Bipolar, transvenous, passive-fixation leads (ThinLine,(TM) Sulzer Int
ermedics Inc., Angleton, TX, USA) incorporating coradial individually
coated conductor coils, and a redundant external 55D polyurethane insu
lation sheath were developed. The diameter of the new leads (< 5 Fr) i
s in the range of available unipolar leads and is considerably smaller
than conventional bipolar pacing leads. From January 9, 1994 to Novem
ber 12, 1996, 1,536 model 432-04 (523 atrial) and 430-10 (1,023 ventri
cular) leads were implanted in 1,068 patients at 50 US and 5 Canadian
centers to evaluate their safety and efficacy. The study included a ge
neral phase, with follow-ups at 1, 3, 6, 12, 18, and 24 months; and a
randomized intensive phase with collection of more data and additional
2- and 6-week follow-ups. Capture and sensing thresholds, lead impeda
nce, and handling characteristics were evaluated. Clinical events were
monitored and performance was compared to that of two commercially av
ailable conventional (coaxial) leads: Sulzer Intermedics models 432-03
(atrial) and 430-07 (ventricular). During a total of 17,530 device mo
nths, there were two lead failures, no lead related deaths, 32 explant
s, 37 complications, and no unexpected adverse device effects. Capture
thresholds were lower than those for coaxial controls with identical
electrodes, sensing was comparable, lead impedances were within clinic
ally acceptable ranges, and investigators found overall handling chara
cteristics good to excellent. ThinLine coradial bipolar leads are safe
and effective for cardiac pacing and sensing.