AAMI CDV CI86 recommendations: extension of 15 mm or a tensile force of at most 1 N.

23.2.6 Testing for immunity of implantable leads to tensile forces

This section specifies acceptance testing to show compliance with the requirements for immunity to the stresses of tensile

forces applied to the implantable leads.

Test specimens:

a) Specimen type A shall be an implantable part that is in the same condition as devices shipped to the customer.

b) Specimen type B shall be the implantable lead without the stimulator.

General procedures:

a) Use a saline preconditioning bath of approximately 9 g/l saline at 37 °C ± 5 °C, a tensile load tester, and a voltmeter or an oscilloscope.

b) Keep both specimen types in the preconditioning bath for a minimum of 10 days. Immediately before testing, rinse the test leads in distilled or deionized water, then wipe them free of surface water.

c) Identify that portion of the lead that, when implanted, might be subject to elongation. Devise an appropriate method of clamping the lead so as to include the elongation portion.

Tests:

23.2.6.1 Test 1: Test for specimen type A

The test procedure is as follows:

a) Clamp the specimen type A test sample at the stimulator or at the connector, if applicable. Firmly attach another clamp to the most distal part of the lead subject to elongation. Measure the distance between the clamping points.

b) Subject the lead to an elongation of at least 15 mm or a tensile force of at most 1 N.

c) Sustain the applied tensile stress for at least one minute, then relieve it.

d) Repeat the tensile load application for each lead.

e) Return the test specimen to the saline bath and immerse it again for a minimum of one hour before proceeding.

f) Verify the electrical continuity of each conduction path (open-circuit test) and insulation (short-circuit test) between each pair of wires inside the lead (if applicable).

Acceptable performance is verified if the devices under test comply with the requirements of the manufacturer‘s design verification tests (Section 8.7).

23.2.6.2 Test 2: Insulation test for specimen type B

Specimen type B test samples shall be subjected to the same elongation test as specimen type A samples except both sides of the lead shall be clamped. Following the elongation test, the insulation shall be subjected to a test voltage. The test signal shall be a 1 kHz square wave with a peak-to-peak voltage of twice the maximum peak-to-peak output voltage of the implant system.

The test signal shall be applied between each combination of conducting pairs inside the lead for a minimum of 15 s. The impedance between each pair shall be measured.

Acceptable performance is verified if the devices under test comply with the requirements of the manufacturer‘s design verification tests (Section 8.7) and have impedance between each pair of conducting wires exceeding 100kohm

NOTE—Reports in the literature indicate that pediatric patients will be subject to an increase in skull size of 12 mm (standard deviation of 5 mm) from the round window to the sino-dural angle (Dahm et al., 1993). Leads forming part of an implant system need to be designed to withstand the elongation that might be experienced during the skull growth period. If the lead does not allow an elongation of 17 mm, the manufacturer‘s recommended surgical procedure has to avoid extrusion of the electrode array from the cochlea. The specified force of 1 N is considered to be representative of the elongation force acting during bone growth and during implantation. The test method of Section 23.2.6 takes into consideration the differing designs of lead geometry. Although the most appropriate method of lead attachment is left to the manufacturer’s discretion, it is required that the critical lead portion subject to elongation by skull growth is identified in the design and subjected to a standard test.