What is the management approach for supraventricular tachycardia (SVT) in the intensive care unit (ICU)?

Management of Supraventricular Tachycardia in the ICU

For hemodynamically stable SVT in the ICU, initiate vagal maneuvers (specifically the modified Valsalva maneuver) immediately, followed by adenosine 6 mg IV push if unsuccessful, then proceed to IV calcium channel blockers or beta-blockers; for hemodynamically unstable patients, perform immediate synchronized cardioversion. 1, 2

Immediate Assessment and Stabilization

Critical first step: Determine hemodynamic stability - assess for hypotension (systolic BP <90 mmHg), altered mental status, chest pain, acute heart failure, or signs of shock. 1

Rule out dangerous mimics before treatment:

• Ensure the rhythm is not ventricular tachycardia or pre-excited atrial fibrillation before attempting AV nodal blockade, as calcium channel blockers or adenosine can precipitate ventricular fibrillation in pre-excited AF. 2
• Pre-excited AF requires immediate cardioversion, never AV nodal blocking agents. 1, 2

Management Algorithm for Hemodynamically Stable Patients

First-Line: Vagal Maneuvers

Modified Valsalva maneuver is 2.8-3.8 times more effective than standard technique and should be attempted first. 2

Proper technique:

• Position patient supine before beginning. 1, 2
• Patient bears down against closed glottis for 10-30 seconds, generating intrathoracic pressure of at least 30-40 mmHg. 1, 2
• Modified Valsalva achieves 43% conversion rate versus 17% with standard technique. 2, 3

Alternative vagal maneuvers if modified Valsalva fails:

• Carotid sinus massage (only after confirming absence of carotid bruits by auscultation) - apply steady pressure over right or left carotid sinus for 5-10 seconds. 1, 2
• Ice-cold wet towel to face (diving reflex). 1
• Switching between Valsalva and carotid massage achieves overall 27.7% success rate. 1

Second-Line: Adenosine

Adenosine terminates AVNRT in approximately 95% of patients and orthodromic AVRT in 90-95% of cases. 1, 2

Administration protocol:

• Give 6 mg as rapid IV push through large vein, followed immediately by saline flush. 2
• Have cardioversion equipment ready, as adenosine may precipitate atrial fibrillation that conducts rapidly and can cause ventricular fibrillation. 1
• Minor side effects occur in approximately 30% of patients but last less than 1 minute. 1
• Adenosine also serves diagnostic function by unmasking atrial activity in atrial flutter or atrial tachycardia. 1

Third-Line: IV Calcium Channel Blockers or Beta-Blockers

IV diltiazem and verapamil achieve 80-98% success rates in converting AVNRT to sinus rhythm. 1, 2

Critical safety considerations:

• Use only in hemodynamically stable patients. 1
• Absolutely contraindicated in VT or pre-excited AF due to risk of hemodynamic collapse and ventricular fibrillation. 1
• Avoid in suspected systolic heart failure. 1

Beta-blocker option (esmolol):

• Esmolol is FDA-approved for rapid ventricular rate control in atrial fibrillation/flutter in perioperative or emergent circumstances. 4
• Dosing: 500 mcg/kg bolus over 1 minute, followed by maintenance infusion of 50 mcg/kg/min for 4 minutes, titrating as needed. 4
• Effective maintenance dose range: 50-200 mcg/kg/min; doses above 200 mcg/kg/min provide little additional benefit with increased adverse effects. 4
• Hypotension occurs in 20-50% of patients but is rapidly reversible with decreased infusion rate. 4
• Beta-blockers have excellent safety profile but are less effective than diltiazem for SVT termination. 1

Fourth-Line: Alternative Pharmacotherapy

IV amiodarone may be considered when other therapies are ineffective or contraindicated in hemodynamically stable patients, though evidence is limited to small cohort studies. 1

Management Algorithm for Hemodynamically Unstable Patients

Synchronized cardioversion is first-line therapy when patient exhibits hypotension, altered consciousness, chest pain, acute heart failure, or shock. 1

Cardioversion protocol:

• Perform immediately if vagal maneuvers or adenosine fail or are not feasible. 1
• Use 50-100J initial energy for SVT. 2
• Highly effective in terminating all forms of SVT (AVRT, AVNRT). 1
• Provide adequate sedation/anesthesia in stable patients before cardioversion. 1

Post-Conversion Management

Anticipate and manage reinitiation of tachycardia:

• Atrial or ventricular premature complexes commonly occur immediately after conversion (whether from medications or cardioversion). 1, 2
• These premature beats may reinitiate AVRT or recurrent episodes. 1, 2
• Antiarrhythmic drug may be required to prevent acute reinitiation of tachycardia. 1

Common Pitfalls and Caveats

Never apply pressure to the eyeball - this technique is potentially dangerous and has been abandoned. 1

Avoid calcium channel blockers and beta-blockers in:

• Severe conduction abnormalities or sinus node dysfunction (can be exacerbated). 1
• Acute decompensated heart failure. 1
• Any suspicion of pre-excited AF or Wolff-Parkinson-White syndrome. 1, 2

Esmolol considerations in ICU:

• Not compatible with sodium bicarbonate 5% solution or furosemide. 4
• Can be used for up to 48 hours of continuous infusion. 4
• Reaches steady-state in approximately 30 minutes without loading dose. 4

Vagal maneuvers are most effective for SVTs involving the AV node as requisite component of reentrant circuit (AVNRT, orthodromic AVRT), less effective for other atrial arrhythmias. 2