Endocardial/Shallow Lead Fixation
For endocardial fixation of lumenless leads the delivery catheter is directed to the desired chamber with the tip pointing toward the targeted tissue. The lead is then advanced through the catheter and out to make contact with the tissue, once contact is established the lead is rotated clockwise to secure the fixation helix. The Medtronic 3830 lead has a significantly smaller diameter and tip surface area than most leads, which means that for a given amount of forward force applied the tissue, pressure exerted is higher. With this in mind caution should be taken to not extend the lead out of the delivery catheter if it is firmly pressed against tissue, rather the delivery catheter should be back from the endocardial surface within the targeted chamber and the lead, with its flexible body, advanced to the tissue. The considerable flexibility of the lead prevents significant forward force from being applied to the tissue and reduces the risk of cardiac perforation. When endocardial fixation is desired such as in the right atrial appendage, 4 to 5 clockwise rotations are sufficient to achieve tissue anchoring[10]. Over-torquing the lead may well result in penetration into and through the endocardium. The lead should be rotated with careful attention to the header of the lead, observing the labels to count the rotations, as the number of rotations cannot be assessed fluoroscopically. Fixation can be assessed by introducing and withdrawing lead slack while observing the stability of the lead tip under fluoroscopy. Implantation related injury current should also be present on the bipolar electrogram, See figure 2. If injury current is not observed after initial placement, we suggest applying 1-2 more clockwise rotations to the lead and reassessing; if there is still no injury observed we will typically move the lead to a different position. Once fixation is confirmed the delivery catheter is slit and the lead can be anchored to the fascia.
When placing the lead in the right atrial appendage, endocardial or shallow fixation is desired. Here we typically utilize the pre-formed J shaped delivery catheter (C315J), which is directed to the mid right atrium. We then apply clockwise torque to direct the curvature anteriorly. The lead is advanced from the catheter superiorly to the right atrial appendage when tissue contact is observed (either the lead flexes slightly or the delivery catheter is pushed posteriorly). The lead should not be advanced any further and should be affixed with 3-4 clockwise rotations. If the lead achieves tissue contact before the body of the lead is out of the catheter, then the delivery catheter is likely too high in the atrium directly opposed to tissue and should be advanced. We do not recommend placemen of this lead on the atrial free wall.