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Ablation of the accessory pathway was successful and a repeat EKG the following day showed improving LVEF. She had
no further episodes of SVT during her hospitalization and was discharged on oral metoprolol. At a one-month follow- up visit, the patient reported no further episodes of SVT and the metoprolol was slowly tapered off. A repeat EKG done at that time showed a normal LVEF.
DISCUSSION
SVT is a common diagnosis seen and treated in the ED. Initial management should target the AV node as it is an obligate component of the dysrhythmia. The 2015 American College of Cardiology/American Heart Association/ Heart Rhythm Society (ACC/AHA/ HRS) guidelines recommend vagal to terminate SVT, followed by adenosine if vagal maneuvers are unsuccessful.1 Synchronized cardioversion is
indicated for unstable patients or when pharmacological therapy is ineffective or contraindicated, but is not appropriate for treatment of SVT that terminates and recurs spontaneously. These treatment options are well known and readily available to the Emergency Medicine physician, and due their effectiveness, alternative therapies are seldom required. Nevertheless, this case report highlights the importance of knowing the alternative pharmacological and non-pharmacological therapies for SVT
PHARMACOLOGICAL TREATMENTS
The 2015 ACC/AHA/HRS guidelines list intravenous non-dihydropyridine calcium diltiazem and verapamil, as second-line
treatment options for acute management
of SVT.1 CCB are Vaughan Williams
Class IV Antidysrhythmic medications that work by blocking L-type calcium channels. Dihydropyridine CCBs are selective for vascular smooth muscle, while the non-dihydropyridine CCBs are more cardiac selective, verapamil more so than diltiazem. CCBs have been shown to be very effective in converting SVT to sinus rhythm. A 2009 trial comparing adenosine to a slow infusion of either verapamil
or diltiazem demonstrated superior conversion rates for CCB,2 and a 2017 difference in outcomes between patients treated with adenosine versus verapamil
or diltiazem.3 CCB should be used only
in hemodynamically stable patients and should be avoided in patients with known or suspected heart failure. To minimize
the risk of hypotension, it is recommended that the drug be administered by slow infusion up to 20 minutes. Oral CCBs have been shown to be effective for long-term management of SVT, but there is no data oral CCB monotherapy in the acute setting.
Intravenous beta blockers (BB),
and propranolol, are also listed as second-line treatment options for the acute management of SVT in the 2015 ACC/AHA/HRS guidelines. Beta- blockers are Vaughan Williams Class II Antidysrhythmic medications that work by blocking beta adrenergic receptors. Esmolol and metoprolol selectively block beta1 receptors, while propranolol is a non-selective beta blocker that blocks both beta1 and beta2 receptors. There is limited data on the effectiveness of BB in terminating SVT, and a trial comparing esmolol to diltiazem showed diltiazem was more effective.4 Nonetheless, their treatment option. Oral BBs are listed as a
management of SVT in patients who
are not candidates for, or prefer not to undergo, catheter ablation. Oral BBs are listed as reasonable third-line treatment options for acute management of SVT, but effectiveness of oral BB monotherapy for acute termination of SVT.
Amiodarone is a Vaughan Williams Class III medication that works by blocking potassium channels, sodium channels, calcium channels, and beta receptors. There is limited evidence for the use of intravenous amiodarone in the acute treatment of SVT. The 2015 ACC/ AHA/HRS guidelines list intravenous amiodarone as a third-line treatment option for acute management of SVT that may be considered in hemodynamically stable patients when other therapies
are ineffective or contraindicated. Oral amiodarone is listed as a reasonable third-line treatment option for long-term management of SVT.
Flecainide is a Vaughan Williams Class IC medication that works by blocking sodium channels. It has been shown to
be effective for both acute and long-term management of SVT.5-7 The 2015 ACC/ as a reasonable second-line treatment option for long-term management of SVT. the treatment recommendations for the acute management of SVT. Flecainide is contraindicated in patients with ischemic or structural heart disease and should be reserved for patients for whom CCBs or BBs are ineffective or contraindicated.
Digoxin is a cardiac glycoside that works by inhibiting cellular Na+/K+-ATPase. One small study that randomized patients to digoxin, propranolol, or verapamil drugs for the long-term management
of SVT, but the digoxin dose used was
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