What is aberrancy on an Electrocardiogram (ECG)?

From the Guidelines

Aberrancy on an ECG refers to abnormal ventricular conduction of supraventricular impulses, typically resulting in widened QRS complexes that can mimic ventricular tachycardia. This phenomenon occurs when a supraventricular beat (originating above the ventricles) conducts through the ventricles with a delay or through an alternative pathway, causing the QRS complex to appear wider than normal. Aberrancy most commonly happens with premature atrial contractions or during rapid heart rates when one of the bundle branches (usually the right bundle) fails to conduct properly due to its longer refractory period. To identify aberrancy, look for typical bundle branch block patterns, particularly right bundle branch block morphology with an rSR' pattern in V1, as seen in patients with RBBB or intraventricular conduction delay on ECG, who have an increased risk of left ventricular systolic dysfunction compared with those with completely normal ECGs 1. Other clues include a normal or only slightly prolonged PR interval before the wide complex, and the presence of a P wave preceding the wide QRS. Understanding aberrancy is crucial for distinguishing between supraventricular tachycardias with aberrant conduction and true ventricular tachycardias, as their treatments and clinical implications differ significantly, and may require further diagnostic investigation, such as echocardiography, minimum 24 h ECG monitor, or exercise ECG test, as recommended for athletes with abnormal ECG findings 1.

Some key points to consider when evaluating aberrancy on an ECG include:

• The presence of bundle branch block patterns, such as right bundle branch block morphology with an rSR' pattern in V1
• A normal or only slightly prolonged PR interval before the wide complex
• The presence of a P wave preceding the wide QRS
• The clinical context, such as the presence of symptoms like fatigue, dizziness, or syncope, which may suggest underlying conduction system disease or structural heart disease 1
• The use of ambulatory electrocardiographic monitoring to document clinically significant arrhythmias in asymptomatic patients, which may be beneficial for selected patients with conduction system disease 1.

Overall, recognizing aberrancy on an ECG is essential for accurate diagnosis and treatment of cardiac arrhythmias, and may involve the use of various diagnostic tests and monitoring strategies to guide clinical decision-making.

From the Research

Definition of Aberrancy on an ECG

• Aberrant ventricular conduction is a common electrocardiographic (EKG) manifestation that occurs when the supraventricular electrical impulse is conducted abnormally through the ventricular conducting system 2.
• This results in a wide QRS complex that may be confused with a ventricular ectopic beat, and differentiation is important because the treatment and prognosis are quite different 2.

Causes of Aberrancy

• Aberrant ventricular conduction can be caused by physiologic refractoriness of the His-Purkinje system and in most cases does not reflect underlying conduction system disease 3.
• Functional bundle branch block can be caused by long-short aberrancy (usually physiologic), or acceleration/deceleration dependent aberrancy (usually pathologic) 4.

Diagnosis of Aberrancy

• Electrocardiogram criteria have been proposed to differentiate aberration from ventricular tachycardia, but they are not always accurate 4.
• The 12-lead ECG is valuable in distinguishing aberrancy from VT, but about 1 in 10 wide QRS tachycardias defy differentiation 5.
• Multiple leads are required for accurate assessment of QRS width, presence of AV dissociation or VA block, QRS axis, and morphological criteria 5.

Clinical Implications

• It is important to recognize aberrant ventricular conduction in the context of a broad complex tachycardia, as the differentiation between supraventricular tachyarrhythmias with aberrant ventricular conduction and ventricular tachyarrhythmias carry different therapeutic and prognostic implications 3.
• Hemodynamically unstable patients with a wide-complex tachycardia should be promptly cardioverted 2.