ASTM F2079-09(2022)

Standard Test Method for Measuring Intrinsic Elastic Recoil of Balloon-Expandable Stents

SIGNIFICANCE AND USE
4.1 Minimal stent recoil is a desirable feature of a stent because it minimizes the maximum diameter to which a stent must be expanded to achieve its final relaxed diameter. A stent having a high recoil must be expanded to a greater diameter to achieve its final relaxed diameter than a stent having low recoil. Practically, excessive expansion of the vessel into which the stent is to be implanted may cause tissue damage resulting in a poor immediate result or poor long-term outcome. Stent recoil is affected by intrinsic properties of the material used to construct the stent and the specific geometric design of the stent; therefore, measuring stent recoil is an essential part of evaluating the design.
SCOPE
1.1 The purpose of this test method is to quantify the percentage by which the diameter of a stent decreases from its expanded diameter while still on the delivery balloon to its relaxed diameter after deflating the balloon. This test method is appropriate for stents manufactured from a material that is plastically deformed when the stent's diameter is increased from its predeployed size to its postdeployed size by mechanical means. This test method may be performed in air at room temperature unless there is a known temperature dependence of the material, in which case, the temperature at which the test is conducted shall be stated in the report.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2022
• ICS: 11.040.20 - Transfusion, infusion and injection equipment
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.30 - Cardiovascular Standards

Overview

ASTM F2079-09(2022) is the internationally recognized standard test method for measuring the intrinsic elastic recoil of balloon-expandable stents. Developed by ASTM International, this test method outlines procedures to quantify the percentage decrease in a stent’s diameter after balloon deflation, providing critical insights into stent performance. Minimal recoil is a desirable property, as it reduces the need for excessive stent expansion, helping avoid vessel injury and improve both immediate and long-term clinical outcomes. This standard ensures consistent, replicable results for manufacturers, researchers, and regulatory stakeholders in the medical device industry.

Key Topics

• Intrinsic Elastic Recoil: Assessment of the degree to which a balloon-expandable stent contracts after initial expansion and removal of balloon inflation.
• Test Methodology: Procedures for inflating the stent on the delivery balloon, measuring stent diameter at specified locations, deflating the balloon, and re-measuring the diameter to determine recoil.
• Sampling and Measurement: Recommendations for selecting clinical-quality samples, number of specimens (at least ten per geometry), and specific measurement points to provide robust data.
• Reporting Requirements: Details to be included in test reports, such as stent size, length, measurement data, average and standard deviation of recoil, and test temperature.
• Significance in Design: Stent recoil is influenced by the material and geometric design, making this test central to product development and evaluation.

Applications

The ASTM F2079-09(2022) standard is essential for:

• Device Manufacturers: Evaluating new stent designs and materials by quantifying intrinsic recoil properties, leading to improved product labeling and clinical guidance.
• Quality Assurance: Ensuring product consistency across production batches by implementing standardized test methods.
• Regulatory Submissions: Providing scientifically validated data to regulatory bodies to demonstrate compliance with safety and performance requirements for balloon-expandable cardiovascular stents.
• Research and Development: Comparing the performance of various stent materials and designs, optimizing implants for minimal vessel trauma and improved patient outcomes.
• Clinical Application: Helping clinicians understand stent recoil behaviour, supporting better procedural planning and potentially reducing risks associated with over-expansion of vessels.

Related Standards

Several ASTM and international standards complement or are referenced alongside ASTM F2079-09(2022):

• ASTM F2477 – Test Method for in vitro Pulsatile Durability Testing of Vascular Stents
• ASTM F3067 – Test Method for Radial Compressive Properties of Balloon-Expandable Vascular Stents and Endografts
• ISO 25539-2 – Cardiovascular Implants – Endovascular Devices – Part 2: Vascular Stents
• ASTM F2606 – Managing Risks in the Design and Manufacturing of Medical Devices

Practical Value

Implementing ASTM F2079-09(2022) in balloon-expandable stent testing ensures robust, repeatable, and comparable data crucial to device development and market approval. Accurate assessment of intrinsic elastic recoil helps guide device design to minimize vessel trauma and support positive patient outcomes. This standard is a foundational document for anyone involved in the testing, manufacture, regulation, or clinical use of balloon-expandable vascular stents, facilitating safe and effective cardiovascular interventions.

Keywords: stent recoil, balloon-expandable stents, ASTM F2079, medical device testing, cardiovascular stents, elastic recoil, stent evaluation, stent diameter measurement, regulatory compliance, stent design.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2079 − 09 (Reapproved 2022)
Standard Test Method for
Measuring Intrinsic Elastic Recoil of Balloon-Expandable
Stents
This standard is issued under the fixed designation F2079; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Test Method
1.1 The purpose of this test method is to quantify the 3.1 A sample device representative of product that will be
percentage by which the diameter of a stent decreases from its marketed is either premounted or mounted on the delivery
expanded diameter while still on the delivery balloon to its balloon at the time of use. The delivery balloon is inflated to
relaxed diameter after deflating the balloon.This test method is the nominal expansion pressure indicated for the labeled stent.
appropriate for stents manufactured from a material that is The outer diameter of the stent is measured in at least three
plastically deformed when the stent’s diameter is increased axial locations while the stent is still on the inflated delivery
from its predeployed size to its postdeployed size by mechani- balloon.At each axial location, measurements are taken in two
cal means. This test method may be performed in air at room approximately orthogonal rotational positions. The balloon is
temperatureunlessthereisaknowntemperaturedependenceof deflated and the outer diameter of the stent is remeasured in the
the material, in which case, the temperature at which the test is same positions at approximately the same locations.
conducted shall be stated in the report.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 Minimal stent recoil is a desirable feature of a stent
standard. No other units of measurement are included in this
because it minimizes the maximum diameter to which a stent
standard.
must be expanded to achieve its final relaxed diameter.Astent
1.3 This standard does not purport to address all of the
having a high recoil must be expanded to a greater diameter to
safety concerns, if any, associated with its use. It is the
achieve its final relaxed diameter than a stent having low
responsibility of the user of this standard to establish appro-
recoil. Practically, excessive expansion of the vessel into which
priate safety, health, and environmental practices and deter-
the stent is to be implanted may cause tissue damage resulting
mine the applicability of regulatory limitations prior to use.
in a poor immediate result or poor long-term outcome. Stent
1.4 This international standard was developed in accor-
recoil is affected by intrinsic properties of the material used to
dance with internationally recognized principles on standard-
construct the stent and the specific geometric design of the
ization established in the Decision on Principles for the
stent; therefore, measuring stent recoil is an essential part of
Development of International Standards, Guides and Recom-
evaluating the design.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5. Apparatus
5.1 Ameans to inflate with noncompressible fluid, typically
2. Terminology
water, the delivery balloon on which the stent is mounted. The
2.1 Definitions:
means used must be capable of achieving the pressure required
2.1.1 labeled diameter, n—the nominal deployed size of a
to maintain the expanded diameter of the stent until it can be
stent as indicated on its manufacturer’s label.
measured and may include a device to monitor pressure.
2.1.2 stent recoil, n—the amount, expressed as a percentage,
5.2 A means to measure the outer diameter of the stent
by which the diameter of a stent changes from the expanded
without deforming the stent. Typically, a calibrated optical
diameter measured with the stent on the inflated delivery
system, which does not require contact with the stent, is used.
balloon to the final value measured after deflating the balloon.
The resolution of the measurement system shall be 0.01 mm or
better. The accuracy of the system shall be 2 % of reading or
1 better.
This test method is under the jurisdiction ofASTM Committee F04 on Medical
and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.30 on Cardiovascular Standards. 6. Sampling, Test Specimens, and Test Units
Current edition approved Oct. 1, 2022. Published October 2022. Originally
6.1 Unless otherwise justified, all samples selected for
approved in 2001. Last previous edition approved in 2017 as F2079 – 09 (2017).
DOI: 10.1520/F2079-09R22. testing should be taken from fully processed, clinical quality
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2079 − 09 (2022)
product. It is not required that these devices undergo terminal 7.6 Measure the outer diameter of the stent at the same
sterilization.Cosmeticrejectsorothernonclinicalsamplesmay locations and in the same rotational positions with respect to
be used if the cause for rejection has been shown not to affect the measurement system as in 7.4. These measurements should
stent recoil. be taken no sooner than 10 s after deflating the balloon.
6.2 The number of specimens tested for each unique stent
8. Calculation
geometry should be sufficient to meet sampling requirements
8.1 Calculate the stent recoil for the locations measured in
for desired specification limits. In general, a minimum of ten
7.4 for each stent using the following equation:
specimens is recommended. If a single stent geometry is
Diameter
intended to be used for more than one label
...