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David S. Starr
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Ann Thorac Surg 1981;31:334-338
© 1981 The Society of Thoracic Surgeons

Articles

Acute and Chronic Stimulation Thresholds of Intramyocardial Screw-in Pacemaker Electrodes

David S. Starr, M.D.*, Gerald M. Lawrie, M.D., George C. Morris, Jr., M.D.

Cora and Webb Mading Department of Surgery, Baylor College of Medicine, Houston, TX

Accepted for publication August 15, 1980.

* Address reprint requests to Dr. Starr, 1393 Mt. Everett, Hubbard, OH 44425

Two screw-in intramyocardial electrodes were inserted in the left ventricle of each of 6 mongrel dogs, and the electrical characteristics were studied over a six-month period. The unipolar lead configuration had consistently better threshold and sensing values than the bipolar configuration during this period. Peaking between implantation and 3 weeks later, mean lead thresholds increased significantly (unipolar, 0.4 to 8.2 µJ; bipolar, 0.6 to 10.2 µJ) while R wave amplitude decreased (unipolar, 16.6 to 8.5 mv; bipolar, 10.6 to 5.8 mv). Mean chronic values for stimulation thresholds were as follows: unipolar, 2.6 µJ, and bipolar, 3.1 µJ. Mean values for the R wave amplitude were as follows: unipolar, 10.6 mv, and bipolar, 7.2 mv.

Analysis of the results indicated that with certain exceptions, the optimum system has 2 intramyocardial electrodes, 1 in unipolar configuration and 1 "reserve." In general, adequate values at implantation are a stimulation threshold of 1.4 µ) (e.g., 1.1 v at 500 ohms and 0.6 msec pulse width) and an R wave amplitude of 5 mv.






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Copyright © 1981 by The Society of Thoracic Surgeons.