23-32: SVT With Aberrancy

Maite A. Huis in ‘t Veld; Amal Mattu; R. Jason Thurman

ECG Findings

Wide complex, regular tachycardia (usually > 140 bpm)
QRS morphology consistent with one of the bundle branch block patterns

Pearls

The rapid rate of an SVT may “outrun” the ventricular conducting system’s ability to repolarize quickly, producing a rate-related bundle branch block. The signal then must propagate cell to cell, producing a wide-complex tachycardia. A typical bundle branch pattern usually results.
When a person with a chronic wide-complex (aberrant) bundle branch block enters an SVT, the ECG will display a wide-complex, regular tachycardia. However, when the patient does not have prior ECGs, it can be difficult to distinguish SVT with aberrancy from a ventricular tachycardia (VT). Many different criteria have been proposed to distinguish the two, but unfortunately, most are neither extremely sensitive nor specific. When in doubt, treat as a VT, as many of the typical SVT pharmacologic agents are detrimental in patients with VT and can lead to ventricular fibrillation and death.

FIGURE 23.32A

Supraventricular Tachycardia with Aberrant Conduction, Underlying RBBB. (ECG contributor: Walter Clair, MD.)

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FIGURE 23.32B

Wide-complex tachycardia with a rate of 188 bpm. This patient has sudden onset of SVT with a known underlying RBBB. QRS complexes are wide (lower double arrows) and R-R intervals are regular (upper double arrows).

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FIGURE 23.32C

Wide-complex tachycardia at approximately 150 bpm. The R-R interval is regular, except for one pause, when characteristic atrial flutter waves are apparent (arrowhead).

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FIGURE 23.32D

Irregularity in the R-R interval, as seen most easily in the baseline (double arrows), strongly suggests the presence of rapidly conducted atrial fibrillation with aberrancy.