Sensing Failure Associated with the Medtronic Sprint Fidelis Defibrillator Lead
ABSTRACT The diameter of implantable cardioverter-defibrillator (ICD) leads has become progressively smaller over time. However, the long-term performance characteristics of these smaller ICD leads are unknown.
We retrospectively evaluated 357 patients who underwent implantation of a Medtronic Sprint Fidelis defibrillating lead at two separate centers between September 2004 and October 2006. Lead characteristics were measured at implant, at early follow-up (1-4 days post implant), and every 3-6 months thereafter.
During the study period, 357 patients underwent implantation of the Medtronic Sprint Fidelis lead. The mean R-wave measured at implant through the device was not different (P = NS) when compared with that measured at first follow-up (10.5 +/- 5.0 mV vs 10.7 +/- 5.1 mV). Forty-one patients (13%) had an R-wave amplitude <or= 5 mV measured through the device at implant. Of those patients with an R-wave amplitude <or= 5 mV at implant measured through the device, 63% (n = 26) remained <or= 5 mV for the duration of follow-up. The mean time to R-wave amplitude <or= 5 mV was 96.2 +/- 123 days. During follow-up, 65 (18%) patients developed R-wave <or= 5 mV. Overall 10 lead revisions (2.8%) were performed during the first year of follow-up.
Abnormal R-wave sensing is frequently observed during follow-up with the Medtronic Fidelis ICD lead. Lead revision was necessary in 2.8% of the patients, most often (8 of 10) due to abnormal R-wave sensing along with elevated pacing threshold. Whether this issue is limited to this lead or reflects a potential problem with all downsized ICD leads merits further investigation.
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ABSTRACT: This paper illustrates our experience with the Sprint Fidelis lead (SF, single coil model 6931). We investigated lead failure incidence, analysed for possible predictive factors and examined the efficacy of integrated early ICD warning systems. We analysed 181 consecutive patients with SF (follow up: 406 +/- 250 days). Left ventricular ejection fraction, age, gender, follow up, ICD indication, type of device, duration of implantation, and target vein used for implantation were evaluated as potential predictive factors of lead failure. Additionally, the predictive value of recommended impedance alert adaptations, the potential effects of the sensing integrity counter (SIC), and of the new lead integrity alert (LIA)(R) were studied. Nine lead failures were identified. Lead failure occurred significantly more often in patients with single- and dual-chamber devices. None of the patients under cardiac resynchronisation therapy (CRT) had a lead failure (p=0.04). Seven failures (78%) became apparent through inappropriate shock interventions. Impedance alert adaptations did not prevent any inappropriate shock intervention, but the SIC and the activation of the LIA might have prevented inappropriate interventions. A fractured pace/sense ring conductor was identified as the most vulnerable part of the SF lead (in 7 failures, 78%). We verified an increased failure rate in patients with the SF lead. Only patients with CRT devices were free from lead failure, suggesting a correlation with increased physical activity. The impedance alert reprogramming did not predict any inadequate shock interventions but LIA may become a new valuable tool for the early detection of lead failure signs.Hellenic journal of cardiology: HJC = Hellēnikē kardiologikē epitheōrēsē 51(3):219-25. · 0.79 Impact Factor
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ABSTRACT: An optimal pilot embedding scheme is proposed for multipath channel identification. The scheme adds the columns of a Hadamard matrix to the transmitted signal to help estimate the channel. At the receiver, the channel is estimated as a function of the mean of the received blocks. A power allocation scheme is derived for approximately determining the optimal amount of power to allocate to the information symbols and the added pilot symbols.Spread Spectrum Techniques and Applications, 2004 IEEE Eighth International Symposium on; 01/2004
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ABSTRACT: Direct sequence code division multiple access (DS-CDMA) signals exhibit cyclostationary properties which imply a redundancy between frequency components separated by multiples of the symbol rate. In this paper a multiple access interference canceller (frequency shift canceller) that explores this property is presented. This linear frequency domain canceller operates on the spread signal in such way that the interference and noise at its output is minimized (minimum mean squared error criterion). The frequency shift canceller (FSC) performance was evaluated for a UMTS-TDD scenario and multi-sensor configurations, where the cases of diversity and beamforming were considered. All these configurations are evaluated concatenated with a parallel interference canceller (PIC-2D). The results are benchmarked against the performance of the conventional RAKE-2D detector, the conventional PIC-2D detector and single user scenario, and we observe considerable performance gains with the FSC especially for the diversity case and a performance close to the single user case when it was evaluated jointly with PIC-2D.Spread Spectrum Techniques and Applications, 2004 IEEE Eighth International Symposium on; 09/2004