Cancellation of esophageal electrocardiograms.

Cancellation of juxtacardiac esophageal electrocardiograms, as demonstrated in this study, indicates certain limitations of the equivalent cardiac dipole hypothesis. A new and more fundamental theory developed here shows that in large measure cancellation occurs because the cancellation network is in effect a relatively insensitive electrocardiographic connection, and because there is always prior assurance that a given complex can be completely canceled at any 2 desired instants during the cycle. The new theory also explains the paradox that proximity electrocardiograms can be canceled even though local action currents exert a relatively powerful influence on such leads.