Medtronic 4968-60 Technical Manual

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CAPSURE® EPI 4968
Steroid eluting, bipolar, epicardial lead
Technical Manual
Caution: Federal law (USA) restricts this device to sale by or on the order of a physician.
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The following list includes trademarks or registered trademarks of Medtronic in the United States and possibly in other countries. All other trademarks are the property of their respective owners.
CapSure, Medtronic
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Contents

1 Device description 3 2 Accessory descriptions 3 3 Indications for use 4 4 Contraindications 4 5 Warnings and precautions 4 6 Adverse events 5 7 Clinical study 8 8 Directions for use 18
9 Specifications (nominal) 25 10 Service 27 11 Medtronic warranty 27

1 Device description

The Medtronic CapSure Epi Model 4968 steroid eluting, bipolar, epicardial lead is designed for pacing and sensing in either the atrium or ventricle.
The porous electrode surfaces are platinized with platinum black and have been coated with the steroid dexamethasone sodium phosphate.
Each electrode contains a maximum of 1.0 mg of dexamethasone sodium phosphate, a portion of which is in a silicone rubber binder. Upon exposure to body fluids, the steroid elutes from the electrode. Steroid suppresses the inflammatory response that is believed to cause threshold rises typically associated with implanted pacing electrodes.
The Model 4968 lead’s silicone suture pads are triangular shapes with 2 suture holes and grooves. The lead also features an MP35N nickel-alloy conductor, silicone rubber insulation, and a bipolar connector (IS-1 BI)1.

1.1 Contents of package

The lead and accessories are supplied sterile. Each package contains:
1 Model 4968 lead
1 lead end cap
1 tunneler
product documentation

2 Accessory descriptions

Dispose of all single-use accessories according to local environmental requirements.
Lead end cap – A seal that is placed on the tip of a lead when the lead is abandoned in the body to prevent transmission of electrical signals.
1
IS-1 refers to an International Standard (ISO 5841-3) whereby pulse generators and leads so designated are assured of a basic mechanical fit.
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Tunneler – A tool used to pass a lead from its point of insertion to the subcutaneous pocket.

3 Indications for use

The Model 4968 lead is designed to be used with a pulse generator as part of a cardiac pacing system. The lead has application where implantable epicardial atrial or ventricular, single chamber or dual chamber pacing systems are indicated.

4 Contraindications

The lead should not be used on a patient with a heavily infarcted or fibrotic myocardium. It is also contraindicated for the patient whose myocardium is suffused with fat.
Do not use this device in patients for whom two single doses of
1.0 mg of dexamethasone sodium phosphate may be contraindicated.

5 Warnings and precautions

Inspecting the sterile package – Inspect the sterile package with
care before opening it.
Contact your Medtronic representative if the seal or package is damaged.
Do not store this product above 40 °C (104 °F).
Do not use the product after its expiration date.
Sterilization – Medtronic has sterilized the package contents with ethylene oxide before shipment. This lead is for single use only and is not intended to be resterilized.
Single use – The lead and accessories are for single use only.
Necessary hospital equipment – Keep external defibrillation
equipment nearby for immediate use during acute lead system testing, the implant procedure, or whenever arrhythmias are possible or intentionally induced during post-implant testing.
Line-powered and battery-powered equipment – An implanted lead forms a direct current path to the myocardium. During lead implant and testing, use only battery-powered equipment or line-powered equipment specifically designed for this purpose to protect against fibrillation that may be caused by alternating currents. Line-powered equipment used in the vicinity of the patient must be properly grounded. Lead connector pins must be insulated from any leakage currents that may arise from line-powered equipment.
Concurrent devices – Output pulses, especially from unipolar devices, may adversely affect device sensing capabilities. If a patient requires a separate stimulation device, either permanent or temporary, allow enough space between the leads of the separate systems to avoid interference in the sensing capabilities of the devices. Previously implanted pulse generators and implantable cardioverter defibrillators should generally be explanted.
Steroid use – It has not been determined whether the warnings, precautions, or complications usually associated with injectable dexamethasone sodium phosphate apply to the use of this highly
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localized, controlled-release lead. For a list of potential adverse effects, refer to the Physicians’ Desk Reference.
Handling the steroid tip – Reducing the available amount of steroid may adversely affect low-threshold performance. Avoid reducing the amount of steroid available prior to lead implant.
Do not allow the electrode surface to come in contact with surface contaminants.
Do not wipe or immerse the electrode in fluid, except blood, at the time of implant.
Handling the lead – Before implanting the lead remove the tip protector.
If the lead is damaged, do not implant it. Return the lead to a Medtronic representative.
Protect the lead from materials that shed particles such as lint and dust. Lead insulators attract these particles.
Handle the lead with sterile surgical gloves that have been rinsed in sterile water or a comparable substance.
Do not severely bend, kink, or stretch the lead.
Do not use surgical instruments to grasp the lead or connector pin.
Do not immerse leads in mineral oil, silicone oil, or any other liquid, except blood, at the time of implant.
Chronic repositioning or removal – Chronic repositioning or removal of the lead after it has been implanted in the patient is not recommended. If removal is unavoidable, return the lead to Medtronic.
If a lead is abandoned, it should be capped to avoid transmitting electrical signals from the pin to the heart.
A lead that has been cut off should have the remaining lead end sealed and it should be sutured to adjacent tissue to avoid migration.
Repositioning the lead after it has been implanted may adversely affect a steroid lead’s low-threshold performance.
Magnetic resonance imaging (MRI) – An MRI is a type of medical imaging that uses magnetic fields to create an internal view of the body. Do not conduct MRI scans on patients who have this device or lead implanted. MRI scans may result in serious injury, induction of tachyarrhythmias, or implanted system malfunction or damage.
Diathermy treatment (including therapeutic ultrasound) –
Diathermy is a treatment that involves the therapeutic heating of body tissues. Diathermy treatments include high frequency, short wave, microwave, and therapeutic ultrasound. Except for therapeutic ultrasound, do not use diathermy treatments on cardiac device patients. Diathermy treatments may result in serious injury or damage to an implanted device and leads. Therapeutic ultrasound is the use of ultrasound at higher energies than diagnostic ultrasound to bring heat or agitation into the body. Therapeutic ultrasound is acceptable if treatment is performed with a minimum separation distance of 15 cm (6 in) between the applicator and the implanted device and leads.

6 Adverse events

Due to the similarity in design and function, Model 4965 unipolar clinical data supports the safety and efficacy claims for the Model 4968 lead and is included here for reference purposes.
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The clinical investigation of the Model 4965 Pacing lead studied 661 devices implanted in 381 patients for a total of 9681 cumulative device months of experience (3054 Atrial, 6627 Ventricular). Mean duration of implantation was 14.6 months (range 0 to 62 months). Forty-eight (48) patients (12.6%) with Model 4965 pacing leads died during the course of the clinical study. None of the deaths were determined to be lead related. Lead related adverse events (AEs), including 43 complications (6.5% of leads) and 57 observations (8.6% of leads), were reported during the clinical investigation. The adverse events that occurred during more than one time are summarized in Table 1 and Table 2.

Table 1. Mean duration of implantation is 14.6 months (range 0 - 62 months).

Frequency of adverse events for atrial leads
Type of adverse event
Observations
Muscle stimu­lation
Undersensing 6 2.7%
Oversensing 6 2.7%
Elevated thresholds
Total obser-
a
vations
Complica­tions (loss of lead)
Lead fracture 5 2.2%
Total compli-
b
cations
a
Observations are adverse events which are corrected by non-invasive measures (e.g. reprogramming).
b
Complications are adverse events that resulted in loss of the lead function (e.g. unable to sense or unable to pace the heart).
# of leads (n=224)
12 5.4%
5 2.2%
29 12.9%
5 2.2%
% of leads [95% CI]
[2.4 - 8.3%]
[0.6- 4.8%]
[0.6- 4.8%]
[1.0 - 5.2%]
[8.6 - 17.3%]
[1.0 - 5.2%]
[1.0 - 5.2%]
# of patients (n=201)
12 6.0%
6 3.0%
6 3.0%
5 2.5%
29 14.4%
5 2.5%
5 2.5%
% of patients [95% CI]
[2.7 - 9.2%]
[0.6 - 5.3%]
[0.6 - 5.3%]
[1.1 - 5.8%]
[9.6 - 19.3%]
[1.1 - 5.8%]
[1.1 - 5.8%]
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Table 2. Mean duration of implantation is 14.6 months (range 0 - 62 months).

Frequency of adverse events for ventricular leads
# of
leads Type of adverse event AE
(n=437)% of leads
[95% CI]
Observations
Elevated thresh­olds
10 2.3%
[0.9 - 3.7%]
Undersensing 9 2.1%
[0.7- 3.4%]
Muscle stimulation 7 1.6%
[0.4 - 2.8%]
Oversensing 2 0.5%
[0.2- 1.7%]
Total observa-
a
tions
28 6.4%[4.1 -
8.7%]
Complications (loss of lead)
Lead fracture 20 4.6%
[2.6 - 6.5%]
Exit block 6 1.4%
[0.3 - 2.5%]
Other causes 5 1.1%
[0.6 - 2.7%]
Elevated pacing thresholds
4 0.9%
[0.4 - 2.4%]
Loss of capture 3 0.7%
[0.3 - 2.0%]
Total complica-
b
tions
a
Observations are adverse events which are corrected by non-invasive measures (e.g. reprogramming).
b
Complications are adverse events that resulted in loss of the lead function (e.g.
38 8.7%[6.1 -
11.3%]
unable to sense or unable to pace the heart).
# of patient s (n=355)% of patients
[95% CI]
10 2.8%
[1.1 - 4.5%]
9 2.5%
[0.9 - 4.2%]
7 2.0%
[0.5 - 3.4%]
2 0.6%
[0.2 - 2.1%]
28 7.9%[5.1 -
10.7%]
16 4.5%
[2.3 - 6.7%]
5 1.4%
[0.7 - 3.3%]
4 1.1%
[0.5 - 2.9%]
4 1.1%
[0.5 - 2.9%]
3 0.8%
[0.4 - 2.5%]
32 9.0%[6.0 -
12.0%]
There are additional complications related to the use of epicardial leads that include, but are not limited to, the following:
fibrillation
heart wall damage
cardiac tamponade
muscle or nerve stimulation
pericardial rub
infection
In addition, the lead may not perform optimally in patients with thin-walled myocardiums.
The potential complications listed above may occur at a higher rate with the use of these leads in pediatric patients.
Typical complications resulting in patient symptoms can often be resolved as follows in the following chart.
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Complication Symptom
Lead dislodgement Intermittent or continu-
Lead conductor fracture or insulation failure
Threshold elevation or exit block
a
Transient loss of capture or sensing may occur for a short time following a surgery until lead stabilization takes place. If stabilization does not occur, lead dislodgement may be suspected.
ous loss of capture or
a
sensing
Intermittent or continu­ous loss of capture or
a
sensing
Loss of capture
a
Corrective action to be considered
Replace the lead
Replace the lead
Adjust the pulse gener­ator output or replace the lead.

7 Clinical study

7.1 Model 4968 Post Approval Study

Study title: Model 4968 Post Approval Study
Product: Medtronic Model 4968 CapSure Epi Steroid-Eluting Bipolar
Epicardial Pacing Lead
Number of centers: 86
Number of subjects: 370 enrolled

Table 3. Study summary

Number of subjects 370 subjects
Number of subjects with ≥ five years of follow-up 101 subjects
Cumulative Device Experience 179.2 months
1st Quartile Device Experience 10.5 months
Median Device Experience 26.7 months
3rd Quartile Device Experience 59.6 months
Number of Enrolling Centers 86
Final Report Data Cut Off Date 02 March 2010

7.1.1 Study objective

Medtronic conducted the Model 4968 Post Approval Study to perform long-term surveillance on the Model 4968 CapSure Epi Steroid-Eluting Bipolar Epicardial Pacing Lead. This study was required by the FDA as part of the requirement to satisfy the PMA conditions of product approval.

7.1.2 Study design

The Model 4968 Post Approval Study was a prospective non-randomized, multicenter study conducted at 86 centers in the United States, Canada, Europe, and Australia. The study required 100 subjects to be enrolled and followed for 5 years post implant. Data for the 4968 Post Approval Study was collected following the Medtronic System Longevity Study protocol.
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7.1.3 Subject population

Subjects who met the following inclusion/exclusion criteria were eligible for enrollment into the study.
Inclusion criteria:
Provision of written informed consent and/or authorization for access to and use of health information by subjects or appropriate legal guardians as required by an institution’s Investigational Review Board, Medical Ethics Board, or Research Ethics Board
Availability of implant, follow-up and product-related event data
Implanted with a Model 4968 lead actively being used for pacing or sensing application
Exclusion criteria
Subjects who received an implant at a non-participating center and data cannot be confirmed within 30 days after implant
Subjects inaccessible for follow-up at a study center
Subjects with exclusion criteria required by local law (EMEA only)

Table 4. Subject Demographics

Category Data Type Statistics
Age n 349
Mean 30
Minimum 0
STD 29
Q1 5
Median 15
Q3 60
Maximum 86
Gender Female 138 (37.3%)
Male 232 (62.7%)
Race Black or African
American
Race/Ethnicity not collected in previous study protocol
Hispanic or Latino 1 (0.3%)
Not reportable per local laws or regula­tion
Other 1 (0.3%)
White 16 (4.3%)
5 (1.4%)
345 (93.2%)
2 (0.5%)

Table 5. Summary of Subject Demographics by Age Group

Baseline demo­graphics category
n 21 155 49 145
Unknown 0–12 13–19 20+
Age Group
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Table 5. Summary of Subject Demographics by Age Group
Total
2 leads in 1 subject provided invalid
implant date
(631 lead implanted in 370 subject)
(excluded from analyses)
20 subjects implanted inactive Model 4968
leads
(excluded from analyses)
Age group (0-12)
315 leads in 146
subjects
Age group (13-19)
123 leads in 58 subjects
Age group (20+)
169 leads in 144
subjects
Age unknown (missing
date of birth)
2 leads in 1 subject
(continued)
Gen­der
Race Black or
Male (%) 14
(66.7%)
Female (%)
7 (33.3%)
0
African
(0.0%)
American
Hispanic or Latino0(0.0%)
White 0
(0.0%)
94 (60.6%)33(67.3%)91(62.8%)
61 (39.4%)16(32.7%)54(37.2%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
5 (3.4%)
1 (0.7%)
16 (11.0%)
Subject race/ethnicity data was not required for patients enrolled under previous versions of the study protocol. This information was not available for 345 (93.2%) subjects.

7.1.4 Results

The total number of Model 4968 leads implanted in this study was 631. Of those, 609 contributed a total device experience of 179.2 months. Twenty (20) leads in 20 subjects were not active after implant and two leads in one subject did not report a valid implant date. These 22 leads were not included in the analysis.

Figure 1. Enrollment flowchart

Device experience was calculated from implant to exit date, maximum follow-up date, or date of a lead event. The range of device experience was from 0 to 179.2 months.
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Table 6. Summary of device experience for all Model 4968 leads

N Mean Mini-
mum
609 38.6 0 10.5 26.7 59.6 179.2 22
st
1 Quar­tile
Median3
rd
Quar­tile
Maxi­mum
Num­ber of Leads Missing Device Experi­ence
All Model 4968 lead-related complications reported are included in Table 7. Among the total of 609 Model 4968 leads with follow-up experience, seven (7) failure modes were identified during the course of this study: Insulation breach (2), high impedance (3), over-sensing (6), failure to sense (4), lead conductor fracture (6), and failure to capture/loss of capture (13), and threshold rise, sudden (1).

Table 7. Summary of Model 4968 lead related adverse effect

Event
Insulation breach
High impedance 3 0.49% (0.10%, 1.43%)
Oversensing 6 0.99% (0.36%, 2.13%)
Failure to sense 4 0.66% (0.18%, 1.67%)
Lead conductor fracture
Failure to capture/loss of capture
Threshold rise, sudden
Total 35 5.25% (4.04%, 7.90%)
Number of leads with com­plication
2 0.33% (0.04%, 1.18%)
6 0.99% (0.36%, 2.13%)
13 2.13% (1.14%, 3.62%)
1 0.16% (0.00%, 0.91%)
Event Rate (n=609)
95% Confi­dence Interval
The life-table method was used to analyze lead survival probability. The overall five-year survival probability of the Model 4968 lead was
92.3%, with 95% confidence interval of (88.3%, 95.04%) (Figure 2). Note that although the maximum follow up time for the study leads was
179.2 months, the survival curve and table is truncated at the 90
th
month due to the small number of observations (less than 50 leads) remaining. Table 8 provides the life-table estimate of the survival probability of the Model 4968 leads.
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Figure 2. Overall Model 4968 lead survival probability

Years after Implant
Survival Probability (%)
%
n
# Failed
88.8%
Lead 4968

Table 8. Life Table Estimates for the Overall Model 4968 Survival Probability

Survival
Lower
Limit of
Time
Interval
Distribu-
tion
Func-
tion Esti­mate
0 1 1 1 1 97 560.5
3 0.998 0.987 1 0 17 502.5
6 0.998 0.987 1 1 26 481
9 0.996 0.985 0.999 0 29 452.5
12 0.996 0.985 0.999 1 25 425.5
15 0.994 0.981 0.998 2 21 401.5
18 0.989 0.973 0.995 2 28 375
21 0.984 0.966 0.992 4 25 346.5
24 0.972 0.95 0.985 1 26 317
27 0.969 0.946 0.982 0 12 297
30 0.969 0.946 0.982 2 21 280.5
33 0.962 0.937 0.978 1 10 263
36 0.959 0.932 0.975 0 15 249.5
39 0.959 0.932 0.975 1 10 237
42 0.955 0.926 0.972 1 17 222.5
45 0.95 0.92 0.969 1 8 209
48 0.946 0.914 0.966 0 12 198
51 0.946 0.914 0.966 1 15 184.5
54 0.941 0.907 0.962 1 7 172.5
57 0.935 0.899 0.959 2 15 160.5
60 0.923 0.883 0.950 1 10 146
63 0.917 0.875 0.946 0 11 134.5
66 0.917 0.875 0.946 1 21 118.5
69 0.909 0.863 0.94 1 8 103
12
SDF
Lower
95.00% Confi­dence
Limit
SDF
Upper
95.00% Confi­dence
Limit
Num-
berFail
ed
Num-
ber
Cen-
sored
Effec-
tive
Sam-
ple
Size
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Table 8. Life Table Estimates for the Overall Model 4968 Survival
Probability (continued)
72 0.901 0.851 0.934 0 11 92.5
75 0.901 0.851 0.934 0 6 84
78 0.901 0.851 0.934 0 6 78
81 0.901 0.851 0.934 1 5 72.5
84 0.888 0.831 0.927 0 9 64.5
87 0.888 0.831 0.927 0 6 57
90 0.888 0.831 0.927 0 5 51.5
The long-term performance of the Model 4968 lead is provided for patient age groups: 0 – 12 (Figure 3), 13-19 (Figure 4) and 20+ years (Figure 5) at the time of lead implant.
Three-hundred-fifteen (315) leads were implanted in 146 subjects 12 years or younger, 123 leads were implanted in 58 subjects ages 13 – 19 years, and 169 leads were implanted in 144 subjects with age 20 years or older. A total of 101 leads completed five years follow-up. Table 9 provides the life-table estimate of the survival probability of the Model 4968 leads in subjects of different age groups. Figures 3-5 provide the survival function estimates of the model 4968 lead for each patient cohort. The 5-year survival probability was 89.3% (83.1%,
93.4%) for patients 12 years old or younger, 93.9% (83.8%, 97.8%) for patients 13-19 years of age and 98.9% (92.5%, 99.8%) for patients with age 20 or older.

Table 9. Life Table Estimates for Model 4968 Survival Probability for Each Age Group

Month Age: 0 — 12 Age: 13 — 19 Age: 20+
% Sur­vival
0 100.0 1 315 100.0 0 123 100.0 0 169
3 99.7 0 277 100.0 0 93 100.0 0 141
6 99.0 0 268 100.0 1 91 100.0 0 135
9 99.7 0 262 98.9 0 86 100.0 0 119
12 99.7 0 243 98.9 1 80 100.0 0 115
15 99.7 2 228 97.6 0 75 100.0 0 109
18 98.8 1 217 97.6 1 71 100.0 0 101
21 98.3 3 202 96.2 0 63 100.0 1 94
24 96.8 1 188 96.2 0 55 98.9 0 87
27 96.3 0 171 96.2 0 49 98.9 0 83
30 96.3 1 168 96.2 1 45 98.9 0 78
33 95.7 1 158 93.9 0 38 98.9 0 72
36 95.1 0 152 93.9 0 37 98.9 0 68
39 95.1 1 147 93.9 0 33 98.9 0 62
42 94.4 1 139 93.9 0 31 98.9 0 61
45 93.7 1 128 93.9 0 27 98.9 0 58
48 92.9 0 122 93.9 0 26 98.9 0 56
Fa ile d
N %
Sur­vival
Fai led
N %
Sur-
FailedN
vival
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Table 9. Life Table Estimates for Model 4968 Survival Probability for
Years after Implant
Survival Probability (%)
%
n
# Failed
84.5%
Lead 4968 Ages 0 to 12
Years after Implant
Survival Probability (%)
%
n
# Failed
93.9%
Lead 4968 Ages 13 to 19
Each Age Group (continued)
51 92.9 1 116 93.9 0 24 98.9 0 52
54 92.1 1 106 93.9 0 22 98.9 0 48
57 91.2 2 101 93.9 0 22 98.9 0 45
60 89.3 1 91 93.9 0 20 98.9 0 40
63 88.3 0 84 93.9 0 19 98.9 0 37
66 88.3 1 80 93.9 0 17 98.9 0 32
69 87.2 1 75 93.9 0 8 98.9 0 24
72 86.0 0 72 93.9 0 5 98.9 0 21

Figure 3. Five-year survival probability ages 0 — 12

Figure 4. Five-year survival probability ages 13–19

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Figure 5. Five-year survival probability ages 20 and older

Years after Implant
Survival Probability (%)
98.9%
Lead 4968 Ages 20 and higher
%
n
# Failed

7.2 Model 4968 Clinical Study summary

There have been 35 lead related complications (35 leads and 30 subjects) and 67 lead related observations during the Model 4968 Study. All events were reviewed and adjudicated by the Medtronic System Longevity Study Technical Review Committee. Events reported to Medtronic that were not classified as complications were documented as lead observations.

7.2.1 Study Subject Death

During the Model 4968 Lead Study, thirty-four deaths were reported. No evidence was received indicating that any of the deaths were device related.

7.2.2 Study conclusions

As part of the requirement to satisfy the PMA Conditions of Approval for the Medtronic Model 4968 CapSure Epi Steroid-Eluting Bipolar Epicardial Pacing Lead, 101 subjects have been followed for a minimum of five years to assess the long-term safety of the lead. This document provides the final report on the Model 4968 Lead.
The safety performance for the overall 5-year survival probability of the Model 4968 lead was 92.3%. The 5- year survival probability was
89.3% for patients 12 years old or younger, 93.9% for patients 13 – 19 years of age and 98.9% for patients 20 years of age or older.
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7.2.3 Performance in the Literature

The Model 4968 lead is a steroid eluting bipolar epicardial lead market released in 1999 for the US. As of 1 August 2011, the total registered US. implants since the lead was commercially available was 22,839. Epicardial leads are used in patients with difficult venous access, intracardiac shunting, very small patient size, and concomitant cardiac surgery which may preclude transvenous pacing. Other than the Model 4968 Post Approval Study (PAS), which is part of the Medtronic CRDM Product Performance Report (PPR), there have been no other Medtronic studies actively enrolling patients with Model 4968 leads. Medtronic Model 4965 and 4968 leads, along with epicardial leads manufactured by other companies, were studied as permanent epicardial pacing leads in children reported by Thomson (2004)2. This study enrolled pediatric patients under 18 years of age (median 1.9 years). It was observed that the lead survival was 92%, 86% and 76% at 1, 2 and 5 years for steroid-eluting epicardial leads. The causes of lead failures were increasing pacing thresholds, lead fracture, sub-optimal pacing, lead displacement and infection. Thomson’s study observed a significant effect of ‘decade of implant’ which includes a team approach: follow-up by a consultant electrophysiologist in a dedicated clinic and implant by an experienced surgeon with in-theater system interrogation. The author commented that implanters’ technique and experience contributed to the lead survival.
One 4968 PAS study center, University Children’s Hospital, Zurich, Switzerland, reported Model 4968 lead survival rates of 239 Model 4968 leads3. A total of 114 pediatric patients were enrolled and followed up for up to 12.2 years. Lead failures occurred in 8% of the leads. The most common complications were lead fractures and high thresholds. Lead survival at 2 and 5 years was 99% and 94% for atrial leads and 96% and 85% for ventricular leads, respectively. Kaplan-Meier estimates of patient survival at 2, 5, and 10 years after study enrollment were 98% (95% CI: 95% to 100%), 95% (95% CI: 90% to 100%, and 95% (95% CI: 83% to 100%) respectively. Additionally, the estimated lead survival was compared by site, and no significant difference was found between the left and right implant sites. Median atrial and ventricular pacing thresholds remained below
1.2 V at 0.5 ms.
2
John D. R. Thomson, Michael E. Blackburn, et al., Pacing Activity, Patient and Lead Survival Over 20 Years of Permanent Epicardial Pacing in Children, The Annals of Thoracic Surgery 2004; 77:1366-1370
3
Maren Tomaske, MD, Bart Gerritse, PhD, Leo Kretzers, MS, Rene Pretre, MD, Ali Dodge-Khatami, MD, PhD, Mariette Rahn, MD, and Urs Bauersfeld, MD. A 12-Year Experience of Bipolar Steroid-Eluting Epicardial Pacing Leads in Children. Annals of Thoracic Surgery 2008;85:1704-1711
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Fortescue et al.4 retrospectively compared steroid-eluting epicardial leads to thin transvenous pacemaker leads in pediatric and congenital heart disease patients. A total of 256 steroid-eluting epicardial leads (in 184 patients) were implanted in patients who were 0.0 to 54.6 years (median 6.3 years). Of those, 156 were Model 4968 leads. Lead failures for the steroid-eluting epicardial leads included, chronic dislodgment, fracture, high thresholds, insulation break, infection, and other. Lead survival for the steroid-eluting epicardial leads at 1, 3 and 5 years was 96%, 92% and 58%, respectively. There was no statistical difference when comparing the steroid-eluting epicardial and transvenous lead survival probabilities.
Between 1996 – 2004, 41 pediatric patients (mean age 8.6 years) were implanted with the Medtronic Model 4968 lead in a study reported by Dodge-Khatami et al.5. At 1 and 5 years, the atrial lead survival was 94% and 86% respectively. The ventricular lead survival at 1 and 5 years was 97 and 86%. Reoperations for new lead placement were required in 5 patients: two for lead fracture, one for insulation break, one for over-sensing, and one pacing system infection. Reprogramming was completed in three devices: atrial lead dysfunction, pacing failure, and ventricular lead fracture.
A recent publication by Kubus, et al.6 evaluated clinical outcome for permanent epicardial pacing in children. One hundred and nineteen patients (median age 1.8 years, inter-quartile range 2.9 – 11.1 years) were implanted with 242 epicardial leads; 161 of the leads were Model 4968 bipolar steroid-eluting leads. The steroid-eluting leads showed a significantly higher freedom from exit block (95.3 vs 76.2% (non-steroid leads) at 5 years p < 0.001). The authors concluded that steroid-eluting epicardial leads may be used on an individual basis to effectively delay transvenous pacing and to protect venous access to the heart for further decades of cardiac pacing. The difference in epicardial vs transvenous lead survival had become marginal. To decrease the risk associated with mechanical lead damage, the use of bipolar Medtronic Model 4968 leads along with the activation of appropriate automatic polarity switch algorithms in the event of a detected change in impedance should be advocated.
4
Elizabeth B. Fortescue, Charles I. Berul, Frank Cecchin, Edward P. Walsh, John K. Triedman, and Mark E. Alexander, Comparison of Modern Steroid-Eluting Epicardial and Thin Transvenous Pacemaker Leads in Pediatric and Congenital Heart Disease Patients, Journal of Interventional Cardiac Electrophysiology 14, 27-36, 2005
5
Ali Dodge-Khatami, Alexander Kadner, Hitendu Dave, Mariette Rahn, Rene Pretre, Urs Bauersfeld Left heart atrial and ventricular epicardial pacing through a left lateral thoracotomy in children: a safe approach with excellent functional and cosmetic results, European Journal of Cardio-thoracic Surgery 28 (2005) 541-545
6
Petr Kubus, Ondrej Materna, Roman A. Gebauer, Tomas Matejka, Roman Gebauer, Tomas Tlaskal, and Jan Janousek. Permanent epicardial pacing in children: long-term results and factors modifying outcome, Europace (2011) in press 10.1093/europace/eur327
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Surgical lead placement requires a different implant technique compared to transvenous implants. The event classification methods used for these published studies can be different in comparison to the Model 4968 PAS. In summary, epicardial leads, specifically Model 4965 and Model 4968, are valuable choices for pediatric patients to avoid long term vascular injury and for patients with unsuccessful transvenous lead implants. Technique and experiences are critical to minimize lead implant procedure related complications. The above published results demonstrated stable and consistent performance of the Medtronic Model 4968 lead. This bipolar steroid-eluting epicardial lead provides an alternative for treating patients who are indicated for pacing or resynchronization therapy

8 Directions for use

8.1 Attaching the electrode to the epicardium

The attachment site should be an avascular area free of infarcts, fat, or fibrosis. A minimum of 1.0 cm space should separate the electrodes.
A white band in the electrode pad indicates the cathode (this electrode is electrically connected to the connector pin).
A variety of surgical approaches can be used, including subxiphoid, left thoracotomy, median sternotomy, transxiphoid, and trasmediastinal (Figure 6).

Figure 6. Surgical approaches

1 Medial sternotomy 2 Left thoracotomy
Surgical technique for the subxiphoid approach
1. Maximize exposure to the epicardial surface. Note: The pericardial sac should be tied back to maximize exposure to the myocardium.
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3 Subxiphoid
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2. Before implantation, the epicardial lead can be used as a mapping probe by resting the electrode against the epicardium. Stimulation thresholds and sensing signal amplitudes can be measured at various sites in order to locate a suitable attachment site (Figure 7). Each time the electrode touches the epicardium some steroid elutes. Therefore when determining the best electrical placement for the electrode, move the electrode as minimally as possible.

Figure 7. Exposing the epicardial surface and using the lead as a mapping probe

1 Xiphoid 2 Heart outline 3 Suture
4 Gently grasp the lead directly
over the suture groove
5 Base of the heart
3. Once an optimal electrode position is confirmed for either the atrium or ventricle, stable fixation through proper suturing of the electrodes is critical for maintaining good chronic electrode performance. Suture holes are provided as guides and allow for a variety of suturing options (Figure 8).

Figure 8. The Model 4968 suture pads have 2 suture holes for attachment to the epicardium. The top and side views of the electrodes illustrate the suture holes and grooves that allow many suturing possibilities.

The recommended suturing technique is the double needle approach, using non-absorbable sutures, to suture through the epicardium (Figure 9).
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Figure 9. Using a double needle approach

Insert both needles through the distal suture holes on the electrode head. Suture through the epicardium and tie (Figure 10).

Figure 10. Suturing through the epicardium and tying

Proper suturing of the electrode is critical for maintaining good chronic electrical performance (Figure 11). Loosely attached electrodes might allow some movement, irritating the epicardium, and eventually resulting in elevated thresholds.
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Figure 11. Proper suturing of the electrode

1 Recommended 2 Not recommended
To avoid causing trauma to tissue near the electrodes, which may result in higher thresholds, suture the electrodes perpendicular to the heart surface (Figure 12).

Figure 12. Acceptable electrode suturing

1 Recommended 2 Not recommended
Note: A suture should not pass under the electrode. To avoid buckling of the electrode, tie the suture securely, without placing undue tension on the lead (Figure 13).

Figure 13. Acceptable suture tying

1 Recommended 2 Not recommended
4. Suture through the proximal groove to assure a stable 3 point fixation (Figure 14).
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Figure 14. Suturing through the proximal groove

5. Confirm the electrical measurement. See the section titled Section 8.2, “Taking electrical measurements”, page 23.
Guidelines for a left thoracotomy approach
1. Use the suturing technique described in the previous section: “Surgical technique for the subxiphoid approach.”
2. Leave a moderate amount of the lead on both sides of the thoracic exit point to prevent stretching of the lead body (Figure 15).

Figure 15. Using a left thoracotomy approach

3. Leaving the lead body deep in the abdominal musculature, exit the thorax through the subxiphoid space. Exit the thorax at an angle, not parallel, to the midsagittal plane to reduce acute bending of the lead at the subcostal border. Tunneling the lead laterally or exiting the thorax near the subxiphoid area may reduce the potential for conductor coil fracture (Figure 16). Caution: Excessive pressure on the lead body insulation may cause an insulation breach. An insulation breach may adversely affect lead performance. Excessive pressure may be caused by, but is not limited to, the following conditions: overlapping the lead body with a portion of the lead body, compressing the lead body with the pulse generator, and passing the lead body over or through the ribs.
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Figure 16. Tunneling the lead

1 Costal and subcostal areas to avoid while tunneling 2 Approximate lower costal region

8.2 Taking electrical measurements

Low stimulation thresholds and adequate sensing of intracardiac signal amplitudes indicate satisfactory lead placement. Medtronic recommends using a voltage source such as a pacing system analyzer for obtaining electrical measurements.
A low stimulation threshold provides for a desirable safety margin, allowing for a possible rise in thresholds that may occur within 2 months following implantation.
Adequate sensing amplitudes ensure that the lead is properly sensing intrinsic cardiac signals. Minimum signal requirements depend on the pulse generator’s sensitivity capabilities. Acceptable acute signal amplitudes for the lead must be greater than the minimum pulse generator sensing capabilities including an adequate safety margin to account for lead maturity.

Table 10. Recommended electrical measurements at implant

Using a pacing sys­tems analyzer
Ventricle Atrium Ventricle Atrium
Maximum acute stimula­tion thresholds
Minimum acute sensing amplitudes
a
At pulse duration setting of 0.5 ms.
a
1.5 V
4.0 mV 2.0 mV
a
1.5 V
Using an external pulse generator
a
3.0 mA 3.0 mA
Initial electrical measurements may deviate from the recommendations because of acute cellular trauma. If this occurs, wait 5 to 15 minutes and repeat the testing procedure. Values may vary depending on the lead type, pulse generator settings, cardiac tissue condition, and drug interactions.
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If electrical measurements do not stabilize to acceptable levels, it may be necessary to reposition the lead and to repeat the testing procedure.
For more information on obtaining electrical measurements, consult the technical manual supplied with the testing device.

8.3 Connecting the lead to the pulse generator

If a separate pocket is created for the pulse generator, the lead should be passed within muscle layers to the pocket while avoiding sharp angle bends to the lead body. Attach the connector end of the lead to the tunneler and pass the tunneler to the pocket incision. When removing the lead from the tunneler, hold the lead connector tightly near the pin and gently pull and twist off.
Connect the lead to the pulse generator according to the instructions in the pulse generator manual. Do not use excessive force to connect the lead.
The connector on the Model 4968 is a bipolar connector (IS-1 BI). IS-1 Unipolar (UNI) and IS-1 Bipolar (BI) leads always have the label identification “IS-1 UNI” or “IS-1 BI” on the connector.
Caution: To prevent undesirable twisting of the lead body, wrap the excess lead length loosely under the pulse generator and place both into the subcutaneous pocket (Figure 17).

Figure 17. While rotating the pulse generator, loosely wrap the excess lead length and place it under the pulse generator

Caution: When placing the pulse generator and lead into the subcutaneous pocket:
Do not coil the lead. Coiling the lead can twist the lead body and may result in lead dislodgment (Figure 18).
Do not grip the lead or pulse generator with surgical instruments.

Figure 18. Do not coil the lead body

After implantation, monitor the patient’s electrocardiogram continuously during the immediate postoperative period. If a lead dislodges, it usually occurs during the immediate postoperative period.
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8.4 Using a lead end cap

Use a lead end cap to seal off the connector pin (Figure 19) if the lead is being reserved for pulse generator connection at a future date, or if the lead has been abandoned, (i.e., any leads not explanted but not connected to the pulse generator).
Insert the end cap over the lead connector pin so that the sealing rings on the lead are fully covered. Only sterile water may be used to facilitate this application. No adhesives are necessary. Tie a non-absorbable, synthetic ligature in the end cap’s groove.

Figure 19. Using the lead end cap

Caution: Do not secure the ligature so tightly that it damages the end
cap and the lead.
The end cap can be removed a later date without damaging the lead.

9 Specifications (nominal)

Parameter Model 4968
Type Bipolar
Chamber Ventricle or Atrium
Fixation Sutures
Length 25–110 cm (9.84 to 43.31 in)
Connector IS-1 BI
Materials Conductor: MP35N
Insulator: Treated silicone rubber
Electrode: Platinum alloy
Connector pin: Stainless steel
Connector ring: Stainless steel
Electrode con­figuration
Electrode sur­face area
Platinized, porous, steroid eluting
6.0 mm2 (Cathode)
2
14.0 mm (Anode)
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Parameter Model 4968
Resistance Unipolar: 65 Ω (35 cm) (13.78 in)
Bipolar: 102 Ω (35 cm) (13.78 in)
Steroid Dexamethasone sodium phos-
phate
Amount of steroid 1.0 mg maximum (each electrode)
Steroid binder Silicone rubber

Figure 20. Specification drawing (nominal)

1 9.7 mm (0.382 in) 2 Diameter: 1.0 mm (0.040 in)
2
3 14 mm 4 View A-A 5 7.6 mm (0.299 in)
2
6 6 mm 7 View B-B 8 A-A
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9 B-B
10 Electrode surface area anode:
14 mm2/6 mm
2
11 15 cm (5.91 in) 12 Diameter: 3.2 mm (0.126 in) 13 25–110 cm (9.84 to 43.31 in) 14 Insulation material: Silicone
rubber
15 Diameter: 1.6 mm (0.063 in)
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10 Service

Medtronic employs highly trained representatives and engineers located throughout the world to serve you and, upon request, to provide training to qualified hospital personnel in the use of Medtronic products. Medtronic also maintains a professional staff to provide technical consultation to product users. For more information, contact your local Medtronic representative, or call or write Medtronic at the appropriate telephone number or address listed on the back cover.

11 Medtronic warranty

For complete warranty information, see the accompanying warranty document.
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World Headquarters
*M950513A001*
Medtronic, Inc. 710 Medtronic Parkway Minneapolis, MN 55432 USA www.medtronic.com Tel. +1 763 514 4000 Fax +1 763 514 4879
Medtronic USA, Inc.
Toll-free in the USA (24-hour technical consultation for physicians and medical professionals) Bradycardia: +1 800 505 4636 Tachycardia: +1 800 723 4636
Europe/Africa/Middle East Headquarters
Medtronic International Trading Sàrl Route du Molliau 31 Case Postale 84 CH-1131 Tolochenaz Switzerland www.medtronic.com Tel. +41 21 802 7000 Fax +41 21 802 7900
Medtronic E.C. Authorized Representative
Medtronic B.V. Earl Bakkenstraat 10 6422 PJ Heerlen The Netherlands Tel. +31 45 566 8000 Fax +31 45 566 8668
Technical manuals: www.medtronic.com/manuals
© Medtronic, Inc. 2012 M950513A001A 2012-12-11
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