What are the electrocardiogram (ECG) findings on supraventricular tachycardia (SVT)?

From the Guidelines

Supraventricular tachycardia (SVT) on ECG is characterized by a narrow complex tachycardia with heart rates between 150-250 beats per minute, and the key findings include regular, rapid rhythm with narrow QRS complexes (less than 120 ms), absent P waves or abnormal P wave morphology, and a sudden onset and termination. The diagnosis of SVT can be challenging, and a 12-lead ECG obtained during tachycardia and during sinus rhythm may reveal the etiology of tachycardia 1. The ECG findings in SVT can vary depending on the type of arrhythmia, and it is essential to distinguish SVT from ventricular tachycardia (VT) to provide appropriate treatment.

Key ECG Findings in SVT

• Narrow QRS complexes (less than 120 ms)
• Regular, rapid rhythm
• Absent P waves or abnormal P wave morphology
• Sudden onset and termination
• Retrograde P waves may be hidden within the QRS complex or appear immediately after as a pseudo-R' in lead V1 or pseudo-S in inferior leads in atrioventricular nodal reentrant tachycardia (AVNRT)
• Retrograde P waves are typically visible after the QRS complex in atrioventricular reentrant tachycardia (AVRT)
• Visible P waves with abnormal morphology preceding each QRS in atrial tachycardia

Distinguishing SVT from VT

• SVT typically has narrow QRS complexes, while VT has wide QRS complexes (greater than 120 ms)
• AV dissociation, fusion complexes, and concordance of the precordial QRS complexes can help diagnose VT 1
• The Brugada criteria and the Vereckei algorithm can also be used to distinguish VT from SVT 1

Clinical Implications

• Accurate diagnosis of SVT is crucial to provide appropriate treatment and prevent potential complications
• Vagal maneuvers or adenosine administration during ECG recording can help reveal the underlying mechanism by transiently blocking the AV node and exposing atrial activity
• A 12-lead ECG obtained during tachycardia and during sinus rhythm is essential to reveal the etiology of tachycardia and guide treatment decisions 1

From the Research

ECG Findings on SVT

• The electrocardiography (ECG) findings for supraventricular tachycardia (SVT) can be normal if the arrhythmia is not present at the time of the examination 2.
• ECG is crucial in diagnosing SVT, and the underlying mechanism can be deduced from electrocardiography during tachycardia, comparing it with sinus rhythm, and assessing the onset and offset of tachycardia 3.
• A Holter monitor or event recorder may be needed to confirm the diagnosis of SVT if the ECG findings are normal 2.

Diagnosis and Management

• The diagnosis and management of SVT involve the use of vagal maneuvers, adenosine, beta-blockers, and calcium channel blockers as first-line therapies 2, 4, 3.
• Adenosine is effective in terminating SVT, with a success rate of 93% in converting SVT to sinus rhythm 4.
• Catheter ablation is a curative treatment option for SVT, with a success rate of 95% and a recurrence rate of less than 5% 2.

Treatment Options

• Treatment options for SVT include:
  • Vagal maneuvers
  • Adenosine
  • Beta-blockers (e.g., metoprolol)
  • Calcium channel blockers (e.g., diltiazem, verapamil)
  • Class Ic antiarrhythmics (e.g., flecainide, propafenone)
  • Catheter ablation 2, 4, 3
• The choice of treatment depends on the frequency of symptoms, risk stratification, and patient preference 3.