In a hemodynamically stable inpatient with supraventricular tachycardia, what is the step‑by‑step management, including vagal maneuvers, adenosine dosing, selection of esmolol versus diltiazem, and criteria for synchronized cardioversion or electrophysiology referral?

Complex Management of Supraventricular Tachycardia in the Inpatient Setting

For hemodynamically stable inpatients with SVT, begin with vagal maneuvers (modified Valsalva), followed by adenosine 6 mg rapid IV push as first-line pharmacologic therapy; if adenosine fails or is contraindicated (asthma, severe COPD), use IV diltiazem 15–20 mg over 2 minutes, which achieves 64–98% conversion rates. 1, 2

Step 1: Immediate Hemodynamic Assessment

• Unstable patients (hypotension, altered mental status, shock, chest pain, acute heart failure) require immediate synchronized cardioversion (50–100 J) without attempting vagal maneuvers or drug therapy—this restores sinus rhythm in nearly 100% of cases. 1, 3

• Stable patients (normal blood pressure, alert, no chest pain, no pulmonary edema) proceed to vagal maneuvers and pharmacologic therapy. 1

• Critical pitfall: Do not delay cardioversion in unstable patients to attempt adenosine or vagal maneuvers—this risks cardiovascular collapse. 1, 3

Step 2: Vagal Maneuvers (First-Line for Stable Patients)

• Modified Valsalva maneuver (patient supine, bearing down 10–30 seconds to generate 30–40 mmHg intrathoracic pressure) terminates SVT in approximately 43% of attempts. 2

• Carotid sinus massage (5–10 seconds steady pressure after confirming absence of carotid bruit) is an effective alternative with overall vagal maneuver success rates of 27–28%. 1, 2

• Never apply pressure to the eyeball—this technique is dangerous and abandoned. 1, 2

Step 3: Adenosine Administration (First-Line Pharmacologic Agent)

Dosing Protocol

• Initial dose: 6 mg rapid IV push (over 1–2 seconds) via the most proximal peripheral vein (antecubital preferred), followed immediately by a 20 mL saline flush. 1, 2

• Second dose: If no conversion within 1–2 minutes, give 12 mg rapid IV push with saline flush. 1, 2

• Third dose: If still no response, administer a second 12 mg dose (maximum cumulative dose 30 mg). 2

• Efficacy: Adenosine terminates 90–95% of AVNRT and 78–96% of AVRT episodes. 1, 2

Dose Adjustments

• Reduce to 3 mg in patients taking dipyridamole or carbamazepine, cardiac transplant recipients, or when administered via central venous access. 2

• Increase dose in patients with high caffeine, theophylline, or theobromine levels (competitive adenosine receptor antagonists). 2

Absolute Contraindications

• Asthma or active bronchospasm (risk of severe bronchospasm). 1, 2

• Second- or third-degree AV block or sick sinus syndrome without a pacemaker. 2

• Pre-excited atrial fibrillation (Wolff-Parkinson-White)—adenosine may precipitate rapid ventricular response; have a defibrillator immediately available. 2

Expected Response & Side Effects

• Average time to termination is 30 seconds after an effective dose. 2

• Common transient side effects (<60 seconds): flushing (most common), dyspnea, chest discomfort. 2

Step 4: Alternative Pharmacologic Options (When Adenosine Fails or Is Contraindicated)

Diltiazem (Preferred Alternative)

• Dosing: 15–20 mg (≈0.25 mg/kg) IV over 2 minutes; a slower infusion over 20 minutes reduces hypotension risk. 1, 4

• Efficacy: Converts 64–98% of SVT cases; superior to esmolol in head-to-head trials. 1, 4

• Recent evidence: A 2025 multicenter cohort study showed diltiazem achieved 82.4% conversion versus 66.8% for adenosine (p=0.08), and successfully rescued 35% of adenosine failures. 5

• Advantage over adenosine: Fewer side effects (no flushing, dyspnea, or chest discomfort) and effective for rate control if conversion to atrial fibrillation occurs. 5, 6

Verapamil (Acceptable Alternative)

• Dosing: 2.5–5 mg IV over 2 minutes, with clinical effect typically within 3–5 minutes. 1

• Efficacy: Comparable to diltiazem (64–98% conversion). 1, 7

Beta-Blockers (Third-Line)

• Metoprolol: 2.5–5 mg IV every 2–5 minutes (maximum 15 mg over 10–15 minutes). 1

• Esmolol: Useful for short-term control, particularly when concurrent hypertension is present. 1

• Evidence limitation: A 1999 randomized trial showed esmolol converted only 4/16 (25%) SVT cases versus 28/28 (100%) for diltiazem (p<0.001). 4

• Caution: Use carefully in severe COPD; avoid simultaneous IV administration with calcium-channel blockers due to synergistic hypotension and bradycardia. 1

Absolute Contraindications for Calcium-Channel Blockers

• Ventricular tachycardia cannot be excluded (may precipitate hemodynamic collapse). 1

• Pre-excited atrial fibrillation (WPW syndrome)—AV-nodal blockade enhances accessory-pathway conduction and may trigger ventricular fibrillation. 1

• Suspected systolic heart failure or severe left-ventricular dysfunction (negative inotropic effects risk cardiovascular collapse). 1, 3

• Hemodynamic instability (hypotension, shock). 1

Step 5: Synchronized Cardioversion (Rescue for Stable Patients)

• When all pharmacologic options fail or are contraindicated, elective synchronized cardioversion with appropriate sedation achieves 80–98% success in hemodynamically stable patients. 1

• Energy: Start with 50–100 J synchronized. 3

Step 6: Post-Conversion Management

Immediate Monitoring

• Continuous cardiac monitoring is essential immediately after conversion—premature atrial or ventricular complexes frequently trigger recurrent SVT within seconds to minutes. 2, 8

• Obtain a 12-lead ECG in sinus rhythm to assess for pre-excitation (delta waves) and identify the SVT mechanism. 8

Management of Recurrence

• If immediate recurrence occurs, administer a longer-acting AV-nodal blocker (oral diltiazem, verapamil, or beta-blocker) to prevent re-initiation. 2, 8

• If adenosine unmasks atrial flutter or atrial tachycardia, manage with a longer-acting AV-nodal blocker for rate control rather than attempting rhythm conversion. 2

Diagnostic Considerations

• Check serum electrolytes (potassium, magnesium, calcium) and correct abnormalities—hypokalemia and hypomagnesemia predispose to arrhythmias. 3

• Review medications for QT-prolonging agents or recent changes that could have triggered the arrhythmia. 3

Step 7: Criteria for Electrophysiology Referral

• Refer for catheter ablation as first-line definitive therapy for patients with recurrent symptomatic SVT—single-procedure success rates are 94–98% with low complication rates. 8

• Indications for referral: Frequent episodes (>2 per year), patient preference for definitive cure, occupational requirements (pilots, bus drivers), or failure of pharmacologic prophylaxis. 1, 8

Step 8: Long-Term Pharmacologic Prophylaxis (If Ablation Declined)

• Oral beta-blockers, diltiazem, or verapamil are first-line for ongoing prevention of recurrent AVNRT. 1, 8

• Dosing: Verapamil up to 480 mg/day or diltiazem equivalent, titrated to effect. 1

• Patient education: Teach self-administered vagal maneuvers (modified Valsalva, carotid massage, ice-water facial immersion) for future episode termination. 8

Special Populations

Pregnancy

• Vagal maneuvers remain first-line. 2

• Adenosine is safe and effective during pregnancy. 2

• If hemodynamically unstable, synchronized cardioversion is indicated. 2

Adult Congenital Heart Disease

• Adenosine is appropriate for SVT termination. 1

• IV diltiazem or esmolol may be used cautiously, monitoring for hypotension. 1

• Avoid flecainide in the presence of significant ventricular dysfunction. 1

Post-Cardiac Arrest or Severe Heart Failure

• Immediate synchronized cardioversion is first-line—do not attempt adenosine or calcium-channel blockers. 3

• Adenosine may precipitate atrial fibrillation with rapid ventricular response; calcium-channel blockers and beta-blockers will worsen hemodynamics and risk cardiovascular collapse. 3

Critical Pitfalls Summary

• Never delay cardioversion in unstable patients to attempt vagal maneuvers or drug therapy. 1, 3

• Never administer calcium-channel blockers when ventricular tachycardia or pre-excited atrial fibrillation is possible—this may precipitate ventricular fibrillation and death. 1

• Never use adenosine in patients with asthma due to severe bronchospasm risk. 1, 2

• Never combine IV calcium-channel blockers with IV beta-blockers—synergistic hypotension and bradycardia. 1

• Always obtain a 12-lead ECG during tachycardia to differentiate SVT from VT and identify pre-excitation. 1, 2

• Never apply pressure to the eyeball as a vagal maneuver. 1, 2