Medtronic 4968-60 Technical Manual

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.

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

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.

3

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

4

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.

5

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%]

6

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.

7

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.

8

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

9

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.

10

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.

11

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

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

13

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

14

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.

15

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

16

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

17

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.

18

3 Subxiphoid

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).

19

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.

20

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).

21

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.

22

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.

23

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.

24

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)

25

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

26

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)

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.

27

World Headquarters

*M950513A001*

Medtronic, Inc.
710 Medtronic Parkway
Minneapolis, MN 55432
USA
www.medtronic.com
Tel. [phone]
Fax [phone]

Medtronic USA, Inc.

Toll-free in the USA (24-hour
technical consultation for
physicians and medical
professionals)
Bradycardia: [phone]
Tachycardia: [phone]

Europe/Africa/Middle East
Headquarters

Medtronic International
Trading Sàrl
Route du Molliau 31
Case Postale 84
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www.medtronic.com
Tel. [phone]
Fax [phone]

Medtronic E.C. Authorized
Representative

Medtronic B.V.
Earl Bakkenstraat 10
6422 PJ Heerlen
The Netherlands
Tel. [phone]
Fax [phone]

Technical manuals:
www.medtronic.com/manuals

© Medtronic, Inc. 2012
M950513A001A
2012-12-11