From the Guidelines
Supraventricular tachycardia (SVT) is a rapid heart rhythm originating above the ventricles, characterized by sudden onset of palpitations with heart rates typically between 150-250 beats per minute, and its management should prioritize vagal maneuvers and adenosine as first-line treatments, with catheter ablation considered for recurrent episodes, as recommended by the most recent guidelines 1. The pathophysiology of SVT primarily involves abnormal electrical circuits or automaticity in the atria or AV node, with common mechanisms including AV nodal reentrant tachycardia (AVNRT), accessory pathway-mediated tachycardias like Wolff-Parkinson-White syndrome, and atrial tachycardias from enhanced automaticity.
Key Points:
- The incidence of SVT is 1–3 cases per 1000 persons, with a prevalence of 0.2% in the general population, increasing with age and more common in women than men 1.
- Symptoms of SVT include palpitations, chest discomfort, fatigue, light-headedness, shortness of breath, anxiety, dizziness, dyspnoea, and uncommonly, syncope.
- Management of SVT begins with vagal maneuvers, such as the Valsalva maneuver or carotid sinus massage, to increase parasympathetic tone and slow AV node conduction.
- If vagal maneuvers fail, first-line pharmacological treatment is adenosine (6mg IV rapid push, followed by 12mg if needed), which temporarily blocks AV node conduction, often terminating the arrhythmia.
- For hemodynamically unstable patients, immediate synchronized cardioversion at 50-100J is indicated.
- Long-term management options include calcium channel blockers (verapamil 120-360mg daily or diltiazem 120-360mg daily), beta-blockers (metoprolol 25-100mg twice daily), or class IC antiarrhythmics like flecainide (50-200mg twice daily) for prevention.
- Definitive treatment with catheter ablation is highly effective (success rates >95% for AVNRT) and should be considered for recurrent episodes, especially in younger patients to avoid lifelong medication, as supported by recent guidelines 1.
- Patients should be educated about recognizing symptoms and performing vagal maneuvers at home before seeking emergency care for persistent episodes.
From the FDA Drug Label
ADENOSINE INJECTION, USP for intravenous use INDICATIONS AND USAGE Adenosine Injection, a pharmacologic stress agent, is indicated as an adjunct to thallium-201 myocardial perfusion scintigraphy in patients unable to exercise adequately ( 1) WARNINGS AND PRECAUTIONS • Cardiac Arrest, Ventricular Arrhythmias, and Myocardial Infarction. Fatal cardiac events have occurred. WARNINGS AND PRECAUTIONS • Sinoatrial (SA) and Atrioventricular (AV) Nodal Block. First-, second- or third-degree AV block, or sinus bradycardia can occur.
The pathophysiology of Supraventricular Tachycardia (SVT) is not directly addressed in the provided drug label. However, the label does mention that adenosine injection can cause Sinoatrial (SA) and Atrioventricular (AV) Nodal Block, which can lead to sinus bradycardia or AV block.
- The management of SVT may involve the use of adenosine injection as a pharmacologic stress agent, but the label does not provide direct information on the pathophysiology of SVT.
- Key points to consider when using adenosine injection include:
- Contraindications: second- or third-degree AV block, sinus node disease, known or suspected bronchoconstrictive or bronchospastic lung disease, and known hypersensitivity to adenosine injection.
- Warnings and precautions: cardiac arrest, ventricular arrhythmias, and myocardial infarction, as well as sinoatrial and atrioventricular nodal block. 2
From the Research
Pathophysiology of Supraventricular Tachycardia (SVT)
- SVT is an abnormal rapid cardiac rhythm that involves atrial or atrioventricular node tissue from the His bundle or above 3, 4, 5, 6, 7
- The condition is caused by reentry phenomena or automaticity at or above the atrioventricular node 4, 7
- Reentry accounts for most cases and has been localized to the A-V node and less frequently to the sinus node, the atria themselves, and A-V nodal bypass tracts (Wolff-Parkinson-White syndrome) 7
- SVT often terminates before presentation, and episodes may be erroneously attributed to anxiety 5
Management of Supraventricular Tachycardia (SVT)
- Diagnostic evaluation may be performed in the outpatient setting and includes a comprehensive history and physical examination, electrocardiography, and laboratory workup 3
- Extended cardiac monitoring with a Holter monitor or event recorder may be needed to confirm the diagnosis 3, 4, 5
- Acute management of paroxysmal SVT is similar across the various types and is best completed in the emergency department or hospital setting 3
- In patients who are hemodynamically unstable, synchronized cardioversion is first-line management 3
- In those who are hemodynamically stable, vagal maneuvers are first-line management, followed by stepwise medication management if ineffective 3, 4, 6
- Beta blockers and/or calcium channel blockers may be used acutely or for long-term suppressive therapy 3, 4, 6
- Catheter ablation has a high success rate and is recommended as the first-line method for long-term management of recurrent, symptomatic paroxysmal SVT, including Wolff-Parkinson-White syndrome 3, 4, 5, 6
Types of Supraventricular Tachycardia (SVT)
- Atrioventricular nodal reentrant tachycardia 3, 4
- Atrioventricular reentrant tachycardia 3, 4
- Atrial tachycardia 3, 4
- Wolff-Parkinson-White syndrome 3, 4, 5, 6