Supraventricular Tachycardia Medications

Immediate Assessment: Hemodynamic Stability Determines Everything

For hemodynamically unstable patients (hypotension, altered mental status, shock, chest pain, or acute heart failure), proceed directly to synchronized cardioversion after sedation—this restores sinus rhythm in nearly 100% of cases and no medications should delay this intervention. 1, 2

For hemodynamically stable patients, medications follow a strict algorithmic sequence after vagal maneuvers fail. 1, 3

Acute Medication Management for Stable SVT

First-Line: Adenosine (90-95% Success Rate)

Adenosine is the preferred first-line pharmacologic agent, terminating 90-95% of AVNRT and 78-96% of AVRT episodes. 1, 3, 4

Dosing protocol: 3

6 mg rapid IV push (over 1-2 seconds) via proximal vein (antecubital preferred)
Follow immediately with 20 mL saline flush
If no conversion in 1-2 minutes: 12 mg rapid IV push + flush
If still no conversion: repeat 12 mg dose once more
Maximum cumulative dose: 30 mg total

Dose adjustments: 3

Reduce to 3 mg initial dose for: patients on dipyridamole or carbamazepine, cardiac transplant recipients, or central venous administration
Increase dose for: patients with significant theophylline, caffeine, or theobromine levels

Absolute contraindications: 3

Asthma or active bronchospasm (risk of severe bronchospasm)
Second- or third-degree AV block without pacemaker
Pre-excited atrial fibrillation (Wolff-Parkinson-White syndrome)

Common transient side effects (<60 seconds): flushing, dyspnea, chest discomfort 3

Critical safety requirement: Defibrillator must be immediately available because adenosine can precipitate rapid atrial fibrillation. 3, 2

Second-Line: Calcium Channel Blockers (64-98% Success Rate)

When adenosine fails or is contraindicated (e.g., asthma), intravenous diltiazem is the preferred alternative, achieving 64-98% conversion. 1, 3, 4

Diltiazem dosing: 1, 3

15-20 mg (≈0.25 mg/kg) IV over 2 minutes
Slow infusion over up to 20 minutes reduces hypotension risk 2

Verapamil alternative: 1, 3

2.5-5 mg IV over 2 minutes
Clinical effect within 3-5 minutes

Absolute contraindications (life-threatening if violated): 1, 2, 5

Ventricular tachycardia cannot be excluded (may cause hemodynamic collapse)
Pre-excited atrial fibrillation (can trigger ventricular fibrillation and death)
Suspected systolic heart failure (negative inotropic effects)
Hemodynamic instability

FDA warning: Diltiazem may rarely cause second- or third-degree AV block; symptomatic hypotension occurs in 3.2% of patients. 5

Third-Line: Beta-Blockers (Slightly Less Effective)

Intravenous beta-blockers are reasonable alternatives with excellent safety profiles, though slightly less effective than calcium channel blockers. 1, 2

Metoprolol dosing: 3

2.5-5 mg IV every 2-5 minutes
Maximum cumulative dose: 15 mg over 10-15 minutes

Esmolol alternative: useful for short-term control, especially with concurrent hypertension 1

Caution: Use carefully in severe COPD; avoid concurrent IV administration with calcium channel blockers due to synergistic hypotensive and bradycardic effects. 1, 4

Last Resort: Synchronized Cardioversion

When all pharmacologic therapy fails or is contraindicated in stable patients, synchronized cardioversion with appropriate sedation achieves 80-98% success. 1, 2

Long-Term Medication Management

First-Line: AV Nodal Blockers

Oral beta-blockers, diltiazem, or verapamil are first-line for ongoing prevention of recurrent AVNRT. 1, 2

Diltiazem or verapamil: up to 480 mg/day reduces episode frequency 2
Beta-blockers: equally effective with excellent safety profile 2

Second-Line: Class IC Antiarrhythmics (86-93% Effectiveness)

Flecainide or propafenone are reasonable when AV nodal blockers fail, with 86-93% probability of 12-month effectiveness. 2, 6

Absolute contraindication: Never use in patients with any structural heart disease, ischemic heart disease, or left-ventricular dysfunction—risk of fatal pro-arrhythmia. 2

Third-Line: Class III Antiarrhythmics

Sotalol (80-160 mg twice daily) may be used when first-line agents fail; requires careful monitoring for pro-arrhythmia. 2, 6

Dofetilide is an option when beta-blockers, calcium channel blockers, and Class IC agents are ineffective or contraindicated. 2, 6

Special Populations

Pregnancy

Vagal maneuvers remain first-line 3
Adenosine is safe and effective 3
Cardioversion if hemodynamically unstable 3

Adult Congenital Heart Disease

Adenosine appropriate for SVT termination 1
IV diltiazem or esmolol may be used cautiously, monitoring for hypotension 1
Avoid flecainide with significant ventricular dysfunction 1

Critical Pitfalls to Avoid

Never delay cardioversion in unstable patients to attempt medications 2
Never use calcium channel blockers when VT or pre-excited AF is possible—can cause ventricular fibrillation and death 1, 2
Never prescribe flecainide or propafenone to patients with any structural heart disease 2
Never combine IV calcium channel blockers with IV beta-blockers 4
Never use adenosine in asthma—risk of severe bronchospasm 3
Never apply eyeball pressure as a vagal maneuver—dangerous and abandoned 1, 2, 4

Post-Conversion Monitoring

Continuous cardiac monitoring is essential immediately after conversion because premature complexes commonly trigger recurrent SVT within seconds to minutes. 3

If immediate recurrence occurs, administer a longer-acting AV nodal blocker (diltiazem or beta-blocker) 3
Observe for approximately 4 hours with continuous monitoring 4
Consider electrophysiology consultation for recurrent symptomatic SVT 4

Definitive Treatment Consideration

Catheter ablation should be offered to all adults with symptomatic recurrent SVT—it achieves 94.3-98.5% single-procedure success with <5% recurrence and <1% risk of heart block, making it superior to chronic medication. 2, 6

What are the acute and long‑term medication options for managing supraventricular tachycardia, including considerations for patient stability, contraindications, and comorbid conditions?

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