What is the initial treatment for unstable supraventricular tachycardia (SVT) with a pulse?

From the Guidelines

For a patient with unstable supraventricular tachycardia (SVT) with a pulse, the recommended initial treatment is synchronized cardioversion, as it is the most effective method to rapidly restore a normal heart rhythm and prevent further deterioration. This approach is supported by the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.

Key Considerations

• Synchronized cardioversion should be performed immediately at an initial energy level of 50-100 joules.
• Prior to cardioversion, if the patient's condition allows, consider brief sedation.
• If the first shock is unsuccessful, energy levels can be escalated in a stepwise fashion.
• Unstable SVT is characterized by serious signs and symptoms related to the rapid heart rate, including hypotension, altered mental status, shock, acute heart failure, or chest pain indicating ischemia.

Rationale

The rationale for immediate cardioversion rather than medications is that when a patient is hemodynamically unstable, the fastest method to restore normal rhythm is needed to prevent further deterioration. Oxygen should be administered, IV access established, and continuous cardiac monitoring maintained throughout. After successful cardioversion, underlying causes should be investigated and treated to prevent recurrence. For stable SVT patients, vagal maneuvers and adenosine would be considered first, but the presence of instability necessitates this more aggressive initial approach, as outlined in the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.

Additional Measures

• Vagal maneuvers, such as the Valsalva maneuver or carotid sinus massage, may be considered in stable patients with SVT, but are not recommended as the initial treatment for unstable patients.
• Adenosine may be used in stable patients with SVT, but its use in unstable patients is not recommended due to the potential for worsening hemodynamic instability.

From the Research

Initial Treatment for Unstable Supraventricular Tachycardia (SVT) with a Pulse

• The initial treatment for unstable SVT with a pulse is synchronized electrical countershock, as it is the treatment of choice for hemodynamically unstable patients 2, 3.
• Alternatively, intravenous adenosine can be used as the drug of choice in hemodynamically unstable patients with supraventricular tachycardia 3.
• In cases where electrical cardioversion is not possible, digoxin may be considered as an alternative treatment option, although its use in this context requires further investigation 4.
• Vagal maneuvers, such as the Valsalva maneuver, can also be effective in converting SVT to sinus rhythm, with a modified Valsalva maneuver showing a higher success rate than the traditional method 5.

Pharmacologic Treatment

• Adenosine is the recommended first-line therapy for patients with paroxysmal SVT, with a response rate of 86% 6.
• The factors associated with adenosine failure are unclear, but a history of paroxysmal SVT and older age may be associated with an increased chance of adenosine success 6.
• Other pharmacologic agents, such as verapamil, digitalis, and procainamide, may be used in specific cases, depending on the patient's condition and medical history 2, 3.