Introduction

ICDs increase survival in patients at high risk of sudden cardiac death . ICD leads have been called the ‘weakest link’ of the ICD systems . Indeed, 8 years after implantation, ICD lead survival is reportedly as low as 60% .

Medtronic Sprint Fidelis defibrillator leads (Medtronic, Inc., Minneapolis, MN, USA) were removed from the market in October 2007 because of a high rate of lead failure. An increased risk of failure of Sprint Fidelis leads was reported only a few months earlier by Hauser et al. . Such lead failure may result in painful, inappropriate ICD shocks, failure to deliver life-saving therapy and, rarely, death .

With 268,000 leads implanted worldwide, correct identification of patients who will develop lead failure is essential. This need is amplified by the fact that the patients with Sprint Fidelis leads were implanted between 2004 (market launch in USA) and 2007 (worldwide withdrawal), and will most likely undergo defibrillator generator replacement in the next 3 years. It would be optimal to identify patients at high risk of Sprint Fidelis lead failure in order to implant a prophylactic alternative ICD lead, with or without removal of the Sprint Fidelis lead, at the time of the generator replacement. Reoperation for lead replacement soon after generator replacement would expose patients to a higher risk of procedural complications and, more specifically, might expose them to an increased risk of infections . Consequently, it would be of great interest to determine the clinical profile of patients at high risk of lead failure.

The risk factors for Sprint Fidelis lead failure are poorly understood. Younger age at implantation , female sex , greater left ventricular ejection fraction and noncephalic venous access are reportedly associated with greater risk. However, studies evaluating risk factors for Sprint Fidelis lead dysfunction often had low statistical power and reported conflicting results. Current data do not allow risk stratification of patients with Sprint Fidelis leads.

We sought to identify demographic and implant technique-related factors predisposing to Sprint Fidelis lead failure.

Methods

Results

Patients implanted with Sprint Fidelis leads were mostly men (86.6%) and most had nonischaemic heart failure. The majority of patients had an ejection fraction < 35% and received model 6931 leads ( Table 1 ).

During a median follow-up period of 2.80 years (interquartile range 2.29; mean 2.49; range 0.01–5.32), we observed 33 Sprint Fidelis lead failures (12.3%) resulting in 3-year and 5-year survival rates of 87.4% ± 2.6% and 65.6% ± 7.5%, respectively ( Fig. 1 , Panel A). We also identified 37 deaths, 18 cardiac transplantations and 13 Sprint Fidelis lead removals without signs of lead dysfunction (four lead dislodgments, six infections, two prophylactic replacements and one suspected dysfunction, which was ruled out after product analysis). No deaths related to lead dysfunction were identified.

Sprint Fidelis lead survival in the whole cohort (Panel A) and in subsets of patients divided according to age (< 62.5 or > 62.5 years; Panel B).

Table 2 reports the clinical presentation of patients with Sprint Fidelis lead failure. Seventeen patients had inappropriate ICD shocks, with one patient receiving 36 shocks. However, out of the last 10 patients with lead dysfunction, only two experienced inappropriate ICD shocks.

Table 2

Case descriptions of fractured Sprint Fidelis leads.

Patient	Time since implantation at lead fracture	Number of inappropriate shocks due to lead failure	Oversensing	Impaired detection threshold	High pacing impedance	Lead extraction
1	1.65	16	Yes	Yes	No	Yes
2	1.28	2	Yes	No	No	No
3	3.56	N/A	Yes	Yes	Yes	Yes
4	0.94	36	Yes	No	Yes	No
5	3.29	14	Yes	No	Yes	Yes
6	2.72	N/A	Yes	No	No	No
7	1.32	1	Yes	Yes	No	Yes
8	4.12	4	Yes	Yes	No	Yes
9	0.85	N/A	Yes	Yes	Yes	Yes
10	2.34	27	Yes	No	No	No
11	2.98	2	Yes	No	No	No
12	3.26	9	Yes	No	No	No
13	2.40	15	Yes	No	Yes	Yes
14	3.49	7	Yes	Yes	No	Yes
15	3.51	N/A	No	No	Yes	Yes
16	1.50	N/A	No	Yes	Yes	Yes
17	2.53	N/A	Yes	Yes	No	Yes
18	1.20	6	Yes	Yes	No	No
19	2.27	30	Yes	No	Yes	No
20	2.99	23	Yes	No	No	No
21	4.69	6	Yes	No	No	Yes
22	1.74	N/A	Yes	No	No	No
23	1.46	N/A	Yes	No	Yes	No
24	3.28	6	Yes	No	Yes	No
25	0.90	N/A	Yes	No	Yes	No
26	2.34	N/A	No	No	Yes	No
27	2.35	N/A	Yes	Yes	No	No
28	2.37	N/A	Yes	No	Yes	No
29	4.15	22	Yes	No	No	Yes
30	2.24	N/A	Yes	No	No	Yes
31	4.31	N/A	No	No	No	No
32	1.99	N/A	Yes	No	Yes	No
33	4.46	N/A	Yes	No	Yes	No

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