**3. Challenges of long term ICD therapy**

The long-term benefit of ICD therapy has to be evaluated compared to the ratio of potential‐ ly serious complications.

A number of important medical and technological advances in ICD therapies have been made in the last years which helped to reduce the interventional stress for patients and to improve their daily safety[14-19]: the introduction of transvenousendocardial leads, subpec‐ toral or subfascial implantation of smaller and more powerful ICD devices, introduction of diagnostic tools as e.g. monitoring of intrathoracic fluid status, ST segment changes as well as the introduction of remote home monitoring systems. However, ICD therapy is still asso‐ ciated with significant morbidity and some mortality, especially in long-term follow up.

#### **3.1. Lead failure**

One of the major risks of long-term ICD therapy is lead failure, mostly presented as lead fracture or insulation defect. The annual lead failure rate increases with time and reaches 20% in 10-year old leads.[20] Mechanical stress on leads is the most frequent cause for lead failure and can be reduced by avoiding the medial subclavian puncture during ICD implan‐ tation (preferred approach is through the cephalic vein or lateral subclavian puncture) and by avoiding subpectoral device implantation (preferred subfascial pocket, if possible). How‐ ever, careful evaluation required, for the latter may result in pocket complications necessi‐ tating revision operations.

With the introduction of leads with multilumen design in 1997, lead survival curves initially improved but were still limited due to missing long-lasting insulation material. Silicon which is most often used for lead insulation has a good biocompatibility and flexibility, has a high friction resistance but prone to abrasion of lead insulation material. Even today in a certain type of ICD lead (RIATA®, SJM, Sylmar, CA) with silicon insulation (removed 2010 from distribution), time-dependent incidence of lead failure of 8-33% were reported.[21-24] The same lead model with a silicone-polyurethane copolymer (Optim™, SJM, Sylmar, CA) showed no increased incidence of lead failure, suggesting a better abrasion resistance.[22,25]

Apart from lead insulation material, very small diameter of the ICD lead seemed to be a fur‐ ther risk factor of lead failure.[26] The 6.6 Sprint fidelis® lead (Medtronic, Inc., Minneapolis, MN) is prone to increased chance of lead fracture due to most likely less stress resistance. In 2008 this high-voltage ICD-lead was removed from the market. Actually, incidence of lead failure of 17% at 5 years of follow-up is reported for this lead.[27] Therefore, implanted Sprint fidelis and several Riata lead models should be carefully examined at the time of gen‐ erator replacement.

#### **3.2. Inadequate ICD therapy**

**Figure 3.** Cumulative incidence of first adequate ICD therapies after elective device replacement in patients with pri‐

The long-term benefit of ICD therapy has to be evaluated compared to the ratio of potential‐

A number of important medical and technological advances in ICD therapies have been made in the last years which helped to reduce the interventional stress for patients and to improve their daily safety[14-19]: the introduction of transvenousendocardial leads, subpec‐ toral or subfascial implantation of smaller and more powerful ICD devices, introduction of diagnostic tools as e.g. monitoring of intrathoracic fluid status, ST segment changes as well as the introduction of remote home monitoring systems. However, ICD therapy is still asso‐ ciated with significant morbidity and some mortality, especially in long-term follow up.

One of the major risks of long-term ICD therapy is lead failure, mostly presented as lead fracture or insulation defect. The annual lead failure rate increases with time and reaches 20% in 10-year old leads.[20] Mechanical stress on leads is the most frequent cause for lead failure and can be reduced by avoiding the medial subclavian puncture during ICD implan‐ tation (preferred approach is through the cephalic vein or lateral subclavian puncture) and by avoiding subpectoral device implantation (preferred subfascial pocket, if possible). How‐ ever, careful evaluation required, for the latter may result in pocket complications necessi‐

mary prevention without prior adequate ICD therapy

ly serious complications.

86 Cardiac Defibrillation

**3.1. Lead failure**

tating revision operations.

**3. Challenges of long term ICD therapy**

Inadequate ICD therapy is a significant clinical issue. In literature it`s reported that 12-30% of ICD patients receive inadequate ICD therapies, mainly caused by supraventricular tachy‐ cardias, T-wave oversensing and lead failure.[28-30] Such unnecessary ICD therapies are as‐ sociated with increase of posttraumatic disorders as depression and anxiety.[31]It is still a matter of debate, if aside of morbidity, inadequate ICD shocks also have worse impact on the outcome of ICD patients.[30,32] However, it is our firm conviction, that the number of unnecessary ICD therapies triggered by SVTs can be considerably reduced by adequate ICD programming by an experienced physician. Furthermore, newer ICD algorithms reduced in‐ adequate ICD therapy triggered by T-wave oversensing by 97% while maintaining 100% sensitivity for detection of true ventricular arrhythmia.[33]The safety, efficacy and perform‐ ance of further new ICD discrimination algorithms is actually evaluated in a prospective multi-center trial.[34]

Since the introduction of the Lead Integrity Alert™ (LIA) by Medtronic in 2008, inadequate ICD therapies decreased by up to 50% in patients with fractured Sprint fidelis leads.[35,36] Moreover, it has been reported that this algorithm has the potential to early detect lead fail‐ ure of the affected Riata family®.[37]

#### **3.3. Risk of ICD generator replacement**

Device replacement is associated with significant morbidity and some mortality. Data from a multicenter prospective registry of 1081 ICD patients who underwent device replacement (79% males, mean age 64±13 years) showed a complication rate of 4.3%. Major complications were observed in 2,6%, mostly infections or lead revisions. On multivariate analysis the presence of advanced Canadian Cardiovascular Society angina class (CCS ≥2), advanced NYHA stages (≥III), complex device systems (especially cardiac resynchronization systems), any previous surgery, and low operator procedure volume were predictive factors for over‐ all complication after ICD replacement. Any complication was associated with an increased risk of mortality at 45, 90, and 180 days after device replacement with a HR of 8.58, 9.91 and 4.06, respectively (p=0.005 to 0.069).

**References**

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Long-Term Benefit and Challenges of Implantable Cardioverter Defibrillator Therapy

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[3] Grimm W, Marchlinski FE. Shock occurrence in patients with an implantable cardi‐ overter-defibrillator without spontaneous shocks before first generator replacement

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[6] Koller MT, Schaer B, Wolbers M, Sticherling C, Bucher HC, Osswald S. Death with‐ out prior appropriate implantable cardioverter-defibrillator therapy. A competing

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It is strongly recommended that risks for complications after ICD replacement should not be underestimated. Even if generator replacement is technically less challenging than a new de‐ vice implantation, it should be preferably performed by experienced operators.
