Introduction of Cardiac stent

1. CARDIAC STENT
Metal Stent

2. N-OVATIVE HEALTH TECHNOLOGIES
N-ovative Health Technologies (NHT) Pvt Ltd, based at National University of Sciences &
Technology (NUST), Islamabad, is a state-of-the-art medical device manufacturing facility. It is
actively working in research and development of healthcare technologies as well as mass
production of life-saving medical devices and implants such as Bare Metal stents, Drug-
Eluting Stents, Angioplasty Balloon Catheters, Diagnostic Angiographic Catheters, ventilators
etc. Under special directives of the Prime Minister’s Office and Supreme Court of Pakistan,
N-ovative Health Technologies (NHT) Pvt Ltd was established at NUST owing to the
university’s well-established research and development ecosystem. NHT is sponsored by the
Ministry of Sciences & Technology (MOST) with the mandate of indigenously manufacturing
cost-effective high-quality medical devices

3. Introduction
A stent is a metal or plastic tube inserted into the lumen of an anatomic vessel
or duct to keep the passageway open, and stent is the placement of a stent.
Coronary stents (CS) are expandable tubular metallic devices which are
introduced into coronary arteries that are clogged due to an underlying
atherosclerosis disease. This revascularization procedure is termed as a
percutaneous coronary intervention (PCI) or coronary angioplasty with stent
placement. With the introduction of coronary stents, coronary dissection and
vascular recoil were eliminated due to the expandable, metallic meshwork of
the stent, which prevents negative remodeling. This activity reviews the
presentation, evaluation, and management of coronary artery steno sis and
stresses the role of an inter professional team approach to the care of affected
patients.

4. OBJECTIVE
• Coronary angioplasty greatly increases blood flow
through the previously narrowed or blocked coronary
artery.
• Chest pain generally should decrease
• Stent may eliminate your need for coronary bypass
surgery. Stenting is much less invasive than bypass
surgery.
• It reduce the chances of Heart-Attack
• It prevent muscles of Heart

5. DESIGN OF CARDIAC STENT
• The design of cardiac stent is made on 3-D Modeling Software “Solid Work”
• The format of cardiac stent is SLDPRT files contain a 3-D object or more
specifically “part” that can be combined with other “parts” to create an assembly file in
SOLIDWORKS assembly. These files are easy to open and edit in SOLIDWORK

6. COMMANDS OF SOLIDWORKS
•First apply Helix & Spiral Command on a Circle
•Then apply Sweep Command on other side of Circle after selecting the plane
•Above both commands repeat one time
•Apply the extrude command on front plane circle to hollow the shape
•After selecting Sweep 1 & Sweep 2 Command apply Circular Command

7. Manufacturing Cyclic Process

8. MECHANICAL PROPERTIES
Coil
Most common in nonvascular applications, the coil design allows for retrievability after
implantation . These designs are extremely flexible, but their strength is limited, and their
low expansion ratio results in high-profile devices.
Helical spiral
These designs are generally promoted for their flexibility. With no or minimal internal
connection points, they are very flexible but also lack longitudinal support. As such, they
can be subject to elongation or compression during delivery and deployment and,
consequently, irregular cell size. With internal connection points, some flexibility is
sacrificed in exchange for longitudinal stability and additional control over cell size

9. Metallurgy of Cardiac Stent
• Stents are produced from thin-walled tubes made of high-quality metal alloys such
as stainless steel, cobalt-chromium alloys.
• These are elastic structures made from metal or polymers, which are typically a
tubular shape. These are implanted into the human body to give support to blood
vessels, food pipes, and other organs.

10. ELECTROFORMING
In this process, electroplating is performed on a mandrel in a given
pattern. When the desired thickness has been reached, the mandrel is
etched away from the electroformed stent, leaving a free standing
structure, a fully functional stent

11. DIE-CASTING
This is another technique in which the stent can also be formed by
subjecting one or more. The metal may be cast directly in a stent-like form or
cast into sheet or tubes from which the inventive stents are produced by
using any of the method mentioned here.

12. LASER CUTTING CARDIAC STENT
Laser cutting of stents has developed rapidly in line with demands from the medical
device industry. It is possible to laser cut extremely complex shapes in 1 to 25 mm
outer diameter tubes with walls as thin as 0.2 mm. Together with the trend to
further reduce strut dimensions from about 110 µm down to merely 60 to 85 µm,
these requirements demand an accurate laser cutting system.
The Type of laser cutting that we use is femto second laser or fiber laser

13. LASER CUTTING CARDIAC STENT
The lasers with longer pulses have longer beam–material interaction time, which
results in a larger heat-affected zone on the stent work piece. Shorter pulse
durations (femto-second lasers) result in an unaffected or minimally heat-affected
zone but at a slower speed.
EFFECTIVENESS OF FIBRE LASER ISNTANT CUTTING
Polymer and metal stents can be cut with hybrid femto-second lasers. An ultrafast laser
has extremely short pulse widths, which prevent heat damage when cutting stents.
This in turn makes post-processing simple, using an ultrasonic bath and water instead
of chemicals

14. ELECTRO-POLISHING
The stents which’s material were 304 or 316L type stainless steel were polished without
stirring the electrolyte mixture. The stent was fixed on the two sides in horizontal
position. The temperature of the electrolyte was 40 °C for the 304 type stent, and 75 °C
for the 316L stent. In the electrolyte a perforated stainless steel cylinder served as a
cathode. For sufficient fixing of the stents a special clip was used. Material of the clip was
90Pt10Ir alloy; the weight of the clip did not change under the entire electro-polishing
process

15. PICKLING OF UNDESIRED MATERIAL
Acid pickling is one of the major methods to remove the burr and the depositions in
metal stent. Beside acid pickling, Annealing and cooling process are also take place at
room temperature In this study, as a pre-treatment of polishing the Metal stents,
pickling was tested for various times in an acid solution at room temperature. Its effect
on the surface morphology, dimension changes, and mechanical behavior of the Metal
stents was evaluated. The burr and depositions could be removed practically. The
removal (weight loss) of the material increases linearly with the pickling time. The burr
and depositions were removed totally from the cutting zone when pickling time
reached a specific value. Experimental relations among weight loss, dimensions,
mechanical properties and pickling time of the Metal stents were established.

16. WELDING EXTENDED & LOOPWIRE
The method of making the stent may further include the steps of
(i) Extending at least one of the mated stent wires to provide an extended stent wire;
(ii) Looping the extended stent wire so the extended end abuts a proximal pair of
stent wires
(iii) Welding extended and looped wire to the proximal pair of wires. Desirably, the
step of looping includes forming the wire into an arch with equilateral sides, having
an apex, but not having other sharp bends.

17. LASER WELDING OF METAL STENT
Stents, especially for cardiac and vascular applications, can be manufactured by braiding or knitting
thin metal wires. Welds are needed to join the individual wires together in order to ensure the
functionality of the stent. Depending on the geometry, 10 to 100 individual welds are present on
each metal wire stent, and all welds need to be perfect quality. For mass production of stents, an
automatic camera-based vision system is used to position the stent relative to the target area of the
laser spot. The laser spot is positioned exactly in the middle of the trench between the two adjacent
wires. A stable laser-pointing accuracy and the accuracy of the laser optics all contribute to the
desired precision

18. LASER SNIPPING OF METAL STENT
Laser welding of the metal wires, the excess wire needs to be removed. Although it is
possible to cut the wire manually, for larger series of cardiovascular stent preparation
laser snipping is a reliable, traceable (production data stored and accessible according
to FDA standards), low-cost, repeatable and fast technology. For laser-snipping systems,
dependent on the application, a nanosecond, pico-second or femto-second laser is used
to cut the wire.

19. MICROSCOPIC ANALYSIS OF STENT
Stents need to maintain the highest quality standards so we
analysis of stent on electron microscope,
• Spot inspection
• Check Defects in stent after Laser Cutting.
• See Geometry of Thread of stent.

20. PASSIVATION
• Passivation is carried out by dipping the stent materials in a solution containing 25%
(v/v) concentrated HNO3 and deionizer water (balance) for30 minutes [135]. Nitinol
stent can be passivated by using nitric acid solution. The passivation treatment reduces
the content of Ni or NiO and increases the surface withTiO2 content which improves
the corrosion behavior of the materials.
•Passivation treatment is important to improve the corrosion resistance of the
materials

21. DRUG COATING
•It is the main additional property usually added to stents in the current clinic
practice. The main stent currently used in clinic is DES. There are a variety of
coating techniques to incorporate drugs to the stent
•Coating by submerging the stent in a solution of drug and/or polymer in a
solvent. The stent is then left to dry, allowing for evaporation, in the air/oven. In
this technique the drug/polymer can vary their concentration and/or their
homogeneity

22. CONCLUSION
The design and development of Metal stents have led to the revolution toward true
biological solutions. The artery needs a mechanical support for its healing and
remodeling that is provided by the Metal stents for over a period of time up to its
complete cure. Stainless steel is considered as the elements for such applications as its
mechanical properties and biocompatibility in human body possess ultimate assets for
the application of stents in load bearing. The results of implantation of all the Metal
stents including SS316L, iron, and magnesium demonstrate that even though the
degradation rate of these stents is yet to be modified, the simulation and FEA analysis
performed on its modeled structure of these materials have the adequate strength to
withstand the load that is dispersed on its walls, which is a major setback leading to a
clear obstruction in the development of alternative material like polymer.