Atrial flutter causes pseudo late potentials on signal-averaged electrocardiogram

Abstract

Signal-averaged electrocardiography (SAECG) is a useful tool for determining which patients are at risk for sustained ventricular tachycardia. 1–3 In patients at risk for sustained ventricular tachycardia, SAECG often shows high-frequency and low-amplitude electrical activity at the terminal portion of the QRS complex. 4–6 This electrical activity is thought to be due to slow conduction in scarred or abnormal ventricular myocardial tissue and is usually not apparent on the standard 12-lead surface electrocardiogram. 7–10 During atrial flutter, flutter waves may occur before, during or after ventricular systole. Atrial flutter waves that occur during ventricular diastole frequently appear as “sawtooth” waves on the standard 12-lead electrocardiogram, particularly in the inferior limb or anterior chest leads. However, atrial flutter waves that occur during ventricular systole may be obscured by the QRS complex. To test the hypothesis that atrial flutter waves that coincide with the terminal portion of the QRS complex cause low-amplitude electrical activity and thus result in a pseudo late potential on the electrocardiogram, we performed SAECG in 9 patients during atrial flutter and normal sinus rhythm.