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Background
Paroxysmal supraventricular tachycardia (PSVT) is a group of supraventricular arrhythmias characterized by abrupt onset and termination of rapid, regular heart rhythms originating above the ventricles. It typically presents with heart rates between 150–250 bpm and includes reentrant mechanisms involving the atrioventricular (AV) node or accessory pathways. Episodes are paroxysmal, meaning they start and stop suddenly, often triggered by exertion, stress, or stimulants.
II) Classification/Types
By Mechanism:
- AV Nodal Reentrant Tachycardia (AVNRT) – Most common; reentry circuit within or around the AV node
- AV Reentrant Tachycardia (AVRT) – Accessory pathway outside the AV node (e.g., Wolff-Parkinson-White syndrome)
- Atrial Tachycardia – Ectopic atrial focus; less common
By Duration:
- Paroxysmal: Sudden onset/offset, self-terminating
- Persistent: Lasts longer than 30 seconds or requires intervention to terminate
Pathophysiology
PSVT usually arises from a reentrant circuit involving the AV node or an accessory pathway. A premature atrial or ventricular impulse encounters a region with differential conduction velocities, leading to a self-perpetuating loop of electrical activity. The AV node plays a central role in most cases (AVNRT or AVRT). Ectopic atrial tachycardias are less common but may involve increased automaticity or triggered activity from an atrial focus.
Epidemiology
- Common in young adults, especially females
- AVNRT accounts for ~60% of PSVT cases
- AVRT (e.g., WPW) more common in younger males
- Incidence increases in patients with structural heart disease
- May occur in structurally normal hearts
Etiology
I) Causes
- AV nodal dual pathway physiology
- Accessory pathways (e.g., WPW syndrome)
- Atrial ectopic foci
- Excess sympathetic tone (exercise, stress)
- Stimulants (e.g., caffeine, nicotine)
- Digitalis toxicity (rarely)
II) Risk Factors
- Female sex (especially for AVNRT)
- Young to middle-aged adults
- Family history of pre-excitation syndromes
- Underlying structural heart disease
- Excessive stimulant intake
- History of previous SVT
Clinical Presentation
I) History (Symptoms)
- Sudden-onset palpitations (regular and rapid)
- Lightheadedness or presyncope
- Dyspnea
- Anxiety or chest tightness
- Fatigue with exertion
- Syncope (rare)
- May be asymptomatic between episodes
II) Physical Exam (Signs)
- Regular, rapid heart rate (typically 150–250 bpm)
- Normal heart sounds, no murmurs
- Neck pulsations (cannon A waves) during AV dissociation
- Often normal between episodes
- Signs of hypotension or diaphoresis during prolonged tachycardia
Differential Diagnosis (DDx)
- Sinus tachycardia
- Atrial flutter with 2:1 block
- Atrial fibrillation
- Ventricular tachycardia (especially if wide QRS)
- Ectopic atrial tachycardia
- Anxiety or panic attacks
- Pheochromocytoma
Diagnostic Tests
Initial Work-Up
- ECG (during episode): Narrow QRS complex tachycardia, typically regular, no visible P waves or retrograde P waves
- ECG (baseline): May show pre-excitation in WPW (short PR, delta wave)
- Vagal maneuvers: May terminate AVNRT or AVRT
- Adenosine test: Diagnostic and therapeutic; transient AV block reveals underlying rhythm
- Holter monitor or event recorder: For infrequent episodes
- Echocardiography: Evaluate structural heart disease
- Electrophysiology study (EPS): If diagnosis uncertain or ablation planned
Treatment
I) Initial Approach
Hemodynamically unstable:
- Immediate synchronized cardioversion
Stable:
- Attempt vagal maneuvers (Valsalva, carotid massage)
- Administer adenosine if vagal fails
II) Medications
Drug Class | Examples | Notes |
AV nodal blockers | Adenosine | First-line; rapid termination of AVNRT/AVRT |
Beta-blockers | Metoprolol, Esmolol | Control rate/prevent recurrence |
Calcium channel blockers | Verapamil, Diltiazem | Alternative to beta-blockers; avoid in WPW with AF |
Antiarrhythmics | Flecainide, Propafenone | For recurrent PSVT; use in structurally normal heart |
Radiofrequency ablation | Catheter ablation | Curative for AVNRT/AVRT with >95% success rate |
Consults/Referrals
- Cardiology: Initial diagnosis and management
- Electrophysiology: For ablation consideration
- Emergency Medicine: For acute presentation
- Primary care: Long-term follow-up after ablation or medication adjustment
Patient Education, Screening, Vaccines, Education
- Recognize triggers (stress, caffeine, exertion)
- Perform Valsalva at home if trained
- Adherence to prescribed medications
- Discuss curative ablation options
- Avoid stimulants and alcohol if sensitive
Screening/Prevention
- Holter/event monitor for recurrent symptoms
- EPS in patients with frequent or poorly tolerated episodes
- Screen for pre-excitation in young patients with syncope
Vaccinations
- Routine age-appropriate vaccines
- No arrhythmia-specific vaccines required
Follow-Up
Short-Term
- Monitor ECG for recurrence
- Evaluate response to vagal maneuvers or adenosine
- Reassess for structural disease or pre-excitation
Long-Term
- Assess need for ablation in recurrent cases
- Monitor medication side effects
- Lifestyle modification and stimulant avoidance
- Repeat Holter if symptoms persist
Prognosis
- Excellent prognosis with curative ablation (>95% success, low recurrence)
- Most cases managed effectively with vagal maneuvers or adenosine
- Rare progression to more serious arrhythmias
- Does not typically require anticoagulation unless associated with AF
