Paroxysmal supraventricular tachycardia (PSVT) refers to a group of arrhythmias characterized by sudden-onset episodes of rapid heart rate originating above the ventricles. These arrhythmias can abruptly begin and end, with heart rates often ranging between 150 and 250 beats per minute. PSVT episodes can occur in structurally normal hearts and are frequently observed in young adults, though they may present at any age.
Pathophysiology: Electrical Reentry and Ectopic Triggers
PSVT primarily results from reentrant electrical circuits within the atrioventricular (AV) node or accessory pathways that bypass the normal conduction system. The two most common types are atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reciprocating tachycardia (AVRT).
- AVNRT: Dual AV node pathways allow impulses to reenter and loop, causing tachycardia
- AVRT: Accessory pathways (e.g., in Wolff-Parkinson-White syndrome) bypass the AV node
Clinical Presentation and Symptoms of PSVT
Common Symptoms
Patients with PSVT often experience the following during an episode:
- Palpitations: Described as a sudden, racing heartbeat
- Dizziness or Lightheadedness: Due to reduced cardiac output
- Chest Discomfort: Pressure or pain without ischemia
- Shortness of Breath: Particularly in patients with structural heart disease
- Anxiety and Fatigue: As secondary effects of tachycardia
Duration and Frequency
- Episodes may last seconds to several hours
- Frequency varies from rare occurrences to multiple daily events
- Abrupt onset and termination is a key diagnostic clue
Diagnostic Evaluation of PSVT
Electrocardiogram (ECG/EKG)
A 12-lead ECG captured during an episode is the cornerstone for diagnosing PSVT.
- Narrow QRS Complexes: Typically <120 ms
- P Waves: Often absent, retrograde, or buried in QRS complex
- Regular Rhythm: Unlike atrial fibrillation
Holter Monitoring and Event Recorders
- 24-48 Hour Holter Monitoring: Useful for frequent episodes
- Event Monitors or Loop Recorders: Beneficial for intermittent or rare symptoms
Electrophysiological Study (EPS)
Invasive but definitive, EPS is used to localize reentrant circuits and is often performed before catheter ablation.
Classification of Paroxysmal Supraventricular Tachycardia
| Type | Mechanism | ECG Features | Clinical Notes |
|---|---|---|---|
| AVNRT | Reentry within AV node | Narrow QRS, hidden P waves | Most common form of PSVT |
| AVRT | Reentry via accessory pathway | Short PR, delta wave (if WPW) | Seen in Wolff-Parkinson-White syndrome |
| Atrial Tachycardia | Ectopic atrial focus | Abnormal P wave morphology | Less common, can be multifocal |
Management and Treatment of PSVT
Acute Episode Management
Vagal Maneuvers
First-line non-pharmacologic techniques to terminate reentrant tachycardia:
- Valsalva Maneuver: Forced exhalation against a closed airway
- Carotid Sinus Massage: Stimulates vagus nerve to slow AV conduction
- Cold Water Facial Immersion: Used in pediatric cases
Pharmacologic Therapy
If vagal maneuvers fail:
- Adenosine: Rapid IV push, temporarily blocks AV node
- Beta-Blockers: Metoprolol or esmolol, particularly in AVNRT
- Calcium Channel Blockers: Verapamil or diltiazem for rate control
Chronic Management and Prevention
Medical Therapy
- Beta-blockers or Calcium Channel Blockers: For patients with frequent or prolonged episodes
- Antiarrhythmic Drugs: Flecainide, propafenone may be considered in structurally normal hearts
Catheter Ablation
A curative procedure performed by electrophysiologists:
- Success Rate: >95% in AVNRT and AVRT
- Low Risk Profile: Preferred in young patients and those with drug intolerance
- Procedure: Radiofrequency or cryoablation used to eliminate reentry circuits
PSVT in Special Populations
PSVT in Pregnancy
- Often triggered by hormonal changes, increased blood volume, and autonomic shifts
- Treatment: Vagal maneuvers and beta-blockers considered safe; adenosine may be used when necessary
- Ablation: Typically deferred until postpartum unless refractory
Pediatric PSVT
- Frequently related to accessory pathways
- Symptoms may include irritability, feeding difficulty, and poor weight gain in infants
- Management: Vagal maneuvers, adenosine, and pediatric electrophysiology referral
Complications and Prognosis
Although PSVT is often benign, complications may arise in specific contexts:
- Heart Failure: In patients with prolonged episodes and underlying heart disease
- Syncope or Near Syncope: Due to reduced cerebral perfusion
- Anxiety Disorders: Secondary to recurrent palpitations
- Progression to Other Arrhythmias: Rare, but possible in the context of structural heart changes
Most individuals with PSVT have an excellent prognosis, especially when managed with catheter ablation or well-tolerated medications.
Summary Table: Key Features of PSVT
| Feature | Details |
|---|---|
| Origin | Above the ventricles (supraventricular) |
| Onset/Offset | Sudden, paroxysmal |
| Heart Rate | 150–250 bpm |
| ECG Finding | Narrow QRS, regular rhythm |
| First-line Termination | Vagal maneuvers |
| Definitive Treatment | Catheter ablation |
| Common Type | AVNRT |
| Diagnostic Tools | ECG, Holter, EPS |
Paroxysmal supraventricular tachycardia is a common yet manageable arrhythmia that often affects young, otherwise healthy individuals. With clear clinical features, diagnostic markers, and highly effective treatments such as vagal maneuvers and catheter ablation, PSVT can be effectively controlled or even cured. Proper identification, tailored treatment strategies, and lifestyle modification remain crucial for optimal patient outcomes.
