Discussion

Abstract

5 ] conduction times are prolonged in patients with a history of atrial flutter. The values obtained, each representing the time needed for the sinus node impulse to reach the LA, differ markedly. In order to compare the values of HRA to LA conduction time obtained by different workers, the LA recording site must be known. More detailed mapping of LA depolarization will allow easier comparison of the atrial conduction times obtained from different LA sites.A patent foramen ovale occurs in 15-28% of normal individuals [ 131 and at the same location in the interatrial septum as a secundum atrial septa1 defect. These defects are easily crossed by acatheter introduced from the femoral vein [14]. Thus a high incidence of catheter passage across patent foramen ovales is expected during electrophysiological studies. These interatrial communications should be routinely sought, as they allow recording of a high LA electrogram, which provides useful clinical information regarding the sequence of atrial depolarization.