Concern has been expressed about the potential for risks and complications of transvenous lead implantation in diseased RV myocardium. These relate not only to an increased risk of perforation, but also to suboptimal sensing, pacing, and defibrillation efficacy. Although procedure-related deaths were extremely rare in all series following patients with ARVC/D after ICD implantation, both procedural complications and long-term performance complications of the leads were not uncommonly encountered (Table 20.1).
Lead perforation in various (mainly non-ARVC/D) ICD populations has been reported with an incidence of 0.6% to as high as 5.2% [19,20]. There were no reported lead perforations in any of the referenced ARVC/D series. Repeated note is made by several of the implanting groups of the need for meticulous ventricular lead placement to ensure adequate R-wave sensing and pacing thresholds. This is due to the consideration that diseased RV myocardium (replaced by fibrofatty deposits) may render satisfactory sensing, pacing, and defibrillation thresholds difficult to achieve. Uniformly, screw-in leads are preferred. Although a higher number of RV sites were tested prior to lead fixation in the ARVC/D series, a lower final R-wave amplitude was achieved in ARVC/D patients compared with patients with other diseases [11,14,17]. It appears that final pacing and defibrillation thresholds (at least acutely) are comparable .
When followed over time, undersensing or pacing failure (due to exit block) may be encountered with significant frequency in ARVC/D patients as a result of progressive fibrofatty myocardial replacement at the RV lead tip. In series with relatively short follow-up periods, this problem was not reported [11,12]. However, late after implantation, this problem is encountered with considerable frequency. Five patients out of 132 required an additional RV lead in Corrado's cohort , and eight of the 60 patients described by Wichter et al. required lead revision or implantation of an additional pace/sense lead late after implantation (median, 65 months) . Corra-do et al. further report the need for additional subcutaneous or epicardial patches or high-energy de vices in order to achieve a 10-J margin of safety for defibrillation at implant .
In following ARVC/D patients with ICDs, particular attention must be given to these considerations, and particular care must be employed to note any progressive loss of R-wave sensing amplitude or pacing threshold during follow-up, which may not only indicate device or lead compromise, but also possibly disease progression . This is especially true in this generally young patient population, who will require a device for the remainder of their lives. Lead failure relates not only to a compromise in pace/sense or defibrillation function by the mechanisms described, but also to the mechanical issues of lead insulation failure and fracture . An increase in failure rates of transvenous leads has been reported late after implantation (beyond 4-5 years), and this incidence tends to increase with time after implant [20,21]. This has been verified by Wichter et al. in ARVC/D patients undergoing long-term follow-up, with a high rate of lead-related complications (cumulatively 37% at 7 years) . Lead failure may also contribute to inappropriate or inadequate delivery of ICD therapy.
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