Defibrillator Leads - Is Smaller Necessarily Better - 2006 Abstract from Cornell

I recently found an abstract from 2006 that discussed the Sprint Fidelis. Although the full article has never been published, I thought the results of the abstract are interesting - 17% incidence of abnormal RV sensing! Wow!

Link

Defibrillator leads: Is smaller necessarily better?

Mirchandani, Sunil; Stein, Kenneth M; Markowitz, Steven M; Iwai, Sei; Shah, Bindi K; Cheung, Jim W; Tan, Vivian R; Dhruvakumar, Sandhya; Dobesh, David P; Nemirovsky, Dmitry; Lerman, Bruce B; Mittal, Suneet | Circulation, 2006; 114

Background: The diameter of ICD leads has become progressively smaller over time. Smaller leads may allow for easier passage into the right ventricle (RV), increased compatibility with systems incorporating multiple leads, and improved durability. However, the long-term performance characteristics of these smaller leads are unknown.

Methods: The Medtronic Sprint Fidelis family of ICD leads (models 6931 and 6949) has a 6.6 Fr caliber and is the first generation of defibrillator leads capable of passing through a 7 Fir sheath. The lead provides true bipolar sensing and has an active fixation mechanism. We evaluated consecutive patients (pts) who underwent implantation of a Fidelis lead (between 9/04-10/05) to determine the incidence of abnormal sensing (R wave <= 5 mV) during follow-up as well as the need for a lead revision in these pts.

Results: The study consisted of 185 pts (133M, age 65 +/- 16 years) with a mean EF of 32 +/- 10 %. At ICD implantation, 8 (4%) pts were pacemaker (PPM) dependent. In the remaining 177 pts, the mean R wave was 13.0 +/- 6.2 mV, as measured through the Medtronic PSA. Nine (5%) pts were subsequently lost to follow-up. In the remaining 168 non-PPM dependent pts with follow-up, initial ICD interrogation occurred at a median of 6 (1,12) days post-ICD implantation. The mean R wave at follow-up was significantly lower than at implant (9.9 +/- 5.0 mV, p < 0.001). A decrease in the R wave (range: 0.1-16.9 mV drop) was observed in 129 (71%) pts at first follow-up. A R wave : 5 mV was observed in 29 (17%) study pts. In addition, 7 (4%) pts required a RV lead revision within the first 8 weeks of implant due to abnormal RV sensing and an elevated RV pacing threshold.

Conclusions: A 17% incidence of abnormal RV sensing was observed during follow-up of pts implanted with the Medtronic Sprint Fidelis ICD lead. This necessitated an early revision of the system in 4% of pts. Whether this problem is related specifically to the design of this particular lead or is a limitation of smaller defibrillator leads in general is unknown.