From the Guidelines
The initial investigation and treatment for Supraventricular Tachycardia (SVT) in a 75-year-old female with a 1st degree AV block should begin with a 12-lead ECG to confirm the diagnosis and rule out other arrhythmias, followed by vagal maneuvers such as the Valsalva maneuver or carotid sinus massage to attempt termination of the SVT, as recommended by the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.
Initial Investigation
The diagnosis of SVT should be confirmed with a 12-lead ECG, which is essential for identifying the type of SVT and ruling out other arrhythmias. Basic laboratory tests, including electrolytes, renal function, thyroid function, and cardiac enzymes, should also be obtained to identify potential underlying causes of SVT.
Initial Treatment
First-line treatment involves vagal maneuvers, such as the Valsalva maneuver or carotid sinus massage, to attempt termination of the SVT. If these are unsuccessful, intravenous adenosine should be administered, starting with 6 mg as a rapid bolus, followed by a 12 mg dose if needed, with careful cardiac monitoring, as recommended by the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
Alternative Medications
Alternative medications, such as diltiazem (0.25 mg/kg IV over 2 minutes) or verapamil (5-10 mg IV), may be considered, but should be used cautiously in elderly patients due to potential hypotensive effects. Beta-blockers, like metoprolol (5 mg IV slowly), may also be considered, but should be used with caution in patients with pre-existing AV block, as they can worsen AV conduction.
Synchronized Cardioversion
Synchronized cardioversion at 50-100 joules is reserved for hemodynamically unstable patients, as recommended by the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1.
Long-term Management
Following acute management, the patient should be evaluated for underlying causes of SVT and may require long-term management with oral medications, such as beta-blockers or nondihydropyridine calcium channel antagonists, or consideration of catheter ablation, as outlined in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. The pre-existing 1st degree AV block necessitates careful monitoring during treatment, as certain antiarrhythmic medications could exacerbate conduction delays.
From the FDA Drug Label
Use adenosine injection with caution in patients with pre-existing first-degree AV block or bundle branch block. Do not use in patients with high-grade AV block or sinus node dysfunction (except in patients with a functioning artificial pacemaker).
The initial investigation and treatment for Supraventricular Tachycardia (SVT) in a 75-year-old female with a 1st degree atrioventricular (AV) block should be done with caution.
- Adenosine can be used, but with careful consideration of the patient's condition, as it may worsen the AV block.
- The patient should be closely monitored for any signs of worsening AV block or other adverse reactions.
- Alternative treatments may be considered if adenosine is not suitable. 2 2
From the Research
Initial Investigation for SVT
- The initial investigation for Supraventricular Tachycardia (SVT) in a 75-year-old female with a 1st degree atrioventricular (AV) block includes a comprehensive history and physical examination, electrocardiography, and laboratory workup 3.
- Extended cardiac monitoring with a Holter monitor or event recorder may be needed to confirm the diagnosis 3.
Treatment for SVT
- The acute management of paroxysmal SVT is similar across the various types and is best completed in the emergency department or hospital setting 3.
- In patients who are hemodynamically unstable, synchronized cardioversion is first-line management 3.
- In those who are hemodynamically stable, vagal maneuvers are first-line management, followed by stepwise medication management if ineffective 3.
- Beta blockers and/or calcium channel blockers may be used acutely or for long-term suppressive therapy 3.
- Adenosine or calcium channel antagonists (CCAs) are commonly used to terminate SVT, with no significant difference in conversion rate between the two 4.
- Nondihydropyridine calcium channel blockers, such as verapamil and diltiazem, may be as effective as adenosine, without the negative short-term side effects 5.