Discussion
The current series is the largest to date evaluating the relationship between multi-lead defibrillator therapy delivered via the cephalic vein, and ICD lead failure. We found a very low incidence of lead failure in this solely CRT-D based study (0.33%/year). The findings have important practical applications as CRT-D system implantations via the cephalic are efficient and safe (4), whilst ICD lead failures maintain a degree of concern (7).
This multi-centre study reported a very low overall lead failure rate which is at odds with some previous series (7) but is validated by at least one previous large series (0.45%/year) (9). This low failure rate may reflect our conservative practice: A policy of concentrating on products with a track record of long-term safety and late adoption of less tested technology. The higher incidence of failure in the prior literature may represent a publication bias; it is reasonable to suppose that colleagues are more likely to report an unsatisfactory experience than to describe lead performance that is in line with expectation.
This series demonstrates that cephalic vein access for multi-lead defibrillator therapy does not affect lead longevity: The rate of lead failure was similarly low for cephalic and non-cephalic routes (0.4%/year vs 0.14%/year, p=0.34). This is in stark contrast to a recent report by Barbhaiya et al which found that cephalic access was associated with a high rate of lead failure in multi-lead ICD therapy (11% per year for non-Linox and 19% per year for Linox leads) (7). There are significant differences between the two reports. Their method was to implant a maximum of two leads via the cephalic vein, whereas most of our patients received three leads by this route. Barbhaiya et al described only 46% of their cohort as having multi-lead ICD systems, our study population consists entirely of CRT-D devices (≥ 2 leads) and they implanted only 18% of ICD leads via the cephalic vein, while we used it in 74%. This implies that their series included only around 55 ICD leads implanted via the cephalic as part of a multi-lead system compared to 465 in our series.
Sample size alone cannot account for the contrast between our results and those of Barbhaiya et al. As their series included just 6 instances of lead failure including 4 (67%) implanted via the cephalic route, the association may have been a chance event detected on post-hoc analysis. Inter-institution differences in implantation technique could also have played a role: Barbhaiya et al demonstrated that the phenomenon they described was not attributable to a single operator (10), but institutional culture determines the idiosyncrasies of operative technique as much as inter-individual variation. All of the predominantly cephalic operators in our series derived at least part of their methodology from one mentor.
We believe that many small technical (11) and methodological differences could play a role in lead durability: for example, our policy is to place all leads via peel-away sheaths to protect the tip from stress produced by passage through a tortuous cephalic vein. In our series, 75% of the operators would be considered as ‘cephalic-operators’ with a similar well-honed technique and experience in accessing this vein, maintaining consistency and minimising error. Our population also had a low proportion of leads that have exhibited a high rate of failure such as the Linox (Biotronik, Berlin, Germany).
The Cox regression analysis found that venous access route does not predict lead failure, in keeping with prior reports (12). Consistent with previous findings, we found leads implanted in women were much more likely to fail (13) (figure 2 ). The naturally smaller female frame may enforce tighter angulation within the thoracic vasculature, applying stress on the implanted leads. Due to their smaller size, women are also more likely to have excess redundant lead folded within the pocket, increasing lead tension at this site.
Hypertension emerged as an independent risk factor for lead failure in our series, but has previously not been identified as a predictor. It stands to reason as a hazard to lead durability: Hypertension results in shear stress on the vascular system leading to remodelling with increased tortuosity and angulations in the arterial system. The venous system is not directly altered by arterial hypertension, but the close anatomic relationship could expose venous leads indirectly to the angulations of the associated arteries.