Intra-atrial block

Intra-atrial conduction block is an electrocardiographic manifestation mainly characterized by P wave widening, with P wave duration exceeding 0.12 seconds, notched peaks, and voltage that may or may not be increased. It is seen in atrial enlargement and atrial myocardial infarction caused by various etiologies. Complete conduction block between the left and right atria is a rare arrhythmia, manifested on ECG as dissociation of the left and right atria: the sinus node impulse is conducted to only one atrium while the other atrium is controlled by an ectopic atrial pacemaker, forming another group of ectopic atrial waves parallel to the sinus P waves, with a slow rate that cannot be conducted down to excite the ventricles. It is mostly seen in the pre-terminal state.