Invasive assessment of atrial repolarization by intracardiac electrogram

Invasive assessment of atrial repolarization by intracardiac electrogram

Assessment of atrial repolarization on surface ECG is difficult as it is obscured by the QRS complex during sinus rhythm. It may be evident in complete heart block when independent P waves occur. Otherwise QRST cancellation algorithms have to be used to assess atrial repolarization waves. Another option is to record intracardiac electrograms from within the atrium which will delineate the atrial depolarization better. Monophasic action potentials can be measured from various sites in the right atrium using intracardiac electrodes.

Variations in the monophasic action potential while stimulating the atrium at a constant drive cycle length can give an assessment of the dispersion of atrial repolarization, akin to the QT dispersion in case of the ventricle. Choi et al [1] have noted significantly increased dispersion of monophasic action potential duration measured at 90% repolarization (MAPD90), suggesting heterogeneity of atrial repolarization in Brugada syndrome which may be a risk factor for the development of atrial fibrillation.

Reference

1. Kee-Joon Choi, Jun Kim, Sung-Hwan Kim, Gi-Byoung Nam, You-Ho Kim. Increased dispersion of atrial repolarization in Brugada syndrome. Europace. 2011 Nov;13(11):1619-24.