Critical Alerts

• Unstable = Cardiovert: Hypotension, AMS, chest pain, acute heart failure
• Adenosine is diagnostic AND therapeutic: Terminates most re-entrant SVTs
• Give adenosine rapidly: Push fast with flush, closest port possible
• Wide complex SVT may be VT: If unsure, treat as VT
• Vagal maneuvers first: Safe, can terminate
• WPW with AF is DANGEROUS: Avoid AV nodal blockers

Key Diagnostics

Emergency Treatments

Overview

Supraventricular tachycardia (SVT) is a broad term encompassing any tachyarrhythmia arising from above the ventricles. In clinical practice, "SVT" often specifically refers to paroxysmal supraventricular tachycardia (PSVT), a narrow complex, regular tachycardia typically due to re-entrant mechanisms. Most are benign but can cause significant symptoms and rarely hemodynamic compromise.

Classification

Types of SVT:

Other Supraventricular Tachycardias (Broader Definition):

AVNRT (AV Nodal Reentrant Tachycardia)

• Most common PSVT
• Two pathways within AV node (slow and fast)
• Typical AVNRT: Antegrade slow, retrograde fast
• P waves buried in or just after QRS
• "Pseudo R′" in V1 or "pseudo S" in inferior leads

AVRT (AV Reentrant Tachycardia)

• Uses accessory pathway (bypass tract)
• Orthodromic (most common): Antegrade AV node, retrograde accessory pathway → Narrow QRS
• Antidromic (rare): Antegrade accessory pathway, retrograde AV node → Wide QRS
• WPW syndrome: Pre-excitation (delta wave) at baseline

Epidemiology

• Prevalence of PSVT: 2.3 per 1000 adults
• Incidence: 35 episodes per 100,000 person-years
• Age: AVNRT more common in adults; AVRT more common in younger patients
• Gender: AVNRT more common in women (2:1)
• WPW prevalence: 1-3 per 1000

Etiology

Precipitants:

Unstable SVT (Cardiovert Immediately)

Wide Complex SVT

Narrow Complex Tachycardia

Wide Complex Tachycardia

When in Doubt: Treat wide complex tachycardia as VT

ECG Interpretation

Systematic Approach:

1. Rate (usually 150-250 bpm)
2. Regularity (regular in PSVT; irregular = AF, flutter with variable block, MAT)
3. QRS width (narrow <120 ms = supraventricular)
4. P waves (look for hidden P waves in ST or T waves)
5. Compare to prior ECG (baseline BBB? Pre-excitation?)

Finding Hidden P Waves:

Laboratory Studies

Response to Adenosine

Discharge Criteria

• Converted to sinus rhythm
• Hemodynamically stable
• First episode with clear precipitant
• No concerning symptoms at presentation
• Able to follow up

Admission Criteria

• Prolonged episode requiring multiple interventions
• Underlying cardiac disease
• Cardiac ischemia
• Heart failure
• Unable to convert or maintain sinus rhythm
• Requires initiation of antiarrhythmic

Cardiology Follow-Up

• All new SVT episodes
• Consider Holter/event monitor if diagnosis uncertain
• Ablation referral for recurrent episodes

Condition Explanation

• "Your heart went into a fast rhythm called SVT."
• "It's caused by an electrical 'short circuit' in the heart."
• "It's usually not dangerous, but it makes you feel awful."
• "We were able to fix it with [describe treatment]."

Vagal Maneuvers at Home

• Teach modified Valsalva
• "Try these at home if it happens again."
• "If you feel faint, have chest pain, or can't stop it, call 911."

Warning Signs

• Prolonged episode (>15-20 minutes)
• Chest pain
• Syncope or near-syncope
• Severe shortness of breath

Lifestyle Modifications

• Reduce caffeine
• Limit alcohol
• Manage stress
• Adequate sleep
• Avoid decongestants

WPW Syndrome

• Pre-excitation on baseline ECG (short PR, delta wave)
• Risk of sudden death if AF develops (rapid ventricular rate)
• Ablation recommended for symptomatic WPW
• Avoid AV nodal blockers if AF develops

Pregnancy

• SVT relatively common
• Vagal maneuvers first
• Adenosine is safe
• Beta-blockers relatively safe (prefer metoprolol, labetalol)
• Avoid electrical cardioversion unless unstable (safe if needed)

Pediatric

• AVRT more common than AVNRT in children
• WPW more commonly symptomatic
• Adenosine dosing: 0.1 mg/kg (max 6 mg), then 0.2 mg/kg (max 12 mg)
• Vagal maneuvers: Ice to face (diving reflex)

Elderly

• More likely to have underlying heart disease
• More sensitive to hypotension
• Use lower doses of medications
• Carotid massage with caution (check for bruits)

Performance Indicators

Documentation Requirements

• ECG during tachyarrhythmia
• Rate, rhythm, QRS width
• Stability assessment
• Interventions and response
• Rhythm at discharge
• Follow-up plan

Diagnostic Pearls

• Regular narrow complex at 150 bpm: May be flutter with 2:1 block—look for flutter waves
• Pseudo R′ in V1: Think AVNRT
• Compare to prior ECG: Baseline BBB or pre-excitation?
• Adenosine is diagnostic: Watch the response on the monitor
• Wide complex + irregular: WPW with AF until proven otherwise
• Short RP interval: Likely AVNRT or orthodromic AVRT

Treatment Pearls

• Modified Valsalva works better: Leg elevation component is key
• Push adenosine FAST: With immediate saline flush
• Warn the patient: "You'll feel strange for a few seconds"
• Have defibrillator ready: Rarely degenerates
• If adenosine fails twice, move on: Rate control or cardioversion
• NEVER AV nodal blockers in WPW + AF: Can cause VF

Disposition Pearls

• Most SVT can go home: If converted, stable, first or rare episode
• Teach vagal maneuvers: Patient empowerment
• Refer all for cardiology follow-up: Consider ablation
• WPW needs urgent outpatient EP referral: Definitive treatment is ablation