From the Guidelines
The criteria for diagnosing supraventricular tachycardia (SVT) include a heart rate typically greater than 100 bpm at rest, with the mechanism involving tissue from the His bundle or above, and can be characterized by regular or irregular rhythm, narrow QRS complexes, and absent or abnormal P wave morphology. To diagnose SVT, perform a 12-lead ECG during the tachycardia episode, looking for key features such as sudden onset and termination of tachycardia, no discernible P waves or P waves hidden within the T waves, and QRS complexes that look similar to the patient's normal QRS 1.
Key Diagnostic Features
- Heart rate typically greater than 100 bpm at rest
- Regular or irregular rhythm
- Narrow QRS complexes (less than 120 milliseconds)
- Absent or abnormal P wave morphology
- Sudden onset and termination of tachycardia
- No discernible P waves or P waves hidden within the T waves
- QRS complexes that look similar to the patient's normal QRS
Additional Diagnostic Steps
- Carotid sinus massage or Valsalva maneuver to attempt termination
- Adenosine administration (6-12 mg IV rapid push) to temporarily block AV node conduction SVT occurs due to a reentry circuit or abnormal automaticity in the atria or AV node, and the rapid heart rate and absence of normal P waves distinguish it from sinus tachycardia, with narrow QRS complexes indicating that ventricular activation is still occurring through the normal conduction system, differentiating SVT from ventricular tachycardia 1.
Types of SVT
- Atrial tachycardia (AT)
- Atrioventricular nodal reentrant tachycardia (AVNRT)
- Atrioventricular reentrant tachycardia (AVRT)
- Junctional tachycardia
- Multifocal atrial tachycardia (MAT)
- Paroxysmal supraventricular tachycardia (PSVT) Each type of SVT has distinct ECG characteristics and clinical presentations, and accurate diagnosis is crucial for effective management and treatment 1.
Clinical Presentation
- Palpitations
- Chest discomfort
- Fatigue
- Light-headedness
- Shortness of breath
- Anxiety
- Dizziness
- Dyspnoea
- Syncope (uncommon) The clinical presentation of SVT can vary depending on the type of SVT, the frequency and duration of episodes, and the presence of underlying heart disease 1.
From the Research
Diagnostic Criteria for Supraventricular Tachycardia (SVT)
The diagnostic criteria for SVT include:
- Altered consciousness, chest pressure or discomfort, dyspnea, fatigue, lightheadedness, or palpitations as presenting symptoms 2
- A comprehensive history and physical examination, electrocardiography, and laboratory workup as part of the diagnostic evaluation 2
- Extended cardiac monitoring with a Holter monitor or event recorder to confirm the diagnosis 2
- A 12-lead electrocardiogram (ECG) with a QRS complex duration less than 120ms and a heart rate greater than 100 beats per minute to define narrow complex tachycardias (NCTs) 3
- Early measurement of natriuretic peptides to guide the clinician to rule out tachycardia and/or SVT 4
Types of SVT
The common types of SVT include:
- Atrioventricular nodal reentrant tachycardia
- Atrioventricular reentrant tachycardia
- Atrial tachycardia 2, 5
Diagnostic Challenges
The diagnostic challenges in SVT include: