A low-threshold, non-dislocating endocardial electrode.

Threshold curves with large and small surface intracardiac pacemaker electrodes are compared. The 2 msec. impulse threshold with a 47 sq. mm. electrode was 3.6 v. (4.3 mA.) on the fourteenth postoperative day, when it reached its maximum, and 2.8 v. (3.1 mA.) one month after the operation. These values were 45 and 30 per cent lower with a 6 sq. mm. electrode. Thresholds increased by about 20 per cent when the impulse duration was shortened from 2 to 0.5 msec. The small surface electrode consumed about 35 per cent less current than the 47 sq. mm. one. A newly designed large area-small surface electrode with the shape of an open cage, seems to have the advantages of less increase in postoperative thresholds and good attachment to the endocardial wall.