Acute Assessment and Management of Supraventricular Tachycardia

Immediate Evaluation

Assess hemodynamic stability first by looking for hypotension, syncope, signs of myocardial ischemia (chest pain, ST‑segment changes), or acute heart failure (pulmonary edema, severe dyspnea) 1, 3
Check the baseline ECG for pre‑excitation (delta waves) to identify Wolff‑Parkinson‑White syndrome; AV‑nodal blockers are contraindicated in pre‑excited atrial fibrillation 1, 4
A narrow QRS complex (<120 ms) favors typical SVT, whereas a wide QRS complex requires evaluation for ventricular tachycardia or SVT with aberrancy 2

Proceed immediately to synchronized cardioversion without attempting vagal maneuvers or pharmacologic therapy 1, 2, 3
Unstable is defined as the presence of hypotension, syncope, ongoing chest pain with ischemic ECG changes, or acute heart failure 2
Cardioversion is highly effective and avoids delays and complications associated with drug therapy 1
Keep a defibrillator on hand because premature ventricular complexes may occur after cardioversion and re‑initiate tachycardia 1, 4

Perform vagal maneuvers with the patient supine 1, 2, 3
Modified Valsalva (10–30 s bearing down to generate ≥30–40 mmHg intrathoracic pressure, then immediate supine positioning with leg elevation) is the most effective technique 1, 2
Carotid sinus massage is acceptable after confirming the absence of a carotid bruit; apply steady unilateral pressure for 5–10 s 1, 2
Ice‑cold wet towel applied to the face triggers the diving reflex and can terminate SVT 1, 2
Overall success rate of vagal maneuvers is ≈27.7 % when techniques are alternated and up to 43 % with the modified Valsalva 1
Do not apply pressure to the eyeballs; this practice is unsafe and abandoned 1, 2

Give IV adenosine if vagal maneuvers fail 1, 2, 3
Initial dose: 6 mg rapid IV push followed by a 20 mL saline flush; if ineffective, a second dose of 12 mg may be administered 2
Success rate of 90–95 % for terminating AVNRT and AVRT 1, 2
Have cardioversion equipment immediately available because adenosine can precipitate atrial fibrillation with rapid ventricular response that may progress to ventricular fibrillation 1, 4
Minor side effects (e.g., flushing, chest discomfort) occur in ≈30 % of patients and resolve within <1 minute 1
Adenosine also serves a diagnostic purpose by terminating AVNRT/AVRT or unmasking atrial activity in atrial flutter or atrial tachycardia 2

If adenosine is ineffective, IV diltiazem or verapamil may be used in stable patients 5, 2, 3
Reported success rates for verapamil, diltiazem, or adenosine range from 80–98 % 1, 2
Critical warning: Ensure the rhythm is not ventricular tachycardia or pre‑excited atrial fibrillation before administering calcium‑channel blockers; these agents can cause hemodynamic collapse and ventricular fibrillation in such settings 5, 2
Avoid calcium‑channel blockers in patients with suspected systolic heart failure 5, 2
IV β‑blockers (e.g., esmolol, metoprolol) are reasonable alternatives with an excellent safety profile, though they are slightly less effective than diltiazem 5, 2

For stable patients who fail pharmacologic therapy, perform synchronized cardioversion with adequate sedation 1, 2, 3

Unstable patients: immediate synchronized cardioversion 1, 6
Stable patients: IV procainamide or ibutilide are preferred anti‑arrhythmic agents 1, 6
Never use digoxin, β‑blockers, diltiazem, verapamil, or amiodarone because they can accelerate conduction over the accessory pathway and precipitate ventricular fibrillation 1, 7

Offer catheter ablation as the primary definitive treatment for SVT 8, 9, 7
Provides a cure without the need for chronic medication and is associated with low complication rates 8, 9
Particularly indicated for patients with recurrent symptomatic SVT, those in high‑risk occupations (e.g., pilots, bus drivers), or individuals preferring to avoid lifelong drug therapy 8, 9

Without pre‑excitation: first‑line oral agents are β‑blockers, diltiazem, or verapamil 8, 9
Second‑line: flecainide or propafenone may be used in patients without structural heart disease or ischemic coronary disease 8, 9
Contraindication: flecainide and propafenone must be avoided in the presence of structural or ischemic heart disease due to pro‑arrhythmic risk 8, 9
With pre‑excitation (WPW): AV‑nodal blockers (β‑blockers, calcium‑channel blockers) are contraindicated 4, 7; flecainide or propafenone are acceptable if no structural heart disease exists 9, 7

Teach all patients how to perform vagal maneuvers at home, including the modified Valsalva technique (forceful exhalation against a closed airway for 10–30 s while supine) and the use of an ice‑cold wet towel on the face 8, 9
Home vagal maneuvers empower patients to terminate SVT episodes without emergency department visits 8

Do not administer calcium‑channel blockers or β‑blockers in wide‑complex tachycardia of unknown origin, as the rhythm may be ventricular tachycardia and these drugs can cause cardiovascular collapse 5, 2, 7
Do not give AV‑nodal blockers in pre‑excited atrial fibrillation because they can precipitate ventricular fibrillation 1, 7
Do not delay synchronized cardioversion in unstable patients; attempting drug therapy wastes critical time 1, 2
Ensure carotid sinus massage is performed unilaterally only after confirming the absence of a carotid bruit 1, 2
Keep a defibrillator readily available when administering adenosine, as it may trigger dangerous arrhythmias 1, 4