From the Guidelines
Paroxysmal supraventricular tachycardia (PSVT) is primarily caused by reentry circuits in the heart, with atrioventricular nodal reentrant tachycardia (AVNRT) being the most common mechanism, accounting for about 60% of cases, as stated in the most recent guidelines 1.
Etiology of PSVT
The etiology of PSVT can be attributed to various mechanisms, including:
- Reentry circuits, which are the most common cause
- Abnormal automaticity, where tissues exhibit enhanced diastolic phase 4 depolarization, leading to an increase in firing rate compared to pacemaker cells 1
- Triggered activity, associated with disturbances of recovery or repolarization, generating afterdepolarizations that can trigger early action potentials 1
Common Causes of PSVT
The most common causes of PSVT include:
- Atrioventricular nodal reentrant tachycardia (AVNRT), accounting for about 60% of cases
- Accessory pathway-mediated tachycardias, particularly Wolff-Parkinson-White syndrome, representing about 30% of cases
- Atrial tachycardia, causing approximately 10% of PSVT cases, stemming from an ectopic focus in the atria that fires rapidly
Risk Factors for Developing PSVT
Risk factors for developing PSVT include:
- Congenital heart defects
- Coronary artery disease
- High blood pressure
- Thyroid disorders
- Caffeine consumption
- Alcohol use
- Certain medications
Presentation and Treatment of PSVT
PSVT typically presents with sudden onset of rapid heartbeat, palpitations, chest discomfort, shortness of breath, dizziness, and occasionally syncope. While most episodes are benign and self-limiting, recurrent episodes may require treatment with medications like beta-blockers, calcium channel blockers, or antiarrhythmics, or definitive treatment with catheter ablation for persistent cases, as recommended in the guidelines 1.
From the Research
Etiology of Paroxysmal SVT
- Paroxysmal supraventricular tachycardia (PSVT) is caused by reentry, and the tachycardias are classified electrophysiologically according to the anatomic location of the reentry circuit 2
- The most common form of PSVT is atrioventricular nodal reentry, which occurs when there are two conducting pathways with different conduction times and refractory periods in the atrioventricular node 2
- Another common form of PSVT is atrioventricular reciprocating tachycardia, which depends on an anatomically distinct accessory pathway that conducts impulses between the atria and ventricles, bypassing the AV node 2
- PSVT can also be caused by focal atrial tachycardia, which is a less common type of supraventricular tachycardia 3
Mechanisms of PSVT
- Reentry is the primary mechanism of PSVT, which occurs when an electrical impulse circulates repeatedly in a closed circuit, causing a rapid heart rate 2, 4
- The presence of inhomogeneous, accessory, or concealed conducting pathways can contribute to the development of reentry and PSVT 4
- The anatomic location of the reentry circuit can affect the type of PSVT and its treatment 2, 3
Types of PSVT
- Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common type of PSVT, accounting for approximately 50-60% of cases 5, 3
- Atrioventricular reentrant tachycardia (AVRT) is another common type of PSVT, which uses an accessory pathway to conduct impulses between the atria and ventricles 2, 5
- Focal atrial tachycardia is a less common type of PSVT, which originates from a single focus in the atria 3