered mental status or other signs of circulatory compromise should be treated immediately with 100 percent oxygen and positioning to assist breathing and minimize shock.

Unstable Patients

• Patients who display a combination of the signs and symptoms described above are unstable and might be at risk of death. Basic life support providers should continue to support the patient's breathing and circulation and effect prompt transport. Additionally, advanced skilled providers, such as paramedics, immediately begin monitoring the patient's heart rhythm via ECG and establishing an intravenous line if possible. In most emergency medical systems, an unstable patient found to have an SVT is immediately cardioverted through synchronized electric shock. If the patient is conscious and time permits, the patient is sedated via IV medication to minimize the pain and discomfort associated with cardioversion. Repeat cardioversions and coordination with anti-dysrhythmic IV medications are sometimes required.

Stable Patients

• Some patients experiencing SVT might only be aware of a racing heartbeat or pulse. Absent more ominous symptoms, such patients are usually stable and can be treated through vagal maneuvers and IV medication.

  Heart rate is controlled by the vagus nerve; stimulating it slows the heart. Vagal maneuvers are physical techniques that stimulate the vagus nerve to induce a slower heart rate. Two common vagal maneuvers are carotid massage and Valsalva maneuvers. In carotid massage, trained individuals apply external pressure to the carotid artery in the neck to stimulate the nerve, which raises blood pressure there and slows heart rate. Patients instructed in Valsalva maneuvers can sometimes accomplish the same thing through creating pressure or tension in their torso or neck. “Bearing down,” or imitating the act of a difficult bowel movement, is a frequently used Valsalva technique.

  Adenosine, Verapamil, Metaprolol and other IV medications are often used to treat SVT. In rare cases of SVT that are suspected of being caused by the patient having too little blood circulating in his body, a fluid challenge might be appropriate. A fluid challenge introduces a large volume of IV fluid into the patient. Such a fluid bolus will sometimes temporarily correct the underlying, low-volume cause of SVT.

Standards

• Cardiac care standards are constantly revised and updated. Local protocols, standards of care and physician-directed medical control determine appropriate EMS treatment for any and all patient care.