Supraventricular Tachycardia (SVT) with Aberrancy on ECG

Introduction

Supraventricular Tachycardia (SVT) with aberrancy refers to a rapid heart rhythm originating above the ventricles, which presents with a wide QRS complex on electrocardiography (ECG). This happens due to abnormal conduction through the ventricles, often because of pre-existing bundle branch block or rate-related conduction delay.

Key Concepts

1. Differentiating SVT with Aberrancy from Ventricular Tachycardia (VT)

• SVT with aberrancy arises from the atria or AV junction and becomes wide due to a pre-existing conduction defect.
• Ventricular Tachycardia (VT) originates within the ventricles and is inherently a wide-complex tachycardia.
• Correct differentiation is crucial because misdiagnosis can lead to inappropriate treatment.

2. Criteria Used for Diagnosis

Several ECG criteria help in differentiating SVT with aberrancy from VT: - Brugada Criteria - Vereckei’s aVR Algorithm - Absence of AV dissociation (supports SVT) - Response to vagal maneuvers or adenosine (SVT typically terminates, VT does not) - History of structural heart disease (favoring VT)

Common Causes of Aberrancy in SVT

• Bundle Branch Block (BBB): A pre-existing block in the right or left bundle branch prolongs ventricular depolarization.
• Rate-Related Aberrancy: At very high heart rates, the conduction system may transiently fail to propagate impulses normally.
• Accessory Pathway Conduction: In conditions like Wolff-Parkinson-White (WPW) syndrome, abnormal pathways can participate in the tachyarrhythmia.

Management Approach

Initial Steps:

1. Assess hemodynamic stability (Blood pressure, consciousness, signs of shock)
   • Unstable patient: Immediate synchronized cardioversion.
   • Stable patient: Proceed with pharmacologic interventions.

Pharmacologic Treatment:

• Adenosine (First-line if SVT suspected): Can terminate SVT but won't affect VT.
• Beta-blockers or calcium channel blockers: If sinus rhythm is restored.
• Amiodarone (if VT still suspected): Broad-spectrum antiarrhythmic used cautiously.

When to Seek Specialist Consultation

• Uncertain ECG diagnosis between SVT with aberrancy and VT.
• Recurrent or poorly controlled arrhythmias.
• Structural heart disease concerns.

Conclusion

SVT with aberrancy presents a diagnostic challenge due to its resemblance to VT on ECG. A careful assessment of the patient's history, response to treatment, and application of validated electrocardiographic criteria can aid in differentiation. Whenever doubt exists, treating as ventricular tachycardia is a safer approach.

Source recommendations

1. American Heart Association (AHA) Supraventricular Tachycardia Guidelines

1. https://www.ahajournals.org/doi/10.1161/cir.0000000000000311
2. https://www.heart.org/en/health-topics/arrhythmia/about-arrhythmia/tachycardia--fast-heart-rate
3. https://professional.heart.org/en/science-news/-/media/028ddd505f514ea2b3a4e74bb72e3557.ashx
4. https://pubmed.ncbi.nlm.nih.gov/26399662/
5. https://professional.heart.org/en/science-news/guideline-for-the-management-of-adult-patients-with-supraventricular-tachycardia

2. European Society of Cardiology (ESC) Guidelines for the Management of Supraventricular Tachycardia

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Supraventricular-Tachycardia
2. https://academic.oup.com/eurheartj/article/41/5/655/5556821
3. https://pubmed.ncbi.nlm.nih.gov/31504425/
4. https://www.acc.org/Latest-in-Cardiology/ten-points-to-remember/2019/09/10/12/36/2019-ESC-Guidelines-for-Supraventricular-Tachycardia
5. https://www.ahajournals.org/doi/10.1161/01.cir.0000091380.04100.84