IMPLANTABLE TINE ELECTODE LEAD

A body implantable lead of the type having a lead body, at least one electrode carried by the lead body and tissue engaging tines extending at an acute angle from the lead body at a location adjacent the electrode. The present invention correlates the tensile stiffness of the lead body with the stiffness of the tines to optimize the tine holding force. The tines provide an adequate holding force to minimize unintentional lead dislodgements without requiring in an excessive force for intentional dislodgement of the lead for repositioning. Tine length and the angle at which they extend from the lead body are also discussed as affecting the probability of tine engagement with cardiac structure as well as having an effect on the holding force. In a preferred embodiment, the lead body has a spring constant (as defined herein) of 2.0 lb-in./10 in. or less and a tine stiffness (also defined herein) of less than 5x10-3 lb-in.2. The tines are from two to six millimeters long and extend from the lead body at an angle from 30 DEG to 80 DEG . More preferably, the tine stiffness is 3x10-3 lb-in.2 or less with the tines being from four to six millimeters long and forming an angle with the lead body from 45 DEG to 60 DEG . In the preferred embodiments, the exposed surface of the lead body and the tines are formed of a body compatible urethane. In the most preferred embodiment, the tine stiffness is approximately 2.5x10-3 lb-in.2.